Cole, Logan W. , Chang, Tien-Hao , Lindqvist, Charlotte .
Phylogenetic analyses of low-copy nuclear loci show reticulate evolutionary patterns among Hawaiian endemic labiates and New World Stachys relatives (Lamiaceae).
The Hawaiian native labiates (Lamioideae, Lamiaceae) represent one of the largest plant diversifications in the Hawaiian archipelago, exhibiting great variation in floral, fruit, and ecological features. Prior studies have demonstrated that this Hawaiian radiation originated from American members of the genus Stachys, a large and near-cosmopolitan group of labiates commonly known as hedge nettles. Significant evidence has pointed to a hybrid origin, involving different polyploid lineages of Stachys, and possibly explaining the extent to which morphological diversification has occurred in this group. To further investigate the origin of the Hawaiian lineage within New World Stachys, which themselves appear to have undergone rapid diversification, phylogenetic analyses of low-copy loci such as a putative homolog of the axial regulator AFO (ABNORMAL FLORAL ORGANS), a member of a small transcription factor family, and a segment of waxy, also known as granule-bound starch synthase, have been employed. These analyses suggest a weak phylogenetic hierarchy among New World Stachys and the Hawaiian species, as well as extensive reticulation within this lineage. The results are indicative of multiple reductions in molecular diversity across the evolutionary history of New World Stachys and the Hawaiian group. In analyses with both of these loci, the Hawaiian species are polyphyletic, with some members grouping with temperate North American Stachys and others grouping with other North and South American Stachys. Evolutionary relationships between taxa, although poorly resolved, convey a pattern that is best explained through two colonizations of North America by Old World Stachys and a hybridization event between members of Stachys, followed by a single colonization of the Hawaiian Islands. Together with information from prior studies, which have established the monophyly of the Hawaiian lineage, these results suggest the occurrence of trans-specific polymorphisms in both loci among the Hawaiian taxa that may have been the result of hybridization.
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1 - University at Buffalo, Biological Sciences, 109 Cooke Hall, Buffalo, NY, 14260, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Delaware C/Hyatt
Date: Wednesday, July 11th, 2012
Time: 10:15 AM