Abstract
Spatially explicit simulations of gene flow within complex landscapes could help forecast the responses of populations to global and anthropological changes. Simulating how past climate change shaped intraspecific genetic variation can provide a validation of models in anticipation of their use to predict future changes. We review simulation models that provide inferences on population genetic structure. Existing simulation models generally integrate complex demographic and genetic processes but are less focused on the landscape dynamics. In contrast to previous approaches integrating detailed demographic and genetic processes and only secondarily landscape dynamics, we present a model based on parsimonious biological mechanisms combining habitat suitability and cellular processes, applicable to complex landscapes. The simulation model takes as input (a) the species dispersal capacities as the main biological parameter, (b) the species habitat suitability, and (c) the landscape structure, modulating dispersal. Our model emphasizes the role of landscape features and their temporal dynamics in generating genetic differentiation among populations within species. We illustrate our model on caribou/reindeer populations sampled across the entire species distribution range in the Northern Hemisphere. We show that simulations over the past 21 kyr predict a population genetic structure that matches empirical data. This approach looking at the impact of historical landscape dynamics on intraspecific structure can be used to forecast population structure under climate change scenarios and evaluate how species range shifts might induce erosion of genetic variation within species.
Highlights
Global climate change is expected to pressure species to shift species ranges at an unprecedented rate potentially causing significant biodiversity decline (Johnson et al, 2017; Pacifici et al, 2015; Parmesan & Yohe, 2003; Pecl et al, 2017; Peñuelas et al, 2013; Ripple et al, 2015; Thomas et al, 2004; Urban, 2015)
In contrast to previous approaches integrating detailed demographic and genetic processes and only secondarily landscape dynamics, we present a model based on parsimonious biological mechanisms combining habitat suitability and cellular processes, applicable to complex landscapes
We provide a parsimonious method to simulate intraspecific genetic structure over a temporally dynamic landscape, which can be compared to empirical data
Summary
We used a set of 1,297 caribou and reindeer genotyped at 16 nuclear microsatellite markers (Yannic et al, 2018; Yannic, Pellissier, Ortego, et al, 2014). We precomputed matrices of connectivity between all the cells that are suitable for the species for all 100-year time steps from the LGM to the present. We applied a principal coordinate analysis (PCoA) on the pairwise distance matrices obtained from our model as well as the CavalliSforza chord distance Dc (Cavalli-Sforza & Edwards, 1967) and FST value from 1,297 caribou individuals sampled from 57 locations around their circumpolar distribution (Yannic et al, 2018; Yannic, Pellissier, Ortego, et al, 2014). The landscape and the dispersal parameters modulate the simulation outputs, which generate alternative expectations for the present genetic structure among populations that can be compared to the data. This formed a contact zone between the two genetically differentiated groups
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