ECR feature: Plant diversification with Esther Dale

Esther Dale studies plant diversification as a postdoc at Manaaki Whenua – Landcare Research in Dunedin and the University of Otago, Department of Botany. Her recent publication in the Journal of Biogeography tests biome conservatism in Australian Acacia using species distribution modeling. Esther discusses the implications of her findings, particularly that hyper-diverse Australian Acacia provides a rare example of a plant lineage in which most species occur across multiple biomes.

Esther Dale in the Palm House at the University of Copenhagen Botanical Garden

Links: Google Scholar | Twitter

Institution: Manaaki Whenua – Landcare Research, Dunedin; University of Otago, Department of Botany

Current academic life stage: Postdoc

Research interests: I study plant diversification, focusing on the role of shifts between different biomes in lineage evolution.

Current study system: Australian Acacia—they’re hyper-diverse, with over 1000 species, making them one of the most diverse vascular plant genera globally. Australian Acacia have managed to occupy many different, contrasting ecosystems such as desert and tropical rainforest.

Recent paper in Journal of Biogeography: Dale EE, Larcombe MJ, Lee WG, Higgins, SI (2020). Diversification is decoupled from biome fidelity: Acacia–a case study. Journal of Biogeography47(2):538– 552. DOI: 10.1111/jbi.13768

Motivation for the paper: We were interested in examining how plant lineages evolve in relation to the biomes that they occupy. Biome conservatism, the tendency for lineages to remain in their ancestral biome, is regarded as relatively typical in plant lineages. We wanted to explore whether biome conservatism constrains diversification by keeping lineages within a particular biome, if diversification is primarily occurring within biome boundaries, and if diversification is associated with specialisation to a single biome. We decided to use Australian Acacia to test this because it is hyper-diverse (over 1000 species!), it has a published phylogeny, and distribution data were available.

Acacia aneura in Mallee. This vegetation would be classified as Mediterranean (WWF Biomes), Short Low-productivity Non-seasonal (Functional Biomes), or Eremaean (Crisp Biomes and González-Orozco Biomes). Photo credit: Matthew Larcombe.

Key methodologies: We used species distribution modelling to identify which biomes each species occurs in. We had noticed with the distributional data that some biomes were under-sampled, which might make species seem more specialised to certain biomes than they are in reality. To minimise this source of bias, we used predicted distributions rather than distribution records to determine the biomes occupied. In addition, there are a variety of different biome maps with different numbers of biomes. Previous biome conservatism work has used a variety of different biome maps and we thought it was likely that the biome typology used would influence the conclusions being drawn. We used four different biome typologies to check that our findings were robust over multiple different biome concepts.

(left) Esther at the Brisbane Botanic Gardens Mt Coot-tha examining Acacia disparrima. (right) Esther at Kings Plains National Park, New South Wales. The vegetation in this area would be classified as Temperate Forest (WWF Biomes), Tall High-productivity Non-seasonal (Functional Biomes), Southeastern Temperate (Crisp Biomes), or Euronotian (González-Orozco Biomes). Photo credit: Zoë Stone.

Unexpected challenges: In contrast to the expectation under biome conservatism, we observed that most species (91%) occurred in multiple biomes. This was quite surprising because it contrasts some previous work demonstrating biome conservatism as widespread. It indicates that specialisation of species to a single biome cannot be assumed, and analyses examining biome shifts and biome conservatism should allow for species that occupy multiple biomes. The main challenge with this research was the size of the dataset. It involved 481 species, 151735 occurrence records, and global environmental data layers with a 1 km resolution, meaning we needed to be efficient with our analyses. Most of us working on this project hadn’t worked on Australian species before and were not familiar with the history of the flora or climate, so it was challenging taking on such a characteristically Australian group without much experience of Australian ecosystems. However, it was probably also useful—we hope—to be able to contribute a fresh perspective.

Major result and contribution to the field: We found a consistent pattern of cross-biome diversification with all four biome typologies. Higher diversity clades had greater niche size, indicating that diversification is linked to occupying new niche space rather than partitioning the ancestral niche. Our work demonstrates that Acacia can easily overcome biome boundaries, and diversification in Acacia is not constrained by biome conservatism. This contributes a rare example of a lineage where most species occur in many biomes, with diversification occurring across biome boundaries. Our findings also indicate that lineages can have many species that occur in multiple biomes, so analyses should allow for species that occupy multiple biomes.

What are the next steps? We are interested in applying what we’ve learned from looking at Acacia, with its large spatial and taxonomic scale, to New Zealand plant lineages. We are keen to follow on from these findings by exploring how diversification is affected by new biomes appearing, and whether biome shifts are associated with trait innovations. New Zealand will provide an interesting contrast to our Acacia work because there are fewer biomes and smaller focal lineages. In New Zealand there has been a clear sequence of different biomes becoming available, which presents an excellent opportunity for examining the role of new biomes and biome shifts in lineage evolution. New Zealand is a fantastic system for testing hypotheses about plant evolution because of the quirks of the flora, like high incidences of polyploidy, divarication, and small inconspicuous flowers, and its isolation, making it a natural experiment in evolution.

If you could study any organism on Earth, what would it be and why? I would love to be able to study subantarctic megaherbs. The subantarctic islands are known for their megaherbs, which tend to be much larger and have flowers that are brighter in colour than their New Zealand mainland relatives. It would be fun to examine their evolutionary history to understand how they have adapted to the conditions in the subantarctics, and what selection pressures are driving these changes.

Any other little gems you would like to share? This type of work would not be possible without the excellent body of herbarium specimens in Australia, so a big thanks to all the collectors, herbarium curators, and the Atlas of Living Australia who do such important work!

Eucalyptus regnans forest in Gippsland Victoria. This vegetation would be classified as Temperate forest (WWF Biomes), Tall High-productivity Non-seasonal (Functional Biomes), Southeastern Temperate (Crisp Biomes), or Euronotian (González-Orozco Biomes). Photo credit: Matthew Larcombe.

Mountainous Matters

Writing the perspective Why Mountains Matter for Biodiversity (Perrigo et al. 2020) was a chance for myself, along with Carina Hoorn and Alexandre Antonelli, to explore and distill some of the ideas that came up while editing a book that was published two years ago: Mountains, Climate and Biodiversity (Hoorn et al., 2018).

One of many early versions of a figure from the paper that were exchanged by the authors to make sure all the processes they showed were as accurate as possible.

Mountains are increasingly discussed in relation to biodiversity and, more specifically, biogeography. This is logical: mountains are much less affected by direct human activity as compared with lowlands, meaning they tend to be more “natural” systems to study. They are important when it comes to climate change as well. Often, a population must move a shorter distance to track a suitable habitat on a mountain, as the climatic variation from increasing altitude parallels the changes seen in increasing latitude in many ways. 

