Marlowe, K. , Hufford, Larry .
Evolution of Synthyris sect. Dissecta (Plantaginaceae) on Northern Rocky Mountain Sky Islands.
Migration opportunities for alpine plants in sky island landscapes are often limited by ecological and elevational barriers, although these have been hypothesized to shift temporally with climate change, including glaciations. Synthyris sect. Dissecta (Plantaginaceae) is restricted to sky islands of the Northern Rocky Mountains (NRM; S. dissecta and S. canbyi) and Olympic Mountains (S. lanuginosa). We used phylogeography to examine modes of speciation and range changes, including the origin of the NRM-Olympic Mountains disjunction. Sequences of cpDNA trnT-trnL and psbA-trnH intergenic spacers had 22 haplotypes among 302 individuals from 16 populations that encompassed the three species. Haplotype clades were not exclusive to species, which we infer to be a signature of widespread regional gene flow in the ancestral lineage of sect. Dissecta and subsequent random capture of haplotypes in species lineages. The initial speciation event, giving rise to S. lanuginosa in the Olympic Mountains and its sister clade in the NRM, was inferred from nested clade analysis (NCA) to result from allopatric fragmentation. Synthyris lanuginosa is characterized by unique haplotypes, potentially a consequence of long temporal isolation from its sister clade in the NRM, possibly due to Pleistocene glaciations that may have eradicated once continuous populations across Canada. Synthyris canbyi, which has a distribution north of but continuous with that of S. dissecta in northwestern Montana, is genetically depauperate. We infer that the origin of S. canbyi, with its low haplotype and nucleotide diversity, was associated with a northward range expansion followed by isolation from S. dissecta. The NCA indicated limited migration in S. dissecta with possible isolation by distance. Populations of this species appear to have been isolated not only on interglacial sky islands, but also during glaciations when valley glaciers prevented gene flow among populations in different NRM ranges.
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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: 1:30 PM