Bruno Busnello Kubiak

DNA metabarcoding diet analysis for species with parapatric vs sympatric distribution: a case study on subterranean rodents

Closely related sympatric species commonly develop different ecological strategies to avoid competition. Ctenomys minutus and C. flamarioni are subterranean rodents parapatrically distributed in the southern Brazilian coastal plain, showing a narrow sympatric zone. To gain understanding on food preferences and possible competition for food resources, we evaluated their diet composition performing DNA metabarcoding analyzes of 67 C. minutus and 100 C. flamarioni scat samples, collected along the species geographical ranges. Thirteen plant families, mainly represented by Poaceae, Araliaceae, Asteraceae and Fabaceae, were identified in the diet of C. minutus. For C. flamarioni, 10 families were recovered, with a predominance of Poaceae, Araliaceae and Asteraceae. A significant correlation between diet composition and geographical distance was detected in C. minutus, whereas the diet of C. flamarioni was quite homogeneous throughout its geographical distribution. No significant differences were observed between males and females of each species. However, differences in diet composition between species were evident according to multivariate analysis. Our results suggest some level of diet partitioning between C. flamarioni and C. minutus in the sympatric region. While the first species is more specialized on few plant items, the second showed a more varied and heterogeneous diet pattern among individuals. These differences might have been developed to avoid competition in the region of co-occurrence. Resource availability in the environment also seems to influence food choices. Our data indicate that C. minutus and C. flamarioni are generalist species, but that some preference for Poaceae, Asteraceae and Araliaceae families can be suggested for both rodents.

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

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.

Wet soils affect habitat selection of a solitary subterranean rodent (Ctenomys minutus) in a Neotropical region

Subterranean rodents are characterized by limited individual mobility and patchy distribution of local populations. Habitat patches where the species is absent may either be unoccupied, but suitable patches, or in fact unsuitable as habitat due to specific habitat features. In the coastal plain of southern Brazil, Ctenomys minutus (Ctenomyidae) inhabits sandy grasslands and dunes. The aim of our study was to analyze the relationship between the distribution of this subterranean rodent and its environment. We considered vegetation and soil features. Our results showed that habitat occupancy patterns of C. minutus are determined by soil moisture and vegetation (food supply), but there might be other habitat features that regulate the habitat choice of this mammal. Habitat discontinuities in the coastal plain of southern Brazil, with numerous barriers to dispersal, are responsible for restricting individuals to their natal areas. This might result in increased intraspecific competition within each population and, consequently, in inbreeding.

Medium- and large-sized mammals in a steppic savanna area of the Brazilian Pampa: survey and conservation issues of a poorly known fauna

The wildlife of the Brazilian Pampa is threatened by large-scale habitat loss, due in particular to the expansion of soybean cultivation and the conversion of grasslands areas into extensive areas of silviculture. It is essential to study how the mammal fauna copes with the highly fragmented, human-influenced, non-protected landscape. Our study presents the results of a survey of the large- and medium-sized mammals of a typical human-influenced steppic savanna area of the Pampa biome. The survey was conducted exclusively with the use of camera traps over a period of 16 months. The relative frequencies of species in the area were evaluated. We recorded 18 species, some of them locally threatened (Tamandua tetradactyla, Alouatta caraya, Leopardus colocolo, Leopardus geoffroyi, Leopardus wiedii, Puma yagouaroundi, Mazama gouazoubira and Cuniculus paca). Several species were found to thrive in the area; however, many species were considered rare, and undoubtedly new species could be recorded if we continued the sampling. Our results contribute to the knowledge of faunal diversity in the Pampa biome and associated habitats, warn about threats and provide support for conservation measures.

New record and distribution extension of the rare Atlantic Forest endemic Abrawayaomys ruschii Cunha & Cruz, 1979 (Rodentia, Sigmodontinae)

We recorded three individuals of Abrawayaomys ruschii Cunha & Cruz, 1979 in Chapeco, Santa Catarina state, expanding the known geographic distribution of the species in approximately 370 km west from its nearest locality. It is the second record of the species in this type of physiognomy, characterized by the transition of Seasonal Deciduous and Mixed Ombrophilous forests. Additionally, this is the closest record, about 200 km east, from the recently described Abrawayaomys chebezi Pardinas, Teta & D’Elia, 2009.

