Mekala Sundaram is a postdoc at the University of Georgia in the USA. She is an ecologist interested in unveiling macroecological patterns. Here, Mekala shares her recent work on the influence of current and past climate on the global biodiversity of conifers.

Mekala Sundaram is an ecologist working on the global diversity of conifers.

Personal links. Research Gate

Institute. Center for Ecology of Infectious Diseases, University of Georgia

Academic life stage. Postdoc

Major research themes. Species occurrence, Community assembly and Macroecology

Current study system. My recent research focuses on understanding how conifers are distributed across the globe, where biodiversity hotspots occur, and where they may be expected to occur in the future under different climate change scenarios. Conifers are an interesting study system because there are over 600 species globally that occur in a wide variety of biomes, from tropical forests to boreal biomes. Conifers are also an ancient taxonomic group, first appearing in the fossil record in the Carboniferous period (~300 million years ago).

Recent JBI paper. Sundaram, M., & Leslie, A. B. (2021). The influence of climate and palaeoclimate on distributions of global conifer clades depends on geographical range size. Journal of Biogeography, 48(9): 2286-2297 https://doi.org/10.1111/jbi.14152

Motivation behind this paper. In this paper, we explore the reasons underlying conifers’ distributions. As conifers are an old lineage, current distributions of conifers may be related to current climate patterns or could result from past climatic responses. Regions with stable past climates are hypothesized to be refugia for conifer biodiversity. Therefore, we tested if restricted conifers occur in areas with stable past climates when compared to widespread conifers.

Thuja occidentalis is a widespread conifer found in North America (Photo credit: Dr. Andrew Leslie).

Key methodologies. We gathered geographic ranges of conifers from previous works, modern climate information, and GIS layers of past climates reconstructions for the last 2 million years. We used a novel modelling framework of zeta diversity to disentangle which climate variables explain distributions of restricted conifers versus distributions of widespread conifers. We also employ ensemble species distribution modelling methods to further explore how climate drivers explain distributions of widespread and range-restricted conifers. Both modelling methods provide robust and consistent conclusions.

Unexpected challenges. We faced some computational challenges while analyzing the global distributions of 606 conifer species! Quantitatively combining distributions of 606 species with climate layers in an ensemble modelling framework required lots of computational memory. Also, gathering past climate records from the last 2 million years was difficult, as reconstructing past climates for the entire globe is a challenging endeavour by its nature. To solve the computational problems, we were able to break down modelling into smaller pieces to be completed separately. For past climate information, we were able to gather suitable datasets after an extensive search for paleoclimate records.

Agathis australis is a restricted conifer found in New Zealand, but this specimen was photographed in the Christchurch Botanic Gardens (Photo credit: Dr. Andrew Leslie).

Major results. Our paper advances the field as we directly test how climate patterns from the last 2 million years influence the distributions of a major plant group nowadays. We conclude that geographically restricted conifers are best predicted by past climate patterns, meaning that fluctuations in climate over the last 2 million years have led to some species being restricted in refugial areas or places that have experienced relatively stable climates. Meanwhile, the more widespread conifers are best predicted by modern climates, with several large range species occupying regions with inhospitable climates. Conifer biodiversity hotspots occur in refugial areas where range-restricted species tend to occur, therefore, historical climate patterns may play a role in the formation of these biodiversity hotspots. Our unique methodological approaches have allowed us to disentangle how past climates influence distributions of conifers of different geographic range sizes. These findings and methods have allowed us to test long-standing theories on how plants are distributed and how biodiversity hotspots are formed.

Next steps for this research. The next step is to ask whether species restricted to stable refugial areas are likely to survive in the future. Under a warming climate, species currently restricted to climatically stable biodiversity hotspot regions may be threatened in the future. Therefore, field and modelling studies are needed to test whether taxa can survive under future climate conditions.

Callitris pancheri is a restricted conifer endemic to New Caledonia (Photo credit: Dr. Andrew Leslie).

If you could study any organism on Earth, what would it be? I would like to study a rare species that very little is known about or a non-charismatic species that gets little attention, e.g., aardvark or the rare Wollemia nobilis conifer.

Anything else to add? I have recently switched from studying conifers to studying infectious disease outbreaks to shed light on how humans’ interaction with biodiversity might lead to infectious disease outbreaks. With the ongoing pandemic, there has been great interest in studying how biodiversity should be conserved and understanding how to maintain a healthy environment that minimizes the risk of disease transmission. I am now using methods similar to those described in the conifer paper to examine how biodiversity relates to infectious disease outbreaks.

