title: The ecology of a continental evolutionary radiation: Is the radiation of sigmodontine rodents adaptive?
abstract: Evolutionary radiations on continents are less well-understood and appreciated than those occurring on islands. The extent of ecological influence on species divergence can be evaluated to determine whether a radiation was ultimately the outcome of divergent natural selection or else arose mainly by nonecological divergence. Here, we used phylogenetic comparative methods to test distinct hypotheses corresponding to adaptive and nonadaptive evolutionary scenarios for the morphological evolution of sigmodontine rodents. Results showed that ecological variables (diet and life-mode) explain little of the shape and size variation of sigmodontine skulls and mandibles. A Brownian model with varying rates for insectivory versus all other diets was the most likely evolutionary model. The insectivorous sigmodontines have a faster rate of morphological evolution than mice feeding on other diets, possibly due to stronger selection for features that aid insectivory. We also demonstrate that rapid early-lineage diversification is not accompanied by high morphological divergence among subclades, contrasting with island results. The geographic size of continents permits spatial segregation to a greater extent than on islands, allowing for allopatric distributions and escape from interspecific competition. We suggest that continental radiations of rodents are likely to produce a pattern of high species diversification coupled with a low degree of phenotypic specialization.
authors.affiliation: Programa de Pós-Graduação em Ecologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 91501, Brazil.|Integrative Research Center, Field Museum of Natural History, Chicago, Illinois, 60605.
authors.forename: Renan
authors.initials: R
authors.lastname: Maestri
authors.affiliation: Laboratório de Ciências Ambientais, CBB, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, RJ, 28013, Brazil.
authors.forename: Leandro Rabello
authors.initials: LR
authors.lastname: Monteiro
authors.affiliation: Programa de Pós-Graduação em Ecologia, Universidade Regional Integrada do Alto Uruguai e das Missões, Campus Erechim, RS, 99709, Brazil.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Fornel
authors.affiliation: Integrative Research Center, Field Museum of Natural History, Chicago, Illinois, 60605.|Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, 06511.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Upham
authors.affiliation: Integrative Research Center, Field Museum of Natural History, Chicago, Illinois, 60605.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Patterson
authors.affiliation: Programa de Pós-Graduação em Ecologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 91501, Brazil.|Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 91501, Brazil.
authors.forename: Thales Renato Ochotorena
authors.initials: TR
authors.lastname: de Freitas
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D005075:Biological Evolution; D008334:Mandible / Q000033:anatomy & histology; D010802:Phylogeny; D012641:Selection, Genetic; D016205:Sigmodontinae / Q000033:anatomy & histology*; D012886:Skull / Q000033:anatomy & histology; D013020:South America
keywords: Disparity through time; Neotropics; evolutionary models; evolutionary rates; macroevolution; macroevolutionary adaptive landscape; nonadaptive radiation; tempo and mode of evolution