Ctenomys

Tammone, Mauro N., Lacey, Eileen A. & Pardiñas, Ulyses F. J., 2022, A century of stasis: Taxonomy of Ctenomys (Rodentia: Hystricomorpha) populations in northeastern Patagonia limits, Argentina, Zoologischer Anzeiger 298, pp. 136-147 : 139-141

3.1. Phylogenetic relationships among Ctenomys from northeastern Patagonia

The 28 individuals sequenced as part of this study revealed 24 distinct Cytb haplotypes. The complete genetic data set used in our phylogenetic analyses (n = 136 haplotypes) included 306 polymorphic sites, of which 54 were singletons (mutations appearing in only one of the haplotypes examined). Both BI and ML analyses indicated that animals from eastern Río Negro and Chubut provinces are members of the monophyletic “ magellanicus ” lineage ( PP = 1; MLB = 87; Fig. 2 ; Supplementary Data SD 4). Also included in this lineage is the specimen from Anelo ˜in central Neuqu´en Province as well as those from Pillahuinco and Bariloche in central and western Río Negro Province, respectively .

Our analyses reveal that contained within the “ magellanicus ” lineage are three well-supported clades ( Fig. 2 ) that are structured latitudinally. The northernmost clade (PP = 1; MLB = 98) encompasses populations of Ctenomys ranging from southern Mendoza and central Neuqu´en provinces to the Atlantic coast in Río Negro Province, including specimens of C. bidaui from Península Vald´es in Chubut Province. In particular, specimens from localities in eastern Río Negro Province, including material collected at Monte Bagual, El Condor´, Pozo Salado and El S´otano, comprise a monophyletic group that is associated with C. bidaui (PP = 1; MLB = 97). Also associated with this clade (PP = 1; MLB = 96), although located outside of it, is the specimen from Anelo ˜in Neuqu´en Province. Sister to these animals (PP = 1; MLB = 91) is an unnamed form (PP = 1; MLB = 100; Ctenomys sp. Bardas Blancas; Fig. 2 ) from southern Mendoza Province reported in Tammone et al. (2021). The haplotype obtained from the specimen collected at Laguna Blanca in Neuqu´en Province is sister to all haplotypes included in this northern clade.

The central clade identified within the “ magellanicus ” lineage (PP = 1; MLB = 96) includes populations of Ctenomys that are widely distributed across Río Negro, Chubut and Santa Cruz Provinces ( Fig. 2 ). Within this clade, two well-supported subclades are evident. One (PP = 1; MLB = 83) is a polytypic unit consisting of three branches corresponding to C. contrerasi , C. thalesi , and C. sericeus . This sub-clade also contains the nominal form C. coyhaiquensis proposed to be synonymous with C. sericeus by Teta and D’ Elía (2020) as well as a haplotype misidentified as C. fodax (Teta et al. 2020; see discussion). C. contrerasi is monophyletic (PP = 1; MLB = 84) and includes specimens from Aguada Cecilio and Playas Doradas in Río Negro Province and from Puerto Madryn in Chubut Province. The branch containing C. thalesi is also monophyletic (PP = 1; MLB = 99) and includes specimens from Cabo Raso and Pico Salamanca in southeast Chubut Province. The branch containing C. sericeus appears to be allied with C. thalesi , although with poor support (PP = 0.89; MLB = 59; Fig. 2 ).

The second subclade (PP = 1; MLB = 99) within the central lineage is composed of specimens that have been traditionally recognized as C. haigi . This subclade includes our specimens from Pillahuinco and Bariloche in Río Negro Province. Our analyses suggest that C. haigi is paraphyletic, with the only topotypic sequence available for this species (HM77476) falling outside of the phylogenetic unit defined by the other specimens associated with this name.

The southernmost clade (PP = 1; MLB = 99) within the “ magellanicus ” lineage consists of populations of Ctenomys from Santa Cruz and Tierra del Fuego Provinces in Argentina and adjacent portions of Chile. This subclade is monotypic if the synonymy between C. colburni and C. magellanicus proposed by Teta et al. (2020) is accepted. No geographic partitioning of sequences was evidence between mainland (Santa Cruz) and island (Tierra del Fuego) populations sampled.

Figures

Fig. 2. Phylogenetic relationships among Ctenomys within the “magellanicus” lineage. The tree shown is based on Bayesian inference analyses of Cytb haplotypes (801–1140 bp) for specimens collected within Patagonia. Sequences generated as part of this study are indicated in bold. Black circles denote nodes that were strongly supported by both BI and ML analyses; gray circles indicate nodes that were moderately supported by either BI or ML (threshold values indicated). The map displays the geographic distributions of the northern, central, and southern subclades identified within the “magellanicus” lineage. The phylogenetic tree containing all Cytb sequences considered in this study is provided in Supplementary Data SD4.