<p>A key question in developmental biology is how organisms attain a final size. Deviations in growth patterns can produce different/new phenotypes and these changes can play fundamental roles in ecology and evolution. The size of an organism and of its constitutive organs is determined by the growth rate and the duration of the growing period. In insects, peptide hormones such as insulin-like growth factors have been shown to be involved in determining the growth rates by coordinating metabolism, cell proliferation and cell size. In contrast, steroid hormones, such as ecdysone, are involved in determining life stage transitions, and thus the termination of the growing period. Although it is clear that insulin and steroid hormones are both involved in the regulation of growth, the ways in which these two regulators interact is yet to be determined. Furthermore, it is not clear how organs and body growth are coordinated during development to arrive to their correct proportions. In this study, using the tobacco hornworm Manduca sexta and its wings as a model system, I examine the developmental mechanisms involved in the regulation of organ growth and how developmental processes can drive morphological evolution. First, I examine how the hormonal events that take place during the termination of the body growth period affect wing disk growth. Second, by using gene expression assays and in vitro cultures, I examine the interaction between bombyxin, the Lepidopteran insulin-like growth factor, and ecdysone, the molting hormone, and their contributions to wing imaginal disk growth. Finally, by using three different size strains of M. sexta, I examine the developmental basis of the allometric relationship between the wings and the body. My results show that during the final instar of M. sexta larval development, wing imaginal disks are sensitive to the hormonal events that terminate the growth period. Furthermore, I show that the bombyxin requirement for wing disk growth is restricted to the early days of the final instar unlike the constitutive effects seen in other species. After the larva has passed a particular critical weight, bombyxin is not necessary for wing disk growth, although its absence does decrease the growth rate. In contrast, ecdysone is required for promoting the growth of wing imaginal disks primarily through its stimulation of cell proliferation. Finally, I show how selection on body size has unpredictable consequence for the response of wing size. These results demonstrate how specific allometries have a developmental basis in the cross-talk of the various signals that regulate growth itself. Therefore, direct selection on allometric relationships may not need to be strong in order to hold scaling relationships constant, at least over short evolutionary periods.</p> / Dissertation

京都大学 / 0048 / 新制・課程博士 / 博士(地域研究) / 甲第19833号 / 地博第189号 / 新制||地||66(附属図書館) / 32869 / 京都大学大学院アジア・アフリカ地域研究研究科東南アジア地域研究専攻 / (主査)教授 竹田 晋也, 教授 岩田 明久, 准教授 古澤 拓郎, 教授 神﨑 護 / 学位規則第4条第1項該当 / Doctor of Area Studies / Kyoto University / DGAM

Submitted by Caroline Falcao (caroline.rfalcao@ufpe.br) on 2017-06-29T18:08:30Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) 2012-Dissertação-AnaCarolinaSilva.pdf: 6644945 bytes, checksum: 770aa392360d533cc08e873bc7e5ab6d (MD5) / Made available in DSpace on 2017-06-29T18:08:30Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) 2012-Dissertação-AnaCarolinaSilva.pdf: 6644945 bytes, checksum: 770aa392360d533cc08e873bc7e5ab6d (MD5) Previous issue date: 2012 / A evolução do dimorfismo sexual de forma e tamanho do crânio e mandíbula foi estudada em 31 táxons de marsupiais didelfídeos, a fim de compreender melhor o desenvolvimento desse caráter na família. Para elucidar fatores que poderiam estar condicionando esse dimorfismo nos Didelphidae, foi analisada também a evolução de outros dois elementos: alometrias entre tamanho e forma do crânio e da mandíbula; e bionomia das mesmas 31 espécies. Foi realizado um mapeamento de todos estes caracteres, qualitativos e quantitativos, sobre uma filogenia da família, reconstruindo seus estados ancestrais utilizando métodos de parcimônia. Foram feitas também correlações utilizando contrastes independentes dos dados de dimorfismo sexual para auxiliar a esclarecer os padrões evolutivos do dimorfismo sexual. Tais correlações foram significativas, indicando coevolução entre os tipos de dimorfismo em ambas as estruturas estudadas. Não houve tendência unidirecional de surgimento/desaparecimento e aumento/decréscimo do dimorfismo nos Didelphidae. As reconstruções também indicaram coevolução entre os dimorfismos. Poucas espécies são altamente dimórficas e a maioria apresenta dimorfismo sexual de