Resurrection approach to understanding plant response to drought and pollinator loss
Department of Biological Sciences, University of Pittsburgh
Dr. Tia-Lynn Ashman – Distinguished Professor, Department of Biological Sciences, University of Pittsburgh
Climate driven disruptions are now recognized as causing some of the strongest selection wild populations have ever been exposed. Multiple populations are simultaneously being subjected to similar environmental changes leading to unprecedented rapid, and potentially parallel, evolution. Consequently, not only have edaphic features of habitats been altered but key interactions between species have been disrupted, leading to changes in phenological, morphological and physiological traits of both plants and animals. While parallel responses to climate or land use change are expected and some observed (e.g. earlier flowering times), the question remains whether there is a single shared evolutionary trajectory or variable evolutionary responses across populations. Furthermore, it is not known whether parallel responses represent pan-adaptation, whether divergent responses represent alternative adaptive optima or idiosyncratic site-specificity. And finally, it remains to be seen whether adaptive evolution is rapid enough to rescue populations from decline, and eventual extinction.
Resurrection experiments are a powerful approach to directly address these knowledge gaps. Here descendant and ancestor populations are grown under common (ancestral or contemporary) environmental conditions and phenotype (and fitness) are compared. The fundamental prediction is that similar environmental change leads to similar phenotypic change, however, few resurrection experiments have been performed to date, and most do not have sufficient replication to rigorously address questions of parallelism. Because of the foresight of the Project Baseline– a living genome bank of wild plant seeds- however, we are now in a unique position to rigorously address both the question of repeatability of evolution in response to anthropogenic change and the likelihood of evolutionary rescue.
The present work uses a resurrection approach to address the following questions in a model plant (Mimu/us gutta/us) native to a region experiencing a climate induced Mega-drought and which has been exposed dramatic declines in pollinators over the last decade:
1) 1. Is there a universal evolutionary/plastic phenotypic response to declining pollinators and increased temperature/drought? A) In floral phenotype B) In functional pollination niche or mode?
2. Is there heterogeneity in response, in magnitude or direction? Is magnitude dependent population ancestral traits? Is direction related to current pollinator fauna or historical variation in climate?
In 2021/2022 ‘descendent’ seed from Mimu/us guttatus (=Erythranthe gutta/a) will be collected from the same locations (or closely adjacent) that the Project Baseline team collected ‘ancestral’ seed in 201415. I would aim to collect 3-5 fruits from 30-50 plants in each of the populations if possible.
Both sets of seeds will be involved in a ‘resurrection study’ that I will conduct to evaluate the evolutionary and ecological changes in the plants over the last 6 years in response to regional drought and pollinator declines. I will use a standard resurrection approach of first planting both generations in the greenhouse for a refresher generation, and then comparing traits and ecological interactions of the second generation ancestors and descendants in the greenhouse and common gardens. Additional seeds will be deposited with Project baseline to replenish their stocks.
This project is ongoing until at least 2024, and possibly until 2026.