Collaborative Research: EDGE CMT: Linking genomic variation to complex floral trait adaptation across a species boundary

A fundamental challenge in biology is to understand how DNA differences between individuals determine trait differences, particularly those trait differences that define species. Traditionally, researchers have focused on striking differences that distinguish one species from another. They have then worked to discover the underlying genetic variation explaining those trait differences.

This focus on individual traits considered in isolation has limited our understanding of how changes across the entire genome promote the formation and maintenance of new species with complex trait differences. This project takes a novel approach by leveraging advanced genomic technologies to first identify the precise DNA differences that distinguish focal species of flowering plants from one another, and second to validate the trait differences that result from those DNA-level differences.

The species-distinguishing traits in this system are complex and highly integrated differences between flowers that lead to bee pollination in some species and hummingbird pollination in another. In-line with the goals of NSF EDGE-CMT, outcomes from this project will improve our understanding of how trait complexity first arises and is subsequently maintained between species.

It will further provide a methodological approach for biologists to link variation found between genomes to complex trait differences across the tree of life. This project will strengthen our scientific workforce by providing students and postdoctoral researchers from diverse backgrounds training in the application of genomic and quantitative methods.

Such training can be leveraged across research enterprises, from basic science to novel discoveries in health and agriculture.

The proposed research will use recently developed genetic and genomic resources to dissect the genome to phenome relationship between bee- and hummingbird-adapted floral syndromes that define species in a Penstemon complex. A set of approximately twenty genomic regions, previously shown to be strongly diagnostic of floral syndrome and species identity, will be confirmed using genome-wide association mapping.

Based on preliminary data, these regions are expected to be physically unlinked, scattered genome-wide, and sufficiently narrow to include only 1-2 genes each. These narrow, divergent genomic regions result from natural selection favoring alternative floral trait combinations promoting bee- versus hummingbird-pollination in the face of gene flow and ample recombination.

Using population genomic, transcriptomic and gene functional prediction methods, these loci will be genetically dissected to discover the history of complex trait assembly, the contribution of mutational types to adaptive evolution, and the broader set of adaptive traits that form canonical pollination syndrome phenotypes. The unique genomic architecture in this system provides a novel opportunity for the researchers to dissect the contributions of regulatory versus protein coding mutations to adaptive evolution, determine how selection acts to maintain multi-locus species differences in the face of gene flow, and to test fundamental questions of complex trait evolution.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.