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Systematics and Evolutionary Biology of Spiders (Image 1)
A scanning electron micrograph of the male copulatory organ of the spider Orsonwelles ventus. The spider genus Orsonwelles is a small lineage of gigantic linyphiid spiders endemic to the Hawaiian archipelago. O. ventus was described by Hormiga (2002) and is endemic to the Makaleha Mountains of Kauai.
The work is part of ongoing research in the lab of Gustavo Hormiga, a Ruth Weintraub Associate Professor of Biology at George Washington University, and colleagues. Research focuses on the systematics and evolutionary biology of spiders, with emphasis on orbweavers and their close relatives (Orbiculariae). Most of the species-level systematic work in the lab addresses the following spider lineages: the sheet weaving family Linyphiidae and Pimoidae, and the orb weaving families Tetragnathidae and Mysmenidae.
Hormiga and his team use morphological, molecular and behavioral characters to reconstruct the phylogenetic relationships of their study organisms, to tackle questions that span from species level problems to interrelationships of families. Hormiga's work also includes applying phylogenetic results to more general questions in evolutionary biology such as the evolution of sexual size dimorphism in orbweaving spiders (Hormiga et al., 2000) or the patterns of insular diversification and colonization in the Hawaiian archipelago (Hormiga et al., 2003). This work highlights the importance of reconstructing the history of evolutionary changes for addressing comparative questions. For example, the results of the lab's research show that the extensively studied "male dwarfism" of nephiline spiders (Tetragnathidae), when placed in a phylogenetic context, is in fact a case of female gigantism.
This research was supported by National Science Foundation grants DBI 00-70362 and DEB 97-12353, and by a grant from the National Geographic Society (6138-98). [Image 1 of two related images. See Image 2.]
Credit: Gustavo Hormiga, GWU
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