Evolução e integração de fenótipos complexos em insetos: estudo de caso em Teleopsis Dalmanni (Diptera:Diopsidae) e em espécies de Anastrepha do grupo Fraterculus (Diptera: Tephritidae)

Abstract

Complex traits are affected by multiple traits and processes, whose interaction shape and determine their evolutionary patterns. This work uses quantitative evolutionary genetic methodologies to understand the evolutionary forces affecting the morphological differentiation of complex traits in two different evolutionary models, with the goal of quantifying the magnitude of selection and its response modulated by the covariance of morphological traits. Teleopsis dalmanni are stalk-eyed flies whose exaggerated ornament is a response to mating choice on males with larger stalk-eyes for mating. However, few works explore the unintentional effect of this selection on other body parts, and the impact of the energy balance on the evolution of different traits. In two strains subjected to bidirectional artificial selection for large and small stalk-to-body ratios, we found phenotypic changes on target and non-target selected traits. Given this change, the genetic variance / covariance G matrix showed that these traits are positively correlated and the prediction of the response vectors to the selection also shows a correlated response. A separate experiment on individuals exposed to different levels of resource constraints detected a change in response to selection depending on resource availability, showing unintentional pattern selection among traits, possibly as compensation for extreme stalk-eye lengths, to maintain high flying capability in mating performances. A second case study investigated the evolutionary potential of morphological traits used to identify species and targets of sexual selection for species belonging to five groups of the genus Anastrepha (fraterculus, grandis, pseuparallela, serpentina and striata), which represent a portion of the great diversity in the genus, with a special focus on the fraterculus group, which harbors some of the most widely distributed species in the genus. We found significant phylogenetic signal for some of the traits linked to sexual identification and selection among species groups, and within the fraterculus group only for the aculeus apex and wing shape. A correlation analysis of ancestral matrix Principal components revealed that the studied species do not follow the Brownian stochastic model, suggesting that their evolution is shaped by selection. Considering that environmental heterogeneity (plasticity) could play a relevant role in the adaptation of these species, we quantified the environmental influence of hosts in two polyphagous species, A. fraterculus and A. obliqua. Plasticity vectors positively correlated with selection and response to selection gradients indicate a possible host specificity that affected mainly the aculeus apex, the aculeus width in their non-serrated portion, the wing size and width, the eye size and the head width. These results, together with the high intraspecific variation and phylogenetic signal only for a limited number of traits, though corroborate the relevant role of the aculeus on taxonomy, raise a cautionary flag for its use in species identification, particularly among species of the fraterculus group, which are phylogenetically closer, and suggests that host attributes should be considered to avoid potentially confounding results. Thus, our study contributes to the elucidation of morphological evolutionary patterns in these insect models, by considering poorly explored quantitative models as well as direct and indirect environmental pressure inferences.