Ida M. Mienna is a PhD student at Norwegian University of Science and Technology, having recently completed her master’s degree at Norwegian University of Science and Technology. Her current work focuses on understanding the spatial ecology of the forest-tundra ecotone in Fennoscandia, especially through investigating drivers of change and establishing a high resolution monitoring system using drone imagery and airborne laser scanning. Ida discusses her recent work on the flora of Norway, which explores evolutionary signals in plant distributions using DNA from herbarium specimens.
Although Ida’s study did not require any data collection in the field, she went on many trips to understand the ecology and spatial distribution of vascular plants in Norway. Here Ida is posing with the orchid Nigritella nigra, a priority species in Norway, at its northernmost known locality in the world.
Institution: Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences (NMBU); Department of Natural History, NTNU University museum, Norwegian University of Science and Technology (NTNU)
Current academic life stage: PhD
Research interests: In general, I am really interested in anything that has to do with spatial ecology. I guess that is why I find research within community ecology and plant biodiversity distributions exciting, as these have clear spatial patterns in them. For my master’s in biology I was introduced to the spatial phylogenetics approach that I used in this study, which combines spatial ecology and evolutionary history. For my PhD, I am currently going into depth on how one can use remote sensing techniques to study changes in spatial distributions of communities. So, to summarise, I am interested in research that involves field, lab or computer work – it does not matter, as long as it has a spatial component to it!
Current study system: I am working with the forest-tundra ecotone, also known as the treeline. In general, the treeline is expected to increase in elevation with rising temperatures, but the extent to which this happens and what other factors may affect its dynamics are still not well understood. Thus, I am looking into drivers like herbivory density in addition to temperature. Establishing a high-resolution monitoring system also is important as the treeline is not changing rapidly; for this I am exploring the use of remote sensing, i.e. drone imagery and airborne laser scanning.
Recent paper in Journal of Biogeography: Mienna, I.M., Speed, J.D.M., Bendiksby, M., Thornhill, A.H., Mishler, B.D., Martin, M.D. 2020. Differential patterns of floristic phylogenetic diversity across a postglacial landscape. Journal of Biogeography 47: 915-926. https://doi.org/10.1111/jbi.13789
Motivation for the paper: Exploring spatial distributions of biodiversity is important so that we know where we should focus our conservation efforts, but often we focus on areas where we have the most species. Research also often focuses on areas already known to be species rich and that have long evolutionary histories. In this study we wanted to explore the flora of Norway, which consists of plants that had to immigrate to the area after the Fennoscandian Ice sheet retreated 22-9.7 thousand years ago. We wanted to discover if there were any evolutionary signals in the plants’ distributions and if we found patterns that you normally would not find by looking at species diversity alone (i.e. potential places with concentrations of relatively young or old species).
Key methodologies: To study evolutionary patterns, we needed to make a phylogeny of the native Norwegian flora, which is—as far as we know—the first time this has been done. Most of the DNA sequences were downloaded from various sequence databases, but not all species had available data. Instead of sampling our own data from the field, we collected DNA samples from herbarium specimens, which was really nice as I worked at a museum with all the resources needed around me. Information about plant distributions were downloaded from GBIF, so for these data we did not need to go into the field either. The phylogeny and the distribution data were then combined to study the evolutionary patterns. We also modelled different diversity patterns to see if predictors like temperature, precipitation and time since the area was covered by ice affected the spatial patterns.
(left) The vascular plant Pedicularis hirsuta, which in Norway can only be found in the northern mountains. This species is regarded as near-threatened and is expected to decline in numbers with increasing temperatures. (right) To estimate the phylogenetic diversity of vascular plants across Norway, a phylogeny based on DNA sequences was made. Many of the sequences came from DNA samples sampled from herbarium specimens, like this one.
Unexpected challenges: Working with DNA from herbarium specimens is not as easy as working with fresh samples, and there were some struggles in the lab getting the PCR to work. However, having helpful and experienced supervisors is always good and we managed to get (almost) all three gene sequences for all species. Working with big data is also not that straightforward as many of the data have errors (e.g. a downloaded DNA sequence was actually from another species or the species occurrence was inaccurate) and finding ways to remove as many of the errors as possible while not removing valid data can be difficult. However, we believe that the methods we used to avoid these errors worked quite well in the end.
Major result and contribution to the field: We found spatial patterns that had not been seen in Norway, but also patterns that were concordant with previous studies. The cold and dry mountainous areas had significantly lower phylogenetic diversity than the rest of the country, suggesting that the species there were relatively closely related to each other. The warmer and wetter coastal areas had significantly higher phylogenetic diversity, suggesting phylogenetic overdispersion possibly due to competitive exclusion. We also found that in the northern parts, many areas have quite young plants (i.e. recently evolved). As this pattern also was mainly found in dry and cold climates, we suggest that recent speciation due to stressful environments may be the factor behind these patterns. All these results show an evolutionary signal in the distribution of the vascular flora of Norway.
What are the next steps? Currently, we are expanding the study area to include Sweden and Finland in addition to Norway, representing the native flora of the Fennoscandian Peninsula. This area, like Norway, was covered by the Fennoscandian Ice Sheet, meaning that all plants in the area came after the ice melted. We will do the same analyses as in our previous paper, but also see if the distributions have changed in the last 100 years and if their future distributions will be affected by climate change. In addition, we are interested in seeing if the protected areas actually contain most of the phylogenetic and species diversity.
If you could study any organism on Earth, what would it be and why?
I have never really studied one organism alone, but rather communities. Funnily enough, considering that I chose to study terrestrial plants, I have always found colourful marine organisms like nudibranchs and polychaetes fascinating. Unfortunately, I have a little bit of thalassophobia, so I will stay on land studying colourful plants for now.
Any other little gems you would like to share? During my master’s in biology when I started working on this paper, I did not, as mentioned above, do any field work related to my research. However, I had a motivation to learn more about my study organisms, which led me to go hiking in the forests and mountains to learn the names of the plants and their ecology. I think this is when I realised that I needed to do a PhD, as just doing one simple task was not enough and I needed to explore further to understand what I did not understand.
Norway only has about 1250 native vascular plant species, but the country stretches widely both in latitude (50-71° N) and longitude (4-32° E) and has a large topographic variation (0-2469 m a.s.l.), making it a very interesting study area. This picture shows a south-facing slope with high, relatively vascular plant diversity.