Juan David is a postdoc at the Museo Nacional de Ciencias Naturales in Spain. He is an ecologist interested in explaining how historical events shape current biodiversity patterns. Here, JD shares his recent research on how past and current processes impact beta diversity in Neotropical streams.
Juan David González-Trujillo is a postdoc researcher at the National Museum of Natural Sciences (Madrid, Spain).
Institute. Museo Nacional de Ciencias Naturales (Madrid, España)
Academic life stage. Postdoctoral researcher
Major research themes. My research interests are in the intersection between community ecology and historical biogeography. I am particularly interested in understanding how historical events have shaped current biodiversity patterns and how they allow us to forecast future changes.
Current study system. I did my master’s and Ph.D. studies on freshwater biodiversity, focusing majorly on disentangling the community assembly process. However, I partially left that field after finishing my doctoral dissertation. The reason? As you may read in our JBI paper, we cannot understand present-day biodiversity without understanding each region’s historical background, ecosystem, or study system. So, I wanted to dig deeper into “the past of the present-day patterns“. That desire comes true as a postdoc researcher since I am currently exploring how climate shaped mammal’s food web structure during the Pleistocene. To do so, I train machine learning algorithms to retrodict paleo-communities’ trophic structures and then check the predictions against the fossil record.
Recent paper in JBI. González‐Trujillo, JD, Saito, VS, Petsch, DK, Muñoz, I, Sabater, S. Historical legacies and contemporary processes shape beta diversity in Neotropical montane streams. J. Biogeogr. 2021; 48:101–117. https://onlinelibrary.wiley.com/doi/10.1111/jbi.13986
Motivation behind this paper. Previous studies have revealed that species turnover may be partially or entirely shaped by historical drivers linked to past climatic (e.g., temperature oscillation) and geological (e.g., mountain uplift) events. However, the study of such interplay between ecological and evolutionary processes is biased towards terrestrial communities. In riverine ecosystems, for instance, research has focused on determining the effect of contemporary drivers, such as the network’s dendritic structure or the flow regime. Therefore, we wanted to fill such a gap by testing if past events have contributed to shaping present-day biodiversity in montane rivers. We chose montane rivers as they host high biodiversity and provide essential benefits to human societies, yet still are inadequately studied.
Key methodologies. Modeling the effect of historical legacies among contemporary drivers is quite challenging. Our paper used a path-length matrix, which recreated the basin’s evolutionary history during the Tertiary and Quaternary. To create such a matrix, we should recover information on the geologic and climatic events occurring during the Tertiary and Quaternary that contributed to shaping the current pools of species observed in the basin. We used the occurrence of such events (e.g., uplifts and glaciation events along the Andean chains) to sort study rivers based on their time of appearance and to model their historical relationships (figure below). The path-length matrix was included among other contemporary factors, as descriptors of insect and diatom species turnover among rivers. Additionally, to have a more comprehensive picture of the interplay between historical and contemporary forces, we assessed species turnover by quantifying different facets of beta diversity, such as taxonomic, functional, and phylogenetic. These facets are rather complementary. For example, while the functional facet provides insight into contemporary processes’ effect, the phylogenetic facet can reveal the signature of those processes at the evolutionary scale.
Cladogram representing the path length matrix modeling the evolutionary history of ecoregions in the Orinoco basin (right). On the left, a graphical illustration of the hypothetical reconstruction of the Orinoco basin.
Unexpected challenges. One of the major challenges was to describe the biological traits of insect species. In the Neotropics, such information is scarce and spare. Thus, we had to go through tons of published and unpublished literature, as well as observe the individuals in the field. The latter being the funniest activity, as I spent a lot of time under the water watching invertebrates using my beach googles! A more conceptual challenge was to choose between Balsega’s and Podani’s partitioning frameworks, as the pros and cons of both frameworks have been promoted and criticized in recent years. After going deeper into their computation, we decided to include both since they can be complementary to study the functional turnover causes and consequences. Our results showed that exploring both frameworks was the right choice. While the Baselga’s framework indicated that functional spaces are similar among the Orinoco basin, the Podani’s framework indicated that functional distances are closer between taxa belonging to rivers with similar evolutionary history. Such difference suggests that even if two communities share functional spaces, their functional dissimilarity may depend on which clades belong to each community. The implications of this phylogenetic constraint on functional diversity are worth further study in the future.
Major results. Our paper provides evidence supporting that past historical events have contributed to shaping the present-day diversity and distribution of benthic communities. Specifically, historical events seemed essential in separating lineages (and taxa) in different regions regardless of the long time available for dispersal (thousands or millions of years). Therefore, we stressed that knowing the historical background of a region is essential to better understand the mechanisms supporting (meta)community-level patterns. In the Neotropics, at least, the historical background of the tropical basins seems to be required to explain beta-diversity patterns, even when contrasting disparate communities such as diatoms and insects.
A ‘taster’ of rivers from the Orinoco basin. From left to right: Páramo, high-Andean, Alluvial fans.
Next steps for this research. The Andes are one of the greatest cradles of biodiversity in the world. A significant part of that biodiversity is due to historical events (e.g., historical isolation). Therefore, the next logical step is to expand our study area and explore the extent to which our results are generalizable along the Andean mountain chain. Besides, other tools may complement the assessment of species turnover. Including genetic information and phylogeographic methods, for instance, would be useful to disentangle historical legacies from contemporary processes. In this regard, I am currently exploring the phylogeographic patterns of several invertebrate species in a micro basin that crosses two ecoregions with distinct climatic histories.
If you could study any organism on Earth, what would it be? I want to study the ecology, genetics, and biogeography of non-biting midges (Chironomidae). Chironomidae is a widespread and mega-diverse family inhabiting all freshwater ecosystems. Biogeographers, such as Lars Brundin, have used non-biting midges to uncover dispersal paleo routes. Paleoecologists, such as Ian Walker, have used chironomid heads to reconstruct paleoclimates. Ecologists, such as August Thienneman, have found in Chironomidae a great bioindicator species for environmental pollution. Therefore, it seems to be a perfect group for performing studies in the intersection between community ecology and historical biogeography.
Anything else to add? During fieldwork, I met different people who are extraordinarily committed to nature conservation. It was amazing to talk with them, as they know a lot about nature and biodiversity. I was so surprised – and inspired – to find that they had a unique classification system of rivers and biodiversity. Some were empiric naturalists; they know where to find every fish species, its feeding behavior, preferred microhabitat, and even the mating period. Sadly, some of them are not with us anymore. The avarice for natural and mineral resources is threatening environmental leaders in Colombia. With their loss, cultural and historical legacies are also at risk.