title: Geographic variation in skull shape of the water rat Scapteromys tumidus (Cricetidae, Sigmodontinae): isolation-by-distance plus environmental and geographic barrier effects?
abstract: The geographic variation in skull size and shape of the swamp rat Scapteromys tumidus was examined in samples from eight geographic clusters in almost of its distribution in southern Brazil and Uruguay. For analysis we used two-dimensional geometric morphometric methods for dorsal, ventral and lateral views of the skull. The geometric descriptors showed no significant differences in skull size between geographic clusters, while differences in shape were highly significant. We found a significant and moderate correlation between geographic and morphological distances, corroborating the isolation-by-distance model. Samples from the Rio Grande do Sul central coastal plain were the most differentiated, segregating completely from all other samples in canonical variate analysis for the dorsal view. The most visible variable regions in skull were the zygomatic arch (mainly the squamosal root of zygomatic) and the lateral braincase borders. Once correlation between geographic and morphological distances were not strong, it is possible that other factors (environmental heterogeneity and/or geographic barriers) may are acting in S. tumidus skull differentiation.
authors.affiliation: Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Gonçalves, 9500, Prédio 43435, 91501-970 Porto Alegre, RS, Brasil, Universidade Federal do Rio Grande do Sul, Departamento de Zoologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre RS , Brazil.
authors.forename: Fernando M
authors.initials: FM
authors.lastname: Quintela
authors.affiliation: Programa de Pós-Graduação em Ecologia, Departamento de Ciências Biológicas, Universidade Regional Integrada do Alto Uruguai e das Missões, Campus de Erechim, Avenida Sete de Setembro, 1621, 99700-000 Erechim, RS, Brasil, Universidade Regional Integrada do Alto Uruguai e das Missões, Departamento de Ciências Biológicas, Universidade Regional Integrada do Alto Uruguai e das Missões, Erechim RS , Brazil.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Fornel
authors.affiliation: Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Gonçalves, 9500, Prédio 43435, 91501-970 Porto Alegre, RS, Brasil, Universidade Federal do Rio Grande do Sul, Departamento de Zoologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre RS , Brazil.|Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (UFRGS), Avenida Bento Gonçalves, 9500, Prédio 43323, 91501-970 Porto Alegre, RS, Brasil, Universidade Federal do Rio Grande do Sul, Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre RS , Brazil.
authors.forename: Thales R O
authors.initials: TR
authors.lastname: Freitas
mesh_terms: D063147:Animal Distribution; D000818:Animals; D001938:Brazil; D017753:Ecosystem; D005260:Female; D008297:Male; D012727:Sex Characteristics; D016205:Sigmodontinae / Q000033:anatomy & histology*; D012886:Skull / Q000033:anatomy & histology*; D014583:Uruguay