Isabel Haro-Bilbao and Josh Thia met while completing their PhD’s at the University of Queensland, Australia. Both had interests in the ecology of marine organisms, which led them to collaborate on a project investigating genetic differentiation in the wahoo, a large, highly dispersive pelagic fish. Isabel and Josh share how they used population genomic approaches to characterise previously unidentified stocks in this important species of recreational, subsistent and commercial fisheries.

(left) Isabel in Santa Barbera while attending a tuna conference and catching up with coauthor, John Baldwin, to get wahoo samples. (right) Josh out surveying experimental plots in rural Australia for agricultural pests (sporting his signature field work bucket hat).

Personal links. [Josh]: Twitter | Webpage | Google Scholar | ResearchGate

Institute. [Isabel]: The University of Queensland. [Josh]: The University of Melbourne.

Career life stage. [Isabel]: Masters of Economics. [Josh]: Postdoc.

Major research themes.

[Isabel]: I am currently completing a master’s degree in economics, and my interest focuses on multidisciplinary small-scale fisheries management that combines ecology and economics. I aim to find tailored solutions for sustainable fisheries that balance the environmental, social, and economic impacts.

[Josh]: My current main research focus is on arthropod pests of Australian agriculture, specifically with respect to the molecular mechanisms and evolution of pesticide resistance. However, I am interested in all sorts of organisms and systems, including the wonders of the wet and watery ocean!

Recent paper in JBI. Haro‐Bilbao, Isabel, Riginos, Cynthia, Baldwin, John D., Zischke, Mitchell, Tibbetts, Ian R., Thia, Joshua A. (2021). Global connections with some genomic differentiation occur between Indo‐Pacific and Atlantic Ocean wahoo, a large circumtropical pelagic fish. Journal of Biogeography 

DOI: https://doi.org/10.1111/jbi.14135

Wiley Content Link: https://onlinelibrary.wiley.com/share/author/KQBXQ77KD7EUBYPEUPEM?target=10.1111/jbi.14135

Motivation behind this paper. This paper was birthed as a collaboration during our respective PhDs at the University of Queensland. We wanted to test the long-standing assumption that wahoo, Acanthocybium solandri, exist as a single, globally homogeneous population. Wahoo are an important fish in subsistent and recreational fisheries, are increasing in their commercial value, and there is a need to understand their stock structure for fisheries management. Like many large, pelagic fish, wahoo have extraordinary dispersal capacity and large population sizes. These factors have likely limited the ability of prior works to identify putative stocks, which have inferred genetic differentiation from a small number of genetic markers. We wanted to exploit population genomic techniques to increase our power to detect subtle genetic differentiation in a globally distributed sample of wahoo populations.

(left) A fisherman processing wahoo at a local market, Santa Cruz Island, Galapagos… he isn’t the only one with an interest in wahoo! (Photo credit: Jonathan Erazo) (right) Isabel taking notes at the fish market. (Photo credit: Jonathan Erazo)

Key methods. Our sampled wahoo populations spanned the Indo-Pacific and Atlantic Oceans. We tested for genetic differentiation between the Indo-Pacific and Atlantic, a well-known biogeographic break, and tested whether patterns of genetic differentiation were due to ongoing gene flow, low drift due to large population sizes, or a combination of both. We characterised genetic variation using single nucleotide polymorphisms (SNPs) obtained through a pooled reduced-representation (ezRAD) method. These SNPs were used to estimate genetic differentiation of populations across oceanic regions. We also used demographic analyses to test three population genetic scenarios: isolation with no gene flow, symmetric gene flow, and asymmetric gene flow. These scenarios were tested both within and between ocean basins to understand the spatial scales of gene flow.

Challenges overcame. One of the obvious financial and logistic challenges of a global study is obtaining samples representing as many sites as possible across the species distribution. Whilst Isabel had the opportunity to collect samples, we also pulled in samples from collaborations with Jonh Baldwin and Mitchell Zischke. Both had researched wahoo and had well-preserved, documented samples from across the globe, which were essential in our tests of inter-oceanic differentiation.

Fishing boats in Santa Cruz Island, Galapagos, adorned with pelicans. (Photo credit: Jonathan Erazo)

Major results. Our paper is the first to use genome-wide SNPs to examine genetic differentiation across the global distribution of wahoo. With the power of thousands of genomic markers, we debunked the previous hypothesis that wahoo is a single homogeneous population. We found that two discrete genetic stocks exist, one in the Indo-Pacific and one in the Atlantic. This regional structuring shows similarity to the yellowfin tuna, suggesting that similar forces may influence large, pelagic fish species. The genetic differentiation between ocean regions was subtle, and our demographic analyses indicated that this differentiation occurs against a background of high gene flow throughout the evolution history of wahoo. We did not find any clear support for asymmetric gene flow, as might be expected from other marine taxa that exhibit greater movement from the Indo-Pacific into the Atlantic. However, high dispersal and subtleties in genetic differentiation probably reduced our ability to identify asymmetries in gene flow.

