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iDEA: DREXEL LIBRARIES E-REPOSITORY AND ARCHIVES

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Population genetics and conservation of the American crocodile on the pacific coast of Costa Rica

Details
Title
Population genetics and conservation of the American crocodile on the pacific coast of Costa Rica
Author(s)
Cotroneo, Laurie Anne
Advisor(s)
Spotila, James R., 1944-
Keywords
Environmental sciences; Crocodiles; Population genetics
Date
2010-05
Publisher
Drexel University
Thesis
Ph.D., Biology -- Drexel University, 2010
Abstract
Crocodylus acutus ranges widely in the American neo-tropics. It is listed as vulnerable by the International Union for the Conservation of Natural Fauna and Flora (IUCN) and on Appendix I of the Convention for the International Trade in Endangered Species of Wild Flora and Fauna (CITES). Despite this listing, C. acutus remains poorly studied throughout much of its range. The objective of this study was to characterize the population genetic structure of C. acutus, on the Pacific coast of Costa Rica. Population assessments were conducted in four areas, Las Baulas, Santa Rosa and Palo Verde National Parks and the Osa Conservation Area to determine encounter rates, size class distributions and distributions within the areas. Non-hatchling crocodiles were encountered at rates ranging from 1.2 to 4.3 crocodile km-1. These encounter rates were comparable to or higher than other crocodilian studies. I collected 183 samples and genotyped them at nine microsatellite loci to describe the genetic diversity, gene flow, population subdivision and landscape genetics of C. acutus on the Pacific coast of Costa Rica. Crocodile populations on the Pacific coast were moderately genetically diverse with an average heterozygosity of 0.57. No population was in Hardy-Weinberg Equilibrium at all nine microsatellite loci. This suggested that genetic change was occurring. This change was probably caused by migration into and out of areas along the Pacific coast. There were 2.4 effective migrants per generation along the entire coast. The isolation by distance model was not supported over a straight-line, coastline or a cost distance analysis. Crocodiles were hypothesized to use a combination of streams and rivers, oceanic and overland routes for dispersal. Two model-based clustering analyses indicated that crocodiles were segregated into three populations along the coast. Las Baulas National Park formed an isolated cluster with both methods. This level of population subdivision supported the presence of metapopulations along the Pacific coast of Costa Rica and not one panmictic population. The results of this study show that crocodile populations in Costa Rica should not be managed as separate entities. Instead, they should be managed as interacting units of one large population.
URI
http://hdl.handle.net/1860/3311
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