The general prevalence of sexual reproduction over asexual reproduction among metazoans testifies to the evolutionary, long-term benefits of genetic recombination. Despite the benefits of genetic recombination under sexual reproduction, asexual organisms sporadically occur throughout the tree of life, and a few asexual lineages persisted over significant evolutionary time without apparent recombination. The study of asexual organisms therefore may provide clues to answer why almost all eukaryotes reproduce via meiosis and syngamy and why asexual eukaryotes are almost always evolutionarily short-lived. Towards understanding the evolution of asexual lineages in the Hymenoptera, I first review the diversity of reproductive systems in the Hymenoptera, introduce the study organism, the fungus-gardening ant Mycocepurus smithii, and discuss my research objectives. Second, I integrate information from reproductive physiology, reproductive morphology, natural history and behavior, to document that that queens of M. smithii are capable of thelytokous parthenogenesis, workers are sterile, and males are absent from the surveyed population. These results suggest that M. smithii might be obligately asexual. To place the origin and maintenance of asexual reproduction in M. smithii in an evolutionary context, I use molecular phylogenetic and population-genetic methods to (i) test if M. smithii reproduces asexually throughout its distribution range; (ii) infer if asexuality evolved once or multiple times; (iii) date the origin of asexual reproduction in M. smithii; and (iv) elucidate the cytogenetic mechanism of thelytokous parthenogenesis. During field collecting for these studies throughout the Neotropics, I discovered a new species of obligate social parasite in the genus Mycocepurus. Social parasites are of great interest to evolutionary biology in order to elucidate mechanisms demonstrating how parasites gained reproductive isolation from their host species in sympatry. I describe this new parasite species, characterize its morphological and behavioral adaptations to the parasitic lifestyle, and discuss the parasite’s life history evolution in the context of social parasitism in fungus-growing ants. The dissertation research integrates population-genetic, phylogenetic, physiological and morphological approaches to advance our understanding of the evolution of reproductive systems and diversity of life-history traits in animals. / text

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-07-12T14:58:32Z No. of bitstreams: 1 arquivo total.pdf: 1625338 bytes, checksum: 8863922d581ee0572be827faee791b95 (MD5) / Made available in DSpace on 2016-07-12T14:58:32Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 1625338 bytes, checksum: 8863922d581ee0572be827faee791b95 (MD5) Previous issue date: 2015-07-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Termitidae family is one of the most both diverse and abundant among the termites and its caste development pattern has an irreversible decision point from the first changes resulting in two strains, one nymphal and other aptera. In this study, it was assessed the patterns of caste development Inquilinitermes fur, a species of Termitidae family which is obligatory inquilines within arboreal nests of Constrictotermes cyphergaster. Twelve nests were collected over a period of one year, with samples taken every 60 days, from October 2011 to August 2012 in a Caatinga area at the Moreira Farm, São João do Cariri, Paraíba. For the analysis of morphometric data, they were used 11 variables including larvae, workers, pre-soldiers, soldiers, nymphs and winged. Principal Component Analysis (PCA) and ANOVA were performed to determine the instars within each lineage and to verify differences among the instars, respectively. The principal results showed that the species has a pattern of caste approximated of the Termitidae family, presenting a nymphal lineage but they have not found the five nymphal instars and another apterous lineage with just one instar for soldier, presoldiers and workers. Sex determinations were made only on workers, soldiers. So, like most studies of Termitinae, we found individuals males and females in the worker caste preceded by two larval instars. Soldiers have also been found males and females, as well as the two species studied Amitermes, which was not found in both sexual dimorphism soldiers as for workers. This pioneering work focused on the castes development patterns of I. fur showed that this species, even though it is obligatory inquilines of C. cyphergaster and has a distinctive life habit, remains the same patterns type of "forked" for the caste differentiation. / A família Termitidae é uma das mais diversificadas e abundantes entre os térmitas e seu padrão de desenvolvimento de castas apresenta um ponto de decisão irreversível a partir da primeira muda originando duas linhagens, uma ninfal e outra áptera. Nesse estudo, o padrão de desenvolvimento de castas de Inquilinitermes fur, uma espécie de Termitidae que é inquilina obrigatória dos ninhos arborícolas de Constrictotermes cyphergaster, foi investigado. Doze ninhos foram coletados durante um período de um ano, com coletas realizadas a cada 60 dias, no período de Outubro de 2011 a Agosto de 2012 em uma área de Caatinga situada na Fazenda Moreira, município de São João do Cariri, Paraíba. Para as análises dos dados morfométricos foram utilizadas 11 variáveis das larvas, operários, pré-soldados, soldados, ninfas e alados. A análise de componentes principais (PCA) e a ANOVA foram utilizadas para determinar os ínstares dentro de cada linhagem. Os dados mostraram que a espécie apresenta um padrão de castas aproximado com a família Termitidae, apresentando uma linhagem ninfal, porém não foram encontrados os cinco ínstares ninfais, e outra linhagem áptera, apresentado apenas um ínstar para soldado, pré-soldado e operário. As determinações de sexo foram feitas em operários, soldados. Assim como a maioria dos estudos feitos com Termitinae, foram encontrados indivíduos machos e fêmeas na casta operária precedida por dois ínstares larvais. Para soldados também foram encontrados machos e fêmeas, assim como as duas espécies de Amitermes estudados, onde não foi encontrado dimorfismo sexual tanto em soldados quanto em operários. Esse trabalho pioneiro no estudo do padrão de desenvolvimento de castas de I. fur mostrou que esta espécie, mesmo sendo inquilina obrigatória de C. cyphergaster e possuir um hábito de vida diferente, mantém o mesmo padrão “bifurcado” de diferenciação de castas.

The traditional view of a lifelong monogamy between a king and a queen has recently been challenged in termites. In several species, multiple parthenogenetically-produced secondary queens replace the primary queen and mate with the primary king; this strategy is referred to as “Asexual Queen Succession” (AQS). The aim of my thesis was to investigate the modalities of reproduction and the ecology of neotropical soil-feeding termites from the Termitinae, with a focus on the inquiline termite Cavitermes tuberosus in the Termes group.In the first axis, we investigated the modalities of reproduction of C. tuberosus. (i) AQS is the main reproductive strategy of this species. (ii) The evolution of AQS requires the propensity of parthenogens to develop into neotenic queens. In C. tuberosus, secondary queens develop from a developmental stage of “aspirants” which participate to the social tasks usually undertaken by workers, as long as the primary queen is alive. (iii) In AQS species, a female-biased sex ratio is expected in the dispersing reproductives. In C. tuberosus, sex ratio varies among years and according to the type of reproductives, and the population sex ratio is balanced. These results raise hints on queen-king conflict over the sex ratio.In the second axis, we described the ecology and symbioses of C. tuberosus. (iv) Wolbachia, an endosymbiotic bacterium mainly known for manipulating the reproduction of arthropods in order to enhance its own transmission, infects all individuals in societies. This bacterium, particularly abundant in a gut-associated bacteriome, may play a role in the nutrition of C. tuberosus; both partners would have evolved a mutualistic symbiosis. (v) Inquiline termites live in a nest built by other termite species and do not forage outside. Physico-chemical measures and microbiota sequencing revealed that C. tuberosus is a generalist nest-feeder.Finally, we expanded our study of the breeding systems in the phylogenetic proximity of C. tuberosus. (vi) We described Palmitermes impostor, a new genus and species as a sister-group to the genus Cavitermes. (vii) AQS is the main reproductive strategy in P. impostor, and queens of Spinitermes trispinosus and Inquilinitermes inquilinus are able to reproduce parthenogenetically. Therefore, it appears likely that the conditional use of sexual and asexual reproductions is a preadaptation common to the whole Termes group, and that it evolved into a stable element of their breeding system at least in some species.Overall, our results open new perspectives in the understanding of reproductive strategies in termites and their relationships with their bacterial symbionts. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished