Roy, Tilottama , Lindqvist, Charlotte .
Origin and diversification of the Hawaiian labiates (Lamiaceae).
Recently diverged and actively evolving groups, where a low degree of genetic divergence can contrast with high degrees of morphological and ecological diversification, pose challenges in discerning origins and evolutionary relationships. Morphologically distinct island radiations derived from continental ancestors may serve as models to study rapid diversification and consequences of polyploidy and hybridization. The Hawaiian labiates (Lamioideae, Lamiaceae) represent one of the largest plant lineages endemic to the archipelago, with about 60 recognized species in three genera. My study is aimed at investigating the diversification within this lineage and its complex origin within the Stachydeae, a largely heterogeneous tribe composed of more than 11 genera, including the polyphyletic and subcosmopolitan genus Stachys. The main hypothesis tested in this study is that the Hawaiian taxa may have diversified from initial hybridizations among North American Stachys. Sequencing and phylogenetic analyses were conducted on two non-coding nuclear ribosomal DNA loci, External Transcribed Spacer (ETS) and 5S-Non Transcribed Spacer (5S-NTS), as well as two non-coding chloroplast loci (cpDNA), rpS16 intron and the trnL-trnF region. Results from cpDNA loci show the Hawaiian labiates to be closely related to a largely Southwestern US/Mesoamerican Stachys lineage. However, based on 5S-NTS and ETS sequences, the Hawaiian lineage appears most closely related to temperate North American Stachys. Although this incongruence between nuclear and organellar DNA data may point towards incomplete lineage sorting, it is consistent with our hypothesis of a hybrid ancestry for the Hawaiian taxa. To investigate this further and to more reliably distinguish hybrid speciation from population genetic processes and lineage sorting, current studies include DNA sequencing and analyses of multiple single/low-copy nuclear loci. Future directions include investigation of nuclear and chloroplast single nucleotide polymorphisms (SNPs) to look at relationships within the Hawaiian mint taxa. A study into the evolutionary patterns of these native labiates may further help in our understanding of species diversification within Hawaii, as well as other similar island endemic biota. This may eventually aid in designing strategies that could help save island flora and fauna, which are often highly endangered.
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1 - The State University of New York at Buffalo, Biological Sciences, 109 Cooke Hall, Buffalo, NY, 14260, USA
2 - University At Buffalo (SUNY), 109 Cooke Hall, Buffalo, NY, 14260, USA
North American Stachys
External Transcribed Spacer (ETS)
5S Non‐Transcribed Spacer (5S‐NTS)
incomplete lineage sorting
low copy nuclear loci
Presentation Type: Oral Paper:Papers for Sections
Location: Delaware C/Hyatt
Date: Wednesday, July 11th, 2012
Time: 9:30 AM