Missouri

Project Title: Molecular Diversity among Massasauga Rattlesnakes: Nuclear Intron Analyses
E-1-44

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Molecular Diversity among Massasauga Rattlesnakes: Nuclear Intron Analyses
E-1-44
1 May 2006 - 31 May 2007

I. NEED
In 1999, the Eastern Massasaug Rattlesnake (Sistrurus c. catenatus;a subspecies) was designated by USFWS as a candidate for listing as a Federal Threatened or Endangered Species. In addition, a USFWS Candidate Status Review considered the possibility that extant populations of Massasauga rattlesnakes in Missouri were potentially of the eastern rather than western (i.e., S. c. tergeminus) subspecies. At that time, data were insufficient to taxonomically assign the Missouri specimens to subspecies, but preliminary results in 2004 suggest that Missouri extant populations belong to western rather than eastern subspecies. However, the question arose at a workshop ("Status, Threats, and Research Survey Needs of the Massasauga Rattlesnake with Emphasis on Midwestern Populations," 26 March 2005, Squaw Creek NWR, MO) regarding potential hybrid status of Missouri populations. Indeed, this remains an unresolved issue. MtDNA cannot effectively evaluate this question due to its maternal mode of inheritance (i.e., individuals receive mtDNA only from their mother). Thus, a Missouri specimen could have a mother belonging to the western subspecies but with the father being from the eastern subspecies.

According to its mtDNA, the Missouri specimen would be erroneously classified as the western subspecies, given its mother. Because of this problem (and others), there is a growing realization that to verify management and/or taxonomic decisions, mtDNA must be complemented with a second, independent molecular marker. A reasonable choice in this regard would be one from the nuclear genome. Introns, which are non-coding segments of DNA that interrupt coding exons, are a likely choice. These markers can now be successfully amplified across divergent taxa, and they are being extensively used to corroborate or refute taxonomic decisions and to clarify questions of hybridity. By reanalyzing genetic samples using introns, information on hybridization between lineages will further address the taxonomic issues of the Massasauga Rattlesnake complex in North America, especially Missouri.

The complete 8-page grant proposal is available as a PDF.

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