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EDITORS’ CHOICE 47(2):
Perrigo, A, Hoorn, C, Antonelli, A. (2020) Why mountains matter for biodiversity. Journal of Biogeography 47(2): 315–325. https://doi.org/10.1111/jbi.13731. OPEN ACCESS
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Critically, in the coming decades mountains will play a key role in biodiversity conservation as refugia for many species. These “Anthropocene nunataks” will be surrounded by seas of land that is exploited by humans, making a barrier to dispersal that may be analogous to the ice sheets that surrounded ice age nunataks.


While hiking up Mt Bisoke in Rwanda (ca. 3700 m), it is possible to observe a progression of vegetation types—influenced by the changing altitude—in a matter of hours. 

In our perspective we outline what we see as some of the biggest challenges we now face in moving the study of mountain biodiversity forward. Among these are the relatively low availability of sufficiently specific data compared to lowlands on, for example, climate, soil-type and vegetation patterns. We also express the need for more studies that incorporate both theoretical and empirical aspects to push method development forward, while highlighting good examples.  

Trans- and inter-disciplinary projects are encouraged throughout academia to explore novel perspectives. But often these are a challenge in practice because we are “speaking different languages,” to steal a phrase I have heard repeatedly about this type of work. Even though geology and biology are just a stone’s throw from one another, there are mountains between us (pun intended…). This became increasingly apparent while working with the various chapters of the book, where differences in terminology and tradition often led to misunderstandings. These were frequently a result of mutual knowledge gaps. 

The table in our perspective is one of our most concrete efforts to overcome this. It summarizes the different methods used for dating mountains. The concept is simple: different methods are used to figure out just how old mountains are. But in practice, especially for biologists, it can be daunting to understand these methods in context and relative to one another. What ages are they good for? When would you use one or the other? Where can you even look to figure out what they mean or how they work, in basic terms? 

However, in the beginning this information wasn’t laid out as a table. Carina Hoorn was the mastermind behind the mountain dating overview, but it was initially a long text with a repeating pattern: dating method, how it works, when it is best used, ages it is relevant for, references, and so on. It was extremely informative, but hard to navigate. After some discussion we realized: maybe this information would be better presented as a table? In the end, it was much easier to both read and interpret this way. The mountain dating table is a cornerstone of this perspective: we hope this accessible overview opens up doors for further cross-disciplinary understanding. 

We see a value in reflecting on a project after its completion, especially one with as many contributors as Mountains, Climate and Biodiversity.  Like Humboldt, whose work was among our constant inspirations for this perspective, we attempted to find key themes in a massive amount of information from various disciplines and from this take the parts we found the most interesting, useful and provocative. 

Finally, we are encouraged by the growing interest in mountain biodiversity we have seen over the last few years. We have received positive feedback and started new discussions stemming from both Mountains, Climate and Biodiversityand the early online version of our perspective. This issue of the Journal of Biogeography features three other mountain-themed papers (Brambach et al. 2020, Li et al. 2020 and Maicher et al. 2020), and follows on the heels of the 2019 special issue celebrating Humboldt’s 250-year birthday and the legacy of his work.  

Written by: Allison Perrigo.

Director, Gothenburg Global Biodiversity Centre, University of Gothenburg, Gothenburg, Sweden. @DrSlimeMold, @GGBC_GU

I would like to thank Carina Hoorn (@carinahoorn), Harith Farooq, and Ferran Sayol who all provided feedback on this blog post, as well as Alexandre Antonelli (@antonelli_lab) for discussions on the content. All three co-authors (AP, CH, AA) are grateful to all of the authors who contributed to Mountains, Climate and Biodiversity

Additional information: antonelli-lab.net; ggbc.gu.se

ECR feature: Tropical entomology with Friederike Gebert

Friederike Gebert is a postdoc working in tropical entomology at the University of Würzberg. Her recent work, published in the Journal of Biogeography, focuses on understanding the patterns and drivers of dung beetle distribution along an elevational gradient on Mt. Kilimanjaro. From the collection of dung beetles to the measurement of mammal dung resources, Friederike provides an insider look into the study of two very different but functionally related groups of organisms on the highest free-standing mountain in the world.

Friederike whilst setting up a pitfall trap at the base of Mt. Kilimanjaro at 870m asl on a study plot located in the savannah

Links: Institutional webpage | Research Gate | Google Scholar | Twitter

Institution: University of Würzburg, Department of Animal Ecology and Tropical Biology

Current academic life stage: Postdoc

Research interests: I am interested in tropical entomology and in the impact of elevation and land use on species’ distributions, traits, and ecosystem services.

Current study system: Currently, I am studying dung beetles and mammals on Mt. Kilimanjaro, Tanzania. The fascinating thing about my research is that I combine the study of two very different, yet closely functionally related groups of organisms on the highest free-standing mountain in the world to investigate the drivers of biodiversity along elevational gradients. Both dung beetles and mammals are of immense importance in ecosystems, the former because they provide many ecosystem services related to dung decomposition, and the latter because they turn over high amounts of biomass and provide an array of services from pollination to the maintenance of habitat heterogeneity.

Recent paper in Journal of Biogeography: Gebert F, Steffan-Dewenter I, Moretto P, Peters MK. (2020) Climate rather than dung resources predict dung beetle abundance and diversity along elevational and land use gradients on Mt. Kilimanjaro. Journal of Biogeography, 47(2):371–381. https://doi.org/10.1111/jbi.13710

Motivation for the paper: The distribution of species along mountains has fascinated biologists for more than two centuries. Even though the patterns of species diversity along elevational gradients are well described, the drivers behind them remain controversial until today. Many hypotheses are discussed, a general disagreement being whether energy-related or climate-related drivers are more important. I wanted to contribute to this current discourse on the predictors of biodiversity by investigating the patterns and drivers of ectothermic organisms—dung beetles—along a huge elevational gradient on Mt. Kilimanjaro. One shortcoming of studies investigating the importance of energy versus the importance of temperature in driving biodiversity gradients is that often, energy resources are not directly measured. Instead, primary productivity is used as a proxy for resources. However, most organisms use specific food resources which may not be represented accurately by primary productivity. Therefore, we tried to measure the energy resources available for dung beetles in the field.

