Since I only recently started my career in digital humanities, I still don’t have any favorites to talk about on here. You can however read more about my past (and always current) interests in evolutionary biology.

Range extensions and the establishment of range margins

What determines species’ range limits? In ecological theory, we would say that a species is stopped from expanding further in space if it reaches the limits of its own niche. An evolutionary biologist would say that the species fails to adapt in order to continue expanding. However, neither of these two answers is telling much about the underlying mechanisms: why is the limit of a niche reached? Why does adaptation fails at the margin of a habitat? In my own work, I assume that a population occupies a habitat along which there is an environmental gradient, i.e. where environmental condition change along the occupied range. Classical population genetics stipulate that adaptation along a gradient fails because of gene flow between the center and the margin of a habitat: such gene flow moves individuals adapted to the center to the margins, where they are maladapted. When migrants mate with locally adapted individuals, they produce maladapted offspring and thus adaptation fails. The evolution of genetic variance plays a major role in order to mitigate the migration load. We also know that population size plays a major role: when maladaptive variants are introduced from the center to the margins, they produce less offspring, and thus reduce the local population size. When selection becomes too weak with respect to the effects of genetic drift (because of the population size decrease), adaptation fails. Recent advances showed that finite range limits are not supposed to form if the underlying environmental gradient changes constantly. A steepening environmental gradient is needed to lead to range margins. I am interested in understanding the steepening-gradient hypothesis, as well as proving its validity in natural systems.

Inferring patterns of isolation by distance

An important issue in different biological applications (here I am thinking in particular of conservation studies) is to correctly measure parameters such as the population density and the dispersal rate of a population. However, this is often not doable in practice: on one hand, it can be impossible to sample or even observe all the individuals of a species, and on the second hand, unless we are in possess of historical demographic data, it is difficult to infer if a sampled individual is originally from the sampling area or if it was the result of a long distance migration event. Isolation by distance refers to the accrual of genetic differentiation with distance within members of a population. It is a relatively easy pattern to measure. Different models to connect isolation by distance to different population parameters exist, but they are often simplified models, e.g. developed within a stepping stone model. In my previous work I worked on a method to detect demographic parameters from patterns of isolation by distance. That proved to be an unsolvable problem (for now, that is). However, I started to realize that ubiquitous patterns of genetic differentiation, such as isolation by distance, can be used to study the evolutionary state of a population. Most of my current ideas revolve around this.

Effects of gene flow and spatial structure on evolutionary rescue

Recent experimental and theoretical studies have highlighted the influence of migration on the probability of evolutionary rescue in structured habitats. Theoretical modelling of a structured population experiencing strong environmental change showed that intermediate migration rates maximize the probability of rescue. Experiments have shown that gene flow between subpopulations generally increases the probability of rescue of a population at risk of extinction. During my PhD, I developed an analytically tractable model to study evolutionary rescue in structured habitats: we were able to assess when gene flow facilitates evolutionary rescue, and we provided useful analytical tools to provide insight about evolutionary rescue in space.