Browsing by Subject "American crocodile"
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Item An examination of the crocodilian mitochondrial control region: structural and functional units and utility in phylogenetic and phylogeographic analysis(Texas Tech University, 2002-12) Ray, David AThe use of molecular markers for elucidating crocodilian phylogenetic relationships has been ongoing for several decades now. While significant progress has been made in understanding how each of the three major morphological groups of crocodilians are related to one another and to the remainder of Archosauria, issues involving the relationships of the two gharial species to the remainder of the order Crocodylia and understanding phylogeny within the family Crocodylidae remain. In this dissertation, I describe the development of a new marker for examining each of these issues as well as problems involving population level relationships. For representatives of each major crocodilian lineage, the mitochondrial control region is characterized from structural and functional perspectives and then utilized as a marker for the determination of phylogenetic relationships within the Crocodylia and for examining the population dynamics of one species, Crocodylus moreletii. I found that the control region of crocodilians contains several features in common with other vertebrate groups as well as several features that deserve special interest, including a series of heteroplasmic tandem repeats. I also found that the control region appears to be useful in resolving relationships at several levels within the order Crocodylia. Finally, while control region sequences reveal little with regard to phylogeography in C. moreletii, the inclusion of these new data have significantly affected our interpretation of other studies with regard to population structure in this species.Item Evaluation of organochlorine residues in Morelet's and American crocodile eggs from Belize(Texas Tech University, 2000-08) Wu, Ted H.Non-viable eggs of Morelet's crocodile (Crocodylus moreletii) and American crocodile (Crocodylus acutus) were collected from various locations in Belize and screened for organochlorine (OC) compounds using gas chromatography (GC) with electron capture detection (ECD). Seven complete clutches (1 non-viable and 6 flooded nests) of eggs from Morelet's crocodiles were also collected to examine distribution of OCs and determine the appropriate minimum number of eggs to sample in the field to obtain an accurate mean p,p-DDE concentration representative of the full clutch. All but one egg (American crocodile. Maps Cay, Nest 2) analyzed tested positive for one or more OCs. The primary contaminant was p,p-DDE (99%). Other OCs detected included p,p-DDT, p,p-DDD, methoxychlor, endosulfan I and II, endrin, aldrin, and a-chlordane. Concentrations of individual OCs on a wet weight calculation ranged from 1 ppb (ng chemical/g egg) to >0.5 ppm (jig chemical/g egg). Total concentration of OCs (sum of all OCs) for one egg collected from a nest at Gold Button Lagoon (GBL) reached as high as 0.7 ppm. No significant difference (p < 0.05) between non-viable eggs from American (n = 12) and Morelet's (n = 13) crocodile nests was observed for egg p,p-DDE concentration using a Wilcoxon rank sum test. However, significant differences were observed with absolute mean p,p-DDE contamination among complete clutches (n = 7) of eggs from Morelet's crocodile using Welch ANOVA (p < 0.0001). Correlation coefficients for DDT and DDT metabolites within complete clutches of eggs varied from an r of 0.95 to 0.24. The weaker correlation coefficients between DDT and DDT metabolites may suggest the possibility of another source of contaminants in eggs besides by maternal transfer. A statistical evaluation of p,p-DDE levels in three complete clutches (GBL 2, 1999; GBL 3, 1997; and GBL 4, 1997) of eggs recommended a minimum sample size of 11. This sample size should give an accurate estimate of contaminant levels in a full clutch of eggs based on an average standard deviation (0.26 ng/g), average clutch size (n = 20), acceptable deviation from the mean (± 0.1), and a confidence interval of 90%. The statistically recommended sample size of 11 eggs was successfully tested on four additional clutches. Sediment and nest media (soil and plant material) collected from GBL and New River Lagoon (NRL) also tested positive for OCs (lindane, aldrin, heptachlor, methoxychlor, endrin aldehyde, p,p-DDT among others). Contaminated media could be a potential source for transfer of volatile OCs into eggs. Based on the 264 egg samples analyzed, Morelet's and American crocodiles from Belize are being exposed to OCs. Such exposure may present a health threat to populations of crocodilians in Central America.Item Population genetics of the American crocodile in Coiba National Park, Panama(2012-08) Bashyal, Ashish; Densmore, Llewellyn D.; Perry, Gad; Bradley, Robert D.Population genetic studies provide information on the various aspects of genetics of species and therefore have a wide spread application in conservation research. This study assesses the genetic diversity, population subdivision, and genetic structure within the populations of the American crocodile (Crocodylus acutus) from eight localities in three sampling regions (mainland, northern and southern Coiba Island) in south -western Republic of Panama. A total of 143 individuals were characterized genetically by amplifying highly polymorphic microsatellite loci developed for Crocodylus. Microsatellite loci utilized in this study showed considerable allelic variation with a total of 61 alleles reported for nine loci across all localities with an average of 6.8 alleles per locus. A model based clustering analysis revealed the presence of three spatially overlapping genetic clusters among the sampled populations. All three estimates of population subdivision (FST, RST, and ΦPT) are consistent with the finding that the fine scale analysis of sampled populations revealed an overall presence of genetic subdivisions among and within the sampled localities. The Panamanian government should consider this information when designing conservation programs for the American crocodile in Coiba national park.