Evolutionary divergence between two closely related species: Drosophila madeirensis and D. subobscura : quantitative genetic differentiation, reproductive barriers and evolutionary potential

• Author(s): Rego, Carla José Azevedo
• Date: 2007
• Persistent ID: http://hdl.handle.net/10451/1680
• Origin: Repositório da Universidade de Lisboa
• Subject(s): Biologia evolutiva; Teses de doutoramento
• Document Type: Doctoral thesis
• Language: English
• Advisor(s): Matos, Margarida Maria Demony de Carneiro Pacheco de, 1958-
• Contributor(s): Repositório da Universidade de Lisboa

Description

Tese de doutoramento em Biologia (Biologia Evolutiva), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008

Speciation and species differentiation are very important issues in Evolutionary Biology. This thesis focuses several aspects related with the differentiation between two closely related species, Drosophila madeirensis and Drosophila subosbcura, namely the contribution of additive and non-additive genetic effects to that differentiation, the contribution of assortative mating to their reproductive isolation, the analysis of hybrid developmental problems expressed as higher fluctuating asymmetry and their underlying causes (developmental noise), and the implications of species differentiation in terms of adaptation to a novel, common environment. The results indicate that negative dominance and epistasis are both involved in the genetic differentiation between these species. Both species present assortative mating, conspecific matings being more likely. Furthermore, the two reciprocal cross directions apparently present different reproductive barriers. In the cross involving D. madeirensis females the barrier is mostly prezygotic, with mating being hard to observe, however, this cross direction yields a high number of hybrids with an even sex-ratio. On the other hand, mating in the reciprocal cross is easy to observe but produces fewer hybrids with a male-biased sex ratio. The analysis comparing fluctuating asymmetry levels between hybrids and parental species indicates that, although hybridization disrupts developmental buffering, hybrid females presenting higher asymmetry, this disruption does not reflect higher developmental noise, as fluctuating asymmetry levels are similar to parental species. The results comparing species differences in life history traits and evolutionary dynamics indicate that these closely related species differ in the adaptation to new conditions (captivity). These findings have important implications for several fields, namely Evolutionary Biology, Speciation, Development and Conservation, which are discussed at the end of this thesis.

FCT (PhD Fellowship: PRAXIS XXI/BD/21479/99)