Evolution of spiders on oceanic islands: The venture of few and gain of many.

Monday, February 5, 2018 - 4:10pm
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Dr. Rosemary Gillespie, University of California - Berkeley, Department of Environmental Science, Policy & Management

Entomology Graduate Student Organization (EGSO) speaker.  Co-sponsored by EEB / EEOB.

Abstract. Adaptive radiation can be considered the linchpin that unites ecology with evolution and is central to understanding evolutionary processes overall. However, the best examples of adaptive radiation tend to be in uniquely isolated insular environments, begging the question of the generality and predictability of the process. In this talk I will examine the predictability of the phenomenon across different oceanic archipelagoes, as well as between lineages within the Hawaiian archipelago.  I will focus on the Pacific Ocean, which contains more islands than the rest of the world's oceans combined. The most remote high islands are those of Polynesia, notably the Hawaiian Islands, and the three archipelagos of French Polynesia: the Society, Marquesas, and Australs. Each of these archipelagos is a hotspot, with islands arranged chronologically from the southeast. I will compare patterns of diversification of spider lineages across the archipelagos to assess the similarity in species, pattern and rate of diversification, and dynamics of community assembly. The Societies show high endemism, in particular on the youngest high island of Tahiti, with the genus Tetragnatha a prominent element of the spider biota at both high and middle elevations; relationships appear to be horizontal, with cloud forest species closely related to each other. The Marquesas show high endemism, with Tetragnatha again a prominent element, the highest diversity being on the older islands. The radiation of Tetragnatha in Hawaii is quite exceptional. So I will then focus on the Hawaiian Islands to compare patterns of adaptive radiation and diversification among different spider lineages.

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