(A) The study system: Mt. Kilimanjaro – this photograph was taken at 1600m from the research station, Nkweseko, which served as the base for the dung beetle study. It shows the south face of Kibo, the summit of Mt. Kilimanjaro at 5895m. Nkweseko research station is located in the cultivated zone of Mt. Kilimanjaro inside the coffee-banana belt. The predominant form of cultivation here is traditional agroforestry of the Chagga people, which is called Chagga homegardens. (B) Here you can see very rich lower montane forest. This beautiful valley is located at 1600m and, unfortunately, is not part of Mt. Kilimanjaro National Park. Therefore, logging is commonplace and a threat to the preservation of this remarkable area. Here, two study plots were located. (C) Here you can see a camera trap set up in the forest. (below) A part of our collection. In total, we collected 10432 dung beetles belonging to 135 species.

Key methodologies: We used baited pitfall traps to collect dung beetles. For measuring dung resources available for dung beetles, we calculated mammal defecation. To get the mammal data, we installed camera traps on the same 66 study sites along an elevational gradient of 3.6km on Mt. Kilimanjaro on which we collected dung beetles. We then estimated mammal defecation from mammal biomass data. To the best of our knowledge, this is the first study to accurately measure the amount of dung resources available for dung beetles. Apart from dung resources, we also investigated the impact of temperature, precipitation, land use and area on dung beetle species richness and abundance by means of path analysis.

A graph illustrating the drivers of dung beetle species richness and abundance. While dung beetle diversity is impacted by climate (temperature and precipitation), the main predictor for mammals (here represented as the dung resources) is net primary productivity, demonstrating the contrasting drivers of endothermic and ectothermic diversity.

Unexpected challenges: Since dung beetles rely upon mammalian dung as a food source for both adults and larvae and are thus closely functionally related to mammals, we expected mammalian dung resources to be one major driver of dung beetle diversity on Mt. Kilimanjaro. As we tried our best to have a good measure of dung resources for dung beetles, we were surprised to find that dung resources did not play a role in predicting dung beetle diversity.  Since most dung beetles are active during the rainy season, I mainly collected dung beetles during the period of the long rains on Mt. Kilimanjaro. Because of muddy roads and paths, it was not always easy to reach the study plots and we had to overcome challenges like trees blocking the road or cars stuck in the mud.

Major result and contribution to the field: We found that even though we tried to meticulously measure the actual dung resources available for dung beetles, temperature was the major driver of dung beetle diversity on Mt. Kilimanjaro. This study shows that along huge environmental gradients, temperature is the main driver of diversity for ectothermic organisms. However, when we looked at the drivers of mammals, which are endothermic, we found that energy resources were the most important drivers. To conclude, our study is an important contribution to the current debate on the drivers of biodiversity as it illustrates that the drivers for montane diversity depend on the thermoregulatory strategy of organisms. Furthermore, our finding that dung beetle diversity is driven by temperature has important implications for biodiversity conservation in the context of climate change, as rising temperatures may have negative repercussions on dung beetles and their associated ecosystem services.

What are the next steps? The next step in this research is to look at the ecosystem services provided by dung beetles to investigate whether climate or biodiversity is more important in shaping ecosystem services along environmental gradients.

If you could study any organism on Earth, what would it be and why? In ecology, we are always in search of general patterns. I especially like organisms that make us question the concept of generality and make us acknowledge that there are always exceptions to the rule, which is one of the most intriguing features of studying biodiversity. That is why, even though I am actually an insect person, I would love to study the Grasshopper Mouse (Onychomys sp.). This mouse is so special because, in contrast to other rodents, it relies on a carnivorous diet and even feeds on scorpions and snakes, being immune to their venom. And since I am an old Dracula fan, I love the fact that this mouse is nocturnal and howls to the moon like a proper werewolf mouse!

Any other little gems you would like to share? During my research on Mt. Kilimanjaro, we collected a total of 80,000 film snippets from camera traps. Whilst most of the videos showed moving grass in the savannah, around 1600 videos did actually show mammals. Our biggest mammal highlight was that we filmed the elusive antelope species Abbott’s Duiker (Cephalophus spadix) for the first time on Mt. Kilimanjaro. This antelope is endemic to Tanzania and only occurs on few isolated mountain massifs. Up to now, the distribution of this species on Mt. Kilimanjaro has not been known – now our research suggests that Mt. Kilimanjaro might be a stronghold for this species. What’s cool is that we were the first ever to film an Abbott’s Duiker pair and a male trying to mate.

(left) Alpine Helichrysum scrub vegetation at 3800m. (right) The highest study plots were located at 4500 m.

Flying foxes – out of Wallacea

How efforts to understand origins and diversity led to efforts to conserve and protect the world’s largest bats

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COVER STORY 47(2):
Tsang, SM, Wiantoro, S, Veluz, MJ, et al. (2020) Dispersal out of Wallacea spurs diversification of Pteropus flying foxes, the world’s largest bats (Mammalia: Chiroptera). J. Biogeography 47(2): 527– 537. https://doi.org/10.1111/jbi.13750
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Long-distance dispersal (LDD) is often regarded as a rare and unpredictable event, causing some to consider it an untestable hypothesis. However, advances in genomics, niche modeling, and computation enable direct and indirect testing of LDD hypotheses, particularly in understanding the evolution of recently diverged taxa. These studies have primarily been conducted on plants and a handful on bird groups, but the role of dispersal in bat diversification is scarcely studied. Historically, research on Paleotropical bats has lagged behind other vertebrates, but recent capacity-building efforts have enabled internationally collaborative research in Southeast Asia. Studying LDD in flying foxes, the world’s largest bats in the genera Pteropus and Acerodon, is difficult because some widespread species are found in more than half a dozen countries, while numerous endemic species are restricted to individual islands or island groups from American Samoa to Zanzibar. By assembling a multi-national team for locating and sampling tissues from these rare bats, we were able to conduct one of the first biogeographic studies of a species-rich mammal taxon in the Indo-Australian Archipelago (IAA). 

The IAA is a fascinating biogeographic laboratory, as the fission and fusion of landmasses over geologic time have both isolated and re-connected areas in rapid succession. Biotic studies in the IAA are few relative to that of other tropical areas, particularly in Wallacea, the area between Borneo and New Guinea. Many islands in Wallacea have never been connected to a continent. Our study suggests that Pteropus originated in Wallacea at a time when the relatively depauperate ecosystems on recently formed islands presented “blank canvases” to which flying foxes dispersed and subsequently diverged from their ancestors. For the most part, the number of flying fox species found in an area seems unaffected by the size of the bat, the distance between islands, or the age of the lineage (with a possible exception in the South Pacific). Flying foxes can carry fruits, swallow seeds whole, and fly nearly 90 km in an evening, potentially over water. They are acknowledged as crucial seed dispersers in the rainforest where they occur, but their impact on plant historical biogeography and diversification, through co-dispersal, for example, is little studied.

