Padrões evolutivos inferidos por transcriptomas de moscas-das-frutas do gênero Anastrepha (Diptera: Tephritidae)

Abstract

Anastrepha is a species-rich genus, with a geographic distribution that covers tropical and subtropical regions of the Americas. Twenty-one species groups have been recognized in this genus, the most economically relevant being the fraterculus group, which has several representatives which are considered important agricultural pests. Moreover, this group also bears cryptic and closely related species that probably diverged with gene flow such as species in the A. fraterculus complex, A. obliqua and A. sororcula. Despite their importance, the evolutionary mechanisms involved in the rapid diversification of this group is unclear as well as their phylogenic relationships. To investigate the mechanisms of differentiation of these species, we analyzed male and female transcriptomes from reproductive and head tissues of A. fraterculus and A. obliqua. We found that male-biased genes evolve faster than female-biased and unbiased genes due to positive selection and relaxed selective constraints. Some of the positively selected and male-biased genes are involved with courtship behavior and fertility, which suggests that these genes may be involved in the differentiation of these species. We also investigated the phylogenetic relationships of Anastrepha lineages evaluating 20 female reproductive transcriptomes belonging to different 10 lineages. We inferred a cluster of high-quality orthologs and reconstructed a robust phylogeny of this group based on thousands of genes using multispecies coalescent methods. Our phylogenetic analysis revealed that the serpentina group is basal to other groups here evaluated, and the bistrigata group is sister to the fraterculus group. The relationships among fraterculus groups specimens showed that A. obliqua formed only one lineage, whereas A. fraterculus complex from Brazil was divided into two groups, one probably including individuals from A. fraterculus Brazil 1 and another which its assignment to previously reported lineage remains unknow. Furthermore, although A. distincta has divergent ecological traits (host specialist) to A. fraterculus (s.l.) and A. turpiniae, the tree revealed that it is closely related to these species. We also found high levels of gene tree discordance due to incomplete lineage sorting and introgression. Interestingly, our findings indicated extensive ancestral introgression among fraterculus group lineages. Our study increased the genetic data available for these economically important species, and established a role of positive selection and hybridization in the diversification of the fraterculus group.