Morphological integration and modularity in skulls of the Rhinella granulosa species group

Author(s)

Monique Nouailhetas Simon

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências
• Defense date: 14 mar. 2016

Examining board members

Gabriel Henrique Marroig Zambonato; Tiana Kohlsdorf; Miguel Trefaut Urbano Rodrigues

• Advisor: Gabriel Henrique Marroig Zambonato

Abstract

Concepts and methods within the theories of morphological integration and quantitative genetics characterize the foundation to study the evolution of complex structures, composed of several traits that interact with each other. In this work, we used the skull as a model of complex structure and we studied its diversification in toad species belonging to the Rhinella granulosa group. The questions addressed were: (1) Is the (co)variance structure similar across species?; (2) Is the (co)variance structure modular in the species, and compatible with developmental or functional interactions among traits?; (3) Do external factors, such as phylogeny and climate, structure the similarity in covariance pattern across species?; (4) Was the diversification of skull mean morphology driven by drift or natural selection?; (5) Is skull divergence associated to climatic variation across species?; and finally, (6) Is there a role for evolutionary constraints in species skull divergence? We scanned all specimens and we validated the use of 3D images to measure 21 linear distances. The skull was represented as covariance and correlation phenotypic matrices (P) among distances. P similarity is very high among species. All species\' P had a modular pattern compatible with functional interactions among bones. Differences in P were concentrated in the snout and associated to differences in climate across species. We detected a selection signal in the three most basal nodes of the phylogeny and local variation in the skull is explained by between-species variation in precipitation seasonality. Evolutionary constraints played a major role in species skull diversification, biasing evolutionary responses towards the direction of size. We conclude that stabilizing and directional selection, connected to climatic variation, as well as evolutionary constraints, acted in species skull diversification (AU)

• FAPESP's process: 11/07584-2 - Morphological integration and modularity in the skulls of species from Rhinella granulosa's group (Lissamphibia: Anura: Bufonidae)
• Grantee: Monique Nouailhetas Simon
• Support type: Scholarships in Brazil - Doctorate