Hot Spots, Cold Spots, and the Geographic Mosaic Theory of Coevolution

Abstract

Species interactions commonly coevolve as complex geographic mosaics of populations shaped by differences in local selection and gene flow. We use a haploid matching-alleles model for coevolution to evaluate how a pair of species coevolves when fitness interactions are reciprocal in some locations ("hot spots") but not in others ("cold spots"). Our analyses consider mutualistic and antagonistic interspecific interactions and a variety of gene flow patterns between hot and cold spots. We found that hot and cold spots together with gene flow influence coevolutionary dynamics in four important ways. First, hot spots need not be ubiquitous to have a global influence on evolution, although rare hot spots will not have a disproportionate impact unless selection is relatively strong there. Second, asymmetries in gene flow can influence local adaptation, sometimes creating stable equilibria at which species experience minimal fitness in hot spots and maximal fitness in cold spots, or vice versa. Third, asymmetries in gene flow are no more important than asymmetries in population regulation for determining the maintenance of local polymorphisms through coevolution. Fourth, intraspecific allele frequency differences among hot and cold spot populations evolve under some, but not all, conditions. That is, selection mosaics are indeed capable of producing spatially variable coevolutionary outcomes across the landscapes over which species interact. Altogether, our analyses indicate that coevolutionary trajectories can be strongly shaped by the geographic distribution of coevolutionary hot and cold spots, and by the pattern of gene flow among populations.

Evolution of gene‐for‐gene systems in metapopulations: the effect of spatial scale of host and pathogen dispersal

“…A number of studies have focused on the geographic mosaic theory (Thompson, 1994) and exploration of the consequences of coevolutionary hot spots and selection mosaics (e.g. Nuismer et al, 1999Nuismer et al, , 2000Gomulkiewicz et al, 2000). Despite the array of underlying ecological and genetic assumptions represented, an overarching theme linking these studies is that spatial structure can result in coevolutionary outcomes that simply cannot occur in isolated local populations.…”

Evolution of plant resistance at the molecular level: ecological context of species interactions

“…For instance, Gomulkiewicz et al (2000) show that the spatial distribution of 'hot' and 'cold' spots can influence strongly the coevolutionary dynamics. Gene flow, natural selection and habitat size were also shown to influence evolution of interactionrelated characters, and to be crucial determinants of an appropriate geographical scale for examining coevolutionary changes (Nuismer et al, 1999).…”

“…Eventually, elucidation of selective forces shaping resistance evolution requires joint analysis of the geographic distribution and dynamics of host and enemy populations. The characterisation of the geographic mosaics of selection is likely to play a crucial role in the interpretation of molecular diversity at resistance genes (Gomulkiewicz et al, 2000;Thompson and Cunningham, 2002).…”

A summer heat wave decreases the immunocompetence of the mesograzer, Idotea baltica

“…Global change may result in a changed pattern of coevolutionary hot and cold spots, as Xuctuations of temperature can aVect host and parasite genotypes into opposite directions (Gomulkiewicz et al 2000). This is likely to disrupt species interactions and evolutionary equilibriums.…”