A gene-regulatory network model for density-dependent and sex-biased dispersal evolution during range expansions

Abstract

Eco-evolutionary dynamics of range expansions are of great interest in the context of global change. Range expansions are spatial phenomena and critically depend on organisms' dispersal abilities. Dispersal has a genetic basis, it can evolve, but also be plastic to external environmental conditions and the internal state of an organism. Importantly, dispersal plasticity itself can evolve which has most often been studied theoretically with a focus on optimal reaction norms under equilibrium conditions. However, under rapidly changing conditions, the rate of dispersal plasticity evolution will impact eco-evolutionary dynamics of range expansions. Rates of evolution in turn depend on the genetic architecture of underlying traits. To elucidate this interplay, we develop an individual-based metapopulation model of the evolution of density-dependent and sex-biased dispersal during range expansions. We represent the dispersal trait as a gene-regulatory network (GRN), which can take population density and an individual's sex as an input and analyse emergent context- and condition-dependent dispersal responses. We compare dispersal evolution and ecological dynamics in this GRN model to a standard reaction norm (RN) approach under equilibrium metapopulation conditions and during range expansions. We find that under equilibrium metapopulation conditions, the GRN model produces emergent density-dependent and sex-biased dispersal plastic response shapes that match theoretical expectation of the RN model. However, during range expansion, the GRN model leads to faster range expansion because GRNs can maintain higher adaptive potential. Our results imply that, in order to understand eco-evolutionary dynamics in contemporary time, the genetic architecture of traits must be taken into account.

Evolutionary ecology of dispersal in biodiverse spatially structured systems: what is old and what is new?

“…Intrinsic individual-level conditions affecting dispersal include sex [74][75][76], age [77], developmental stage [78], body size or condition [79,80] or any proxy of competitiveness, for example. Intrinsic and extrinsic cues can of course be used at the same time and interact to determine dispersal decisions [81].…”