Asexual species which never incorporate novel genetic material from other
lineages will go extinct faster than sexually reproducing species, because adaptive
variability may be lower and a larger number of harmful mutations may accumulate.
One form of asexuality, androgenesis, results in offspring that are clones of the father.
Both androgenetic and sexual species are found in the clam genus Corbicula. I used
genetic data to explore why there are multiple species of androgenetic Corbicula, and
whether genetic exchange occurs between species. I found that in North American
locations where two invasive, androgenetic species co-occur, restriction digest
mapping of rDNA failed to detect recent nuclear exchange. However, in these same
locations, mitochondrial markers were shared between species. In places where only
one species was found, mitochondrial markers were unique to that species. This
suggests androgenetic clams are able to parasitize eggs of closely related species.
Whereas maternal mitochondria are retained in the fertilized egg, maternal nuclear
chromosomes are expelled, and the mother incubates male clones of another species. To look at possible gene exchange over the long term, I compared phylogenetic tree
topologies of one mitochondrial and two nuclear markers from multiple sexual and
androgenetic species. Since several androgenetic species share similar or identical
alleles, androgenesis seems to have evolved relatively recently in Corbicula.
However, since different androgenetic species also have divergent alleles not shared
between species, genetic capture of maternal nuclear DNA from other species may
rarely occur. This rare capture of genetic material from other species may permit the
long-term persistence of androgenesis in Corbicula. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/6875 |
| Date | 04 February 2010 |
| Creators | Hedtke, Shannon M. |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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