Next steps. There are two major extensions of this work. Firstly, although we had great representation of the Atlantic and Indo-Pacific, we did not have any populations from the Mediterranean. The Mediterranean Sea has a unique environment, and it would be intriguing to know whether the classic Atlantic–Mediterranean break also exists in wahoo. Secondly, our study utilised a pooled sequencing approach to maximise the number of individuals and populations we could sample. But pooled sequencing precluded individual-based analyses that could provide insights into processes of dispersal and selection that might shape patterns of genetic differentiation among populations. Future works using individual genotypes would provide more power to unravel the demographic and evoltuionary processes opertating in this species.

If you could study any organism on Earth, what would it be?

[Isabel]: My main interest is in fisheries, and I can think of many fascinating marine animals. However, the most intriguing organisms are still humans. Specifically, I would like to study the mechanisms behind our decision-making process around natural resources exploitation and consumption. Our behaviour has such a significant impact on shaping life on Earth that unveiling those patterns could substantially affect how we address environmental challenges.

[Josh]: There are so many species that spring to mind! But I would love to study pikas, genus Ochotona. I fell in love with these cute little lagomorphs when I saw them featured on a David Attenborough documentary. They live in beautiful alpine talus and meadow habitats and are incredibly industrious; they make hay to survive through the winter!… adorable.

Ruan van Mazijk is a Masters student at the University of Cape Town. He is broadly interested in the ecology and evolution of plants. Ruan shares his recent work on how environmental heterogeneity influences species-area relationships in floral species from the Greater Cape Floristic Region and the Southwest Australia Floristic Region.

Ruan watching the sunset over the foothills of the Cape Fold Belt Mountains (namely in Bainskloof Pass), home to the Cape Floristic Region’s rich montane flora. Photo credit: Hannah Simon.

Personal links. Twitter | ResearchGate | Google Scholar | GitHub

Institute. University of Cape Town (Department of Biological Sciences)

Academic life stage. Masters

Major research themes. (Plant) phylogenetic systematics, macroecology, biogeography and trait ecology

Current study system. I currently work in the Cape Floristic Region (CFR) on the evolution and ecology of its plentiful plant species. My BSc Honours work formed the basis for my recent paper in JBI. My Masters dissertation explores how plant physiology and ecology vary with species’ genome-size in two species-rich clades of sedges, Schoenus and Tetraria. Both these genera have their centres of diversity in the CFR. Schoenus exhibits a broad range of fairly large, polyploid genomes. Tetraria, however, is much less variable, with most species having much smaller genomes than Schoenus. We know that genome-size affects organismal biology in a variety of ways. Most strikingly, plant stomatal dimensions are positively related to the amount of genetic material in cell nucleii. My work aims to demonstrate how other physiological functions of plants related to water- and gas-exchange (via stomata) might be affected by polyploidy-driven variation in genome-size!

Recent paper in JBI. Van Mazijk, R., Cramer, M.D. & Verboom, G.A. (2021). Environmental heterogeneity explains contrasting plant species richness between the South African Cape and southwestern Australia. Journal of Biogeography. DOI: 10.1111/jbi.14118. Wiley Content Link: https://onlinelibrary.wiley.com/share/author/Y2XIBHJBZPVMBXIIUWPA?target=10.1111/jbi.14118.

Motivation behind this paper. Our recent paper was based on my BSc Honours project, albeit very loosely, as the analyses are completely different in this paper. The topic my supervisors and I grappled with was the puzzling similarity in species richness of the Greater Cape Floristic Region (GCFR) and the Southwest Australia Floristic Region (SWAFR), two Mediterranean-type biodiversity hotspots with very different environmental conditions. Despite their climatic similarity the GCFR is rugged and mountainous while the SWAFR is flat, with only gentle hills. We know that complex and heterogeneous environments can support more species through greater niche diversity, and can facilitate speciation through adaptive radiations. Thus, the question follows: how can two plant biodiversity hotspots be so different in topography? What other forms of heterogeneity might be relevant (e.g., soil, rainfall)?

The differences in topography between the GCFR (left, mountainous) and SWAFR (right, flat as a pancake) are really striking! Pictured: Table Mountain National Park, South Africa (left) and Fitzgerald River National Park, Western Australia (CC BY-SA 3.0 Yewenyi).

