While mid- and high-elevation species seem to adequately shift their reproductive phenology to track ongoing climate changes, high-elevation species were less capable of doing so and appeared more genetically constrained to their specific adaptations to an extreme environment (i.e. a short, cold growing season).
Summary
In the alpine landscape, characterized by high spatiotemporal heterogeneity and barriers, divergent selection is likely to lead to local adaptation of plant populations either through adaptive genetic differentiation or through phenotypic plasticity. The relative importance of these processes has rarely been investigated in relation to the spatial scale of environmental heterogeneity. In this study, we used reciprocal transplantation experiments of populations across nearby and distant field sites to shed light on these complementary processes.
We reciprocally transplanted populations of the widespread alpine grass, Poa alpina, within and across regions in the Swiss Alps. We inferred local adaptation at the metapopulation level by comparing fitness of plants transplanted to their site of origin and to nearby or distant novel sites. Additionally, we measured specific leaf area (SLA) and performed selection analyses to investigate directional selection on mean trait value at each field site and on the degree of plasticity of this trait to assess whether plastic responses were adaptive. In parallel, all populations were genotyped with microsatellite markers to assess neutral molecular differentiation.
Molecular differentiation was high among populations within and among regions, indicating restricted gene flow among P. alpina populations. Reproductive biomass was highest in individuals grown in their region of origin, revealing local adaptation to coarse‐grained environmental variability. Similarly, inflorescence height, associated with reproductive biomass, reflected adaptation to fine‐ and coarse‐grained environmental variability. Furthermore, we found evidence that plasticity in SLA across coarse‐grained habitats was correlated with plant fitness, suggesting that plasticity in this trait is adaptive.
Synthesis. Our results revealed adaptive genetic differentiation between P. alpina populations in the Swiss Alps reflecting local adaptation. Furthermore, high phenotypic plasticity in SLA contributed to the maintenance of fitness homoeostasis across habitats. Hence, adaptive genetic differentiation and phenotypic plasticity play a complementary role for adaption of P. alpina to environmental heterogeneity in the Swiss Alps and both may be critical to mitigate local extinction risk under rapid climate change.
• Premise of the study: New microsatellite primers were developed for the diploid herb Anthyllis vulneraria. These primers will be used in upcoming studies focusing on random genetic variation, local adaptation, and phenotypic plasticity in alpine plants.• Methods and Results: The new primers were adjusted to separate PCR amplicons (70 to 170 bp) on precast Spreadex gels using horizontal gel electrophoresis. No capillary sequencer was needed. Three to twelve alleles were found per locus depending on the population studied.• Conclusions: Our preliminary results showed that the three studied alpine populations are predominantly outcrossing, but include variable levels of self-fertilization.
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