Evolução Da Diversificação Craniana Na Família De Roedores Echimyidae: Uma Abordagem Quantitativa

Abstract

An organism is made up of parts that are relatively integrated due to shared development and/or function. These interactions are grounded in the concept of morphological integration and can be responsible for directing the course of phenotypic evolution. Organisms that have a reduced degree of intensity between these associations may be more flexible in responding in the direction that selection is pulling. The opposite is observed for highly integrated traits. Therefore, the initial starting point for investigating the morphological diversity of a taxon consists of assessing how these associations are structured in a character, considering the pattern and magnitude. For this dissertation, we used as a model the skull of Echimyidae rodents, which is characterized by a complex evolutionary history made up of events of occupation and exploration of new areas. The morphological variation of equimids is surprising, with a wide disparity mainly related to locomotion habits and body size. We therefore outlined our study in the framework of quantitative genetics and sought to understand how morphological integration might be acting to promote this intriguing scenario of diversity. This dissertation was subdivided into two main approaches, with the following objectives: (1) Identify the pattern and magnitude of integration in the skull of Echimyidae throughout their evolutionary history and (2) Examine the role of genetic drift and natural selection in the cranial diversification of echimyids. It was possible to observe a relative stability in the pattern of integration, in contrast the intensity of these relationships was variable between the genera studied. Natural selection can explain cranial diversification in the origin of Echimyidae. In addition, we highlight the important role of evolutionary restrictions imposed along evolutionary trajectories, influencing the other possibilities for morphological innovations. This study is an important step towards understanding the morphological diversity of the skull in Echimyidae.