Molecular systematics and population genetics of marine vertebrates from Brazil

• Main Author: Furtado Neto, Manuel Antonio de Andrade
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1998
• Subjects: Argentina; baleen whales; toothed whales
• Online Access: https://research.library.mun.ca/9438/; https://research.library.mun.ca/9438/1/FurtadoNeto_ManuelAntonioDeAndrade.pdf

This thesis examines the implications of patterns of DNA sequence variation in a variety of marine vertebrate species of ecological and fisheries interest from Brazilian waters. -- The degree of genetic variation in the marine and riverine dolphin Sotalia fluviatilis from Brazilian waters was investigated. A unique genotype found only in Sotalia from the Amazon River suggests that the freshwater form may be genetically distinct from the marine form. The species is genetically diverse in the marine environment, but the occurrence of a common genotype in all six coastal locations along the marine coast examined suggests that there is sufficient gene flow in the marine region to prevent local differentiation. -- A previously unexamined mitochondrial locus. COI (cytochrome oxidase I), was used in combination with three other loci to re-investigate phylogenetic relationships of cetaceans. In this data set, the largest sequence yet applied to this problem, the controversial Milinkovitch Hypothesis that sperm whales are more closely related to baleen whales than to toothed whales was not supported. Instead, four different clades with different taxonomic rankings (Physeteridae. Ziphiidae. Delphinida. and Mysticeti) were identified, in agreement with the traditional separation of toothed and baleen whales as distinct clades. Results of the analysis are sensitive to locus combinations and method of phylogenetic reconstruction. -- The species of angel sharks (Squatina. Squatinidae) endemic to the continental shelf of Southern Brazil constitute a monophyletic group. The recently described species S. occulta was found to be more closely related to S. guggenheim than to S. argentina. This phylogeny helps to explain the evolution of reproductive structures (number of ovaries) and patterns of vertical distribution in the water column (from deep to shallow waters) of squatinid sharks. -- Red snapper (Lutjanus purpureus) shows high genetic diversity off the coast of northern Brazil. Two genotypic clades have been identified, one ...