Abstract
There is now clear evidence that species across a broad range of taxa harbor extensive heritable variation in dispersal. While studies suggest that this variation can facilitate demographic outcomes such as range expansion and invasions, few have considered the consequences of intraspecific variation in dispersal for the maintenance and distribution of genetic variation across fragmented landscapes. Here, we examine how landscape characteristics and individual variation in dispersal combine to predict genetic structure using genomic and spatial data from the Glanville fritillary butterfly. We used linear and latent factor mixed models to identify the landscape features that best predict spatial sorting of alleles in the dispersal‐related gene phosphoglucose isomerase (Pgi). We next used structural equation modeling to test if variation in Pgi mediated gene flow as measured by Fst at putatively neutral loci. In a year when the population was recovering following a large decline, individuals with a genotype associated with greater dispersal ability were found at significantly higher frequencies in populations isolated by water and forest, and these populations showed lower levels of genetic differentiation at neutral loci. These relationships disappeared in the next year when metapopulation density was high, suggesting that the effects of individual variation are context dependent. Together our results highlight that (1) more complex aspects of landscape structure beyond just the configuration of habitat can be important for maintaining spatial variation in dispersal traits and (2) that individual variation in dispersal plays a key role in maintaining genetic variation across fragmented landscapes.
Highlights
Dispersal is key to the maintenance of genetic variation and adaptive potential in fragmented landscapes
We further found that patch connectivity alone did not predict genetic differentiation at neutral markers, but rather the effect of landscape on genetic structure was mediated through individual variation in the phosphoglucose isomerase (Pgi) locus; populations with higher frequencies of the Pgi-c allele had lower Fst
Together our results suggest that both individual variation in dispersal traits and landscape matrix heterogeneity are important for predicting spatial patterns of genetic variation
Summary
Dispersal is key to the maintenance of genetic variation and adaptive potential in fragmented landscapes. Few studies have considered the consequences of intraspecific variation in dispersal for genetic outcomes such as the maintenance and distribution of genetic variation across fragmented landscapes (Cheptou et al 2017) This is an important gap given that the genetic makeup of populations can drive the trajectories of both ecological and evolutionary processes (Rius and Darling 2014; Szucs et al 2017; Wagner et al 2017). Because dispersal traits often co-evolve with other aspects of morphology, physiology, and behavior (Clobert et al 2009; Cote et al 2017), individuals might interact with, and respond to, the landscape matrix in different ways (Merckx and Van Dyck 2007; Delgado et al 2010) This could mean that the effects of landscape on gene flow might be missed if intraspecific variation is ignored
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