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| Author(s): |
Daniela Munhoz Rossoni
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2013-12-13 |
| Examining board members: |
Gabriel Henrique Marroig Zambonato;
Leandro Rabello Monteiro;
Diego Astúa de Moraes;
Maria Dulcetti Vibranovski
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| Advisor: | Gabriel Henrique Marroig Zambonato |
| Abstract | |
Here I use a quantitative genetics and morphological integration approaches to understand the evolution of bat skulls of the Phyllostomidae family. These bats display an unprecedented diversity in terms of dietary specialization that is unique in mammals, with insectivorous, hematophagous, nectarivorous, carnivorous, omnivorous and frugivorous species. In this thesis, I compare the covariance and correlation phenotypic matrices, which are a quantification of the relationship among skull traits, in order to investigate whether there is structural similarity between them. Furthermore, I explore possible factors that may affect its stability, such as evolutionary history (phylogeny), dietary habits and functional and developmental associations between cranial traits. Finally, I investigate the presence of modules in the skulls of phyllostomids and assess the evolutionary consequences of the patterns and magnitudes of morphological integration in the evolution of this group. The database comprises 35 cranial measurements of 2665 specimens, including all the subfamilies, representing 45 genera and 48 species. The results indicate that after an approximately 33.9 million years period of evolutionary diversification, the phenotypic variance/covariance structure remained, to some extent, similar among species of phyllostomid bats. While the patterns of covariance and correlation matrices remained relatively similar, the overall magnitude of integration presented considerable variation between species. The cranial traits that diverged the most between the matrices are related to the regions of the skull that display great qualitative morphological variation and are directly related to the dietary habits of the species. The independence between the phylogenetic distance and the structural similarity of variance/covariance matrices indicates that changes and stasis in covariance patterns are, to some extent, decoupled from the evolutionary history of the group. On the other hand, changes in the phenotypic correlation and covariance structure are associated with the dietary habits of the group. While diet and phylogeny are related, these factors differ regarding their association (and potential causality) with evolution, both concerning the average phenotype divergence, as well as the correlation structure between cranial traits. The diet showed a better adjustment than the phylogeny for correlation matrices, as well as for the morphological distance matrices. Furthermore, the results demonstrate that the phyllostomids share the same patterns of cranial modularity for functional and developmental hypothesis, and confirm the modular structure found in other lineages of mammals. Generally speaking, the oral, nasal and cranial vault subregions appear as dominant modules in the skulls of these bats, and focusing on functional and evolutionary history aspects help to better understand the patterns of morphological integration of this group that is so diverse and intriguing. Not all species of bats that were included in this study showed size variation in the first principal component of the covariance matrix. Even if this first principal component is not size related, this component still acts as an evolutionary constrain. This result is evident in the high and significant correlation values between the overall integration indexes and the first principal component, and regarding the correlation between the first PC and the flexibility and constraint indexes. Species with high overall magnitude of integration between the skull traits have less ability to evolve in the direction of the selection and, therefore, are more evolutionary constrained. Species of bats that exhibit lower associations of cranial traits show greater evolutionary flexibility, i.e., greater capacity to respond in the direction in which selection is acting (AU) | |