Project Outcomes Report - NSF Award# 1442486

Project Title: Collaborative Research: Blending Ecology and Evolution using Emerging Technologies to Determine Species Distributions with a Non-native Pathogen in a Changing Climate

Recipient Organization: Virginia Commonwealth University

Project/Grant Period: 03/15/2015 - 02/29/2020

PI: Andrew J. Eckert

Work conducted at Virginia Commonwealth University (VCU) was part of a larger collaborative project striving to understand the role of hybridization between southwestern white pine (Pinus strobiformis) and its closely related sister species, limber pine (P. flexilis), in driving genetic adaptation to abiotic and biotic environments. Southwestern white pine is an important ecological component of the montane conifer forests distributed across the sky island ecosystems of the desert southwest of North America and is currently threatened by range expansion of a non-native fungal pathogen, white pine blister rust (Cronartium ribicola). We generated tens of thousands of genetic markers distributed throughout the large and repetitive genomes of our focal species. When combined with the dense sampling of natural populations gathered by collaborators at Northern Arizona University, novel environmental data from our collaborators at Oregon State University, and spatial models of suitable habitat provided by our collaborators at the USDA Forest Service, we were able to show that hybridization is prevalent along a north-to-south latitudinal gradient between these species and that novel combinations of genetic variants created by hybridization fueled patterns of local adaptation to climate in the hybrid zone. In fact, much of the geographical range that is taxonomically labeled as southwestern white pine in the United States is actually part of a hybrid zone between southwestern white pine and limber pine. More specifically, adaptation to cold temperatures in the hybrid zone was fueled by variants from limber pine, while adaptation to drought conditions was fueled by genetic variants from southwestern white pine. Hybrids between these species thus contained novel combinations of genetic variants affected by natural selection in each species, but that were not found together in either pure species. 

In general, work at VCU provided novel data and knowledge about the ecology and evolution of southwestern white pine. We provided a detailed description of the hybrid zone using tens of thousands of genetic markers genotyped for thousands of sampled trees collected from hundreds of geographical locations. We characterized how diversity at these tens of thousands of genetic markers is structured across natural populations and how evolutionary forces such as natural selection have affected allele frequencies at these markers. We also catalogued hundreds of genetic markers at which hybridization and natural selection have interacted to create patterns consistent with local adaptation. More broadly, the data generated at VCU form the basis of further efforts to link genotypes with ecologically relevant phenotypes, including genetic resistance to white pine blister rust, drought tolerance, survival, and gene expression patterns in needles. All of these data and efforts will ultimately result in better management and gene conservation efforts for southwestern white pine.

Work at VCU was published in diverse, peer-reviewed scientific journals, presented at national and international scientific conferences, and contributed to the training of two postdoctoral scholars, one doctoral student, and 16 undergraduate students. The vast majority of early career scientists receiving training as part of this project used these research experiences to further their career aspirations in academia and private industry. For example, trainees from this project were accepted into doctoral programs and medical schools, moved onto postdoctoral scholar positions at prestigious universities, found employment in private industry, and accepted positions in academia as assistant professors. Most importantly, all trainees gained useful and marketable skills in population genetics, computational biology, genomics, and bioinformatics, while also generating new scientific knowledge about an emblematic tree species of the desert southwest sky islands.

Last Modified: 11/04/2020
Modified by: Andrew Eckert