Phylogeographic Structure and Karyotypic Diversity of the Brazilian Shrew Mouse (<b><i>Blarinomys breviceps</i></b>, Sigmodontinae) in the Atlantic Forest

Abstract

Blarinomys breviceps possesses cryptic and burrowing habits with poorly documented genetics and life history traits. Due to its rarity, only a few specimens and DNA sequences have been deposited in collections worldwide. Here, we present the most comprehensive cytogenetic and molecular characterization of this rare genus. Phylogenetic analyses based on partial cytochrome b sequences were performed, attempting to establish the relationships among individuals with distinct karyotypes along the geographic distribution of the genus in the Atlantic Forest. Classical and molecular cytogenetics, using banding patterns and FISH of telomeric and whole chromosome X-specific painting probes (obtained from the Akodontini Akodon cursor) were used to characterize and compare the chromosomal complements. Molecular phylogenetic analyses recovered 2 main geographically structured clades, northeastern and southeastern with pairwise sequence divergences among specimens varying between 4.9 and 8.4%. Eight distinct karyomorphs are described: (A) 2n = 52 (50A, XX), (B) 2n = 52 (48A, XY+2Bs), (C) 2n = 45 (42A, XY+1B), (D) 2n = 43 (37A, XX+4Bs), (E) 2n = 37 (34A, XY+1B), (F) 2n = 34 (32A, XX), (G) 2n = 31 (27A, XX+2Bs), (H) 2n = 28 (26A, XY), all with the same number of autosomal arms (FN_A = 50). Variation of 0–4 supernumerary chromosomes (Bs) presenting heterogeneity in morphology and distribution of interstitial telomeric sequences (ITSs) is reported. ITSs are also found in some metacentric autosomes. The phylogeographic separation between 2 major lineages with high levels of genetic divergence, and the wide karyotypic diversity indicate that B. breviceps is a diverse group that warrants taxonomic re-evaluation.

The phylogenetic position of the enigmatic Atlantic forest-endemic spiny mouse Abrawayaomys (Rodentia: Sigmodontinae)

“…Such a study would clarify into which of the already known phylogeographic patterns of Atlantic forest mammals (e.g., Colombi et al 2010;Ventura et al 2012;Valdez and D'Elía 2013; see reviews in Martins 2011; Costa and Leite 2012) would A. ruschii fit, or if this species presents a so far undescribed pattern. Similarly, such a study would help assess the alpha diversity of Abrawayaomys (Pardiñas et al 2009b).…”

Intense genomic reorganization in the genus Oecomys (Rodentia, Sigmodontinae): comparison between DNA barcoding and mapping of repetitive elements in three species of the Brazilian Amazon

“…This scenario is made evident by comparing the degree of conservation in the position and location of this sequence compared with 45S rRNA. Ventura et al (2012) described a similar situation in Akodontini, which shows conservation of 5S rDNA chromosomal sites, despite large chromosomal variability within the group.…”

New karyologycal data and cytotaxonomic considerations on small mammals from Santa Virgínia (Parque Estadual da Serra do Mar, Atlantic Forest, Brazil)

“…Blarinomys breviceps presents a peculiar karyotype and it could not be considered species-specific due to the great variability in 2n and FNa (Geise et al 2008, Ventura et al 2012). Moreover, Ventura et al (2012) suggested the existence of more species for the monotypic genus Blarinomys in Atlantic Forest since molecular phylogenetic analyses showed two geographically distinct lineages.…”

“…Moreover, Ventura et al (2012) suggested the existence of more species for the monotypic genus Blarinomys in Atlantic Forest since molecular phylogenetic analyses showed two geographically distinct lineages.…”

“…Their functions and molecular composition remain obscure but, apparently in mammals, these chromosomes neither promote phenotypic alterations nor affect fitness of individuals (Jones and Rees 1982, Trifonov et al 2010). B chromosomes are known in nine Brazilian rodent species (Silva and Yonenaga-Yassuda 2004, Ventura et al 2012). Herein, we found B chromosomes in four out of 13 species of rodents (30,76%, i.e.…”