Gillespie, Emily , Kron, Kathleen A. .
Managing Uncertainty in Northern Hemisphere Historical Biogeography.
Uncertainty in phylogenetic and biogeographic studies represents major obstacles to understanding the history of taxa. Biogeographic uncertainty is particularly problematic in northern hemisphere taxa for several reasons. First, tectonic events are not straightforward. We know that events such as glaciation and exposure of land bridges have likely occurred multiple times, and that the timing of some of these events is uncertain. Second, extinction within lineages may obscure phylogenetic signal that could support various biogeographic hypotheses. The current study attempts to reconstruct the evolutionary history of the northern hemisphere tribe Phyllodoceae (Ericaceae, Ericoideae), and to examine historical biogeography within the group. The lineage exhibits modern distribution patterns consistent with a tertiary relict flora. These patterns of distribution have been previously shown to be the result of a variety of processes, and that distribution pattern alone is insufficent evidence to infer biogeographic history. Therefore, several approaches were employed to manage both phylogenetic and biogeographic uncertainty in attempt to see how successfully these uncertainties could be circumvented. Six molecular markers were analyzed using Bayesian, Maximum Likelihood and Maximum Parsimony methods to generate a phylogeny. Potential vicariance and dispersal events were identified using S-DIVA, which simultaneously incorporates both biogeographic and phylogenetic uncertainty. Relative dating of nodes was carried out in BEAST to identify which vicariance events in different clades are of the same approximate age, and therefore were likely to have resulted from the same biogeographic processes. Based on the relative dating results, hypotheses were generated about potential biogeographic origins of similarly aged nodes. Absolute dating of nodes was conducted in BEAST based upon age constraints consistent with these different hypotheses. This strategy of iteratively refining age estimates for nodes represents a promising way to manage the uncertainty inherent in northern hemisphere biogeographic analyses.
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1 - Wake Forest University, Department of Biology, PO Box 7325, 226 Winston Hall, Winston-Salem, North Carolina, 27109-7325, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 551A/Convention Center
Date: Monday, August 2nd, 2010
Time: 8:00 AM