forma. Os resultados de alometrias entre os sexos foram iguais para crânio e mandíbula, mas elas também não apresentam padrão geral em direção à igualdade ou diferenciação das mesmas entre os sexos. Ambos os estados estão uniformemente distribuídos na filogenia. O comportamento das alometrias no crânio e na mandíbula coevoluiu, mas o padrão de alometrias entre os sexos não é conservado dentro de Didelphidae e não coevoluiu com o dimorfismo sexual, indicando que não explica a evolução deste caráter. Outros fatores, não-alométricos, devem condicionar este caráter nessa família. No entanto, apesar de padrões aparecem dentro de alguns clados, não há também evidência de coevolução entre bionomia e dimorfismo sexual nos Didelphidae. Espécies asazonais são poucas e não dimórficas de tamanho, talvez pelo fato de se reproduzirem continuamente e sofrerem menores pressões seletivas. A semelparidade é rara dentro de Didelphidae, surgindo apenas em Monodelphini e seguindo daí caminhos evolutivos distintos. Espécies semélparas exibem maiores tamanhos de ninhada nos Didelphidae por se reproduzirem uma única vez. Acredita-se que a seleção sexual direcione o padrão de dimorfismo sexual onde os machos são maiores que as fêmeas em espécies semélparas de Didelphidae. Portanto, nem alometrias nem bionomia, a princípio, explicam nem condicionam a evolução do dimorfismo sexual nos didelfídeos. A inclusão de uma maior quantidade de dados reprodutivos de marsupiais didelfídeos seria ideal para testar a veracidade da ausência de coevolução entre estratégias bionômicas e dimorfismo sexual. Associar dados ecológicos ou de padrões de distribuição poderiam ajudar a compreender melhor a evolução das estratégias bionômicas e a sua importância sobre a evolução do dimorfismo sexual nos Didelphidae. / The evolution of size and shape sexual dimorphism of the skull and mandible was studied in 31 taxa of didelphid marsupials, in order to better understand the development of this character in the family. And to elucidate factors that could be conditioning this dimorphism in Didelphidae the evolution of two other elements was also analyzed: allometries between size and shape of the skull and mandible and bionomy of the same 31 species. A mapping of all these qualitative and quantitative characters was carried through on a phylogeny of the family, reconstructing its ancestral states using parsimony methods. Correlations using independent contrasts of the sexual dimorphism data had been made also to assist clarifying the evolutionary standards of the sexual dimorphism. Such correlations were significant indicating coevolution among types of dimorphism in both studied structures. There is no unidirectional trend of sprouting/disappearance and increase/decrease of the dimorphism in Didelphidae. The reconstructions had also indicated coevolution among dimorphisms. Few species are highly dimorphics and the majority of them present shape sexual dimorphism. The results of allometries between the sexes had been the same for skull and mandible, but they also did not present a general pattern directing to the equality or differentiation between the sexes. Both states are uniformly distributed in the phylogeny. The results of the allometries in the skull and mandible coevoluted but the results of allometries between the sexes was not manteined in Didelphidae and they did not coevolute with sexual dimorphism indicating that they do not explain the evolution of this character and that other non-allometric factors must condition this character in this family. Although patterns appear inside of some clades there was no evidence of coevolution between bionomy and sexual dimorphism in Didelphidae. There are few aseasonal species and they are non-sized dimorphics perhaps by reproducing continuously and suffering less selective pressures. The semelparity is rare in Didelphidae arising only in Monodelphini and following from there distinct evolutionary ways. Semelparous species display the largest offspring size by reproducing only once. It is known that sexual selection directs the patterns of sexual dimorphism in those species in which males are larger than females in semelparous taxa of Didelphidae. Therefore neither allometries nor bionomy at first explain the evolution of sexual dimorphism in didelphids. The inclusion of a larger amount of reproductive data for didelphid marsupials would be ideal to test the veracity of the absence of coevolution among bionomic strategies and sexual dimorphism. The association of ecological data or distributional patterns could help in better understanding the evolution of the bionomic strategies and its importance on the evolution of the sexual dimorphism in Didelphidae.