**The AGA grants EECG Research Awards each year to graduate and post-doctoral researchers who are at a critical point in their research, where additional funds would allow them to conclude their research project and prepare it for publication. EECG awardees also get the opportunity to hone their science communication and write three posts over their grant tenure for the AGA Blog. In the first in the series, our EECG awardees write about their research and their interests as an ’embarkation’.
About the Author: Sasha Bishop is a PhD student at the University of Michigan in Ecology and Evolutionary Biology (EEB). Sasha works in Dr. Regina Baucom’s lab studying evolutionary responses to climate change in the common morning glory Ipomoea purpurea.
Current climate change projections predict the possible extinction of half the world’s species by 2100 if humans continue on the current trajectory of carbon emissions (Warren et al. 2018).Even if emissions are reduced and we remain within the 2°C increase identified in the Paris Climate Accord, without mitigating interference, some biodiversity hotspots may still see extinction rates as high as 25% (Warren et al. 2018),prompting the UN to declare a Strategic Plan for Biodiversity as one of their top priorities.
The rapid environmental shifts caused by anthropogenic climate change act as powerful selective agents on populations of plants and animals, with possible responses being: geographic range shifts, development of in situ tolerance via either plasticity or adaptive evolution, and demographic collapse and extinction (Waldvogel et al. 2020). Predictive frameworks projecting future range shifts and changes in population dynamics have highlighted that rapid evolution in response to climate change may be more probable than previously thought (Senner et al. 2018). However, local declines and extinctions remain rampant, demonstrating a disconnect between current theoretical frameworks and empirical evidence. This indicates that these models are not yet based on adequate understanding of the complexity of mechanisms by which adaptation may occur or the evolutionary significance of these novel selective regimes.
Evolutionary response to climate change is complex in part because multiple features of the abiotic and biotic environment are modified simultaneously, sometimes in contrasting directions, leading to the potential decoupling of previously linked environmental cues (Hamann et al. 2021). Further complexity is added due to spatial heterogeneity in environmental changes, resulting in intraspecific variation in response (Senner et al. 2018). The result is that selection may act on suites of correlated phenotypic traits in opposing directions, and differentially across a species’ range. This introduces constraints on adaptive potential that can be investigated by knowing what phenotypic traits are responding to climate change, how they exist in combination within and between populations, and the underlying genetic architecture of these traits.
The common morning glory, Ipomoea purpurea isa widespread, weedy species frequently found to flourish in disturbed habitats such as along roadsides or in agricultural settings (Fang et al. 2013). The species is predominantly outcrossing, meaning it relies primarily on generalist insect pollinators (Fang et al. 2013).Together, these features make I. purpureaan idealsystem in which to isolate the effect of climate change from other human-mediated influences. Its large range allows for the study of spatial variability in response, and its reliance on pollinators allows for assessing both abiotic agents of selection due to climatic changes as well as biotic agents of selection and possible eco-evolutionary feedbacks due to disruptions in the plant-pollinator dynamic.
In ongoing greenhouse and field-based common garden experiments, I am using populations spanning a spatial gradient from southern South Carolina to northern Tennessee and collected at three time points from 2003 to 2016 to test for phenotypic evolution, fitness levels associated with phenotypes, and spatial variability in these evolutionary patterns. The phenotypes measured are all directly involved in plant-pollinator interactions and have shown experimental evidence of being impacted by climatic changes.
This EECG grant will be used to complement this field experiment by performing whole genome re-sequencing of plants from these same populations to identify candidate loci involved in climate change adaptation and to assess signatures of selection across space. Simulation-based studies of climate change adaptation have highlighted that the genetic architecture of traits under selection impacts adaptive potential, yet the genomic regions involved remain largely unknown.
Information generated through this work describing spatial variability at the genome level and identifying a set of potentially adaptive loci aims to provide critical information regarding the mechanism of adaptation and sets this system up to serve as a model for ecological genomics, particularly in the context of continued investigation of the impact of ongoing anthropogenic climate change.
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