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Dissertation
Mating system and dispersal patterns in the diamondback terrapin (Malaclemys terrapin)
Doctor of Philosophy (Ph.D.), Drexel University
Apr 2010
DOI:
https://doi.org/10.17918/etd-3323
Abstract
Long-term demographic studies of the diamondback terrapin (Malaclemys terrapin) indicate high habitat fidelity and low dispersal distances, but population genetic studies indicate high levels of gene flow between populations. In addition to conflicting data between direct and indirect measurements of dispersal in the terrapin, data are currently lacking on how habitat fragmentation affects the dispersal and mating system of the terrapin. Dispersal and mating systems are important to understand because they can affect the level of genetic diversity in a population, and therefore influence its long-term sustainability of a population. In this study, I examined the mating system and fine-scale dispersal patterns of diamondback terrapins in Barnegat Bay, New Jersey. Using both capture-mark-recapture and molecular genetic methods, I compared dispersal patterns of juvenile, male, and female terrapins in Barnegat Bay, NJ. While capture-mark-recapture over a four year study period indicated that all individuals have relatively small dispersal distances (<2 km), mean genetic assignment indices, first generation migrant tests, and spatial autocorrelation indicated that mature males exhibited sex-biased dispersal and mature females exhibited natal philopatry to nesting beaches. To determine how habitat fragmentation affects dispersal and gene flow in the terrapin, I used a landscape genetic approach. Landscape genetic models indicated that estuarine emergent wetland was a landscape feature necessary for effective dispersal and therefore necessary to maintain genetic diversity in the terrapin. Because mating systems can also affect the level of genetic diversity, I also analyzed paternity in 174 nests from five nesting beaches. Multiple paternity was common in nests, the degree of multiple paternity differed significantly among locations, ranging from 12.5 to 45.7 % of clutches, and exhibited a significant non-linear correlation with population sex ratio. Population sex ratios were likely altered by differential mortality of nesting females on roads or of males in commercial crab pots. I confirmed the use of sperm storage both within and between seasons, but found no data to support long-distance movements of individuals to mating aggregations. Utilization of genetic methods has yielded important information regarding terrapin dispersal and mating behaviors that is particularly important in developing conservation and management plans. The data indicate that protection of estuarine emergent wetland and natal nesting beaches is necessary for species survival, and that differential mortality, resulting in skewed sex ratios, can have significant impacts on the mating system of Malaclemys terrapin.
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Details
- Title
- Mating system and dispersal patterns in the diamondback terrapin (Malaclemys terrapin)
- Creators
- Claire Marie Sheridan - DU
- Contributors
- Harold W. Avery (Advisor) - Drexel University (1970-)James Robert Spotila (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Biology; College of Arts and Sciences; Drexel University
- Other Identifier
- 3323; 991014632690404721