Fritsch, Peter W. , Manchester, Steven R. , Almeda, Frank .
Biogeographic patterns in the amphi-Pacific tropical disjunct Symplocos (Symplocaceae) support the boreotropics hypothesis.
Over 90 groups of vascular plants display an amphi-Pacific tropical type of disjunction, i.e., between the Neotropics and the lands bordering the western Pacific Rim. Symplocos (325 species) provides a good example of this distribution pattern, although with some north-temperate outliers, and possesses an excellent Tertiary fossil record. To investigate the biogeographic history of this genus in relation to our current understanding of its phylogeny based on a five-gene analysis, we surveyed endocarp characters of 183 living species (over 400 samples) of Symplocos from seven herbaria and compared them to those of European and North American fossils. From these characters several fossil taxa can be referred to specific extant subclades of Symplocos. Area optimization combined with fossil-calibrated divergence time estimates assessed over the best ML topology assigned Eurasia to the crown node of the genus (Late Cretaceous; 78–83 mya). Dispersal to North America occurred in the Paleocene (58–64 mya), with three subsequent dispersals to South America and the Antilles each (ranging from 54 to 15 mya); all these events involved thermophilic evergreen taxa. The last biogeographical exchange between North America and Eurasia is estimated as Early to Middle Miocene (11–17 mya) and involved the semi-deciduous species S. tinctoria. When Symplocos and other tropical taxa were populating North America and Europe during the Eocene, southern China was apparently arid and northeastern China harbored deciduous forests. We therefore infer that the Asian and New World species of Symplocos likely have their origin in Europe and immigration to Asia and Malesia occurred post-Eocene. These data strongly support the boreotropical nature of Symplocos and add to a growing body of evidence from fossils and phylogenetically based divergence time estimates highlighting the critical role of the Eocene North Atlantic Land Bridge in shaping the geographic distribution of many tropical plant groups.
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1 - California Academy of Sciences, Department of Botany, 875 Howard Street, San Francisco, California, 94103-3009, USA
2 - University of Florida, Department of Botany, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
Asian/North American disjunctions.
Presentation Type: Oral Paper:Papers for Topics
Location: Boulevard B/Hilton
Date: Monday, July 9th, 2007
Time: 11:15 AM