During the course of fieldwork for this study, members of our team located bat species that hadn’t been seen alive in over two decades. We also found that colony sizes are shrinking throughout the IAA; a colony’s crepuscular emergence no longer blankets the sky with black, leathery wings. We observed that species throughout Asia are hunted at unsustainable levels for human consumption, which creates a conservation crisis for bats and a public health hazard for humans, who could be exposed to potentially lethal pathogens. This has motivated us to train multiple grass-roots organizations and local scientists in standardized population monitoring and outreach methods, along with push for localized hunting bans or regulations to prevent further decline. Expansive biogeographic studies like this may not be possible in the future if the current rate of population extirpation continues. Flying foxes and other fruit bats are charismatic but little known. They are perhaps best studied in Australia where roosts are near urban areas, but only 5 of the 65 known species are found there. A majority of species are endemic to single islands or island groups, and these species are understudied, despite their importance for forest regeneration on isolated, oceanic islands. Future studies will examine the environmental impact of flying foxes on terrestrial and marine ecosystems, as many species roost in large aggregates in liminal areas, such as mangroves, that abut vulnerable ecosystems such as coral reefs.

Written by: Susan M. Tsang (1) & David J. Lohman (2)
(1) Research Associate, Department of Mammalogy, American Museum of Natural History; Research Associate, Mammalogy Section, Philippine National Museum of Natural History.
(2) Associate Professor, Department of Biology, City College of New York & PhD Program in Biology, Graduate Center, City University of New York; Research Associate, Entomology Section, Philippine National Museum of Natural History (Philippines).

Additional information: @batgirl_susan, pteropus.net; @dj_lohman, lohmanlab.org


Adult Pteropus vampyrus from Bali, Indonesia.

ECR feature: Epiphytic lichens & atmospheric regimes with Rob Smith

Rob Smith is a postdoc in the Department of Botany and Plant Pathology at Oregon State University, who studies the effects of changing atmospheric regimes on forest vegetation. Rob’s recently published work in the Journal of Biogeography discusses how epiphytic macrolichen vulnerability to climate change can signal atmospheric stresses among a group of organisms that many assume to be indifferent to climate.

Early career researcher (Rob) in typical habitat

Links: Personal webpage | Google Scholar | GitHub

Institution: Oregon State University, Dept of Botany and Plant Pathology

Current academic life stage: Postdoc

Research interests: Forecasting how global changes to atmospheric regimes alter the functioning, persistence and distribution of forest vegetation.

Current study system: Epiphytic lichens – perched upon the branches and trunks of other plants – are tightly linked to the atmosphere.  Despite their mistaken “extremophile” reputation, these lichens live at the mercy of atmospheric nutrients, temperature and moisture.  Climate, therefore, imposes strict limits on individual performance and geographic distributions.  Since most lichens fit in the palm of the hand, they make excellent travel companions, in addition to being well-suited for reciprocal transplants and common garden experiments to better anticipate climate responses.

Recent paper in Journal of Biogeography: Smith RJ, Jovan S, McCune B. 2020. Climatic niche limits and community-level vulnerability of obligate symbioses. Journal of Biogeography, 47(2). DOI: 10.1111/jbi.13719.

Motivation for the paper: We previously looked at climate-driven historical changes in lichen community compositions using a large-scale national forest inventory (FIA, the US Forest Service’s Forest Inventory and Analysis).  Yet, we still lacked the basic ability to forecast future changes at large scales.  Our new vulnerability approach arose from the observation that populations at the physiological “edges” of a species’ realized niche can also reveal its geographic edges – places on the landscape where incremental warming or drying could push a population to local extinction.  For many species together, co-occurrence of such “vulnerable” populations would signal a community on the verge of compositional turnover.  Forest workers would like to anticipate the location and magnitude of compositional changes before they occur.

(A) Climate stress from prolonged drying or warming can change lichen community compositions, including these pale green Alectoria hair-lichens draping western hemlocks in the mist near Cascade Pass, Washington, USA. (B) Bryoria horsehair lichens festoon a subalpine fir, with the glaciers of Mount Rainier in the distance, Washington, USA.  Direct exposure to the atmosphere makes epiphytic lichens sensitive to climate variation. (C) Charismatic epiphytic lichens (like this “oakmoss” Evernia prunastri) are easily transplanted, making them ideal for examining climate tolerance. (D) Installing cameras for daily census of lichen dynamics as part of new work with the Epiphytic Lichen Observation Network (ELON).

Key methodologies: Ecologists often depict environmental responses as community-weighted means (e.g., temperature optima).  Yet, central mean values ignore the “tails” of realized niches – boundaries which define the outer limits of persistence.  By contrast, our vulnerability scores are explicit about how far populations are from their climatic edges, and therefore the conditions under which incremental climate changes would lead to local declines.  Across 400+ epiphytic macrolichen species, and combined with climatic exposure at thousands of FIA plots nationwide, vulnerability scores let us identify geographic “hotspots” of expected compositional changes.

Unexpected challenges: One challenge was to adequately depict the realized climatic niche of several hundred species, including species whose ranges extended well beyond the study area.  We resolved this by introducing hundreds of thousands of herbarium records from all of North America, from tropical to polar regions.  This introduced its own challenge: how best to standardize the unequal sampling efforts typical of natural history collections?  For this, we binned observations into spatial grid-cells of gradually increasing sizes, finally arriving at an acceptable cell-size that “smoothed away” unequal sampling efforts while preserving climate information.

Major result and contribution to the field: We found remarkably high climate-change vulnerability among a group of organisms that many folks assume are indifferent to climate!  This supports the emerging perspective that epiphytic macrolichens can sufficiently signal atmospheric stresses.  Unexpectedly, we also found that communities most vulnerable to warming were concentrated in low‐elevation and southerly locations.  This suggests that warm-edge communities – commonly assumed to be “thermophilic” – may in truth be perilously close to exceeding their climatic limits.  Could the vulnerability approach work for the organisms you study?  You can try it for yourself, using the freely available R package: https://github.com/phytomosaic/vuln.

What are the next steps? We are working to generalize the vulnerability concept to admit multiple drivers that interact.  This is because interactions among atmospheric stressors (climate and nitrogen excesses) and disturbances (wildfires) not only violate species’ tolerances directly, but can also aggravate pest/pathogen risks.  We also need to compare vulnerability among different lineages and morphogroups (forest trees, shrubs, forbs, graminoids, lichens) to identify the most responsive organisms.  Finally, we are developing user-friendly, open-source mapping tools that let forest workers quickly identify hotspots of compositional changes for adaptation purposes.

If you could study any organism on Earth, what would it be and why? To me, the most fascinating organisms are forest trees, which breathe our air and cycle our carbon.  Even for these everyday organisms, there is some hint of mystery in simple acts like passive water uptake (solely by transpiration! no active pumping!).  Despite being the dominant characters in forests, we are still far from accurately forecasting tree growth, survival and reproduction over large scales in the face of global changes.