The plants of the GCFR (left) and SWAFR (right) have many of the same ecological adaptations and growth forms, nevermind the taxonomic affinities of both these regions’ floras. Pictured are four Proteaceae species (clockwise from top left): Leucospermum reflexum var. luteum, Anigozanthos manglesii (Red and green kangaroo paw) (CC BY 2.0 A. Chapman 2008), Banksia ahsbyi (CC BY 2.5 Gnangarra 2011) and Leucospermum cordifolium (CC BY-SA 3.0 Marco Schmidt 2008).

Methodologies. Using publicly accessible environmental and species occurrence data for both the GCFR and SWAFR, we compiled datasets of environmental heterogeneity that we could correlate to species richness. Not only did we explore the effects of heterogeneity in various environmental variables (e.g., elevation, rainfall, soil properties), but also a composite measure of environmental heterogeneity by summarising individual measures in a principal component analysis (PCA).

Challenges. This paper went through so many different drafts and different versions of the analyses that I’ve almost lost count. However, changes in approach to answering one’s original question can only delay things so much. Rather, these changes acted in concert with a combination of circumstances, external disruptions and the blows these dealt to my mental health. Circumstances included: carrying on with this while doing my MSc, the unfortunate inconvenience of loadshedding in South Africa, the advent of the coronavirus pandemic, and (chronic-, pandemic- and non-pandemic-related) illness in my family. I don’t want to make excuses, but this was a lot! On the upside, these challenges taught me a lot about myself and how to navigate some very difficult times.

Challenges. This paper went through so many different drafts and different versions of the analyses that I’ve almost lost count. However, changes in approach to answering one’s original question can only delay things so much. Rather, these changes acted in concert with a combination of circumstances, external disruptions and the blows these dealt to my mental health. Circumstances included: carrying on with this while doing my MSc, the unfortunate inconvenience of loadshedding in South Africa, the advent of the coronavirus pandemic, and (chronic-, pandemic- and non-pandemic-related) illness in my family. I don’t want to make excuses, but this was a lot! On the upside, these challenges taught me a lot about myself and how to navigate some very difficult times.

A selection of study species for my MSc (clockwise from top left): Schoenus compar, Schoenus albovaginatus, Tetraria ustulata, Tetraria thermalis. The tribe Schoeneae (Cyperaceae) is super morphologically variable, with T. thermalis reaching up to 2m (ca. 6ft 7in) tall and little S. albovaginatus getting down to 20cm (ca. 8in). These plants might be plain-looking at first, but their intricate inflorescence morphology and impressive contribution to a given fynbos landscape’s biomass make them hard to ignore!

Major results. We found evidence for a common positive relationship between floristic richness and environmental heterogeneity across the GCFR and the SWAFR, although the GCFR was more environmentally heterogeneous and species-rich. There are, of course, some region-specific effects. And those are also slightly dependent on spatial scale, although almost always positive effects across scales. We can conclude that the greater richness per unit area of the GCFR compared to the SWAFR is explainable in terms of the GCFR’s greater environmental heterogeneity. This helps support the idea that environmental heterogeneity is important in driving plant biodiversity. However, more work is required to understand how the effects of environmental heterogeneity change at different spatial scales, and it would be great to replicate this study in other geographic regions.

Next steps. Quite intuitively, the next step would be to apply a similar analysis across all five Mediterranean-type ecosystems (the GCFR, SWAFR, Mediterranean Basin, California and central Chile), to see whether the richness-heterogeneity relationship is applicable to them all, and to determine what forms of environmental heterogeneity vary between these floristic regions.

Additionally, in the context of the broader question, “How important is environmental heterogeneity (and which kinds) across Mediterranean-type ecosystems?”, it makes sense to expand the analysis to include absolute environmental variables. This will allow us to account for the importance of heterogeneity-type variables relative to absolute environmental variables. Though, this starts to get more complicated, and changes what the models are asking from, “Does heterogeneity matter in X regions?” to “Which matters more: heterogeneity or absolute conditions?” or “Let’s predict species richness as best we can”. With the latter, it starts becoming important to incorporate spatial structure and spatial autocorrelation into the models. This is easier said than done, and even easier done than to interpret the results!

This is what makes me oh-so-happy to work in the fynbos around Cape Town. Clockwise from the top are the views from atop Observation Peak, in the crevices of the Silvermine region of Table Mountain National Park, and on the slopes of the Kogelberg.

If you could study any organism on Earth, what would it be? Plants, both great and small, are definitely my jam, having grown up in the fynbos of the southwestern Cape. But I’ve also got big soft spots for lichens, insects, birds, cnidarians, cetaceans and seals! If I’m studying something I find personally interesting and/or “beautiful”, then I’m happy.

