Seleção sexual e a ordem Odonata: uma abordagem teórica e experimental
Pestana, Gabrielle Cristina
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Sexual Selection theory was proposed by Darwin in 1871 and, thenceforth, has been widely discussed and tested in several taxonomic groups. Complementary hypotheses were formulated by different researchers aiming to understand the mechanisms and evolutionary processes related to sexual secondary characters and reproductive behaviors. Insects of the order Odonata, also known as dragonflies and damselflies, are used as models due to the presence of coloring patterns on the body and wings that act as sexual ornaments, and the diversity of behaviors related to reproduction. Thus, studies on the use of sexual traits before and after copulation, in different mating systems, are carried out with different species in this group. In this context, the present dissertation is focused in evolutionary models of sexual selection in odonates as study models. The first part contains two chapters: the first is a review of the mechanisms, costs and some hypotheses related to sexual selection, mainly related to the presence and function of sexual ornaments in males; and the second chapter, a scientometric analysis of published studies on the role of male sexual ornamentation and the different sperm competition strategies. The results of the scientometric analysis showed a difference in pre- and post-mating studies, in relation to the years in which there is a greatest number of publications with these themes, countries where the studies were developed, species analyzed and main authors. In the second part of this dissertation an observational study was carried out in order to verify the relationship between pre- and post-mating sexual traits, analyzing wing pigmentation proportion, sperm viability, total number of sperm, muscle mass, fat reserve and body size in two species: H. longipes and H. rosea. The results were discussed based on two hypotheses of sexual selection: the sperm competition game, which proposes a trade-off between sexual traits; and the fertility-linked phenotype, which predicts that the male sexual ornament co-vary with the individual's fertility. The results obtained suggest that both hypotheses can be corroborated, since males of H. longipes, presented a trade-off between the traits evaluated, while males of H. rosea presented a positive relationship between these traits.
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