Spatial heterogeneity alters the trade-off between growth and dispersal during a range expansion

Abstract

Eco-evolutionary processes play a key role shaping the invasion dynamics of populations expanding in new habitats. The expansion process is driven by co-evolving species traits, in particular, those traits related to body dimensions, competitive skills, movement abilities controlling also their responses to landscape heterogeneity gradients. Typically, individuals who invest more in the development of their traits related to the dispersal strategy reduce investment in reproduction. Thus, there are two possible trading-off eco-evolutionary strategies: growing faster or dispersing faster (R-D trade-off). We explore the spreading dynamics of a consumer species exploiting a resource in a heterogeneous environment through a reaction-diffusion model. We focus on the co-evolution of growth rate and dispersal traits for assessing the phenotype having the highest spreading speed and leading the expansion front. We evaluate spreading properties numerically and analytically, when theoretical formulas are available. We found that the perfect symmetry of the effects of growth and dispersal on the speed of propagation is broken in the presence of competition between phenotypic traits. While the latter tends to favor R-strategies in spatially homogeneous environments, D-strategies become more effective in certain heterogeneous configurations, especially when heterogeneities affect dispersion.