Anything else to add? Within my lab, this paper took infamously long for me to get published, not least because of the reasons I described above. I know that isn’t particularly unique or exciting as an answer to an interview question, but I think it’s relatable for many. After many, very different drafts of this paper, I feel like (but am obviously not) a veteran of the scientific process. I guess I just want to send my thoughts and well-wishes out to anyone else trapped in “Manuscript Rewriting Hell”, and say this: you can look forward to an indescribable feeling of relief when it’s done!

Leo Ohyama is currently working toward his PhD at the University of Florida. He is an ecologist broadly interested in processes that shape the distribution of biodiversity. Leo shares his recent work on how species divesity scales across space in ant species across the globe.

Leo digging for ants in the flatwoods of Florida, USA before his interest in programming got him into an air conditioned room.

Personal links. Twitter | ResearchGate

Institute. University of Florida, Biodiversity Institute

Academic life stage. PhD

Major research themes. Broadly I am interested in how and why global biodiversity patterns are assembled and whether we can apply predictive frameworks to better understand the future of the biosphere. I am also interested in scaling up natural history to global scales through the collection and curation of traits-based data in ants (sociometric data). My themes of research lie along macroecology, island biogeography, and community ecology.

Current study system. Ants! Ants are one of the most widespread and globally distributed groups of invertebrates on the planet and make up anywhere from 15 to 20% of terrestrial biomass. They are also one of the most well-sampled invertebrates in island systems and have thrived and found success in colonizing islands around the world. Given their success they are a key insect group to include in studies that attempt to understand the spatial scaling of biodiversity.

Recent paper in JBI. Ohyama L, Holt RD, Matthews TJ, Lucky A. The species-area relationship in ant ecology. Journal of Biogeography. 2021;00:1-18 https://onlinelibrary.wiley.com/share/YH8KA4IE8XF5NXMMNHVU?target=10.1111/jbi.14149

Motivation behind this paper. The motivation was really two-fold. The first one being that while patterns of ant diversity have been well documented across the planet, no one has really looked at the scaling properties of all these studies at a global scale. To me, understanding these scaling properties are just as important as understanding the general patterns of diversity as they can link local-scale processes to global-scale processes. Islands in both mainland and insular areas are an excellent system to leverage to understand these scaling properties given that ants have been well sampled across many islands around the globe.

The second motivation was that this paper was conceptualized during the beginning of the pandemic when my fieldwork was cancelled. Without any fieldwork and extra time, working on a more computational, data-synthesis project was ideal as I could work on it remotely, although it involved many weeks of reading and reviewing the literature. This was happening before finalizing and proposing my dissertation research topic. Being able to survey the literature, run analyses, and write up this paper really helped me flesh out my plans for what I wanted to do with the rest of my dissertation.   

Heavily armored ‘tank ants’ (Nomamyrmex esenbeckii) are a species of army ants that roam the forest floors of Ecuador and were recorded in several mainland fragments from the studies leveraged for the paper. They are top-predators in tropical rainforests, and specialize in raiding the nests of leaf-cutter ants. Their long raiding parties are often protected by fierce guards, fending off anything that comes too close. Picture by Philipp Hönle

Key methodologies. A novel methodology that we utilized in this study was the application of piecewise models to identify specific breakpoints which estimate the spatial scales where the slope of species-area relationships significantly shifted. These models were made available from a new function in the ‘sars’ package (Matthews & Rigal, 2021), of which one of my co-authors, Tom Matthews, was a developer. These breakpoints can be compared between different systems, such as mainland and insular systems, which helps us better see how species-area relationships change at different spatial scales among different systems.

Unexpected results and challenges. We surprisingly found that the rate at which species richness increases across area was higher in mainland relative to insular systems. This is opposite to what is often observed in the literature across a variety of taxa. Additionally, we found that precipitation was a key driver in the scaling of ant biodiversity, which contrasted other works that suggested precipitation was less influential on ant biodiversity. In terms of challenges, this was my first time writing a paper where all the co-authors were only reachable over zoom and email. In fact, two of the authors were in different countries and time zones. However, my co-authors were amazingly supportive, and I was able to proactively seek out zoom meetings with other colleagues to discuss the paper and get insight when needed.

