Data from: The influence of contemporary and historic landscape features on the genetic structure of the sand dune endemic, Cirsium pitcheri (Asteraceae)

Narrow endemics are at risk from climate change due to their restricted
habitat preferences, lower colonization ability and dispersal distances.
Landscape genetics combines new tools and analyses that allow us to test
how both past and present landscape features have facilitated or hindered
previous range expansion and local migration patterns, and thereby
identifying potential limitations to future range shifts. We have compared
current and historic habitat corridors in Cirsium pitcheri, an endemic of
the linear dune ecosystem of the Great Lakes, to determine the relative
contributions of contemporary migration and post-glacial range expansion
on genetic structure. We used seven microsatellite loci to characterize
the genetic structure for 24 populations of Cirsium pitcheri, spanning the
center to periphery of the range. We tested genetic distance against
different measures of geographic distance and landscape permeability,
based on contemporary and historic landscape features. We found moderate
genetic structure (ave Fst =0.14), and a north -south pattern to the
distribution of genetic diversity and inbreeding, with northern
populations having the highest diversity and lowest levels of inbreeding.
High allelic diversity, small average pairwise distances and mixed genetic
clusters identified in Structure suggest populations in the center of the
range represent the point of entry to the Lake Michigan and a refugia of
diversity for this species. A strong association between genetic distances
and lake level changes suggests that historic lake fluctuations best
explain the broad geographic patterns, and sandy habitat best explain
local patterns or movement.