Gruenstaeudl, Michael , Santos-Guerra, Arnoldo , Jansen, Robert K. .
Time and sequence of dispersal events in the Macaronesian island lineage Tolpis - testing the utility of event- and model-based inference.
The biogeographic evolution of the small genus Tolpis (Asteraceae) is intriguing. Its contemporary distribution may be the result of no less than three independent dispersal events from continental to island habitats. An initial colonization introduced Tolpis to the Macaronesian archipelagoes of the Azores and Madeira. In a second dispersal the Canary Islands were colonized. The two events were separated by a back-dispersal, possibly even reintroduction, of Tolpis to the mainland. This led to the establishment of at least two species now widespread in the Mediterranean and North Africa. One of the continental species is also found on the Canary Islands, representing either an independent dispersal or recent human introduction. The Canary Islands were the geographic source for the colonization of the Cape Verde archipelago.
This talk outlines sequence and direction of Tolpis' mainland-to-island and inter-island dispersals. Event- and model-based inference methods were employed for biogeographic reconstructions. Our analyses comprised simple mapping of geographic ranges, ancestral area optimizations under parsimony and likelihood, and inference of colonization pathways by modeling dispersal events as stochastic Markov chain processes. The utility of these methods is discussed, and their results compared. We also report on estimating divergence times in Tolpis using relaxed molecular clocks with cross-validated calibration points. Phylogeographic hypotheses are evaluated assuming that island endemics must not be older than their islands' geological ages. The timing of selected dispersal events and their concomitance with climatic changes is discussed.
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1 - University of Texas at Austin, Section of Integrative Biology, 1 University Station, #A6700, Austin, TX, 78712, USA
2 - Jardín de Aclimatación de La Orotava, Puerto de la Cruz, Canary Islands, Tenerife, Spain
molecular clock analysis
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood D/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 9:00 AM