Genetic differentiation is determined by geographic distance inClarkia pulchella

Abstract

1Both environmental differences and geographic distances may contribute to the genetic differentiation of 2 populations on the landscape. Understanding the relative importance of these drivers is of particular inter-3 est in the context of geographic range limits, as both swamping gene flow and lack of genetic diversity are 4 hypothesized causes of range limits. We investigated the landscape genetic structure of 32 populations of the 5 annual wildflower Clarkia pulchella from across the species' geographic range in the interior Pacific North-6 west. We tested whether climatic differences between populations influenced the magnitude of their genetic 7 differentiation. We also investigated patterns of population structure and geographic gradients in genetic 8 diversity. Contrary to our expectations, we found an increase in genetic diversity near the species' northern 9 range edge. We found no notable contribution of climatic differences to genetic differentiation, indicating 10 that any processes that might operate to differentiate populations based on temperature or precipitation 11 are not affecting the putatively neutral loci in these analyses. Rather, these results support seed and pollen 12 movement at limited distances relative to the species' range and that this movement and the subsequent 13 incorporation of immigrants into the local gene pool are not influenced by temperature or precipitation 14 similarities among populations. We found that populations in the northern and southern parts of the range 15 tended to belong to distinct genetic groups and that central and eastern populations were admixed between 16 these two groups. This pattern could be the result of a past or current geographic barrier associated with 17 the Columbia Plateau, or it could be the result of spread from separate sets of refugia after the last glacial 18 maximum. 19

Gene flow improves fitness at a range edge under climate change

“…Inter‐annual climate variability was very similar in each of the seed collection sites (data not shown), so we do not further consider variability in climate, and focus on averages only. Pairwise population genetic differentiation (F ST ) was calculated from 2982 SNPs that were genotyped in up to 12 parental individuals from each population (genotyping and alignment methods are described in Bontrager and Angert ). F ST was calculated using the implementation of Weir and Cockerham () in the R package hierfstat (Goudet and Jombart ).…”

Implications of genetic heterogeneity for plant translocation during ecological restoration

“…However, to date, no published study has documented this in plant species. Several studies have found significant effects of topographic barriers on genetic differentiation in plant species, including seas (Jaros et al., 2017), lakes and terrain (Ju et al., 2018), rivers (Geng et al., 2015), mountains (Reeves & Richards, 2014; Zhu et al., 2017), and basins (Bontrager & Angert, 2018). Our data agree with these studies and indicate that populations from opposite sides of the Continental Divide are genetically more isolated, despite spatial proximity (Figure 3).…”

Implications of genetic heterogeneity for plant translocation during ecological restoration

“…However, to date, no published study has documented this in plant species. Many studies have found significant effects of geographic barriers on genetic differentiation in plant species, including: seas (Jaros et al, 2017), lakes and terrain (Ju et al, 2018), rivers (Geng et al, 2015), mountains (Zhu et al, 2017; Reeves and Richards, 2014), and basins (Bontrager and Angert, 2018). Our data agree with these studies and indicate that populations from opposite sides of the Continental Divide are genetically isolated, despite what may appear to be close geographic proximity (Fig.…”