Phylogeny, biogeography, and speciation in the genus Austinixa and related genera (Crustacea: Brachyura: Pinnotheridae) /
This study used molecular data for the first time to explore evolutionary relationships, speciation, and population genetics of the pinnotherid crab genera Austinixa and Pinnixa. The results are discussed in terms of biogeographic history, speciation patterns, and taxonomic implications. COI had l...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2001.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=726102821&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This study used molecular data for the first time to explore evolutionary relationships, speciation, and population genetics of the pinnotherid crab genera Austinixa and Pinnixa. The results are discussed in terms of biogeographic history, speciation patterns, and taxonomic implications. COI had low levels of phylogenetic signal, while 16s rDNA exhibited significant levels of signal. 16s and combined 16s/COI gene trees were well-resolved, with A. patagoniensis basal to the rest of Austinixa. Austinixa felipensis (eastern Pacific) is the next to branch off, and is basal to a clade consisting of the remaining six species. The species endemic to the Gulf of Mexico (A. aidae and A. chacei) are sister species, as are the northern and southern Caribbean species (A. gorei and A. aidae). The position of A. cristata (U. S. western Atlantic) is unresolved with respect to these taxa. Phylogeographic patterns in Austinixa are consistent with allopatric speciation due to numerous climatic and oceanographic fluctuations during the last 5-6 my. Austinixa aidae and A. hardyi were almost identical in both mitochondrial sequences, raising questions about the validity of A. hardyi as a distinct species. Analysis of morphometric characters using multivariate (PCA) and univariate allometric adjustment methods, support the mtDNA data in suggesting A. aidae and A. hardyi are a single species. A second phylogenetic analysis included Austinixa and representative species of Pinnixa from the Pacific and Atlantic. This more inclusive analysis suggests that Austinixa is paraphyletic with respect to A. patagoniensis. However, these trees were not statistically different from constraint trees forcing Austinixa to be monophyletic. Sympatrically distributed species of Pinnixa from the Pacific were monophyletic and exhibit a pattern of rapid divergence as compared to Austinixa and the species of Pinnixa from the Atlantic. Sympatric speciation via host shift is likely to have been common among these species. Significant population genetic subdivision exists between sympatrically distributed large form and small form P. chaetopterana living with ecologically different hosts in the northern Gulf of Mexico. Both forms in the Gulf of Mexico are more genetically similar to each other than either is to large form crabs from the western Atlantic. |
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| Item Description: | Vita. "Major Subject: Zoology". |
| Physical Description: | xiii, 144 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 116-130). |