Molecular phylogenies, chromosomes and dispersion in Brazilian akodontines (Rodentia, Sigmodontinae)

Abstract

ABSTRACT.A new molecular phylogeny for akodontine rodents from Brazil was proposed. The phylogenetic tree was enriched with the area of occurrence and with information on the karyotype of the samples. Based on this enriched tree, and with a described methodology, hypotheses were proposed on the karyotype and area of occurrence of the ancestors of each Clade. Thus it was possible to discuss hypotheses on chromosome evolution of the group, and on dispersion events from the "area of original differentiation" of akodontines in the Andes. Chromosome evolution started with high diploid numbers (2n=52) and showed a tendency to reduction (until 2n=14 in more recent clades). Independent side-branches of the tree showed 2n reduction and in one case the 2n increased. At least four dispersion events from the Andes down to South-eastern Brazil were proposed. The results should suggest the direction of new studies on comparative karyology. KEYWORDS.Brazilian akodontines, chromosome evolution, biogeography, molecular phylogeny. RESUMO. Filogenia molecular, cromossomos e dispersão em akodontinos do Brasil (Rodentia, Sigmodontinae).Uma nova filogenia molecular para roedores akodontinos do Brasil é proposta. A árvore filogenética foi enriquecida com a área de ocorrência e com informações sobre o cariótipo das amostras. Baseado nisto, e com a metodologia descrita, foram propostas hipóteses sobre as características do cariótipo e sobre a área de ocorrência dos ancestrais de cada clado. Assim, foi possível discutir hipóteses sobre evolução cromossômica do grupo, e sobre eventos de dispersão a partir da área de diferenciação original dos akodontinos nos Andes. A evolução cromossômica começou com números diplóides altos (2n=52) e mostrou uma tendência a redução (até 2n=14 em clados mais recentes). Ramos independentes da árvore mostraram redução do 2n e num caso aumentou o numero diplóide. Foram propostos pelo menos quatro eventos de dispersão dos Andes até o Brasil Sul-Oriental. Os resultados indicam a direção de novos estudos em cariologia comparada. PALAVRAS-CHAVE.Akodontinos do Brasil, evolução cromossômica, biogeografia, filogenia molecular.

Geographic distribution of the genera of the Tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae) in South America: patterns of distribution and diversity

“…The subsequent rise of the Andes during the Miocene, forming the eastern Cordillera of Colombia and Venezuela and the western Cordillera of Colombia and Ecuador, had increased the heterogeneity of the Andean environments throughout the late Tertiary, resulting in the differentiation of the tribe (Reig, 1986). Despite all criticisms to Reig's AOD hypothesis, it is noteworthy that recent phylogenies (Smith & Patton, 1999;Weksler, 2003Weksler, , 2006Steppan et al, 2004;Percequillo et al, 2011), new data on the fossil record (Pardiñas, 2008;Verzi & Montalvo, 2008), and new evidence on Andean orogeny (Hoorn et al, 1995(Hoorn et al, , 2010 are concordant with the Reig hypothesis (1984Reig hypothesis ( , 1986 regarding the timing of arrival of Sigmodontinae in South America; hypotheses on the patterns and processes of diversification for this group are still very preliminary (Patton et al, 2000;Costa, 2003;Almeida et al, 2007;Barros et al, 2009;Smith et al, 2001;Miranda et al, 2007;among others), but evidence so far suggests a much more complex scenario than that envisioned by Reig.…”

“…Despite these deficiencies, based on substantive advances in our understanding of the geographical distribution, taxonomy and phylogenetic relationships, several authors have hypothesized the place and pattern of geographical diversification, as well as the time of origin and radiation patterns, of this group (Simpson, 1950(Simpson, , 1969Hershkovitz, 1966Hershkovitz, , 1972Patterson & Pascual, 1968Savage, 1974;Baskin, 1978Baskin, , 1986Marshall, 1979;Reig, 1980Reig, , 1984Reig, , 1986Jacobs & Lindsay, 1984;Slaughter & Ubelaker, 1984;Steppan, 1995;Engel et al, 1998;Smith & Patton, 1999;Pardiñas et al, 2002;Steppan et al, 2004;Barros et al, 2009;Valencia-Pacheco et al, 2011).…”

Chromosomal variation in Argentine populations of Akodon montensis Thomas, 1913 (Rodentia, Cricetidae, Sigmodontinae)

“…Its species are widely distributed in South America and inhabit a variety of habitats, among subtropical and tropical moist forest as well as desert regions (Musser and Carleton 2005). From a taxonomic point of view, the genus includes morphologically very similar species, and cytogenetic data is valuable for identifying them, such as Akodon cursor (Winge, 1887) and Akodon montensis (Yonenaga-Yassuda et al 1975; Barros et al 2009). This genus has high karyotypic variability, with chromosome numbers varying from 2n=46 (FN=46) in Akodon serrensis Thomas, 1902 to 2n=10 (FN=14) in Akodon sp.…”

“…This genus has high karyotypic variability, with chromosome numbers varying from 2n=46 (FN=46) in Akodon serrensis Thomas, 1902 to 2n=10 (FN=14) in Akodon sp. (Barros et al 2009). In different species, several chromosome variations were described, including pericentric inversions and Robertsonian translocations in autosomes, modifications of sex chromosomes and the presence of B chromosomes (Silva and Yonenaga-Yassuda 1998; Fernández-Donoso et al 2001; Bianchi 2002).…”

Pequenos mamíferos não-voadores do Planalto Atlântico de São Paulo: identificação, história natural e ameaças

“…É registrada para a Mata Atlântica, do Espírito Santo a Santa Catarina, incluindo Minas Gerais (Gonçalves 2006, Moreira et al 2009, Barros et al 2009), e para uma mata de Araucária alterada no Paraná (BarrosBatestti et al 2000). É associada a áreas de altitudes elevadas, sendo mais freqüente acima de 1400 m (Moreira et al 2009).…”