Abstract
The field of landscape genetics has been rapidly evolving, adopting and
adapting analytical frameworks to address research questions. As
landscape genetic analyses have shifted away from Mantel-based
analytical frameworks, studies are increasingly using regression-based
frameworks to understand the individual contributions of landscape and
habitat variables on genetic differentiation. This paper outlines
appropriate and inappropriate uses of multiple regression for these
purposes. Of concern is the prevalence of studies seeking to explain
genetic differences by fitting regression models with effective distance
variables calculated independently on separate landscape resistance
surfaces. When moving across the landscape, organisms cannot respond
independently and uniquely to habitat and landscape features. Therefore,
independent resistance surfaces and their effective distance measures
have no mechanistic meaning or relevant statistical interpretation.
There are also tremendous challenges to fitting and interpreting
regression models that include ‘independent’ effective distance measures
as predictors, including statistical suppression. As such, regression
analyses seeking to understand how landscape resistance affects gene
flow should be univariate models, with the creation of a single
resistance surface being a necessary precursor to the regression
analysis. There are, however, important statistical advances underway
that explicitly model the covariance of allele frequencies or genetic
distances as functions of spatial landscape variables. The growth and
evolution of landscape genetics as a field has been rapid and exciting.
It is the goal of this opinion paper to highlight past missteps and to
ensure that future use of regression models will appropriately consider
the process being modeled, which will provide clarity to model
interpretation.