Microgeographic Patterns of Genetic Divergence and Adaptation across Environmental Gradients in Boechera stricta (Brassicaceae)

Abstract

Abiotic and biotic conditions often vary continuously across the landscape, imposing divergent selection on local populations. We used a provenance trial approach to examine microgeographic variation in local adaptation in Boechera stricta (Brassicaceae), a perennial forb native to the Rocky Mountains. In montane ecosystems, environmental conditions change considerably over short spatial scales, such that neighboring populations can be subject to different selective pressures. Using accessions from southern (Colorado) and northern (Idaho) populations, we characterized spatial variation in genetic similarity via microsatellite markers. We then transplanted genotypes from multiple local populations into common gardens in both regions. Continuous variation in local adaptation emerged for several components of fitness. In Idaho, genotypes from warmer environments (low elevation or south facing sites) were poorly adapted to the north-facing garden. In high and low elevation Colorado gardens, susceptibility to insect herbivory increased with source elevation. In the high elevation Colorado garden, germination success peaked for genotypes that evolved at similar elevations as the garden, and declined for genotypes from higher and lower elevations. We also found evidence for local maladaptation in survival and fecundity components of fitness in the low elevation Colorado garden. This approach is a necessary first step in predicting how global change could affect evolutionary dynamics.

Plasticity contributes to a fine‐scale depth gradient in sticklebacks’ visual system

“…Although typically we find negligible shifts in water temperature over the vertical depth range examined in this study (D. I. Bolnick, unpublished data), the thermocline in Gosling Lake occurs much deeper than the range of nest depths surveyed here. Regardless of the causal mechanism, phenotypic variation along small geographical scales may be more common than previously appreciated and may play an important role in maintaining genetic and phenotypic diversity (Anderson, Perera, Chowdhury, & Mitchell‐Olds, ; Langin et al., ; Richardson, Urban, Bolnick, & Skelly, ).…”

Phenological shifts of native and invasive species under climate change: insights from the Boechera–Lythrum model

“…This species is broadly distributed across climatic gradients from Utah to Alaska, at elevations from 700 to 3900 m [26,27]. Populations of B. stricta in Montana, Idaho and Colorado are locally adapted in contemporary landscapes [25,28,29], and genetically based elevational clines are present in a number of functional traits including flowering phenology and size at flowering [30]. When grown in a common garden, plants from higher altitudes flower earlier, at a smaller size and for a shorter duration than genotypes from lower elevations [30].…”

“…Song et al [32] documented high inbreeding levels in B. stricta, with an average F IS ¼ 0.89 [31]. Flowering phenology is also constrained by genetic trade-offs with other traits such as size at flowering [36] and resistance to insect herbivory (r G ¼ 20.74 + 0.15; p , 0.0001, N ¼ 24 maternal families, from data available in [28,30]). As in other systems [42], these genetic correlations could restrict adaptive responses to climate change.…”

“…Climate change is altering snowpack and snowmelt in two ways: (i) warming winter temperatures shift precipitation from snow to rain, reducing the total winter snow bank and (ii) warming spring temperatures melt the remaining snow earlier than in the historical records [38]. Increased evapotranspiration from warming in concert with declining snowpack significantly reduces water availability [28]. For example, snowmelt at the Rocky Mountain Biological Laboratory (RMBL; Gothic, Colorado, elevation: 2900 m) has been advancing by 7.4 days/ decade since 1991 [47], similar to other observed changes in the region [38,48,49].…”

Modern Approaches to Local Adaptation

“…In this issue, Jill Anderson, Nadeesha Perera, Bashira Chowdhury, and Thomas Mitchell-Olds apply the provenance trial approach to one of the best-studied examples of local adaptation, the forb Boechera stricta over elevational gradients in the Rocky Mountains (Anderson et al 2015). They nicely show the complexities of local adaptation, including how it can vary with respect to what biotic or abiotic environmental variable is being considered, how it can be strong in some localities and weak elsewhere, and how even local maladaptation can be possible in some circumstances.…”