Mammal body size evolution: the prevalence of Cope's rule

• Grant number: 14/20385-7
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: October 31, 2014
• End date: February 27, 2015
• Field of knowledge: Biological Sciences - Biology
• Principal Investigator: Tiago Bosisio Quental
• Grantee: Mauro Toshiro Caiuby Sugawara
• Supervisor: Luke J. Harmon
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: University of Idaho, United States
• Associated to the scholarship: 13/10885-0 - Diversification dynamics of Placentalia (Mammalia): integrating the fossil record with molecular phylogenies, BP.MS

Abstract

Body size is known to strongly influence many aspects of the biology of a species. The dynamic of body size evolution has been widely studied using two approaches: analysis of taxonomic fossil occurrences, and comparative analysis using a phylogenetic framework for extant species. The analysis of the fossil record is the most direct way of investigating the evolutionary dynamic of a lineage and usually encompasses millions of years, but the biases of the fossil record limit this analysis to a few lineages. On the other hand, phylogenetic comparative studies of extant species allows one to explicitly take into account the phylogenetic relationships among several species, although there are many limitations to the study of deep-time evolution using only extant molecular data. Despite this clear complementarity, however, there is little integration between these two approaches.One striking pattern that emerges from the analysis of the fossil record is the tendency of body size to increase with time, known as Cope's rule. In mammals, fossil analyses strongly supports the hypothesis of Cope's rule, but only for clades where the fossil record is sufficient for such analysis. Moreover, the tendency of lineages to evolve a larger body size has been evoked to explain the skewed distribution of body size among extant mammal species. Nevertheless, evidence for Cope's rule has never been found in studies based solely on molecular phylogenies. This inconsistency highlights the weakness and strengths of both approaches. From the fossil perspective we have direct evidence but a rather limited taxonomic breath to investigate the prevalence of Cope's rule, and in most cases a lack of phylogenetic hypothesis to test such trend. From the molecular phylogeny perspective, large-scale mammal phylogenies are becoming more and more prevalent, but we are limited to indirect inferences based solely on extant species.In this project I will integrate data from both fossil and extant species in an explicitly phylogenetic context to better understand the evolution of the body size of mammals, and specifically to determine the overall prevalence of Cope's rule across mammalian orders. (AU)