A new species ofAkodonMeyen, 1833 (Rodentia: Cricetidae: Sigmodontinae) endemic from the Brazilian Cerrado

Abstract

Akodon is the second most diverse genus of sigmodontine rodents, comprising 40 extant species. Widely distributed through different environments of South America, the genus ranges from forested to open-vegetation areas, from semiarid to mesic regions, and from Andean altitudes to the lowlands of eastern Brazil. In Brazil, most species are from the Atlantic Forest, inhabiting lowland and montane habitats, with a few taxa also present in areas transitional with the Cerrado and Pantanal. Based on an integrative approach of genetics (cytogenetic and molecular data) and morphology (qualitative and quantitative external and craniodental data), we present in this contribution the hypothesis of a new species of Akodon based on specimens collected in the southwestern limit of the Cerrado domain, in the seasonally dry forests of the Serra da Bodoquena, Mato Grosso do Sul, Brazil. The new species was recovered as a distinct lineage sister to Akodon philipmyersi, a poorly known species from the Northern Campos grasslands of Misiones Province, Argentina, and can be distinguished from its congeners by its karyotype (2n = 40, FN = 40), morphology (morphometric, pelage, and skull characters), as well as by its degree of genetic divergence (above 7.5% in Cytb sequences). This new species is endemic to the Cerrado, one of the world’s biodiversity hotspots, and to Serra da Bodoquena, one of the top priority areas for conservation in Brazil. Moreover, the new species increases the number of lineages of Akodon in Brazil, emphasizing the richness and endemism currently found in the Cerrado domain, and the importance of the open formations to the diversification of Neotropical taxa.

Historical biogeography of a rapid and geographically wide diversification in Neotropical mammals

“…However, it is important to note that under the crown ages estimated for these genera by Maestri et al (2017), Akodon is the genus with the highest rate (0.45; Oligoryzomys: 0.31; and Thomasomys: 0.27). The rates of Akodon and Oligoryzomys get much closer (0.52 and 0.49 respectively), but also above that of Thomasomys (0.38) if crown ages estimated by Steppan and Schenk (2017) S5 for the former) are not as well understood as in Oligoryzomys (see generic accounts in Patton et al, 2015 and the recent discussions on species limits for Akodon and Thomasomys in Brandão et al, 2021 andPacheco, 2021 respectively). It is also relevant to note that in a study of the diversification of the whole sigmodontine subfamily, a MEDUSA analysis detected shifts to higher rates at the nodes leading to Akodon and Thomasomys, but not with Oligoryzomys (Parada et al, 2015).…”

“…The rates of Akodon and Oligoryzomys get much closer (0.52 and 0.49 respectively), but also above that of Thomasomys (0.38) if crown ages estimated by Steppan and Schenk (2017) are used. Additionally, it is worth noting that species boundaries in Thomasomys and Akodon (in particular for the former) are not as well understood as in Oligoryzomys (see generic accounts in Patton et al, 2015 and the recent discussions on species limits for Akodon and Thomasomys in Brandão et al, 2021 and Ruelas & Pacheco, 2021 respectively). It is also relevant to note that in a study of the diversification of the whole sigmodontine subfamily, a MEDUSA analysis detected shifts to higher rates at the nodes leading to Akodon and Thomasomys , but not with Oligoryzomys (Parada et al, 2015).…”

“…However, it allows the comparing of groups that, as said, are not included with their whole species richness in each phylogeny. The number of living species of each genus was taken from Mammal Diversity Database (2020) and subsequent publications (Brandão et al, 2021; Brito et al, 2021; Ruelas & Pacheco, 2021). Three dating schemes were used to obtain the crown ages of the three genera of interest—Parada et al (2015), Maestri et al (2017) and Steppan and Schenk (2017).…”

Habitat Heterogeneity and Geographic Location as Major Drivers of Cerrado Small Mammal Diversity Across Multiple Spatial Scales

“…Taxonomic identifications were based on morphological, karyological, and/or molecular data. Nomenclature and classification follow Voss and Jansa (2009) for the marsupials and Patton et al (2015) for the rodents, and also follow recently published arrangements and species descriptions (Nascimento et al, 2013;Bonvicino et al, 2014a;Hurtado and Pacheco, 2017;Weksler et al, 2017;Suárez-Villota et al, 2018;Silva et al, 2019;Brandão et al, 2021;Fegies et al, 2021).…”

“…Inventories based on standardized sampling design and high capture effort, with the use of complementary sampling methodologies in poorly surveyed areas, are highly recommended [e.g., central and eastern Mato Grosso (Brandão et al, 2019); southeastern and western Goiás (Hannibal et al, 2021); central Minas Gerais and eastern Mato Grosso do Sul (Mendonça et al, 2018)], as shown here, to provide robust datasets and increased knowledge on species diversity and distribution in the biome. The collection of vouchers and tissue samples, as well as karyotype data from the surveyed small mammals, is the basis for the description of new taxa (e.g., Bonvicino et al, 2014a;Brandão et al, 2021). Indeed, improvements on the systematics of several genera have contributed with the high richness found in open habitats, as well the high β-diversity found across localities, as previously widely distributed taxa are currently represented by distinct restricted-range species [e.g., former concepts of Oligoryzomys fornesi Bonvicino, 2005, 2015); Oryzomys subflavus (Percequillo et al, 2008); Thrichomys apereoides (Nascimento et al, 2013); and Micoureus demerarae (Silva et al, 2019)].…”