Skull shape and size variation within and between mendocinus and torquatus groups in the genus Ctenomys (Rodentia: Ctenomyidae) in chromosomal polymorphism context

Abstract

We tested the association between chromosomal polymorphism and skull shape and size variation in two groups of the subterranean rodent Ctenomys. The hypothesis is based on the premise that chromosomal rearrangements in small populations, as it occurs in Ctenomys, produce reproductive isolation and allow the independent diversification of populations. The mendocinus group has species with low chromosomal diploid number variation (2n=46-48), while species from the torquatus group have a higher karyotype variation (2n=42-70). We analyzed the shape and size variation of skull and mandible by a geometric morphometric approach, with univariate and multivariate statistical analysis in 12 species from mendocinus and torquatus groups of the genus Ctenomys. We used 763 adult skulls in dorsal, ventral, and lateral views, and 515 mandibles in lateral view and 93 landmarks in four views. Although we expected more phenotypic variation in the torquatus than the mendocinus group, our results rejected the hypothesis of an association between chromosomal polymorphism and skull shape and size variation. Moreover, the torquatus group did not show more variation than mendocinus. Habitat heterogeneity associated to biomechanical constraints and other factors like geography, phylogeny, and demography, may affect skull morphological evolution in Ctenomys.

Geographic Mosaic of Extensive Genetic Variations in Subterranean Mole Voles Ellobius alaicus as a Consequence of Habitat Fragmentation and Hybridization

“…The hypothesis of the leading role of chromosomal evolution in Ctenomys [ 45 ] was not supported by mtDNA and microsatellite data. Attempts to find a correlation between morphological and chromosomal variability in Ctenomys have also not been successful [ 46 , 47 ].…”

Redefining the Distributional Boundaries and Phylogenetic Relationships for Ctenomids From Central Argentina

“…Considering the evidence provided by molecular data sets used in this study, it is suggested that C. talarum and C. pundti complex could be considered as the same biological species, or lineages going through a recent or incipient differentiation process. To confirm any of these hypotheses, a multidisciplinary approach will be necessary, such as a study of the type material of each species (Stolz et al, 2013;Tammone et al, 2016;Sánchez et al, 2019), deep chromosome studies (Castilho et al, 2012;Kubiak et al, 2020), wider multi-locus/genomic analyses (MacManes et al, 2015;Lopes et al, 2020), environmental and ecological features (Kubiak et al, 2017;Lopes et al, 2020), and mainly exhaustive approaches on phenotypic variation at different levels (Freitas et al, 2012;Gonçalves, 2021), in conjunction with complex and deeper morphometric analyzes that integrate classical and geometric morphometry (Borges et al, 2017;Fornel et al, 2018;Leipnitz et al, 2020).…”

A new species of the highly polytypic South American rodent Ctenomys increases the diversity of the magellanicus clade

“…In addition, remarkable morphological homogeneity is frequent even among long-standing differentiated species (D'Elía et al 2021). In such a still largely inconclusive scenario, however, major systematic and phylogenetic knowledge has been generated in just over two decades (e.g., Lessa and Cook 1998;D'Elía et al 1999;Mascheretti et al 2000;Slamovits et al 2001;Castillo et al 2005;Parada et al 2011;Gardner et al 2014;Bidau 2015;Freitas 2016Freitas , 2021Caraballo and Rossi 2018;Fornel et al 2018;Leipnitz et al 2020;Teta and D'Elía 2020;D'Elía et al 2021;De Santi et al 2021). One of the most significant advances is the recognition of informal groups of species based on increasingly well-supported clades (Parada et al 2011;Freitas et al 2012;Gardner et al 2014;Caraballo and Rossi 2018;Londoño-Gaviria et al 2018;Leipnitz et al 2020;De Santi et al 2020, 2021Carnovale et al 2021).…”