UVM Theses and Dissertations
Format:
Print
Author:
Lehr, Margaret
Dept./Program:
Biology
Year:
2004
Degree:
M.S.
Abstract:
Cryptic species (reproductively isolated natural populations that are morphologically indistinct) are common within the Anopheles genus, especially among species that have been incriminated in the transmission of human malaria. Because of the problematic use of morphology to distinguish among members of species complexes, cytogenic and molecular tools have become increasingly important. A predominantly exophilic and zoophilic species, Anopheles albitarsis was initially described by Lynch-Arribalzaga in 1878 from Baradero, Argentina. In 1942, Galvao and Damasceno described A. marajoara, a new species related to A. albitarsis, from Ilha de Marajo, Brazil, which was an endophilic malaria vector. Inter- and intra-populational morphological, behavioral, and genetic variation in populations found throughout South America was documented soon after, and it became increasingly evident that A. albitarsis is a complex of several cryptic species. Currently, only three species are described and named: A. albitarsis s.s. Lynch-Arribalzaga 1878, A. marajoara Galvao & Damasceno 1942, and A. deaneorum Rosa-Freitas, however, there is evidence of additional species.
Random amplified polymorphic DNA (RAPD) diagnostic bands are used as a tool to differentiate cryptic mosquito species in the A. albitarsis complex. In Chapter 2, the monophyly of four species currently identified by RAPDs was examined using mitochondrial DNA sequences. Maximum parsimony (MP), maximum likelihood (ML), and Bayesian analyses support monophyly for A. albitarsis s.s., species B, and A. deaneorum. Anopheles marajoara, as identified by RAPD banding patterns, was found to be polyphyletic. The topology and sequence divergence of one of the A. marajoara lineages suggests an unidentified species (species E) located in northern Brazil and Venezuela. This new species corresponds geographically with populations that have been previously differentiated using allozymes and chromosomal inversions. The inability of RAPDs to distinguish between A. marajoara and species E likely due to violations of the assumptions of comigrating band homology. The status of A. marajoara and A. deaneorum as separate phylogenetic species is unresolved in MP and ML and ambiguous under Bayesian analysis.
Because of altered relative abundance and its association with agricultural habitat, a population expansion has been hypothesized in A. marajoara over the last century. In Chapter 3, this hypothesis of population expansion was examined using cytochrome oxidase I sequence data obtained from seven populations of A. marajoara from the states of Para and Amapa. Eleven of sixteen haplotypes were restricted to six populations in the eastern Amazon. These six populations exhibited very little genetic variation compared to the seventh population. Haplotypes from the eastern Amazon formed a star-like network characteristic of population expansion, with all haplotypes differentiated from the most common and geographically widespread haplotype by a single mutation. Nested clade analysis suggested there was restricted gene flow among the populations, with a pattern of contiguous range expansion detected for one of the haplotypes. The mismatch distribution was smooth and unimodal, suggesting a recent population demographic expansion probably occurring during the Pleistocene. In comparison, the related species E showed greater genetic variation within a single population and a bimodal mismatch distribution indicative of a much older and larger population at equilibrium.
Random amplified polymorphic DNA (RAPD) diagnostic bands are used as a tool to differentiate cryptic mosquito species in the A. albitarsis complex. In Chapter 2, the monophyly of four species currently identified by RAPDs was examined using mitochondrial DNA sequences. Maximum parsimony (MP), maximum likelihood (ML), and Bayesian analyses support monophyly for A. albitarsis s.s., species B, and A. deaneorum. Anopheles marajoara, as identified by RAPD banding patterns, was found to be polyphyletic. The topology and sequence divergence of one of the A. marajoara lineages suggests an unidentified species (species E) located in northern Brazil and Venezuela. This new species corresponds geographically with populations that have been previously differentiated using allozymes and chromosomal inversions. The inability of RAPDs to distinguish between A. marajoara and species E likely due to violations of the assumptions of comigrating band homology. The status of A. marajoara and A. deaneorum as separate phylogenetic species is unresolved in MP and ML and ambiguous under Bayesian analysis.
Because of altered relative abundance and its association with agricultural habitat, a population expansion has been hypothesized in A. marajoara over the last century. In Chapter 3, this hypothesis of population expansion was examined using cytochrome oxidase I sequence data obtained from seven populations of A. marajoara from the states of Para and Amapa. Eleven of sixteen haplotypes were restricted to six populations in the eastern Amazon. These six populations exhibited very little genetic variation compared to the seventh population. Haplotypes from the eastern Amazon formed a star-like network characteristic of population expansion, with all haplotypes differentiated from the most common and geographically widespread haplotype by a single mutation. Nested clade analysis suggested there was restricted gene flow among the populations, with a pattern of contiguous range expansion detected for one of the haplotypes. The mismatch distribution was smooth and unimodal, suggesting a recent population demographic expansion probably occurring during the Pleistocene. In comparison, the related species E showed greater genetic variation within a single population and a bimodal mismatch distribution indicative of a much older and larger population at equilibrium.