Systematics/Phytogeography / Taxonomie/ Section
Iles, Will , Rudall, Paula, J. , Sokoloff, Dmitry D , Remizowa, Margarita V , Macfarlane, Terry D , Yadav, Shrirang R , Goh, Justin , Harris, Philip , Feild, Taylor S. , Bateman, Richard M. , Graham, Sean W. .
Phylogenetics of Hydatellaceae.
Hydatellaceae, a small family of highly reduced aquatics traditionally placed in Poales, instead represent a deep split near the base of the angiosperm phylogeny. They are now recognized as the sister group of the water lilies (Nymphaeales). This surprising new phylogenetic position has sparked considerable interest in their morphology and reproductive biology, including new perspectives on their pseudanthia-like reproductive units. This year, four new species were described and all 12 species re-circumscribed as a single genus, Trithuria. We collected plastid DNA sequence data from the majority of species, permitting inference of a preliminary phylogeny of the family. Our tree indicates that Trithuria s.str. (as traditionally circumscribed) is paraphyletic and thus agrees with the concept of a single-genus classification of Hydatellaceae. Molecular phylogenetic data also confirm that fruit/seed morphological characters are phylogenetically more informative than characters linked with sexual system, dioecy, and structure of reproductive unit in this group. There are three main clades in the phylogeny that are well-characterized by fruit characters (a fourth fruit type remains to be sampled). Dioecious species do not form a clade within Hydatellaceae, and the results support our earlier speculation that the dioecious species T. polybracteata is closely related to T. lanterna, and the dioecious species T. austinensis is close to T. australis. Our analysis also indicates a nested position for the two non-Australian species among the Australian species. The Indian Trithuria konkanensis is nested among Northern Australian species, and the New Zealand Trithuria inconspicua among Southern Australian species. Both disjunct distributions were likely the results of relatively recent long-distance dispersal events from Australia. An exciting preliminary conclusion - possibly sensitive to sampling - is that the perennial growth form is derived from the annual one in Hydatellaceae. These ideas will be tested by further molecular sampling within this small but highly interesting family.
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1 - University of British Columbia, Botanical Garden And Centre For Plant Research, 6804 Sw Marine Drive, Vancouver, BC, V6T 1Z4, Canada
2 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3AB, United Kingdom
3 - Moscow State University, Department of Higher Plants, Biological Faculty, 119992, Moscow, Russia
4 - Department of Environment & Conservation, Western Australian Herbarium, Science Division, Brain Street, 6258 Manjimup, WA, Australia
5 - Shivaji University, Vidyanagar, Kolhapur 416 004, India
6 - University of Auckland, Plant Molecular Sciences, School of Biological Sciences, 3A Symonds Street, Private Bag 92019, Auckland, New Zealand
7 - University of Tennessee, Department of Ecology and Evolutionary Biology, Knoxville, TN, 37996, USA
8 - Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
9 - University of British Columbia, Botanical Garden And Centre For Plant Research, 6804 Sw Marine Drive, Vancouver, British Columbia, V6T 1Z4, Canada
Presentation Type: Oral Paper:Papers for Sections
Location: Room 6/Woodward
Date: Tuesday, July 29th, 2008
Time: 10:45 AM