Interview with the authors: glacial refugia and the dispersal of terrestrial invertebrates

Antarctica is an extreme and isolated environment that supports a variety of species. However, we know little about how terrestrial species survive in these kinds of conditions. In a recent paper in Molecular Ecology, McGaughran and colleagues investigated a widespread group of terrestrial invertebrates to understand how species have persisted in this harsh environment. These researchers found that there were many local clusters of individuals with substantially more long-distance dispersal events than were previously identified. These long-distance dispersers were likely aided by wind, providing an interesting example of the link between environmental conditions and population stability. For more information, please see the full article and the interview with McGaughran, lead author of the study, below. 

Antarctic Peninsula taken near the tip. Photo created by Dr. Ceridwen Fraser.

What led to your interest in this topic / what was the motivation for this study? 
During my PhD, I researched genetic and physiological diversity of Antarctic terrestrial invertebrates, spending a collective ~6 months on the ice.  I then stepped away from Antarctic research for several years, completing postdocs in Germany and Australia, but I never forgot my time in Antarctica or my love for its unique environment.  Thus, I’ve maintained collaborative links that have allowed me to continue to contribute to Antarctic research.  In this study, we wanted to see whether genomic data would give us greater insight to the evolutionary history of invertebrates along the Antarctic Peninsula than had been gained with single-gene analysis in the past.  

What difficulties did you run into along the way? 
Getting workable quantities of DNA from tiny (~1 mm) springtails to use in genomic applications is difficult.  In fact, for this study, we tried to extract DNA from several Antarctic springtail species, but were only successful in our attempts with Cryptopygus antarcticus antarcticus.  Low DNA concentrations can also mean that the genomic data we end up with for analysis is patchy.  These aspects provide some challenges, but the methodologies underlying library preparation and sequencing are continually improving and we are excited about the potential of applying genomic methodologies to more Antarctic taxa in the future.

What is the biggest or most surprising finding from this study? 
Using genome-wide data, we were able to find evidence for a greater frequency of dispersal events than had been previously shown with single-gene data.  This was particularly surprising because dispersal for Antarctic invertebrates is hard.  These animals live under the rocks in moist ice-free areas.  As soon as they leave the relative safety of the soil column, they are exposed to freezing and desiccating conditions.  Thus, though we have some evidence to suggest that springtails can survive for short periods in humid air columns or floating on water, our expectation is that such events would be rare.  Finding genetic evidence that suggested several instances of successful dispersal over extremely long geographic distances was therefore surprising.

Moving forward, what are the next steps for this research? 
Much of the Antarctic literature focused toward understanding evolutionary and biogeographic questions has been based on single-gene analyses because genomic approaches are still relatively new.  This previous work has been informative about the fact that many Antarctic terrestrial species have survived glaciation in refugia, but there is much that remains to be discovered.  Antarctica is a kind of barometer for the rest of the world and it is important that we understand how species there have responded to environmental change in the past and how they may do so in the future.  Thus, key to extending this research will be to bring genomic approaches to bear on other populations and species in Antarctica.  This will help us to gain an understanding of how isolated Antarctica really is, and how its endemic species will likely respond to future environmental changes.

What would your message be for students about to start their first research projects in this topic? 
In this genomic and associated bioinformatic era, learning the skills of a well-rounded biologist who has a breadth of understanding that spans the field, the laboratory, and the computer, can be daunting.  As you develop or use novel techniques in Molecular Ecology, my message would be to stick with it through the hard stuff.  It is such an exciting time to be an evolutionary biologist and, though it can involve some really tough moments, the revelations we can achieve about how the world works are key.  Alongside this, I would suggest that collaboration is now more important than ever – don’t feel like you have to reinvent the wheel or be an expert on every single aspect of your research.  Instead, develop your own niche and share in the expertise of those around you to do the best science together.

What have you learned about science over the course of this project? 
When I first started doing research, there was no such thing as genomics or next generation sequencing and we simply didn’t have the means to gain genome-wide data.  In recent years, the face of evolutionary biology has changed due to the revolution in sequencing technology and bioinformatics.  As exemplified by this project, I’ve learned that genomic data can provide new and more nuanced insights into our biological questions of interest.  And, though it can be hard at times to work in such a swift-moving area of research, it is ultimately very rewarding.

Describe the significance of this research for the general scientific community in one sentence.
The environment, especially wind, plays an important role in structuring patterns of genetic diversity among Antarctic populations – thus future climatic changes are likely to have a significant impact on the distribution and diversity of these populations.  

Describe the significance of this research for your scientific community in one sentence.
Bringing genomic data to bear on long-standing evolutionary questions in Antarctica is a worthwhile and fruitful endeavour that will ultimately produce greater insights into understanding and protecting Antarctic taxa.

