Data from: Evidence of local adaptation to fine- and coarse-grained environmental variability in Poa alpina in the Swiss Alps

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.