Havran, J. Christopher , Sytsma, Kenneth J. , Ballard, H. E. .
Evolutionary relationships, interisland biogeography, and molecular evolution in the Hawaiian violets (Viola: Violaceae).
The Hawaiian violets represent a monophyletic lineage of nine taxa currently distributed on six islands of the Hawaiian archipelago. To describe the evolutionary relationships, biogeography, and molecular evolution rates of the Hawaiian violets we conducted a phylogenetic study using nuclear rDNA internal transcribed spacer (ITS) sequences from specimens of each Hawaiian violet species and each island. Bayes Multistate and ACCTRAN analyses were used to elucidate the origins of lineage on the archipelago and their subsequent biogeographic patterns. Tajima tests were used to estimate relative rates of molecular evolution between sister species pairs. Maximum likelihood and parsimony suggest that Viola robusta, formerly classified as a sister species of V. chamissoniana is instead sister to V. maviensis on Moloka'i. ACCTRAN reconstruction suggests an equivocal origin on Kaua'i or Maui Nui while Bayes Multistate analyses provide strong support for an origin of the lineage on Maui Nui. From Maui Nui, the violets underwent interisland dispersal events to Kaua'i and Hawai’i. Violet species on O'ahu (V. tracheliifolia and V. oahuensis) were likely established through dispersal events from Maui Nui and Kaua'i, respectively. The lineage consists of “wet” and “dry” clades restricted to distinct precipitation regimes. Within the “wet” clade, two replicate sublineages occupy ecologically analogous habitat regimes on Kaua’i and the Maui Nui Complex. Ecologically analogous taxa have undergone an apparent parallel evolution in leaf morphology. Relative rate tests show that woody and herbaceous sister species possess equal molecular evolution rates. Woody sister species on Maui Nui have disparate rates of molecular evolution while their herbaceous-woody ecological analogues on Kaua’i express similar rates. The incongruity of molecular evolution rates in taxa on younger islands suggest that these rates may not be determined by growth form (or duration) alone, but may be influenced by other factors including complex dispersal events.
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1 - Ohio University, Department of Environmental and Plant Biology, Porter 315, Athens, OH, 45701, U.S.A.
2 - University of Wisconsin Madison, Department of Botany, Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
3 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 8:15 AM