Any other little gems you would like to share? It’s always fun to hear origin stories, how each person first began to engage the natural world.  My first real entry to forest thinking was the simple result of being an introverted kid – stealing off down the leafy railroad tracks paralleling the Patapsco River to decipher Lao Tzu or Albert Schweitzer under red oaks.  And then, looking up at red oaks, wondering.  There are hundreds of ways to enter your own forest.

Vulnerability scores combine local climate exposure with sensitivities of individual species, like these Bryoria horsehair lichens above White River at Mount Rainier, Washington, USA.

ECR feature: Rafael M. Venegas on phylogenetic community structure

Rafael Venegas is an ecologist with a passion for plants. He is currently a postdoc at the University of Alcalá. He uses phylogenetic methods to address questions in macroecology and biogeography to ultimately understand what shapes biodiversity and ecosystem services. In his recent paper with the Journal of Biogeography, he extends theory on phylogenetic community structure through specific consideration of phylogeny branching patterns. Rafael shares how insights on community assembly can be gained from this new analytical framework.

Rafael Molina Venegas. PhD and current postdoctoral researcher at the University of Alcalá (Madrid, Spain), posing in front of a pine forest (Pinus pinea) in the surroundings of Doñana National Park (southwestern Iberian Peninsula) 

Links: Personal page

Institution: University of Alcalá (Madrid, Spain)

Academic life stage: Postdoc

Research interests: Phylogenetics, macroecology, biogeography, plant biodiversity, ecosystem services.

Current study system: I’ve been working on Mt. Kilimanjaro flora for two years. Kilimanjaro is the highest single free-standing volcanic massif in the world, and includes lush jungles, cloud forests and cold and fire-adapted bushlands and scrublands that spread until the glacier’s domain at 4500 m. This montane vegetation stands in splendid isolation above the surrounding plains, where savanna woodlands and agricultural fields dominate the landscape. The geographical isolation of Kilimanjaro makes its people highly dependent on natural resources (the so-called ecosystem services), creating an interesting socio-ecological context that inspired me to design the project I’m currently leading. This project aims to explore connections between ethnobotanical knowledge (in my opinion one of the most palpable proofs of the reality of ecosystem services) and global plant biodiversity from an evolutionary perspective.

The truth is that phylogenies have always been in the background of my research agenda, including the development and refinement of phylogenetic methods for the study of biodiversity. Indeed, some of my ongoing collaborations concern spatial phylogenetics with a focus on the endemic flora of the Iberian Peninsula (~1975 species and subspecies, 27% of the vascular flora of the region), an outstanding plant biodiversity hotspot in the western Mediterranean. I am particularly interested in evaluating the role that soil conditions have played in the diversification and maintenance of this flora.

(left) Rafael, exploring the forests in the foothills of Mt Kilimanjaro. (right) A chamaephyte community studied by Rafael in the Iberian Peninsula, a hotspot for plant biodiversity in Europe. Amidst the Quercus oaks, purple lavenders (Lavandula pedunculata) and white-flowered gum rockroses (Cistus ladanifer) bloom in the Mediterranean sunshine.

Recent paper in Journal of Biogeography: Molina-Venegas, R., Fischer, M. & Hemp, A. (2019) Disentangling the fundamental branching patterns of phylogenetic divergence to refine eco‐phylogenetic analyses. Journal of Biogeography, 46, 2722-2734. https://doi.org/10.1111/jbi.13692

Motivation for the paper: My first steps in science took me to the field of eco-phylogenetics, which aims to infer community assembly mechanisms by means of the footprint they left on the phylogenetic structure of communities. For example, little phylogenetic divergence (i.e. clustering) may indicate community structure is shaped by environmental filtering, which is a major mechanism in harsh habitats such as Mediterranean saline soils, where closely-related salt-adapted lineages predominate (e.g. Tamaricaceae, Frankeniaceae, Amaranthaceae). However, classical indices of phylogenetic divergence disregard much of the biological information encoded in the phylogenies, because they are simply “blind” to the exact branching pattern of phylogenies. This is problematic because it precludes understanding of how ecological processes affect evolutionary relationships within communities. The prospect of overcoming this methodological shortcoming was the main motivation to work on this paper.

Key methodologies: In this paper, we show that phylogenetic divergence can be driven by different branching patterns that arise from specific ecological processes and propose a method to identify their signature in communities. Let’s picture two communities that experience different assembly processes (see schematic figure below), namely, competitive exclusion between close-relatives due to resource depletion (as predicted by limiting similarity theory, top community) and facilitation by a distant-relative nursery plant that mitigates the harshness of environmental conditions. Both mechanisms lead to increased phylogenetic divergence (more overdispersion), but the underlying branching pattern of such divergences (community phylogenies to the right) are markedly different. Still, the new communities may show similar phylogenetic divergence values, and therefore one may erroneously conclude that the same mechanism is at stake if the underlying branching patterns are ignored. Our method provides a handle to integrate both sources of information (i.e. phylogenetic divergence and the underlying branching patterns) using simple statistical tests.

Hypothetical plant communities experiencing different ecological processes, namely competitive exclusion between close-relatives (top) and facilitation (bottom). In the top-left community, resources are abundant and competition does not occur. When resources are scarce (top-right), competitive exclusion between close relatives comes into play and phylogenetic divergence increases. In the bottom-left, a community of species with narrow thermal niches thrive at an ambient temperature of 25ºC. A temperature increase of 5ºC (bottom-right) could lead to the collapse of the community, but the species can still persist under the canopy of a distantly-related facilitating species that provides microclimatic amelioration and augments phylogenetic divergence in the community.

Unexpected challenges: This research was not planned at all by the time I got involved in the Kili Research Unit, a multidisciplinary project that revolved around Mount Kilimanjaro biodiversity and ecosystem services. Dr. Markus Fischer, my postdoc advisor at the time, and Dr. Andreas Hemp, a botanist with more that 30 years of experience in the flora of East Africa, were interested in studying plant community assembly at Mount Kilimanjaro using phylogenetic information. However, I had a hunch that the tools available were insufficient for the project, so the opportunity presented itself allowing me to incorporate new ideas and concepts into existing theory. Through this I really had to put my statistics and programming skills to the test.

Major results and contribution to the field: Community phylogenetics is a young but controversial discipline, likely because too much has been demanded of both the original conceptual framework and classical descriptors of phylogenetic structure. In think our approach may contribute to mitigate this controversy by providing ecologists a handle to analyse phylogenetic divergence in the light of the underlying branching patterns, which is critical if we are to avoid spurious interpretations of phylogenetic information. I don’t mean by that our method is the ultimate solution, as the community phylogenetic discipline is not without methodological shortcomings that need addressing (see Cadotte et al. 2017, Ecological Monographs, 87, 535-551 for an excellent review), yet it represents one step forward in the field. To make the method more accessible to the community, we implemented it in R language and provided the code in full as a user-friendly function in the Supplementary of the article.

