New data of the long-clawed mouse Pearsonomys annectens (Cricetidae, Sigmodontinae) and additional comments on the distinctiveness of Pearsonomys

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

Background

The phylogenetic position of the sigmodontine genus Abrawayaomys, historically assigned to the tribe Thomasomyini or considered a sigmodontine incertae sedis, was assessed on the basis of nuclear and mitochondrial DNA sequences obtained from four individuals from different localities in the Atlantic forest of Brazil. Sequences of Abrawayaomys were analyzed in the context of broad taxonomic matrices by means of maximum-likelihood (ML) and Bayesian analyses (BA).

Results

The phylogenetic position of Abrawayaomys differed depending on the gene analyzed and the analysis performed (interphotoreceptor retinoid-binding protein (IRBP) ML: sister to Thomasomyini; IRBP BA: sister to Akodontini; cytochrome (Cyt) b ML: sister to Neotomys; and Cyt b BA: sister to Reithrodontini). With the sole exception of the BA based on Cyt b sequences, where the Abrawayaomys-Reithrodon clade had strong support, all sister-group relationships involving Abrawayaomys lacked any significant support.

Conclusions

As such, Abrawayaomys constitutes the only representative so far known of one of the main lineages of the sigmodontine radiation, differing from all other Atlantic forest sigmodontine rodents by having a unique combination of morphological character states. Therefore, in formal classifications, it should be regarded as a Sigmodontinae incertae sedis.

Geographic distribution of Rhyncholestes raphanurus Osgood, 1924 (Paucituberculata:Caenolestidae), an endemic marsupial of the Valdivian Temperate Rainforest

The Chilean shrew opossum (Rhyncholestes raphanurus) is the southernmost representative of the family Caenolestidae (Marsupialia : Paucituberculata). The species lives in temperate forests of southern Chile and Argentina and is currently known from <25 localities, spanning a latitudinal and longitudinal range of 2°44′ (~320 km) and 2°20′ (~190 km), respectively. Species distribution was analysed in a historical, geographic and biogeographic context, with the use of maps at different scales (region, subregion, province, ecoregion, forest types), and two potential distribution models were generated with MaxEnt. The models show a few isolated areas of high prediction values (>50%) in coastal Chile and the Andes from 39°30′ to ~42°S, and most of Chiloé Island, plus a northern and southern expansion of medium to low (<50%) prediction values. The most important environmental variables identified from the models include precipitation and some temperature-related variables. The species occurrence lies within the Andean region, Subantarctic subregion, and Valdivian biogeographic province. At a smaller scale, most of the localities occur in eight of the 22 forest types described for the Valdivian ecoregion, implying narrow ecological requirements. Identification of critical areas through potential distribution modelling may have implications for species conservation and identification of biogeographic patterns.