Data from: Cropland connectivity affects genetic divergence of Colorado potato beetle along an invasion front

The population genetic structure of invasive species can be strongly
affected by environmental and landscape barriers to dispersal.
Disentangling the relative contributions of these factors to genetic
divergence among invading populations is a fundamental goal of landscape
genetics with important implications for invasion management. Here, we
relate patterns of genetic divergence in a global invasive agricultural
pest, Colorado potato beetle (CPB; Leptinotarsa decemlineata), to
environmental and landscape factors along an invasion front in
Northwestern China. We first used microsatellite markers and
spatial-temporal samples to assess broad patterns of genetic diversity as
well as fine-scale changes in patterns of genetic divergence. We then
distinguished the relative contributions of five factors to genetic
divergence among front populations: geographic distance (isolation by
distance), climate dissimilarity (isolation by environment), and
least-cost distances (isolation by resistance) modelled with three
factors: climate suitability, cropland cover, and road networks. Genetic
diversity broadly decreased from West to East, with the exception being
Eastern China. Low levels of genetic diversity and varying degrees of
divergence were observed in Northwestern China, reflecting the potential
effect of landscape heterogeneity. Least-cost distance across cropland
cover was most positively correlated with genetic divergence, suggesting a
role of croplands in facilitating gene flow. The contribution of climate
to genetic divergence was secondary, whether modelled in terms of local
adaptability or connectivity of the climatic landscape, suggesting that
constraints to CPB gene flow imposed by a harsh climate may be ameliorated
in agricultural landscapes. No evidence was found for an obvious effect of
road networks on genetic divergence and population structuring. Our study
provides an example of how agricultural landscape connectivity can
facilitate the spread of invasive pests, even across a broad climatic
gradient. More broadly, our findings can guide decisions about future land
management for mitigating further spread.