What are the next steps? There are still lots of interesting questions in community phylogenetics. For example, testing whether clades that are overrepresented in communities show different modes of trait evolution seems a promising avenue for future research (see Pearse et al 2019, Global Ecology and Biogeography, 28, 1499-1511 for a recent paper). Phylogenies are not magic wands that will unravel assembly mechanisms by means of few phylogenetic metrics, but just an important, exciting and necessary tool for understanding how biodiversity is generated and maintained. After all, elephants will never fly and butterflies will not eat lions because lineages are functionally constrained, meaning that evolutionary history matters. A new generation of eco-phylogenetic methods is coming up, and re-analyzing previous datasets with new available tools might unravel biological information that remains encoded in the phylogenies.       

If you could study any organism on Earth, what would it be and why? I would love to delve into the flora of the Wallacea Islands (particularly Sulawesi and Moluccas) and New Guinea”. On the one hand, this region combines multiple biogeographically interesting factors such as tropicality, isolation (islands) and sharp environmental gradients (mountains), which make the region extraordinarily appealing to me. On the other hand, these islands awaken the sense of adventure that many biogeographers carry inside of us. Even today, there is a continuous dripping of new species of birds, small mammals and plants reported from New Guinea! I have already visited the region once, specifically the Wakatobi archipelago in southeast Sulawesi (mostly a diving trip, so that time was more about coral reefs, likely my favourite animal taxa), and I am determined to come back.

Any other little gems you would like to share? I love teaching. I have taught General Ecology and Botany in bachelor’s degree and phylogenetic methods in postgraduate courses so far, which complements my facet as a researcher. After all, today’s students will be tomorrow’s researchers, the reason why I consider teaching a fundamental duty of scientists. At this point, I have to make a confession; plants are my true motivation in science, and I could not imagine being an ecologist without a focus on plants. And guess what? This is simply because I had good botany teachers during my time as an undergraduate student.

ECR feature: Macroecology with Philipp Brun

(left) Philipp collecting leaves of Taraxacum palustre during a trait sampling campaign in 2019. Photo taken close to Zurich, Switzerland. (right) Adonis vernalis – a rare beauty that was part of our plant trait sampling campaign in 2019. Photo taken close to Martigny, Switzerland.

Links: Institutional webpage | Google Scholar | Research Gate

Institution: Swiss Federal Institute for Forest, Snow, and Avalanche Research

Current academic life stage: Postdoc

Research interests: I am a macroecologist with a broad interest in questions related to species and trait distributions and biodiversity.

Current study system: After working with plankton biogeography during my PhD, in my postdoc I now focus on terrestrial plants in Europe, in particular on the communities of the European Alps. What I particularly like about these plant communities is (i) that I can develop and validate ideas about them while being active outdoors and (ii) that the wealth of observational, trait, and phylogenetic data combined with environmental and remote sensing data provide countless possibilities for creative analyses to deepen our understanding.

Recent paper in Journal of Biogeography: Brun P, Thuiller W, Chauvier Y, Pellissier L, Wüest RO, Wang Z, Zimmermann NE. 2020. Model complexity affects species distribution projections under climate change. Journal of Biogeography 47: 130– 142. DOI: 10.1111/jbi.13734. FULL ACCESS FOR 2020 & 2021.

Motivation for the paper: Since the paper by Merow et al. (2014), the species distribution modelling (SDM) community is generally aware that decisions about model complexity can have important and sometimes problematic implications for study results, but it had never been thoroughly assessed what these implications are for the important SDM application of projecting future range changes. We comprehensively studied how three aspects related to model complexity (parameterization complexity, number of predictor variables, and multicollinearity) affect analyses, using dominant European tree species.

(left) Major European forests (Data Source: https://land.copernicus.eu/). (right) Strong environmental gradients in the European Alps. While the growing season is well on its way close to the valley bottom, the higher altitudes are still deeply covered with snow. Photo taken close to Mount Titlis in the Swiss Alps.

Key methodologies: We made an effort to comprehensively investigate the implications of model complexity in our analysis. We randomly subsampled 300 sets of predictors from a substantial pool of climate, soil, and terrain variables. This gave us the possibility to study the effects of the number of variables considered and their multicollinearity, independent of the actual predictors used. We also compared different levels of parameterization complexity, restricting the algorithms to fit very coarse occurrence-environment relationships at one extreme and allowing them to closely follow the data and identify relationships with very complex shapes at the other. In addition, we varied factors that are often permuted in projection ensembles, i.e., SDM algorithms, emission scenarios, and climate models. All in all, we made almost a million future projections. Given that our observational and environmental data were of high quality (regular, rich sampling design, confirmed absences), our results provide a robust and reliable assessment of the implications of decisions on model complexity relative to aspects of SDM projection design.

Unexpected outcomes: I was surprised to see that, apart from the most common species, high multicollinearity did not notably decrease model performance, even when assessed under environmental block cross-validation. Yet, multicollinearity systematically increased range loss projections, indicating that this violation of model assumptions has a distortive effect on projections that may pass below the radar of common model evaluation.

Major result and contribution to the field: Parameterization complexity should be varied along with SDM algorithms in ensemble projections. The range of suitable options depends on the dataset at hand and may be identified by decent model performance. The number of predictors included should be balanced between providing sufficient information for well-performing models and avoiding too much noise, which deteriorates performance and introduces disagreement between projections. We found 10 predictors to be ideal, but the number may be smaller for less well-designed survey data or flatter environmental gradients. Multicollinearity should be constrained by maximum absolute Pearson correlation coefficients of 0.7, in order to avoid distorted projections.

What are the next steps? I see this work as a contribution to the call of Araújo et al. (2019), to develop standards for methods and data in SDM-based studies. Ultimately, the goal is to reliably predict the impacts of global change on biodiversity.

If you could study any organism on Earth, what would it be and why? Studying the ecology of individual plants at scale using remote sensing data is something I would love to do. Otherwise, I would be keen to know more about the fine-scale distribution and fruiting behaviour of the morel mushroom (Morchella esculenta).

ECR feature: Scale insects with Thomas D. Whitney

Thomas Whitney is currently a postdoc at Washington State University, Puyallup. He studies the ecology and evolution of insect species. His recent work in the Journal of Biogeography has sought to understand the extensive dieback in eastern white pines (Pinus strobus) and its association with a scale insect (Matsucoccus macrocicatrices). It has been unclear if this association is historical or recent, perhaps indicative of a recent host shift. Using population genetic approaches, Thomas sought to determine the likely context of this plant-insect association.

