Oligoryzomys mattogrossae (Allen, 1916)

Bezerra, Alexandra Maria Ramos, Bonvicino, Cibele Rodrigues, Oliveira, Leony Dias de, Castiglia, Riccardo & Lazar, Ana, 2025, New data on the rare Oxymycterus itapeby and the Anajatuba hantavirus host Oligoryzomys mattogrossae (Rodentia: Cricetidae): the importance of surveys in challenging-to-access environments in the Brazilian Cerrado, Journal of Natural History 59 (17 - 20), pp. 1227-1247 : 1234-1239

Phylogeographic aspects of Oligoryzomys mattogrossae

Phylogenetic trees built with 17 species of Oligoryzomys unequivocally assigned the new specimen from ESCAE to O. mattogrossae , placing it with high support (100% bootstraps for ML, 0.99 posterior probability for BI) within the clade including all the haplotypes belonging to this species ( Figure 3 (A)). Both phylogenetic tree and TCS network tentatively retrieved four lineages (L1–4) among the haplotypes belonging to O. mattogrossae ( Figure 3 (B)). Genetic divergence among the lineages ranges from 1.6 to 4.4% ( p -distance). These lineages partially overlap in terms of geographical distribution ( Figure 3 (C), Table 1 ). Lineage 1 (L1) includes two haplotypes from northern Goiás state along the upper Tocantins River; Lineage 2 (L2) consists of two haplotypes, one from northern Goiás state and another from the middle Tocantins River in Tocantins state; Lineage 3 (L3) has a wider distribution in central Cerrado, extending from south-western Bahia state through central and southern Goiás state to eastern Mato Grosso do Sul state; Lineage 4 (L4) is represented solely by the haplotype from ESECAE, within the core Cerrado domain. This haplotype is the most divergent compared to all the others, considering the number of substitutions between it and the closest haplotype ( Figure 3 (B)).

Karyotype and phylogeographic aspects of Oligoryzomys mattogrossae

The karyotype and molecular analyses confirmed the specimen ARB877/MPEG 46619 as O. mattogrossae , a species occurring in Cerrado and Caatinga habitats through central and north-eastern Brazil and Paraguay ( Weksler et al. 2017). This species is characterised by 2n = 62 and FNa = 64 ( Weksler et al. 2017). A chromosomal polymorphism has been detected in this species since specimens from Federal District of Brazil ( Svartman 1989), showed a second karyotype with 2n = 62 and FNa = 65, due to one pericentric inversion affecting one chromosome of a medium sized pair of acrocentric ( Bonvicino et al. 2014).

Three of the four lineages here identified ( Figure 3A ), were already found in a previous phylogeny of O. mattogrossae by Weksler et al. (2017, Fig. 7 ), also using mt-Cytb sequences. Here, we detected cases of co-presence of different lineages in the same locality. This pattern might derive from secondary contact of lineages differentiated in allopatry, but the number of localities is insufficient to correctly interpret patterns. Even if the haplotype from Águas Emendadas Ecological Station (representing lineage 4) is noticeably divergent from the most similar haplotype, we cannot exclude the presence of other lineages in sympatry as is the case for other locations.

The topology of our molecular phylogeny suggests a geographic structure related to two hydrographic basins, the Tocantins-Araguaia (Lineages 1 and 2) and the Paraná (Lineages 3 and 4). Rivers are important geographic barriers for nonvolant small mammal species ( Nascimento et al. 2011; Faria et al. 2013a, 2013b) and the role of rivers in the speciation of some Cerrado and Caatinga endemic species is known (e.g. Nascimento et al. 2013). In this way, our findings denote that further investigations are needed to understand the evolutionary history of O. mattogrossae , an important reservoir of Anajatuba hantavirus (Travassos da Rosa et al. 2010).

Figures

Figure 3. Genetic relationships of Oligoryzomys mattogrossae based on (A) maximum likelihood (ML) tree using cytochrome b (mt-Cytb) sequence data considering the HKY+G + I model. Nodal support indices are indicated at the node (ML/BI). (B) Phylogenetic TCS parsimony network reconstruction. Missing haplotypes are indicated by dashes and black circles. The size of the coloured circles is proportional to the number of individuals for each haplotype. (C) Map showing the two main hydrographic basins (pink and green areas) where the sequenced specimens were collected. The colours of the sample sites match the lineages identified by ML and TCS; the triangle is Águas Emendadas Ecological Station (ESECAE) (this study); and the numbers refer to the localities in Table 1 and Supplementary material I. BI: Bayesian inference, ML: Maximum likelihood.

Figure 7. Gross stomach morphology of Oxymycterus itapeby. Specimen ARB 874/MPEG 46617 in (A) ventral external view with contents, and (B) ventral internal view without contents. The frontal section shows the glandular epithelium confined in a diverticulum (= pouch) (after Carleton 1973). Abbreviations: di: diverticulum (= pouch); o: ostium. Scale bar: 10 mm.