Abstract Detail

Population Genetics/Genomics

Massatti, Rob [1], Knowles, Lacey [2].

The fate of neutral and adaptive variation: interdependencies across a topographically and environmentally complex, climatically dynamic region.

Although genome-wide versus locus-specific patterns of genetic variation often fall under the separate purviews of phylogeographic versus selective studies, respectively, the fate of neutral and adaptive variation is not necessarily determined by independent processes. In fact, such strict focus on studying the evolutionary trajectories of neutral versus adaptive variation can obscure their interdependencies and thereby have important ramifications for understanding a diversity of phenomena. For species with dynamic histories, genetic variation (for the most part) does not reflect in situ accumulation of differences (e.g., during any particular glacial or interglacial period), but rather the sorting of pre-existing or standing genetic variation accumulated over longer periods of time. Under these circumstances, the joint consideration of phylogeographic history and adaptive evolution is critical for correctly interpreting patterns of genetic variation. We apply a framework accounting for these factors to Hilaria jamesii (Torr.) Benth. (Poaceae), a common grass restricted to arid landscapes in the southwestern United States. As a C4 species and given that the climate of this region was heavily impacted by the cycling of glacial and interglacial periods during the Pleistocene, it is unlikely that H. jamesii persisted across large portions of its current distribution. Furthermore, given the physiography and glacial climate of the region, it is likely that this grass persisted in a southerly refugium, where it may have experienced climate variability unlike what it is currently distributed across. To test for adaptive genetic responses and their correlation to post-glacial neutral processes in this system, we apply multivariate environmental association analyses and coalescent simulations detailing alternative historical scenarios. Our study suggests an interdependency among the biogeographic and demographic processes that determine the rate of genetic drift and the variation in the strength of selection, thereby affecting the fate of neutral and adaptive variation. We discuss these results in light of comparative phylogeography, restoration of arid communities across the southwest, and the evolutionary impact of adaptive variation.

1 - U.S. Geological Survey, Southwest Biological Science Center, 2255 N. Gemini Dr., Flagstaff, AZ, 86001, USA
2 - University of Michigan, Ecology & Evolutionary Biology, 1105 North University Avenue, Ann Arbor, MI, 48109, USA

Keywords:
phylogeography
genotype-environment association analysis
Colorado Plateau
adaptive genetic variation
Hilaria jamesii.

Presentation Type: Oral Paper
Session: POPGEN1, Population Genetics/Genomics I
Location: Tucson H/Starr Pass
Date: Monday, July 29th, 2019
Time: 9:00 AM
Number: POPGEN1005
Abstract ID:858
Candidate for Awards:Margaret Menzel Award