(left) Thomas meticulously removing scale insects from a branch in Wisconsin, USA. Not pictured very well are the hundreds of swarming mosquitos. (right) Thomas presenting his work.

Links: Personal webpage | Google Scholar | Research Gate

Institution: Washington State University – Puyallup

Current academic life stage: Postdoc

Research interests: I apply principles in ecology and evolution to better understand insect pests

Current study system: I currently study the little-known Douglas-fir twig weevil (Cylindrocopturus furnissi), a native beetle to the Pacific Northwest of North America. It has long been known to use Douglas-fir (Psuedotsuga menziesii) as a host, but only recently have we noticed it is developing within true firs (Abies spp.) as well. This has caused concern for the Christmas tree industry. This is a mystery, and the possibility of cryptic species, a host-shift, or something else entirely is what stimulates my curiosity about the system.

Recent paper in Journal of Biogeography: Whitney TD, Gandhi KJK, Lucardi RD. In press. Native or non-native? Historical biogeography of an emergent pest, Matsucoccus macrocicatrices. Journal of Biogeography. DOI: 10.1111/jbi.13702

Motivation for the paper: Eastern white pine (Pinus strobus) is an important and widespread tree across eastern North America. Since the early 2000s, the species has suffered from a novel phenomenon of branch dieback and mortality. Only recently was it discovered that an insect-pathogen complex is associated with the symptoms. The pathogen (Caliciopsis pinea) is assumed native, but there was no prior indication as to the past distribution of the insect, the eastern white pine bast scale. It was first described in Canada and was never known south of Massachusetts until 2006. Since then, reports of the insect in association with dieback symptoms have occurred frequently and as far south as Georgia and as far west as Wisconsin. Determining whether this insect has historically co-occurred with eastern white pine throughout the tree’s range was important to rule out or confirm the possibility of an invasive species. This information can help guide management strategies.

(A) Fruiting bodies of Caliciopsis pinea protruding from a bark canker. As part of an insect-pathogen complex, the feeding behaviors of eastern white pine bast scales are hypothesized to create ideal infection courts for this pathogen to penetrate the bark and establish in the cambium. These cankers are leading to white pine dieback symptoms. (B) A cluster of eastern white pine bast scales (Matsucoccus macrocicatrices) found on the bark surface feeding on the host tree’s vascular fluid. (C) Eastern white pine trees exhibiting dieback symptoms. Photo credit: Lori Chamberlain. (D) State, federal, and university researchers attend a field trip in the Southern Appalachian Mountains of Georgia, USA, as part of the first White Pine Health Workshop in February 2018.

Key methodologies: We conducted a population genetics study to assess the presence of structure across the range of the insect. We also looked for evidence of genetic bottlenecking, which would be consistent with a recent introduction from source populations to newly documented populations. We developed a panel of microsatellite markers using next generation sequencing to assess genetic diversity and structure. We also conducted landscape genetic analyses to determine if host tree connectivity (using data from Forest Inventory Analysis) could explain an apparent barrier to insect dispersal located in the Blue Ridge Mountains.

Unexpected challenges: These insects are tiny and very difficult to sample! As of now, there is no method to passively collect them. They must be hand sampled at the 2nd instar juvenile stage. This is the point in their development where they resemble a tiny black pearl – no eyes, no legs, only mouthparts perpetually inserted into the bark of the tree extracting sugars. These sentient sap-filled balloons are cryptically hidden in bark crevices and under lichen, and they require a delicate touch with forceps to pluck them from a branch or trunk. With such a big area of the continent to sample, training others was impractical. Instead, I did all the sampling myself, either travelling to sample in situ with a hand lens or receiving overnight shipments from my colleagues to sample under a microscope. It was tedious, but it was also a joy to explore these remote areas and collaborate with so many good folks.

Major result and contribution to the field: We found that the eastern white pine bast scale is indeed a native species to its newly documented areas. In fact, we found evidence to suggest it may have been associated with eastern white pine in refugial populations located in the Southern Appalachian Mountains during the Last Glacial Maximum. This rules out the possibility of the insect being a non-native invader exploiting naïve hosts. Why this insect has only now become associated with eastern white pine dieback and mortality remains a central question, but this work has successfully narrowed the possibilities.

What are the next steps? There are several steps to take with this system. One will be to investigate the mechanism that allows the insect’s feeding wounds to facilitate infection of the tree by fungal pathogens. Additionally, it will also benefit research efforts to develope a pheromone lure to accurately survey adult males, which will help us gain a better understanding of its density and range-wide distribution.

If you could study any organism on Earth, what would it be and why? I would study ice crawlers (Notoptera: Grylloblattodae), which are insect extremophiles! They live on alpine mountains, cannot tolerate temperatures over 10 °C, and are super rare. I think they’d be interesting to study for their unique biology, sure, but also because they seem to be an interesting system in terms of speciation and evolution. Oh, and how cool would that field work be?

Any other little gems you would like to share? I used to study wolf spiders that inhabit forest leaf litter. If you are unfamiliar, wolf spiders have an iridescent layer behind their retinas. At night, you can easily locate them with a headlamp – their eyes give off a subtle shimmer. It’s a fun thing to try. Whether in a forest, a grassland, or a desert, you’ll be surprised with how many wolf spiders are around.

Biogeography in the Age of Big Data

Journal of Biogeography, 47:1 Special Issue

https://onlinelibrary.wiley.com/toc/13652699/2020/47/1
ALL SPECIAL ISSUE ARTICLES ARE FREE ACCESS for 2020 & 2021

Between 10-13th April, 2018, the annual meeting of the Specialist Group for Macroecology of the Ecological Society of Germany, Austria and Switzerland convened in Zurich, Switzerland around the topic of “Macroecology in the age of big data”. The outcomes of that meeting are now featured in the January 2020 issue of the Journal of Biogeography.  All articles in the special section are free to download from the journal website until the end of 2021.

The “Specialist Group on Macroecology of the Ecological Society of Germany, Austria, and Switzerland” is one of the leading scientific platforms for macroecological topics in central Europe. The primary goal of the annual meeting was to support the development of macroecological research in central Europe and beyond. The special issue papers are a reflection of the macroecological community’s excitement, hopes, and concerns about the emerging power of ‘big data’ to reshape ecological research.

