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Spatial ecology, habitat use, genetic diversity, and reproductive success: measures of connectivity of a sympatric freshwater turtle assemblage in a fragmented landscape

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Title: Spatial ecology, habitat use, genetic diversity, and reproductive success: measures of connectivity of a sympatric freshwater turtle assemblage in a fragmented landscape
Author(s): Banning Anthonysamy, Whitney
Director of Research: Phillips, Christopher A.
Doctoral Committee Chair(s): Brawn, Jeffrey D.
Doctoral Committee Member(s): Phillips, Christopher A.; Douglas, Marlis R.; Schooley, Robert L.; Caceres, Carla E.
Department / Program: Natural Res & Env Sci
Discipline: Natural Res & Env Sciences
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Turtle Spatial Ecology Habitat Partitioning Population Genetics Parentage Reproductive Ecology
Abstract: Habitat fragmentation can have serious conservation implications for long-lived species such as freshwater turtles. Using integrative radio-telemetry and molecular methods, I examined characteristics in five species of turtles that should influence connectivity and long-term persistence of populations among remnant preserves within the Lower Des Plaines River Valley, a fragmented landscape in northeastern Illinois. Comparisons of movement and habitat use among Blanding’s turtle (Emydoidea blandingii), spotted turtle (Clemmys guttata), painted turtle (Chrysemys picta), common snapping turtle (Chelydra serpentina), and eastern musk turtle (Sternotherus odoratus) revealed that E. blandingii made long distance movements and readily moved between wetlands, whereas the other species were more restricted to aquatic movements. However, S. odoratus, C. serpentina, and C. picta were also capable of making long distance aquatic movements (≥ 1 km) via the Des Plaines River. Conversely, C. guttata exhibited the shortest movements and smallest home range. Patterns of macro- and micro-habitat use demonstrated strong partitioning between C. guttata and C. picta, C. serpentina, S. odoratus as well as broad measures of niche breadth and niche overlap for E. blandingii and C. serpentina. These results suggest that E. blandingii and C. serpentina are habitat generalists whereas C. guttata is a habitat specialist. Differences in movement and habitat use were likely caused by species-specific traits and requirements and can impact levels of gene flow within species in fragmented landscapes. Using microsatellite DNA markers, I examined population genetic structure in E. blandingii, C. picta, and C. serpentina. I observed moderate to high levels of genetic diversity in all three species. I detected significant pairwise FST divergence in E. blandingii between an intact site and three fragmented sites as well as between two fragmented sites and in C. serpentina between two fragmented sites. Gene flow was male-biased in E. blandingii across the fragmented sites but differences in patterns of dispersal between males and females in C. picta and C. serpentina were weak. I found no evidence of genetic population bottlenecks in any species, but simulations of future genetic diversity suggest that E. blandingii is more vulnerable to loss of genetic diversity than C. picta or C. serpentina. Finally, I evaluated the mating system of E. blandingii by corroborating field observations of mating attempts during radio-telemetry surveys with genetic parentage analysis. I observed promiscuous mating behavior in E. blandingii as males and females engaged in mounting behaviors with multiple individuals. Males and females mated successfully with multiple individuals, but successful matings did not always correspond with observed mating attempts and parentage was strongly skewed in males. For males, the number of successful mates was positively correlated with total number of offspring sired. Correlation between relatedness of male-female pairs and reproductive success was not evident. Repeat paternity in clutches among years was common but I only documented one confirmed instance of across-season sperm storage. I also only detected 8% multiple paternity in 28 clutches. High variation in reproductive success and low levels of multiple paternity may be attributed to small population size. During this study, I detected differences among species in traits such as vagility, niche breadth, and future levels of genetic diversity. These differences are likely related to species-specific life history traits and should differentially influence how each of these species responds to fragmentation.
Issue Date: 2012-05-22
URI: http://hdl.handle.net/2142/30958
Rights Information: Copyright 2012 Whitney Banning Anthonysamy
Date Available in IDEALS: 2012-05-22
Date Deposited: 2012-05
 

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