Geiger, Jennifer M. O. , Wright, Margaret E. , Christensen, Kris , Fehlberg, Shannon D. , Ranker, Tom A. .
Alternate pathways of fern dispersal to the Hawaiian Islands, Part 1: Hypolepis & Diplopterygium.
THE Hawaiian Islands are the most isolated large group of islands on Earth, yet they are home to nearly 200 species of native ferns and lycophytes. Although species endemism is high (80%), there seems to have been little autochthonous speciation, as Hawaiian fern lineages are generally species-poor. Thus, the probable number of successful colonizations of fern species to the islands compared to the number of extant species is relatively high compared to flowering plants, which generally are represented by more species-rich lineages. Because fern spores are most likely dispersed through the air via the wind, weather and climate patterns are undoubtedly important factors determining the geographical origins of the ancestors of Hawaiian ferns. We are conducting molecular biogeographical studies of multiple groups of Hawaiian ferns to ascertain the likely geographical origin of each group and to explore the nature of shared pathways of dispersal across unrelated taxa. Hypolepis (Dennstaedtiaceae) and Diplopterygium (Gleicheniaceae) are each represented by only one species in the Hawaiian Islands, H. hawaiiensis and D. pinnatum. Comparative cpDNA sequence data strongly support a sister-taxon relationship between H. hawaiiensis and the south Pacific species H. dicksonioides; the latter ranges as far north as the Marquesas Islands (10 deg. S). Thus, the ancestor of H. hawaiiensis may have dispersed to the Hawaiian Islands via a climate-based, trans-equatorial mechanism previously proposed for Metrosideros polymorpha (Myrtaceae), although we will discuss alternative hypotheses. Diplopterygium pinnatum is related to a group of species variously distributed from the southwestern Pacific, eastern Asia, and tapering out into the Pacific. We propose that the ancestor of D. pinnatum arrived in the Hawaiian Islands via the jetstream from the Indo-Pacific.[c.e.:srb]
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1 - Caroll College, Department of Natural Science, 1601 North Benton Ave., Helena, Montana, 59625, USA
2 - University of Colorado, University Museum & Department of Ecology and Evolutionary Biology, 265 UCB, Boulder, Colorado, 80309, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 1:45 PM