Fifteen papers provide a variety of perspectives on, and examples of, modern macroecological research using big data.  According to the overview article by Wüest et al. (2019), several main patterns fall out.  Notably, major new sources of macroecological data have become available in recent years, reducing three major gaps: across spatial scales (the “scale shortfall”), in the biomes covered (the “Wallacean shortfall”) and in the number of taxa covered (the “Linnean shorfall”).  Particularly, advances in airborne and satellite imagery have rapidly increased the volume and variety of data linking multiple spatial scales, increasingly using synchronous or near-synchronous measurements.  Advances in bulk collections and databases are making more clear the locations of discrepancies between predicted and measured biodiversity, which can guide both new collections and assessment of error.  As additional approaches such as eDNA and advances in drone technology accelerate in the coming years, and new satellite programs such as NASA’s Surface Biology and Geology come online, we can expect to see continued rapid growth in data, knowledge, and understanding.

Landmarks in the growth of big data in macroecology and how it has shaped a variety of disciplines, including biology, biogeography and ecology. From Wüest et al. (2019).

Nonetheless, further progress must be made to standardize data collection, data integration, method development and process integration. Particularly, as more data becomes more accessible, and analyses of large datasets become easier, it will become ever more important to be vigilant about the basics of raw data quality, reproducibility of data compilation and analytical methods, and the communication of uncertainties.

The Journal of Biogeography has, for some time now, been listening to the community on these issues and has recognized their emerging importance.  In 2019, we completed implementing our commitment to replicability of studies we publish.  As a condition for publication, Journal of Biogeography requires that data supporting the results in the paper be archived in an appropriate permanent public repository and strongly encourages that the scripts and other artefacts used to generate the analyses presented in the paper should similarly be permanently publicly archived. We hope this will go some way to supporting the community’s efforts to build better biogeographic and macroecological understanding during this period of rapid global change.

We are, thus, delighted to bring this survey of the state of the discipline to you in the pages of the Journal of Biogeography. Particularly we thank the team of editors (Holger Kreft, Wilfried Thuiller, Damaris Zurell), reviewers, and the many authors who provided such a cogent summary and many thought-provoking examples of what is and can be possible.  All articles in the special issue are free access for two years. We hope you enjoy reading them!

References

Wüest, RO, Zimmermann, NE, Zurell, D, et al. 2020. Macroecology in the age of Big Data – Where to go from here? J Biogeogr. 47: 1– 12. https://doi.org/10.1111/jbi.13633

ECR feature: Bird migration behavior with Paul Dufour

Paul Dufour spotting and counting large groups of shorebirds that overwinter and migrate through the bay of Dakhla in the Western Sahara (photo credit: Boris Delahaie).

Links: Research Gate | Flickr

Institution: Laboratoire d’Ecologie Alpine – Grenoble, France

Current academic life stage: PhD

Research interests: Understanding the evolution of migration behavior in birds and its ecological and evolutionary consequences.

Current study system: I am interested in the whole avian class, but I am also studying more specifically the order Charadriiformes, which shows quite exceptional and diverse migration strategies. Also, I have recently started studying populations of Richard’s Pipit in Europe, a species of Asian passerine that normally overwinters in Southeast Asia, which we suspect uses a new migration route towards Western Europe.

Recent paper in Journal of Biogeography: Dufour P, Descamps S, Chantepie S, Renaud J, Guéguen M, Schiffers K, Thuiller W, Lavergne S. 2020. Reconstructing the geographic and climatic origins of long‐distance bird migrations. Journal of Biogeography 47: 155– 166. DOI: 10.1111/jbi.13700. FREE ACCESS for 2020 & 2021

Motivation for the paper: There are still many unanswered questions around biogeographic scenarios that could explain the emergence and evolution of seasonal migration—in particular large geographic migration—in birds. As previous studies on smaller families or clades have shown rather diverse results, we wanted to test whether general evolutionary patterns could be described for large clades of migratory birds. At the same time, we wanted to examine how these evolutionary patterns could be related to the tracking of climatic niches during different seasons.

(A) A group of Brent Geese (Branta bernicla hrota) just returning from their wintering grounds, photographed in Longyearbyen (Svalbard, Norway) when Paul was working on seabird colonies. (B) A Woodchat Shrike (Lanius senator), probably on its way to its breeding grounds, looking for insects on a garbage mound in the middle of the Western Sahara.

Key methodologies: Since our aim was to understand the biogeographic and climatic context for the evolutionary emergence of seasonal migration at global scale, we first manually coded the migration strategies for all current species of birds. While many distribution maps reflect the migration strategy (i.e. strict migratory species), this is not the case for resident or partially migratory species, for which it is necessary to look precisely at the available information in reference handbooks. Similarly, compared to what has been done in the past, we wanted to address the issue of niche tracking between season, in particular through a measurement of climatic overlap, on all extant bird species to study global patterns of these metrics. We also wanted to place this question in an evolutionary context by using phylogenetic regressions.

Unexpected challenges: Describing the niche of a species often requires consideration of the climatic and environmental variables to be taken into account. In the case of our study, we had to make a choice between being able to consider the avian class as a whole and using more variables to define the niche of the species. Since a significant proportion of species overwinter over marine areas, we chose the first option but had to rely on temperature alone to define climatic niches, finding no other variables related to our biological assumptions and available over land and ocean. We believe that addressing this issue by comparing all these different migration strategies at global scale is an interesting approach and that this simplification is acceptable as temperature has been shown to be a good proxy in the distribution of bird species.

Major result and contribution to the field: We found that migratory species, and even more so long-distance migratory species, generally experience a warmer climate on their wintering grounds than on their breeding grounds, although there are notable exceptions. We also confirmed that seasonal migration is a labile trait that has appeared and disappeared at different periods in the history of several avian lineages. As a consequence, we have not reported dominant biogeographic scenarios (i.e., both temperate and tropical ancestors) that could have explained the evolution of migratory behaviour in the major migratory orders. Interestingly, we found an ancestral migratory behaviour deeply rooted in the history of the great radiation of the Passeriformes that could coincide with the great expansion of this clade.

What are the next steps? This last result calls for further analysis of the potential role of migration behaviour in diversification processes. The richness of large groups of migratory birds suggests that migration might be a driver of speciation. Similarly, different migratory species show different strategies or year-round niche tracking: the fact that both short- and long-distance migrants showed lower thermal overlap values than variable‐distance migrants opens up interesting approaches to study the evolution of migration. A first idea might be to test whether migratory birds do not migrate ‘too’ far compare to their optimal climatic niche and to link this result with the progressive shift of breeding and wintering areas.

If you could study any organism on Earth, what would it be and why? There are hundreds of birds that I would like to study (seeing them would be very enjoyable in itself) because their migration strategies are so extraordinary and open the door to a multitude of questions. However, at the moment I am happy to be able to study Richard’s Pipit, an Asian passerine species whose appearance in Europe remains enigmatic. If our hypotheses are correct, we may have the chance to observe really drastic changes in migration routes in a very short period of time.