Plant & Animal Genomes XIV Conference Plant & Animal Genomes XIV ConferenceJanuary 14-18, 2006
Town & Country Convention Center
San Diego, CA
Population surveys of genetic variation at highly variable loci can be used to identify genomic regions that have recently undergone selective sweeps, and thus are likely to contain genes under selection in a particular environment. Here we report the results of an analysis of variation at 128 EST-based microsatellites in wild Helianthus annuus, using populations from the species' typical plains habitat in Kansas and Colorado, as well two xeric desert and two distinct brackish marsh areas in Utah. The test statistics lnRV and lnRH were used to find regions of the genome that were significantly less variable in one or more populations relative to the others. We identified 17 regions with evidence from both lnRV and lnRH for selection in one or more environment. Three distance-based measures provided additional evidence of selection for 15 of these 17 regions. These tests also confirmed that Fsts were significantly higher for most candidate loci, as expected under divergent selection. Overall, a small but detectable percentage (1.5 – 6%) of genes may be involved in adaptation to any particular environment in H. annuus. Spatially separated populations undergoing similar selective pressures evolved in concert at some loci, but show evidence of divergence at other loci. Transcription factors and known stress-induced genes were prevalent among the selected loci. Also, changes in cell wall structure or composition may be involved in adaptation to drought and salt stress.