Data from: Fragmented and isolated: limited gene flow coupled with weak isolation by environment in the paleoendemic giant sequoia (Sequoiadendron giganteum)

PREMISE: Patterns of genetic structure across a species’ range
reflect the long-term interplay between genetic drift, gene flow, and
selection. Given the importance of gene flow in preventing the loss of
diversity through genetic drift among spatially isolated populations,
understanding the dynamics of gene flow and the factors that influence
connectivity across a species’ range is a major goal for conservation of
genetic diversity. Here we present a detailed look at gene flow
dynamics of Sequoiadendron giganteum, a paleoendemic tree species
that will likely face numerous threats due to climate change.
METHODS: We used microsatellite markers to examine nineteen
populations of S. giganteum for patterns of genetic
structure and to estimate admixture and rates of gene flow between eight
population pairs. Also, we used Generalized Dissimilarity Models to
elucidate landscape factors that shape genetic differentiation among
populations.  RESULTS: We found minimal gene flow
between adjacent groves in the northern disjunct range. In most of the
southern portion of the range, groves showed a signal of connectivity
which degrades to isolation in the extreme south. Geographic distance was
the most important predictor of genetic dissimilarity across the range,
with environmental conditions related to precipitation and temperature
explaining a small, but significant, portion of the genetic variance.
CONCLUSIONS: Due to their isolation and unique genetic
composition, northern populations
of S. giganteum should be considered a high
conservation priority. In this region, we suggest germplasm
conservation as well as restoration planting to enhance genetic
diversity.