title: Divergence in Zygodontomys (rodentia: Sigmodontinae) and distribution of amazonian savannas.
abstract: Northern South America presents a diverse array of nonforest or savanna-like ecosystems that are patchily distributed. The distribution of these open habitats has been quite dynamic during Quaternary glacial-interglacial cycles; yet, the relevance of climatically driven vicariance events to the diversification of nonforest Amazonian vertebrates remains poorly known. We analyzed karyologic and mitochondrial DNA sequence data of the genus Zygodontomys, a small cricetid rodent distributed throughout nonforest habitats of northern Amazonia. Samples analyzed represented 4 Brazilian Amazonian localities and 2 French Guiana localities. Karyologic variation among Amazonian Brazilian Zygodontomys populations is high, with, at least, 3 karyomorphotypes. Molecular phylogenetic analyses recovered 3 major clades congruent with known karyotypes, a finding that suggests the existence of 3 species, 2 of which currently undescribed. The French Guiana and Surumú clade, identified as Zygodontomys brevicauda microtinus, is characterized by 2n = 86 and is sister to the clade formed by the 2 nondescribed forms. The Rio Negro-Rio Branco form is characterized by 2n = 82, and the Ferreira Gomes-Itapoá form is characterized by 2n = 84. The distribution of the 3 Zygodontomys lineages identified is in accordance with the geography of the open vegetation patches in Northern Amazonia, and divergence time estimates relate speciation events to the middle-upper Pleistocene, supporting the prominent role of Quaternary climatically driven vicariance events in the diversification of the genus.
authors.affiliation: Instituto Nacional de Câncer, Rio de Janeiro, Brazil. cibelerb@inca.gov.br
authors.forename: Cibele R
authors.initials: CR
authors.lastname: Bonvicino
authors.forename: Pablo R
authors.initials: PR
authors.lastname: Gonçalves
authors.forename: João A
authors.initials: JA
authors.lastname: de Oliveira
authors.forename: Luiz Flamarion B
authors.initials: LF
authors.lastname: de Oliveira
authors.forename: Margarete S
authors.initials: MS
authors.lastname: Mattevi
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial; D019143:Evolution, Molecular; D005260:Female; D014644:Genetic Variation; D005843:Geography; D008297:Male; D010802:Phylogeny; D012730:Sex Chromosomes; D016205:Sigmodontinae / Q000235:genetics*; D013020:South America
chemical_list: D004272:DNA, Mitochondrial