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Parallel evolution of phenological isolation across the speciation continuum in serpentine-adapted annual wildflowers

Citation

Sianta, Shelley; Kay, Kathleen (2021), Parallel evolution of phenological isolation across the speciation continuum in serpentine-adapted annual wildflowers, Dryad, Dataset, https://doi.org/10.7291/D1RT0Q

Abstract

Understanding the relative importance of reproductive isolating mechanisms across the speciation continuum remains an outstanding challenge in evolutionary biology. Here we examine a common isolating mechanism, reproductive phenology, between plant sister taxa at different stages of adaptive divergence to gain insight into its relative importance during speciation. We study 17 plant taxa that have independently adapted to inhospitable serpentine soils, and contrast each with a nonserpentine sister taxon to form pairs at either ecotypic or species-level divergence. We use greenhouse-based reciprocal transplants in field soils to quantify how often flowering time (FT) shifts accompany serpentine adaptation, when FT shifts evolve during speciation, and the genetic versus plastic basis of these shifts. We find that genetically-based shifts in FT in serpentine-adapted taxa are pervasive regardless of the stage of divergence. Although plasticity increases FT shifts in 5 of the pairs, the degree of plasticity does not differ when comparing ecotypic versus species-level divergence. FT shifts generally led to significant, but incomplete, reproductive isolation that did not vary in strength by stage of divergence. Our work shows that adaptation to a novel habitat may predictably drive phenological isolation early in the speciation process. 

Usage Notes

All data manipulation and analyses are described and executed in the R script. Please refer to the README for details.

Funding

National Science Foundation, Award: NSF-DGE-1339067

Society for the Study of Evolution, Award: Rosemary Grant Award

California Native Plant Society, Award: Howard-Kohn Memorial Scholarship

University of California, Santa Cruz, Award: Summer Research Fellowship:Department of Ecology and Evolutionary Biology

Naperville, IL Garden Club, Award: Research Scholarship