Sharing the Space: Distribution, Habitat Segregation and Delimitation of a New Sympatric Area of Subterranean Rodents

Abstract

Subterranean rodents of the genus Ctenomys usually present an allopatric or parapatric distribution. Currently, two cases of sympatry have been recognized for the genus in the coastal dunes of southern Argentina and southern Brazil. In this context, they are ideal models to test hypotheses about the factors that delimit the patterns of space use and to understand interspecific interactions in small mammals. We investigated the vegetation structure, plant biomass and soil hardness selected by two species of subterranean rodents (Ctenomys flamarioni and C. minutus) when distributed in sympatry and allopatry from nine different areas along the line of coastal dunes in southern Brazil. In addition, our work presents a new record of a third area of sympatry for the genus Ctenomys. Ctenomys flamarioni and C. minutus show habitat segregation in the area where they occur in sympatry. These species show segregation in their selection of microhabitats, differing in relation to soil hardness, plant biomass, and plant cover. Ctenomys flamarioni showed a distinction in habitat selection when occurring in allopatry and sympatry, whereas C. minutus selected the same habitat characteristics under both conditions. A possible explanation to the observed pattern is that these species have acquired different adaptations over time which allows them the ability to exploit different resources and thus avoid competitive interactions all together.

Hybridization between subterranean tuco-tucos (Rodentia, Ctenomyidae) with contrasting phylogenetic positions

“…In addition to their morphological similarity, they share the same chromosomal number (2n = 47-48), with the same chromosome G-band pattern among five species (C. flamarioni, C. talarum, C. mendocinus, C. australis and C. porteousi) and have an asymmetric, simple type of sperm with two tails 19,[23][24][25] . C. flamarioni and C. minutus share one of the two sympatric zones described for the genus 26,27 , and in this region, we have information that they can generate hybrids. The common ancestor of torquatus and mendocinus was estimated to have arisen approximately 1.4 million years ago 28 .…”

“…The results of our work demonstrate unequivocally that, in some cases, species that present extensive chromosome organization, phenotype, evolutionary history, sperm morphology and genetics differences, which are usually associated with reproductive isolation, can generate natural hybrids. Furthermore, a series of findings in the field of ecology demonstrated that these two species present modifications during the occupation of microhabitats 27 and morphological character displacement when in sympatry 48 , revealing that species are capable of recognizing individuals of another species and presenting ecological responses due to competition and yet they come into contact during the reproductive period and produce hybrids. Mitochondrial DNA analyses placed hybrid individuals within both species, thus providing evidence of bidirectional gene flow because females may belong to either species; furthermore, microsatellite analysis revealed that the genetic makeup of the hybrid population was the result of admixture between the two parental species.…”

The role of soil features in shaping the bite force and related skull and mandible morphology in the subterranean rodents of genusCtenomys(Hystricognathi: Ctenomyidae)

“…This pattern is likely due to the different characteristics of each environment. Environments with lower bulk density (such as sand dunes) have less biomass than higher density soils (sand fields), as soil density is positively related to the amount of biomass available (food source) (Malizia, Vassallo & Busch, ; Cutrera et al ., ; see the results of Galiano et al ., ; Kubiak, Galiano & Freitas, ). The greater availability of food is likely a key factor in the choice of habitat, leading species with lower bite forces to inhabit locations with higher soil bulk density.…”

Can the environment influence species home‐range size? A case study onCtenomys minutus(Rodentia, Ctenomyidae)

“…Species usually use habitats with similar soil characteristics and availability of resources (Lacey et al ., ). However, some species are found in habitats with sharp differences in resource availability and soil characteristics, as is the case for Ctenomys minutus Nehring, 1887 (Galiano, Bernardo‐Silva & Freitas, ; Galiano, Kubiak & Freitas, ; Kubiak, Galiano & Freitas, ; Galiano et al ., ). This species has solitary habits and its distribution is restricted to the coastal plains of southern Brazil, where populations occur along a linear extension of approximately 500 km (Freitas, ; Freygang, Marinho & Freitas, 2004).…”

“…This species has solitary habits and its distribution is restricted to the coastal plains of southern Brazil, where populations occur along a linear extension of approximately 500 km (Freitas, ; Freygang, Marinho & Freitas, 2004). Along its distribution C. minutus is found in two distinct habitats: sand dunes and sand fields, which have marked differences in habitat characteristics including plant biomass, vegetation cover and soil hardness (see Galiano et al ., ; Kubiak et al ., for details of habitat characteristics for the species in the region) (see Fig. ).…”