Male secondary sexual characters in Lepidoptera may be present or absent in species that otherwise appear to be closely related, an observation that has led to differences of opinion over the taxonomic usefulness of these structures above the species level. An evolutionary issue raised by this debate is whether male secondary sexual characters (1) can be regained after being lost evolutionarily, (2) are not lost after being evolved, or (3) are 'switched on and off' by genes that regulate development. A second evolutionary issue is the conditions under which male secondary sexual characters might be lost or gained evolutionarily. Because these structures are thought to promote species recognition, theory predicts evolutionary losses to be most likely in allopatry; evolutionary gains to be most likely during the process of secondarily establishing sympatry or during sympatric speciation. We updated the species-level taxonomy of the brilliant emerald-winged Neotropical lycaenid butterfly genus Arcas and performed an analysis of phylogenetic relations among species to assess these evolutionary issues. We morphologically detail a scent pouch on the ventral hindwing of Arcas and report that six species possess the pouch with androconia, one possesses the pouch without androconia, and the remaining two species have neither pouch nor androconia. In addition, eight Arcas species have a morphologically species-specific male forewing scent pad, and one lacks a scent pad. This variation appears to be the result of three evolutionary losses and no gains of male secondary sexual organs. The four Arcas species lacking a scent pouch or a scent pad are allopatric with their closest phylogenetic relatives while four of five with both of these structures are sympatric. Although Arcas is a small genus, these results are significantly more extreme than predicted by chance. For taxonomy, this study provides a rationale for the evolutionary loss of male secondary sexual structures and suggests that their absence, but itself, does not indicate a lack of relationship above the species level.

Species inventories are important tools to evaluate biodiversity losses and contribute to the conservation of endangered areas. The Amazon and Cerrado are the largest Brazilian biomes and represent some of the most threatened regions of the country. Due to its location between these biomes, the state of Maranhão, Northeast Brazil, possesses a great variety of habitats and a high local diversity. Nonetheless, few faunistic inventories of diversified groups have been performed in the state. In the specific case of butterflies, a well-known biological indicator, no inventories have been published in the past years. This study aimed to expand the knowledge on the composition of butterflies in Amazon and Cerrado remnants of Maranhão. Butterflies were sampled between 2011 and 2015 across eight municipalities of the state. Captures were made through entomological nets and baited traps. In total, 189 species were sampled, of which 165 were captured in the Amazon, 65 in the Cerrado and 41 in both biomes. We sampled 167 species through entomological nets and 43 through baited traps, representing 12% of similarity in species composition between sampling methods. We estimate that the recorded species represent a small subset of the butterflies from Maranhão. Therefore, long-term researches in poorly studied areas of the state are recommended to identify novel and/or endemic taxa.Keywords: tropical forest, diversity, Lepidoptera, Neotropical region, savanna. Borboletas de remanescentes de Amazônia e Cerrado do Maranhão, nordeste do BrasilResumo: Inventários de espécies são ferramentas importantes para avaliar perdas de biodiversidade e contribuir para a conservação de áreas ameaçadas. A Amazônia e o Cerrado são os maiores biomas brasileiros e representam algumas das regiões mais ameaçadas do país. Devido à sua localização entre estes biomas, o estado do Maranhão, nordeste do Brasil, possui uma grande variedade de habitats e uma alta diversidade local. No entanto, poucos inventários faunísticos de grupos diversificados foram realizados no estado. No caso específico de borboletas, um indicador biológico bem conhecido, nenhum inventário foi publicado nos últimos anos. Este estudo objetivou expandir o conhecimento sobre a composição de borboletas de remanescentes de Amazônia e Cerrado do Maranhão. As borboletas foram amostradas entre 2011 e 2015 em oito municípios do estado. As capturas foram realizadas através de redes entomológicas e armadilhas com iscas. No total, 189 espécies foram amostradas, das quais 165 foram capturadas na Amazônia, 65 no Cerrado e 41 em ambos os biomas. Nós amostramos 167 espécies através de redes entomológicas e 43 através de armadilhas com iscas, representando 12% de similaridade na composição de espécies entre métodos de amostragem. Nós estimamos que as espécies registradas representam um pequeno subconjunto das borboletas do Maranhão. Deste modo, pesquisas de longa duração em áreas pouco estudadas do estado são recomendadas para identificar taxa novos e/ou endêmicos.

Hairstreak butterflies in the Atlides Section of the Eumaeini are biologically notable for a diverse array of male secondary sexual organs. A "species recognition" hypothesis postulates that females use these organs to choose between conspecific and nonconspecific males, thereby promoting reproductive isolation. Alternately, a "sexual selection" hypothesis posits that females use these organs to choose among conspecific males. These hypotheses need not be mutually exclusive but make different predictions about the evolutionary gain and loss of male secondary sexual organs. We analysed most of the Atlides Section (Theclinae, Eumaeini) phylogenetically. Sister lineages were sympatric at 22 of 37 nodes. Nine evolutionary gains occurred in lineages that were sympatric with their phylogenetic sister, and one occurred in a lineage that was allopatric/parapatric with its sister. By contrast, seven of ten evolutionary losses occurred in lineages that were allopatric/parapatric with their sisters. These results are significantly different from those predicted by a sexual selection hypothesis. We conclude that male secondary sexual organs in the Atlides Section function primarily for species recognition and thereby promote sympatric diversification.