Ctenomys dorbignyi, Contreras & Contreras, 1984

Caraballo, Diego A. & Rossi, María Susana, 2018, Integrative lineage delimitation in rodents of the Ctenomys Corrientes group, Mammalia (Warsaw, Poland) 82 (1), pp. 35-47 : 40-41

Ctenomys dorbignyi

This species was originally described by Contreras and Contreras (1984) establishing a narrow distribution in the north of the Corrientes Province. Later, its range was extended, considering four disjunct groups of populations (nucleuses) over the assumption of a common chromosome number 2n = 70 ( Contreras and Scolaro 1986). These nucleuses were designated North (Mbarigüí), South (Paraje Sarandicito, Los ángeles, Esquina and Laguna Itá), East (Contreras Cué) and West (Loma Alta and Mburucuyá), and were differentiated over the base of external and cranial morphometry ( Contreras and Scolaro 1986). Based on discriminant analyses, these authors stated that each nucleus “behaves as a good taxonomic entity”. Karyotypical information was then published by Ortells et al. (1990) who found that Mbarigüí and Paraje Sarandicito had undistinguishable 2n = 70 FN = 84 karyotypes ( Table 1 ). Hence, these two disjunct nucleuses, although they are 350 km away, maintained their adscription to Ctenomys dorbignyi and were identified as relicts of a widespread nearly continuous ancestral stock of the Corrientes group. More recently Argüelles et al. (2001) ascribed to this species a third karyotypically related group of populations from the localities of Paso Vera and San Joaquín de Miraflores, at the Entre Ríos Province. Taking these three nucleuses into consideration C. dorbignyi was considered Near Threatened in the IUCN Red List ( Bidau et al. 2008b).

Notwithstanding, the Entrerrianan populations have a different chromosomal arm number, FN = 88 ( Argüelles et al. 2001), which indicates that, under the applied delimitation criterion this third nucleus is a separate lineage. In addition, when included into the cyt-b phylogeny, the populations of San Joaquín de Miraflores and Paso Vera fall into the clade containing the Ctenomys pearsoni complex ( Figure 3 ), as occurs with the also Entrerrianan population of Médanos which also has a FN = 88 ( García et al. 2000a), confirming these populations are not members of the Corrientes group. The northern (Mbarigüí and Paraje Angostura) and the southern (Paraje Sarandicito) nucleuses split apart in the basal clades of the Corrientes group ( Figure 3 ), and also form unique separate SSR clusters ( Table 1 , see below). Thus, we propose to restrict Ctenomys dorbignyi to the northern populations: Mbarigüí (topotype) and Paraje Angostura. It should be remarked that Contreras et al. (1985) included at least seven additional neighboring populations in the northern nucleus of C. dorbignyi . However, no genetic or cytogenetic studies have been carried out in these populations.

Figures

Figure 3: Phylogeny based on the complete cyt-b sequence of 138 Octodontid taxa. Nodes with Bayesian posterior probability value <0.7 were collapsed into polytomies. Diploid (2n) and fundamental (FN) numbers are shown next to each terminal, based on data published by Argüelles et al. (2001), Tomasco and Lessa (2007), Caraballo et al. (2015) and references therein.