Major results. The major result of this paper is a more comprehensive understanding of how different factors affect spatial scaling in ant biodiversity. We not only find that ant biodiversity scales at higher rates across mainland areas relative to insular ones, but we also find strong differences in these scaling properties across different biogeographical realms while also being heavily influenced by precipitation. Although ant diversity patterns are well studied across the world, the scaling properties of this diversity are less well understood, so our analyses provide much needed insight into these lesser-known areas. Additionally, our thorough review of the many studies allowed us to identify key areas for further research, including the assessment of island age and the interactions between non-native and native ants in insular systems. Finally, we accumulated a decent-sized dataset of ant diversity across a variety of islands and archipelagos around the world that can be used by other scientists to conduct their own studies on spatial scaling.

Next steps. One of my more exciting ideas is actually written in the paper! We discuss how the age of mainland islands (oftentimes habitat fragments) influence the species-area relationship. As such we propose a continental analog to the general dynamic model of island equilibrium. The inclusion of a temporal dimension to the species-area relationship has been explored but the comparison of this between insular systems and mainland systems is less well understood. This idea excites me as it involves two important dimensions, space and time, which are both crucial to the scaling of biodiversity. Temporal scale data is often rare but for ants this is not always the case.

If you could study any organism on Earth, what would it be? That’s a tough question! My initial answer would be ants because I’ve worked with them for a while now and have developed a particular fondness for them. But if I had the opportunity, I would like to study freshwater fish. This is mostly driven by the completely different system that these organisms live in. For example, in river systems, you have water currents and a network of streams and water sheds to consider when thinking about dispersal or other assembly mechanisms in a community. As a person who has mostly stuck to working with ants, these new challenges are mind-bending but also excite me because they prompt new ways of thinking. I guess I am usually more drawn to the questions and would love to keep challenging myself with different organisms, but ants will always be a staple for me (there’s plenty of them around!).

Leo observing harvester ants in the sagebrush landscape of Idaho, USA.

Anything else to add? Two things! First, my inspiration to tackle scaling topics originates from a biogeography class I took when I was a master’s student. One day in this class we spent two hours debating the concept of scale and never came to a conclusion other than “it all depends on scale”. This was a powerful moment for me and really inspired me to keep thinking about scale and the synthesis between different scales which has ultimately led to this paper. The other thing I would like to add is that I was privileged to spend an extensive amount of time doing fieldwork and studying the natural history of ants at the local community scale during my master’s degree. While I enjoy programming and working on the computer, I believe that having a grounded understanding of the study organism, including its natural history is important. It’s also important to tie the inference we make at global scales to these local scale mechanisms or local-scale studies.

Lucas Neves Perillo is a postdoc at the Universidade Federal de Minas Gerais in Brazil. He is a biologist interested in conservation and science communication. Here, Lucas shares his recent work on disentangling the effects of latitudinal and elevational gradients on bee, wasp, and ant diversity in an ancient neotropical mountain range.

Lucas Neves Perillo ready for his fieldwork in neotropical mountains.

Personal links. Twitter | Instagram

Institute. Universidade Federal de Minas Gerais and Bocaina Biologia da Conservação

Academic life stage. Postdoc

Major research themes. Community ecology, Science communication, Insect diversity, Biogeography

Malaise trap mounted at the Pico do Barbado Mountain.

Current study system. Ancient tropical mountains are megadiverse, yet little is known about the distribution of their species. In Brazil, the Espinhaço Mountain Range hosts the campo rupestre ecosystem, the climatically warmest Brazilian biodiversity hotspot. The Aculeata, an insect group composed of bees, wasps and ant species, are pretty diverse and provide an interesting study opportunity in this hotspot because they are easily collected and provide various ecosystem services, such as pollination, seed dispersal and honey. This project was the first to study the Aculeata species distributed throughout the Espinhaço and opens up possibilities for further studies.

Recent JBI paper. Perillo, L.N., Castro, F.S., Solar, R., Neves, F.S. (2021). Disentangling the effects of latitudinal and elevational gradients on bee, wasp, and ant diversity in an ancient neotropical mountain range. Journal of Biogeography, 48(7): 1564-1578 https://doi.org/10.1111/jbi.14095

Pico da Formosa, one of the 12 mountains that we collected the Aculeata specimens.

Motivation behind this paper. I did my master’s project on a mountain near my hometown. When I started my PhD, I wanted to expand my study scale to understand how insect species were distributed in the Brazilian mountain chains. Despite invertebrates’ great diversity and importance to humanity, they are often neglected in conservation policies, especially in mountainous environments. With the objective to explain the variation in invertebrate species diversity over environmental gradients, we started to study how climatic variables were related to different latitudes and elevations. Mountains are true natural biodiversity laboratories, given that in a few kilometers, we can experience considerable variation in temperature, humidity, soil types and vegetation, with the bee, wasp and ant communities following these variations.

