Browsing by Subject "Crocodilians"
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Item Crocodilian evolution, systematics and population genetics: Recovery and ecological interactions of the American crocodile (Crocodylus acutus)(Texas Tech University, 2007-08) Rodriguez, DavidThe goals of this research were to explore the use of genetic markers to infer biological information about crocodilian species and populations. Given that the range of the American crocodile (Crocodylus acutus) is much larger than its sympatric congeners; this species was used as the focal point for my study. The American crocodile is sympatric in Cuba with the Cuban crocodile (C. rhombifer), in Meso-America with Morelet’s crocodile (C.moreletii) and in South America with the Orinoco crocodile (C. intermedius). The New World Crocodylus system, due to its geographic arrangement, presents an interesting opportunity to model broad-scale evolutionary process. Modern conservation biology requires the integration of both ecological and molecular data. The grand purpose of this work is to provide a genetic context spanning a scale from the species level to specific populations, including inter-species interactions in wild populations and breeding strategies. I begin by using mitochondrial markers to infer the phylogenetic relationships of New World crocodiles. I continue with an examination of the genetic structure of American crocodiles in Florida compared to other populations from Meso-America. Then I later relate those findings with breeding strategies of a specific wild population that has colonized and successfully utilized an artificial habitat. I also inspect putative hybridization zones between Morelet’s crocodile and the American crocodile in the Yucatan Peninsula using a combination of multiple microsatellite loci, mitochondrial sequences and morphological assignments. All New World crocodiles formed a highly supported clade with C. niloticus as a sister taxon. ND4-tRNAHis-tRNASer sequences did not provide sufficient resolution among populations of C. acutus, therefore partial control region sequence data were used to make population-based inferences. Two haplotypes were most prevalent within the Florida population, but surprisingly distant haplotypes were also found, indicating the migration of foreign haplotypes into Florida. This hypothesis is supported by government documentation of foreign releases into Florida waters. In Mexico hybridization was found to be not only widespread but bidirectional between the American and Morelet’s crocodile. The majority of hybrids were classified as F2 and C. moreletii-backcrosses. Using microsatellite data from 10 loci I found that nesting efforts within Turkey Point Power Plant (Florida, USA) are the result of inbreeding, and thus this site exhibits very low genetic diversity compared to other crocodilian populations. Relatedness values were very high among (r = 0.5624) and within nests (r = 0.5910 – 0.7457). Additionally, I could not detect multiple paternity within 8 nests due to minimal allelic diversity.Item Geometric morphometrics of Antillean Crocodiles(2012-08) Weaver, Jeremy; Densmore, Llewellyn D.; Bradley, Robert D.; Strauss, Richard E.Geometric morphometrics commonly have been utilized to explore patterns of variation across a wide range of taxa. We present a geometric morphometric analysis of skull shape morphology for New World crocodilians of the genus Crocodylus, placing emphasis on studying variation within the Greater Antillean region of the Neotropics. It has been suggested that the major factor contributing to the modern diversity of Cuban (C. rhombifer) and American crocodiles (C. acutus) in the Greater Antilles is the result of ancient hybridization. Genetic studies found that mitochondrial DNA haplotypes for C. acutus in the Greater Antilles are actually more closely related to C. rhombifer than other American crocodiles throughout the Neotropics. To infer whether genetic relationships are correlated with morphological relationships, we use geometric morphometrics to assess shape variation and compare skull morphology to a reconstruction of a cytochrome-b gene phylogeny. Analysis of skull shape variation using geometric morphometrics of landmark data reveals three broad groups of New World Crocodylus within the given morphospace. Two of these groups correspond to present day Crocodylus whereas the other corresponds to fossil specimens of C. rhombifer. Within these groups, nearly all sub-groups correspond to our current taxonomic understanding of New World Crocodylus; except for the placement of Greater Antillean C. acutus, which clusters much closer to C. rhombifer. This further supports recent studies of Greater Antillean C. acutus dynamics and their genetic phylogenies, indicating a unique evolutionary history.