Testing which axes of species differentiation underlie covariance of phylogeographic similarity among montane sedge species

Co-distributed species may exhibit similar phylogeographic patterns due to
shared environmental factors or discordant patterns attributed to the
influence of species-specific traits. Although either concordant or
discordant patterns could occur due to chance, stark differences in key
traits (e.g., dispersal ability) may readily explain differences between
species. Multiple species’ attributes may affect genetic patterns, and it
is difficult to isolate the contribution of each. Here we compare the
relative importance of two attributes, range size and niche breadth, in
shaping the spatial structure of genetic variation in four sedge species
(genus Carex) from the Rocky Mountains. Within two pairs of co-distributed
species, one species exhibits narrow niche breadth, while the other
species has broad niche breadth. Furthermore, one pair of co-distributed
species has a large geographical distribution, while the other has a small
distribution. The four species represent a natural experiment to tease
apart how these attributes (i.e., range size and niche breadth) affect
phylogeographic patterns. Investigations of genetic variation and
structure revealed that range size, but not niche breadth, is related to
spatial genetic covariation across species of montane sedges. Our study
highlights how isolating key attributes across multiple species can inform
their impact on processes driving intraspecific differentiation.