Adaptive divergence generates distinct plastic responses in two closely related Senecio species

Abstract

The evolution of plastic responses to external cues allows species to maintain fitness in response to the environmental variations they regularly experience. However, it remains unclear how plasticity evolves during adaptation. To test whether distinct patterns of plasticity are associated with adaptive divergence, we quantified plasticity for two closely related but ecologically divergent Sicilian daisy species (Senecio, Asteraceae). We sampled 40 representative genotypes of each species from their native range on Mt. Etna and then reciprocally transplanted multiple clones of each genotype into four field sites along an elevational gradient that included the native elevational range of each species, and two intermediate elevations. At each elevation, we quantified survival and measured leaf traits that included investment (specific leaf area), morphology, chlorophyll fluorescence, pigment content, and gene expression. Traits and differentially expressed genes that changed with elevation in one species often showed little changes in the other species, or changed in the opposite direction. As evidence of adaptive divergence, both species performed better at their native site and better than the species from the other habitat. Adaptive divergence is, therefore, associated with the evolution of distinct plastic responses to environmental variation, despite these two species sharing a recent common ancestor.

Digest: Evolution of plasticity and its potential role in the decline of specialists

“…Although plasticity will be adaptive for environments where the plastic responses maintain high fitness, it may fail to be so in a novel or highly stochastic environment, which suggests that the relationship between adaptiveness and plasticity is variable and more complex than a simple linear relationship (Pfennig 2021). In this study, Walter et al (2022) confirmed that adaptive divergence can lead to differences in plasticity over a comparatively short timescale (∼150,000 years) and analyzed the adaptiveness of these changes in plasticity. Walter et al (2022) studied the evolution of phenotypic plasticity in two ecologically divergent but genetically similar Sicilian daisy species from Mt.…”

“…In this study, Walter et al (2022) confirmed that adaptive divergence can lead to differences in plasticity over a comparatively short timescale (∼150,000 years) and analyzed the adaptiveness of these changes in plasticity. Walter et al (2022) studied the evolution of phenotypic plasticity in two ecologically divergent but genetically similar Sicilian daisy species from Mt. Etna, Senecio chrysanthemifolius, native to disturbed habitats 400-1000 m above sea level, and Senecio aethnensis, endemic to lava flows 2000-2600 m above sea level.…”

“…In this study, Walter et al. ( 2022 ) confirmed that adaptive divergence can lead to differences in plasticity over a comparatively short timescale (∼150,000 years) and analyzed the adaptiveness of these changes in plasticity.…”

“…These models often rely on assumptions about how plasticity and constraint themselves evolve many of which have yet to be experimentally validated (e.g., when organisms evolve convergent phenotypes, their respective phenotypic plasticities begin to resemble each other as well). By demonstrating that differences in plasticity can indeed evolve rapidly and that the adaptive quality of plastic responses can differ between closely related taxa, the work of Walter et al (2022) helps provide a valuable theoretical foundation for developing more accurate dynamic evolutionary modeling.…”

“…Walter et al. ( 2022 ) studied the evolution of phenotypic plasticity in two ecologically divergent but genetically similar Sicilian daisy species from Mt. Etna, Senecio chrysanthemifolius , native to disturbed habitats 400–1000 m above sea level, and Senecio aethnensis , endemic to lava flows 2000–2600 m above sea level.…”