| Over the last three decades, theoretical and empirical research has significantly improved our understanding of the mechanisms and consequences of sexual selection as an evolutionary agent. In this thesis, I reconstruct the phylogenetic history of a hyperdiverse tribe of butterflies, the Eumaeini, that possess an extraordinary diversity of male secondary sexual characters. I use different approaches to study how sexual selection can act as an engine of diversification.;In Chapter 1, I develop an analytical model to investigate the evolution of host-plant specialization. In this model, I propose that sexual selection on adult males can act as a possible mechanism driving phytophagous insect larval diets. The model suggests that female mate-choice for certain diet-derived male pheromones can be exploited by maternal effect genes that preferentially place offspring on specific host plants, resulting in specialization.;In Chapter 2, I reconstruct the phylogeny of the tribe Eumaeini, and study the pattern of diversification of this largely Neotropical group, whose some 1200-1300 species make it the most diverse tribe of butterflies. My results provide support for the monophyly of the Eumaeini, and for at least half of the 83 genera that have been described for this lineage. An analysis of species accumulation through time suggests that Eumaeini underwent an explosive diversification, and that differences in diversification rates between the two main clades in this group relate to their respective geographical distributions.;In Chapter 3, I test the hypothesis that the loss of male secondary sexual characters is as common as the gain of such characters. I survey all secondary sexual characters within the Eumaeini tribe, and study in detail the evolution of two male secondary sexual characters by applying both Bayesian and likelihood approaches. The results indicate that the rate of loss is significantly higher that the rate of gain for the two secondary sexual characters, and that re-gains are extremely rare. The results also suggest that the evolution of both traits is not correlated. I discuss the possibility that the extremely labile nature of these secondary sexual characters have played a key role in promoting the diversification of this group. |