Searching for Aculeata – Pico do Itambé Park.

Key methodologies. The main objective of the project funding my PhD was to understand the distribution of Aculeata species at different latitudes and elevations in the Espinhaço Mountain Range. To achieve this goal, we designed our fieldwork to collect Aculeata specimens on different mountains over varying elevations. We performed fieldwork at 24 study sites across 12 mountains, covering 1200 km from south to north and an elevational range varying from 1000 to 2000 m. At each mountain, we positioned a trap set near the mountaintop and another at the mountain base. Each set consisted of a Malaise trap (flight intercept), four yellow pan traps and four ground pitfall traps. These are complementary methods used to collect different species of bees, wasps and ants. In the laboratory, we pinned the insects, identified them to the lowest taxonomic level possible, and housed them at the scientific collection of the Universidade Federal de Minas Gerais, Brazil. After all these steps, we needed to access climate information from the collection sites to conduct the analyses. For that, we used the free database available at the WorldClim platform.

A nice place to camp! At the Reserva Particular do Patrimônio Natural Santuário do Caraça.

Unexpected challenges. We faced a lot of challenges in this research, especially during fieldwork. The fieldwork took over 120 days, covering 20,000 km by car and 1,398 km on foot, traveling through 40 Brazilian municipalities. We climbed twelve mountain tops searching for insects. In some cases, it took more than 10 hours just to reach the peak. At each mountain, the team camped for ten days. Some places were easily accessible, but we had limited water for drinking and cooking at some camping sites. Some days, it rained so hard that we had to dry our clothes inside the tent. Working with mountain insect communities is not an easy task! The challenge continued in the lab, as we had to sort, organize and identify over 12,000 bees, wasps and ants specimens. It was an amazing project that helped me to learn and evolve as a researcher.

All the equipment that had to fit in our backpacks – with Matteus Carvalho and Arleu Barbosa.

Major results. Our main objective was to disentangle the effects of latitudinal and elevational gradients on the distribution of bees, wasps and ants, and to understand the effects of climatic variables. During fieldwork, we collected 843 species from 17 different families, a considerable number of species! In terms of latitude and elevation, latitude had no impact on diversity over the range studied, and we found a general decrease in diversity towards higher elevations. That is, the variation in species composition increased with elevation and with geographical and environmental distances. Our results showed that variation in species richness and composition across mountains is strongly associated with elevational gradient, which showed stronger climatic variation than the latitudinal gradient. Temperature, wind, and precipitation were important drivers of diversity, with temperature being the most important. Therefore, despite having narrow elevational ranges, tropical mountains have strong biogeographical effects driving diversity due to high variation in conditions and resources availability. Under a scenario of global climate changes, this elevational gradient that spans up to 2072m (the highest point of the entire mountain range) may limit species range shifts, leading to severe biodiversity losses.

The researcher Lucas Perillo with a part of the equipment ready to walk during fieldwork.

Next steps for this research. Unfortunately, the field collections are over. It was definitively my favourite part besides the challenges. Yet, we have a lot of collected material. This study focused only on bees, wasps and ants, but other insects (e.g., herbivores and flies) and spiders can still be explored. The Aculeata data is also being analysed under different perspectives, such as contrasting distributions between specialist and generalist species. We may also have some undescribed species, in which we are still looking for taxonomists to help us explore the wasp families. Lastly, it would be interesting to go back to the same sampling sites in the future to understand how these communities vary over time.

Sphecidae wasp preparing the prey.

If you could study any organism on Earth, what would it be? Despite studying insects since the beginning of my career, I’m also interested in other groups. I would like to participate in projects with large mammals and plants, for example. But what fascinates me are the mountains. If I could work in other mountains around the world, the taxonomic group would not matter. Plants in the Andes, insects in the Himalayas, or mammals in the European mountains… any of those experiences would make me feel super fulfilled!

Chrysididae specimen.

Anything else to add? I appreciate projects that propose public science communication. In Brazil, I coordinate outreach activities in environmental and conservation biology. Podcast, blog, and audiovisual contents are some of the initiatives that I carry out beyond academia. For this paper, I’ve made a short video in English (https://www.youtube.com/watch?v=c-mVpuVtUjI) and a complete one in Portuguese (https://www.youtube.com/watch?v=yXD77HpLksU&t=3s) to share the main findings of the project. I hope you enjoy it!

Ryan Briscoe Runquist is a postdoc at the University of Minnesota in the USA. She is an evolutionary ecologist interested in invasive species and their potential impacts in a changing world. Here, Ryan shares her recent work on predicting invasive species range expansion using Joint Species Distribution Model.

