Considerable genetic diversity and structure despite narrow endemism and limited ecological specialization in the Hayden's ringlet, Coenonympha haydenii

Understanding the processes that underlie the development of population
genetic structure is central to the study of evolution. Patterns of
genetic structure can reveal signatures of isolation by distance, barriers
to gene flow, or even the genesis of speciation. However, it is unclear
how severe range restriction might impact the processes that dominate the
development of genetic structure. In narrow endemic species, is population
structure likely to be adaptive in nature, or rather the result of genetic
drift? In this study, we investigated patterns of genetic diversity and
structure in the narrow endemic Hayden's ringlet butterfly.
Specifically, we asked to what degree genetic structure in the
Hayden's ringlet can be explained by isolation by distance, isolation
by resistance (in the form of geographic or ecological barriers to
migration between populations), and isolation by environment (in the form
of differences in host plant availability and preference). We employed a
genotyping-by-sequencing (GBS) approach coupled with host preference
assays, Bayesian modeling, and population genomic analyses to answer these
questions. Our results suggest that despite their restricted range, levels
of genetic diversity in the Hayden's ringlet are comparable to those
seen in more widespread butterfly species. Hayden's ringlets showed a
strong preference for feeding on grasses relative to sedges, but neither
larval preference nor potential host availability at sampling sites
correlated with genetic structure. We conclude that geography, in the form
of isolation by resistance and simple isolation by distance, was the major
driver of contemporary patterns of differentiation in this narrow endemic
species.