Evolução molecular da família gênica dos receptores de odores e proteínas ligantes a feromônios e genética de populações de genes quimiossensoriais em espécies de Anastrepha do grupo fraterculus
Abstract
This dissertation is divided into three chapters. In the first chapter, we provide a concise
literature review that discusses key theoretical concepts, the rationale, and main objectives
outlined for this study. The second chapter investigates the molecular evolution of the gene
family of odor receptors (ORs) identified in the transcriptomes of two species of fruit flies of
great economic importance: Anastrepha fraterculus and A. obliqua. The results showed a high
percentage of average identities between ORs from these species, as well as recent gene
expansions with signs of positive selection. A comparison of rates of synonymous and nonsynonymous
substitutions among Anastrepha species detected evidence of positive selection
in the gene Or7c, which is associated to an important potential role in aggregation behavior
and host choice for oviposition in D. melanogaster. The third chapter investigates patterns of
molecular evolution in pheromone binding proteins (PBPs), also identified in A. fraterculus
and A. obliqua, as well as studied pattern of polymorphisms, divergence and populational
structure of four chemosensory genes amplified in four species of tephritid flies of fraterculus
group: A. fraterculus, A. obliqua, A. sororcula and A. turpiniae. This study contrasted
previously identified genes with evidence of positive and purifying selection in order to
investigate whether they are contributing to the differentiation among some of the species of
this group. We found no evidence of positive selection in PBPs studied in a more global
comparison, although we found positive selection signals in some of the genes and studied
strains. Population analysis of chemosensory genes in different species of Anastrepha
detected high levels of intraspecific nucleotide and haplotype diversity. Divergence tests
showed that A. obliqua is the most different species of the ones here investigated, having, in
general, high levels of nucleotide substitutions, non-synonymous divergence, as well as fixed
species specific differences, whereas we failed to find similar differences amongst the other
species here studied. The genes Obp28a, Or7c and Or7d were differentiated in A. obliqua,
indicating a potential role in the differentiation of other species in the group, or in this
species’ diversification and adaptation.