Marlowe, K. , Hufford, Larry .
Geographic radiations and speciation in Synthyris (Plantaginaceae) of the Southern Rocky Mountains.
Topographical and ecological complexities in mountainous landscapes create evolutionary opportunities that are altered by climate changes, such as glacial-interglacial cycles, that affect population demography and gene flow. Synthyris sect. Besseya (Plantaginaceae) consists of Southern Rocky Mountain endemics: Synthyris alpina and S. oblongifolia in alpine tundra; S. ritteriana in subalpine/alpine meadows; and S. plantaginea in montane savannas and grasslands. We used phylogeography to infer speciation and migration patterns. Plastid DNA trnT-trnL and psbA-trnH intergenic spacer sequences for 334 individuals from 29 populations encompassing the four species had 34 haplotypes. Our nested clade analysis recovers genetic signatures of restricted gene flow with isolation by distance, which we infer as the likely process leading to an initial speciation event associated with elevation differentiation between early S. alpina-like and S. plantaginea-like lineages. The absence of shared haplotypes between S. alpina and S. plantaginea is consistent with a relatively deep divergence between these two species. Synthyris alpina populations are currently in high elevation, interglacial refugia, but we find evidence of past range expansion to the south and west with possible isolation by distance. Several haplotypes are geographically widespread in S. plantaginea, which has its greatest haplotypic diversity in the Colorado Front Range, pointing toward southward range expansion. We did not recover a signal of isolation by distance in S. plantaginea, from which we infer that gene flow was formerly extensive. Synthyris oblongifolia, which is nested in a paraphyletic S. plantaginea, is restricted to one mountain in southern New Mexico, where it appears to have evolved as a peripheral isolate following southward range expansion of S. plantaginea. Synthyris ritteriana had previously been hypothesized to be an allotetraploid derived from hybridization of S. alpina and S. plantaginea. Consistent with that hypothesis, we recovered haplotypes characteristic of both S. alpina and S. plantaginea in populations of S. ritteriana.
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1 - Washington State University, School of Biological Sciences, Po Box 644236, Pullman, Washington, 99164-4236, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Lake Michigan/Hilton
Date: Tuesday, July 10th, 2007
Time: 1:15 PM