Steinecke, C. | bioRxiv Science

bioRxiv2025

Life-history evolution under artificial selection in a clonal plant

The response of natural populations to selection and the role of genetic correlations in constraining or facilitating evolutionary change is fundamental to adaptation. We use artificial selection to investigate the evolutionary response of clonal reproduction in the common monkeyflower (Mimulus guttatus), a species with extensive life history variation. We first characterize the standing genetic variation in a single perennial population, and then conduct four generations of divergent artificial selection on stolon number--the mechanism of clonal reproduction in this species. To start, stolon number had moderate heritability (H{superscript 2}=0.25) and was negatively genetically correlated with reproductive traits. Artificial selection produced a clear but asymmetrical response. High selection lines made significantly more stolons, while low lines diverged less from controls. Analyses of G matrices revealed that selection not only changed trait means but also genetic correlations, with high lines diverging more in multivariate genetic architecture. Our results demonstrate that single populations harbor sufficient genetic variation to respond rapidly to selection on clonality, and the response is shaped by existing patterns of genetic covariation. The capacity for rapid evolution of clonal traits is particularly relevant as climate change alters selection and shifts the relative advantages of sexual versus clonal life-history strategies.

evolutionary biology↗

bioRxiv2025

Variation in response to water availability across Phlox species

Plants adapt to environmental variation both by evolving divergent trait means and by plastically adjusting trait expression in response to local conditions. While these dual strategies are essential for persistence in diverse environments, how they interact and vary across closely related species is understudied. For plants, water availability is a particularly important selective force that shapes species distributions, selects for growth habit and life history strategy, and can dictate individuals plastic expressions of trait values and reproductive success. Here, we use ecological niche modeling, field soil collections, and a controlled drought experiment to test how biogeography and evolutionary history influence responses to limited water availability in three closely related Texas annual Phlox species and their F1 hybrids. We infer that the species occupy distinct niches that diverge along a primary axis of water availably and soil moisture. Each species has a distinct vegetative growth habit that does not match broad predictions of divergence in response to water availability. Nevertheless, we find that all the species show a significant morphological response to controlled soil dry down with reduced biomass, smaller leaves, and fewer flowers, as would be predicted in a response to drought. We find that Phlox drummondii, which occupies intermediate habitats, exhibits the strongest plastic response to water limitation, despite it not having the broadest environmental niche. Additionally, most hybrids involving P. drummondii display intermediate phenotypes in both wet and dry treatments, while hybrids between P. cuspidata and P. roemeriana show phenotypes consistent with hybrid vigor. These results challenge the hypothesis that species from broader environments evolve greater plasticity. Instead, the most plastic species did not have the broadest niche, suggesting plasticity and niche breadth may evolve independently.

evolutionary biology↗