Population genetics and ecology of regional malaria vectors in Amazonian Brazil

• Main Author: McKeon, Sascha N
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2013
• Subjects: Ecology; Entomology; Genetics; Systematic; Systematic biology
• ISBN: 9781303316227; 1303316226

Species complexes are common among anopheline mosquitoes, but only some members of complexes are disease vectors. Research involving overall patterns of divergence, phylogenetic relationships and population structure is partly driven by the operational need to be able to reliably distinguish component taxa that may be involved in malaria transmission. Anopheles triannulatus, An. nuneztovari and An. albitarsis are broadly distributed species complexes that contain local and regionally important malaria vectors, whose genetic diversity has been largely overshadowed by studies involving An. darlingi, the principal vector of Central and South America. I have analyzed the ecological suitability of habitats and geographical ranges of these species in Amazonian Brazil using larval abundance counts and environmental variables measured in the field. Larval ecology indicates that species such as An. triannulatus and An. nuneztovari may be less restricted geographically, which can increase their capacity to participate in disease transmission by occupying habitats for which An. darlingi is unsuited. Ecological analysis also revealed patterns of habitat specialization among An. albitarsis s.l. species, including An. janconnae, An. marajoara and An. oryzalimnetes. To test the hypothesis that microgeographic differences in environment drive genetic diversity, the population structures of An. triannulatus, An. goeldii and An. marajoara were examined using mtDNA cytochrome oxidase I, nuclear white and ribosomal internal transcribed spacer region 2 sequences. The mtDNA data revealed distinct demographic histories for the three species despite co-distribution in many collection sites. Comparisons between mtDNA and nDNA suggest An. triannulatus has a complex history of fragmentation, secondary contact and recent divergence. Whereas, the population structure of An. goeldii is largely congruent with geography, and likely the result of isolation by distance. Distinct An. marajoara lineages were detected by COI, but unsupported by nDNA, possibly indicating incipient speciation. Analysis with the more conserved barcode fragment of the COI gene revealed significant differentiation based on higher than average intra-population divergence between lineages. Lineage divergence was also supported by a concatenated data set (COI + white). Differences in the distribution of the two lineages suggest Pleistocene climatic changes and niche partitioning may have contributed to the divergence of An. marajoara . Evidence of Pleistocene expansions was detected in all species, indicating that differences in population structure are more likely the result of geographic and ecological barriers than demographic history.