Population genetics of the diamondback terrapin (Malaclemys terrapin)
J. SUSANNE HAUSWALDT*,t and TRAVIS C. GLENN*,t
*Department of Biological Sciences, University
of South Carolina, Columbia, SC 29208,
tSavannah River Ecology Laboratory, P.o. Drawer E, Aiken, SC
29802
Abstract
We examined the population genetic structure of the diamondback terrapins
(Malaclemys terrapin), within and among estuaries. Based on mark-recapture
studies, these estuarine turtles have high site fidelity that is likely
to make them vulnerable to local-extinctions. We tested if observed site
fidelity of adults would be reflected in intraestuarine population genetic
structure of six highly polymorphic microsatellite loci (five tetranucleotide
and one dinucleotide). No evidence was found for population structuring
within the Charleston estuary nor among three different estuaries in South
Carolina. We then examined four other terrapin populations from North
Carolina to New York, as well as from the Florida Keys and from Texas.
With increasing geographical distance, genetic differentiation increased
from South Carolina through New York, but overall values were low. The
dinucleotide locus contributed significantly more to the genetic differentiation
of some population com- parisons than any of the other loci. Interestingly,
terrapins from South Carolina to New York were much more genetically similar
to those from Texas (p = 0.154) than to those from Florida (p = 0.357).
We attribute this pattern to extensive translocations of terrapins during
the early 20th century to replenish diminished populations and to provide
turtle farms with stocks. Terrapins collected in Texas were especially
sought for shipment to the northeastern US because of their larger size.
Our study indicates no population structure within or among adjacent estuaries.
Thus, the mark-recapture information from adult and subadult feeding locations
is a poor predictor of population genetic structure. Additionally, it
appears that past human activities may have drastically altered the genetics
of current populations. Finally, our data suggest that translocation of
eggs or head starting of terrapins within estu- aries or among adjacent
estuaries is acceptable from a genetic standpoint.
Keywords: estuary, microsatellites, population differentiation,
population genetics, South Carolina, turtle
SREL Reprint #2820
Hauswaldt, J. S. and T. C. Glenn. 2005. Population genetics of the diamondback terrapin (Malaclemys terrapin). Molecular Ecology 14:723-732.