R. Briscoe Runquist in front of a population of Leafy Spurge (Euphorbia virgata, formerly E. esula), an ecologically and economically damaging invasive species of the Upper Midwestern United States, which is particularly problematic for pastures and rangelands.

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Institute. University of Minnesota – Twin Cities

Academic life stage. Senior Postdoctoral Research Associate

Major research themes. I am generally interested in the ecology, evolution, and biogeography of plants and how those processes interact with global change – especially in invasive species.

Plant communities along the Zumbrota River in Minnesota, USA.

Current study system. I am currently researching invasive plant species of the Upper Midwestern United States and Central Canada. Most of the plants that I work with are herbaceous short-lived perennials that are causing lots of ecological and economic harm, such as crop losses and damage to ecosystem services like clean water. Although they can cause a lot of damage, invasive species are scientifically rich natural experiments to investigate the interaction of ecological and evolutionary forces in real time. Working in invasion biology is highly integrative at the intersection of basic and applied research and incorporates techniques from genomics to modelling to large field experiments.

Recent JBI paper. Briscoe Runquist, R. D., T. A. Lake, & D. A. Moeller (2021). Improving predictions of range expansion for invasive species using joint species distribution models and surrogate co-occurring species. Journal of Biogeography, 48(7):1693–1705 https://doi.org/10.1111/jbi.14105

Plant communities along the Kettle River in Banning State Park, Minnesota, USA.

Motivation behind this paper. It would be incredibly useful to land managers and governments if scientists could effectively predict which regions are most at risk of invasion. Unfortunately, building these types of predictive models is quite challenging, if not impossible, with our current frameworks. This is because the underlying assumptions of the models, such as the assumption that a plant is not actively expanding its range, are in contrast with the reality that invasive species are a moving target. To overcome this issue, we wanted to use existing knowledge about what plant community members are most likely to co-occur with an invasive species as it enters a new region to help make better predictions about what areas are a greater risk.

Key methodologies. In our new method, we combined a rich dataset of over 10,000 plant communities collected by the Minnesota Department of Natural Resources since 1971 from across the state with a new class of models, called Joint Species Distribution Models (JSDMs). The JSDMs allowed us to identify native species in the state that had particularly similar or dissimilar habitat affinities to our invasive species of interest. We were then able to include in our model information on the sites where these native species occurred to help identify areas in Minnesota that might be subject to invasion. Including these surrogate species as natural indicators of habitat (i.e., phytometers) improved the predictive performance of our models.

Japanese hops (Humulus japonicus) growing in a dense monoculture along the edge of a river (Image Credit: “Japanese Hop” by matthewbeziat is licensed under CC BY-NC 2.0).

Unexpected challenges. We experienced a few different challenges while working on this research project. Our original approach to modelling the potential invasive distribution of these species focused on traditional species distribution model frameworks. However, there were so few records for these species in our study area that we needed to investigate other avenues, which is how we started working with JSDMs. Using JSDMs was challenging in a few different ways; there are several different potential approaches, and they are all relatively new. We investigated a few different JSDM frameworks but eventually settled on gJams because the documentation is helpful, and the results produced by this framework are readily incorporated into our workflow.

Major results. We found that models that incorporated surrogate native species could better predict invasive species occurrences compared to traditional models. Our surrogate models performed especially well along the leading edge of the invasion front. When land managers are trying to gauge invasion risk, models that can predict the expanding range edge occurrences are particularly useful. This is especially true if we are interested in predicting new areas outside of the current range of the invasive species that may be at risk for a future invasion.

Oriental Bittersweet (Celastrus orbiculatus) vines overwhelming a tree. The species causes damage through smothering trees and causing limb breakage due to the vines’ weight [Image Credit: “Oriental Bittersweet (Celastrus orbiculatus)” by Plant Image Library is licensed under CC BY-SA 2.0].

Next steps for this research. In my continued research, I am investigating other model frameworks that can incorporate more information about invasive species biology. The aim of these models is to use a combination of experiments and occurrence data to better estimate a species niche to improve predictions about species distributions and invasion potential. One area that I am particularly excited about is the use of imagery from Earth Observation satellite missions to detect more invasive species populations and help correct our incomplete occurrence record.

If you could study any organism on Earth, what would it be? I love plants, but I would love to do more research with trees. It would be amazing to study the high-altitude conifers in the ancient bristlecone pine forest.

Narrowleaf bittercress (Cardamine impatiens) growing between rocks [Image credit: “Cardamine impatiens (narrowleaf bittercress)” by tgpotterfield is licensed under CC BY-NC-SA 2.0].