Species groups and the evolutionary diversification of tuco-tucos, genusCtenomys(Rodentia: Ctenomyidae)

Abstract

We present the most comprehensive study to date of species groups in Ctenomys (tuco-tucos), a species-rich genus of Neotropical rodents. To explore phylogenetic relationships among 38 species and 12 undescribed forms we sequenced the complete mitochondrial cytochrome-b genes of 34 specimens and incorporated 50 previously published sequences. Parsimony, likelihood, and Bayesian phylogenetic analyses were performed using additional hystricognath rodents as outgroup taxa. The basal dichotomy of Ctenomys splits C. sociabilis from the remaining tuco-tucos, within which 8 main species groups were identified: boliviensis, frater, mendocinus, opimus, magellanicus, talarum, torquatus, and tucumanus. Whereas most of these groups refer to previous clades proposed on the basis of chromosomes or morphology, the torquatus and magellanicus species groups are novel taxonomic hypotheses. However, relationships among species groups are poorly resolved. Furthmore, the positions of C. leucodon, C. maulinus, and C. tuconax are conflicting or unresolved, and they might represent additional independent lineages. On the basis of molecular dating, we estimate that most species groups originated approximately 3 million years ago.

New species of Ctenomys Blainville 1826 : (Rodentia : Ctenomyidae) from the lowlands and central valleys of Bolivia

“…2) the pertinent statistics for characters were: tree length = 1192; consistency index is 0.323, retention index is 0.686. As in previous studies (e.g., Parada et al 2011, Freitas et al 2012 our phylogenetic analysis of all available cytb data also recovered various species groups with relatively high-levels of support; several of these species and species groups occur in Bolivia. Our phylogenetic hypotheses (Figs.…”

“…Our phylogenetic analyses, the most inclusive to date for species in the genus Ctenomys, show that the "boliviensis" group of Ctenomys (sensu Parada et al 2011) is only weakly supported and is composed of two groups of species: One that includes C. bicolor, C. nattereri, C. boliviensis, and C. steinbachi and one that includes three of the four species described in this report: C. erikacuellarae, C. yatesi, and C. andersoni.…”

“…At the time, Cook and Yates (1994) suggested that C. goodfellowi deserved species-level recognition, basing this recommendation on their study of both chromosomes (2N=46) and allozyme differences (allele frequency differences). Anderson (1997), Lessa and Cook (1998), Cook and Lessa (1998), Parada et al (2011), Freitas et al (2012 have since followed the conclusion of Cook and Yates (1994).…”

“…Methods for DNA extraction, amplification, and sequencing were as given in Lessa and Cook (1998), Parada et al (2011), and Freitas et al (2012). Each PCR fragment was sequenced in both directions; sequences were free of indels, premature stop codons, and ambiguities in forward and reverse directions, providing support for a mitochondrial origin (Triant and DeWoody 2007).…”

Integrative lineage delimitation in rodents of the Ctenomys Corrientes group

“…Their subterranean lifestyle has been associated to high population subdivision and low vagility which may have promoted the fixation of chromosomal novelties by genetic drift Kiblisky 1969, Ortells 1995). Within the genus at least eight species groups were defined, although their relationships have not been completely solved, as several groups fall into polytomies (Parada et al 2011) which may reflect the explosive nature of the radiation of tuco-tucos Cook 1998, Castillo et al 2005). One of these clades, the torquatus group comprises species and populations that inhabit the eastern part of Ctenomys' distribution: Ctenomys torquatus Lichtenstein, 1830 in the grasslands of southern Rio Grande do Sul state, Brazil and northern Uruguay; Ctenomys ibicuiensis Freitas et al, 2012 in western Rio Grande do Sul, Brazil; Ctenomys minutus Nehring, 1887 and Ctenomys lami Freitas, 2001 distributed on the southern Brazilian coastal plains; Ctenomys pearsoni Lessa and Langguth 1983 complex distributed along the coastal plains of southern Uruguay; and the Corrientes group, a complex of populations distributed in the homonymous province of Argentina.…”