Isolation-by-distance in landscapes: considerations for landscape genetics

Abstract

In landscape genetics, isolation-by-distance (IBD) is regarded as a baseline pattern that is obtained without additional effects of landscape elements on gene flow. However, the configuration of suitable habitat patches determines deme topology, which in turn should affect rates of gene flow. IBD patterns can be characterized either by monotonically increasing pairwise genetic differentiation (for example, F ST ) with increasing interdeme geographic distance (case-I pattern) or by monotonically increasing pairwise genetic differentiation up to a certain geographical distance beyond which no correlation is detectable anymore (case-IV pattern). We investigated if landscape configuration influenced the rate at which a case-IV pattern changed to a case-I pattern. We also determined at what interdeme distance the highest correlation was measured between genetic differentiation and geographic distance and whether this distance corresponded to the maximum migration distance. We set up a population genetic simulation study and assessed the development of IBD patterns for several habitat configurations and maximum migration distances. We show that the rate and likelihood of the transition of case-IV to case-I F ST -distance relationships was strongly influenced by habitat configuration and maximum migration distance. We also found that the maximum correlation between genetic differentiation and geographic distance was not related to the maximum migration distance and was measured across all deme pairs in a case-I pattern and, for a case-IV pattern, at the distance where the F ST -distance curve flattens out. We argue that in landscape genetics, separate analyses should be performed to either assess IBD or the landscape effects on gene flow.

Population genetic structure, differentiation, and diversity in Tetrix subulata pygmy grasshoppers: roles of population size and immigration

“…We found no evidence for isolation by distance among our populations despite that we performed separate analyses for mainland and insular populations. Such lack of isolation by distance could be interpreted as a complete lack of gene flow or indicate extensive gene flow among subpopulations due to the lack of any distance‐related or physical barriers to dispersal (van Strien et al., ). To discriminate between these competing explanations and further assess the presence and intensity of any isolation by distance, we evaluated the F ST –geographic distance correlation from subsets of mainland population pairs that differed with regard to threshold interpopulation distance (van Strien et al., ).…”

Implications of recurrent disturbance for genetic diversity

“…However, even in IBD models of undisturbed populations, genetic drift will counter spatial patterns generated by gene flow at a certain distance threshold (van Strien et al. ). This is shown by our model (Fig.…”

“…Initial allele assignment at each loci was chosen at random (Gibbs ; van Strien et al. ) from the ten alleles available for each locus, such that simulations began with an expected heterozygosity of 0.9.…”

The genetic characterization of an isolated remnant population of an endangered rodent (Cricetus cricetus L.) using comparative data: implications for conservation

“…Employing nuclear data, a significant isolation by distance based on the Mantel`s test was found (P < 0.01), which argues against male mediated gene flow, but is in accordance with the habitat and population fragmentation. Nevertheless, this pattern might be also produced in the situation when migration is constrained due to distance (Van Strien et al 2015). Thus, analyzed SSR markers, showing clear geographic structuring, may or may not reflect the true demographic history of JW.…”