Biology subjects

Branch, H. A.

Publications and source records attributed to Branch, H. A..

4 recordsLinked to original sources

bioRxiv2026

Divergence in wilt tolerance across the range of Mimulus guttatus in the absence of stomatal regulation

Whether phenotypes and environments predict performance under stress is central to ecology and evolution and can reveal species' vulnerability to global change. We sampled Mimulus guttatus range-wide to test whether reproductive, morphological, and physiological traits predict drought responses. Surprisingly, we find that stomatal response, a key mediator of water balance, did not change as drought intensified. Climate, however, predicted survival after turgor loss: plants from regions with large daily relative to seasonal temperature ranges survived wilting longer. Stress responses also depended on life history: where summers are dry, perennials withstood lower water potentials, whereas annuals increased leaf cooling as they wilted. Known trait associations were not fixed: although many baseline traits tracked climate, none predicted drought responses. Drought performance therefore cannot be inferred from traits measured under well-watered conditions. Lacking stomatal regulation, riparian drought escapers like M. guttatus may be vulnerable if shorter growing seasons bring drought before reproduction.

plant biology↗

bioRxiv2025

Transgenerational plasticity affects fitness and mediates local adaptation

Transgenerational plasticity (TGP) could be as decisive of a factor in phenotypic outcomes as allelic variation and within-generation plasticity. While TGP is often associated with priming offspring to stress in stable environments (where offspring and grandparents are likely to experience similar stresses), our results suggest that TGP is locally adaptive for offspring when grandparents are exposed to environments that match historical conditions, regardless of the offsprings environment. Specifically, we find that Mimulus cardinalis populations from historically wet environments exhibit adaptive TGP in grand-offspring, via increased male and female fitness, only when grandparents experience wet treatments, while TGP is maladaptive when these grandparents experience dry treatments. In contrast, populations from historically dry environments show the opposite. Furthermore, we find that TGP can have a greater effect on both male and female fitness than allelic differences and within-generation plasticity. Our results indicate an additional way that phenotypes arise through local adaption and sheds light on the potential for how rapid evolution might occur.

evolutionary biology↗

bioRxiv2023

Phenotypic lags influence rapid evolution throughout a drought cycle

Climate anomalies pose strong selection which can lead to rapid evolution. These global mean trends occur on a backdrop of interannual variability that might weaken or even reverse selection. However, the impact of climatic interannual variability on rapid evolution is rarely considered. We study evolution through a seven-year period encompassing a severe drought across 12 populations of Mimulus cardinalis (scarlet monkeyflower). Plants were grown in a common greenhouse environment under wet and dry treatments, where specific leaf area and date of flowering were measured. We compare the ability of different climate metrics to explain the rapid evolution of trait values, examining different time-periods, including the collection year, prior years, and cumulative metrics across sequential years. We find that anomalies in mean annual precipitation best describe rapid evolution over our study period. Past climates, of one-to two-years ago, are often related to trait values in a conflicting direction to collection-year climate. Uncovering these complex climatic impacts on evolution is critical to better predict and interpret the impacts of climate change.

evolutionary biology↗

bioRxiv2020

Expansion dynamics and marginal climates drive adaptation across geographic ranges

Every species experiences limits to its geographic distribution. Some evolutionary models predict that populations at range edges are less well-adapted to their local environments due to drift, expansion load, or swamping gene flow from the range interior. Alternatively, populations near range edges might be uniquely adapted to marginal environments. In this study, we use a database of transplant studies that quantify performance at broad geographic scales to test how local adaptation, site quality, and population quality change from spatial and climatic range centers towards edges. We find that populations from poleward edges perform relatively poorly, both on average across all sites (15% lower population quality) and when compared to other populations at home (31% relative fitness disadvantage), consistent with these populations harboring high genetic load. Populations from equatorial edges also perform poorly on average (18% lower population quality) but, in contrast, outperform foreign populations (16% relative fitness advantage), suggesting that populations from equatorial edges have strongly adapted to unique environments. Finally, we find that populations from sites that are thermally extreme relative to the species niche demonstrate strong local adaptation, regardless of their geographic position. Our findings indicate that both nonadaptive processes and adaptive evolution contribute to variation in adaptation across species ranges.

evolutionary biology↗