Dry Valleys taken in the Antarctic Dry Valleys. Photo created by Dr. Angela McGaughran.

McGaughran A, Terauds A, Convey P, Fraser CI. 2019. Genome‐wide SNP data reveal improved evidence for Antarctic glacial refugia and dispersal of terrestrial invertebrates. Molecular Ecology. 28:4941-4957. https://doi.org/10.1111/mec.15269.

Interview with the author: Seed and pollen dispersal distances in two African legume timber trees and their reproductive potential under selective logging

Seed and pollen dispersal, which are critical processes that influence the regeneration of trees, are likely affected by human activities like logging. However, determining how far pollen and seed move is notoriously difficult in the field. Thankfully, modern genetic techniques have provided us new approaches to estimating pollen and seed dispersal, which alleviates some of this issue. Using genetic markers, Dr. Olivier Hardy and colleagues assessed how the movement of pollen and seed in two African timber species is affected by selective logging, where one or two trees per hectare is removed on a 25-30 year cycle. Read below for a behind the scenes interview with Olivier.

Link to the study: https://onlinelibrary.wiley.com/doi/10.1111/mec.15138

Inflorescence of Distemonanthus benthamianus. Photograph by Xander van der Burgt

What led to your interest in this topic / what was the motivation for this study? 
Tropical forests are fascinating but threatened ecosystems. Logging is usually perceived as one of their major threat by the public but selective logging might also be a solution when adequate management plans allows the regeneration of logged tree species, while the revenue generated prevents land conversion. However, forest regeneration is complex because many biotic and abiotic factors can be involved in the process. The extent of seed and pollen dispersal is one of the factors for which few data exist, and it can vary among species or locations. Fundamental research has developed methodologies based on genetic markers to quantify seed and pollen dispersal, so it is a great satisfaction to apply these methods for generating data that should help improving the management of tropical forests.

What difficulties did you run into along the way? 
The study required sampling exhaustively all adult trees of our focal species over several square kilometres in very remote sites of Central African forests, where visibility can be limited to a few tens of meters. This is the kind of field work that would have been very difficult to achieve for a small team of researchers. The collaboration with logging companies, FSC-certified, was a great advantage because we could rely on their field technicians who are trained to conduct similar inventories for planning logging activities.

What is the biggest or most surprising finding from this study? 
First that pollen dispersal distances were so different between two insect-pollinated tree species from the same family but bearing different flower types. It suggests that different flower types could attract different guilds of pollinators with contrasted flight abilities, but for now we ignore who are the pollinators. Second that about 25% of the seeds of the wind-dispersed species were transported over >500 m while their pods do not seem to be efficient gliders and, indeed, the majority falls within <100 m. It suggests that storm winds could play a crucial role in the dissemination of wind-dispersed canopy trees.

Moving forward, what are the next steps for this research?
First, we need to identify the pollinators and seed dispersers. This is challenging, in particular for pollinators because flowers open in the canopy, 20 to 40 meters above the ground and we must invent devices to observe or capture pollinators. Sporty, adventurous and creative PhD or MSc students are welcome! Second, we need to replicate these studies on numerous tree species with different contrasted reproductive characters to be able to derive some generalizations about seed and pollen dispersal according to species traits and environmental conditions. Third, we need to translate these results into recommendations for the sustainable management of tropical forests in collaboration with the forestry sector, and disseminate the messages to policy makers. Fourth, beyond seed and pollen dispersal, many other key processes affect the regeneration cycle and must be considered as well.

What would your message be for students about to start their first research projects in this topic? 
Tropical biology is fascinating for those attracted by fundamental research on biotic interactions, and it is full of opportunities for those inclined towards applied research of societal importance. Some students might be afraid by the remote and little equipped field conditions, and this is obviously constraining. But most students who discovered tropical Africa for the first time returned enthusiastic by their experiences, and some decided to pursue scientific research there.

Describe the significance of this research for the general scientific community in one sentence.
Seed and pollen dispersal investigations are relevant to assess the sustainability of selective logging in tropical forests.

Describe the significance of this research for your scientific community in one sentence.
Seed and pollen dispersal appears to be non-limiting for the natural regeneration of two African tree species under selective logging, while the minimal cutting diameter should be defined by accounting of the relationship between reproductive success and tree size

Citation
Olivier J. Hardy, Boris Delaide, Hélène Hainaut, Jean‐François Gillet, Pauline Gillet, Esra Kaymak, Nina Vankerckhove, Jérôme Duminil, & Jean‐Louis Doucet (2019). Seed and pollen dispersal distances in two African legume timber trees and their reproductive potential under selective logging. Molecular Ecology, 28(12), 3119-3134. https://onlinelibrary.wiley.com/doi/10.1111/mec.15138