Diversity of small land mammals in a subtropical Atlantic forest in the western region of the state of Santa Catarina, southern Brazil

Small land mammals possess features that significantly influence the dynamics of ecosystems and participate in various levels of the food web. In the Brazilian Atlantic Forest the richness of these animals is high, which makes them even more ecologically and numerically relevant in this environment. In this context, we investigated the species composition of small mammals in an unexplored area of southern Brazil, and compared the species composition of this area with other Atlantic Forest regions in order to understand how this community is related to others. The study area was located in an interior Atlantic forest formation, at a transition region between deciduous and Araucaria forests. Small mammals were captured at five collection points using pitfall traps. We compared the species composition found in our studied area with the composition of other 11 studies in different regions by a cluster analysis, and we investigated the presence of spatial autocorrelation between communities with a Mantel test. We recorded 779 individuals from 21 species of small rodents (15 species) and marsupials (six species) during the 13 months of the collection period. This richness was high compared to other studies conducted in the Atlantic Forest formations near to coastline and in interior forest formations. This may be a result of the conditions provided by this transition area (deciduous and Araucaria forests), where could be found elements of the both forests formations, which probably allows the establishment of small mammal species from both forest types. Despite differences in sampling effort of the studies, our results suggest that the interior forest formations may harbor a number of species comparable to the formations near the coast. The species composition of this area was similar to those found in other interior forest formations with the same phytophysiognomy characteristics and at nearby regions, and it was less similar to the distant formations located in southeastern and northeastern Brazil and nearby to the coastline. This can be a result of both the spatial autocorrelation (i.e. more nearby communities tend to have more similar species composition) and the differences of forest characteristics among regions.

Interspecific interactions may not influence home range size in subterranean rodents: a case study of two tuco-tuco species (Rodentia: Ctenomyidae)

Coexistence between species with similar niche requirements is often facilitated by displacement of morphological, behavioral, or physiological characteristics. Experiments comparing treatments with and without the presence of potential competitors are ideal for testing hypotheses of interspecific competition. Here, we investigate a fundamental aspect in the natural history of a species: the home range. We determined whether co-occurrence can influence the home range size of 2 subterranean rodent species, Ctenomys flamarioni and C. minutus. We evaluated home range size in populations of both species in allopatry and sympatry along the coastal plain of southern Brazil. Animals were radiotracked, and the home range size of each individual was estimated using grid cells and minimum convex polygon methods. We found no significant differences in home range size between sites or species, and the interaction was nonsignificant. We also found no relationship between home range size and body mass or sex. Our results suggest that co-occurrence may not influence home range size in these species, perhaps due to environmental adaptations that facilitate coexistence (e.g., microhabitat segregation and dietary modifications). Further, the characteristics of the sandy dune habitat may act as environmental filters, favoring similar home range sizes for both species.

Lineages of Tuco-Tucos (Ctenomyidae: Rodentia) from Midwest and Northern Brazil: Late Irradiations of Subterranean Rodents Towards the Amazon Forest

The genus Ctenomys comprises approximately 70 recognized living species of subterranean rodents endemic to South America. Phylogenetic studies to date, based on mitochondrial DNA data, place 44 recognized species in eight species groups and provide evidence for a burst of speciation early in the history of the genus. Species from Argentina, Uruguay, Bolivia, and southern Brazil are well studied at the phylogenetic level. However, the taxonomic status of the species inhabiting midwest and northern Brazil remains poorly understood. In this study, we construct phylogenies based on maximum likelihood and Bayesian inference methods with cytochrome b gene haplotypes of Ctenomys from midwest and northern Brazil and with haplotypes representative of the genus Ctenomys to place the sampled haplotypes into a phylogenetic framework; we also evaluate skull geometric morphometrics data among sampling sites to assess whether skull morphology corroborates the phylogenetic patterns observed. The results show that the sampling sites used in this study are represented by two species, namely, Ctenomys bicolor , which is present in the state of Rondônia, and Ctenomys nattereri , which is present in Mato Grosso and Bolivia. The results also reveal two lineages of Ctenomys distinct from C. bicolor and C. nattereri , henceforth called Ctenomys sp. “xingu” and Ctenomys sp. “central.” Both the species and lineages share a most recent common ancestor with C. boliviensis and are part of the boliviensis species group.

Can Niche Modeling and Geometric Morphometrics Document Competitive Exclusion in a Pair of Subterranean Rodents (Genus Ctenomys) with Tiny Parapatric Distributions

Species with similar ecological requirements coexisting in the same geographic region are prone to competitively exclude each other. Alternatively, they may coexist if character displacement acts to change the niche requirements of one or both species. We used two methodological approaches (ecological niche modeling [ENM] and geometric morphometrics) to test two hypotheses: given their behavioral, morphological, and ecological similarities, one species competitively excludes the other; and, character displacement enables their coexistence at two sites in which the species are known to occur in sympatry. The results from the ENM-based approach did not provide evidence for competitive exclusion; however, the morphometric analyses documented displacement in size of C. minutus. This result, suggests that C. minutus might exclude C. flamarioni from areas with softer soils and higher food availability. We stress the importance of using multiple methodological approaches when testing prediction of competitive exclusion. However, both methods had limited explanatory power given that the focal species possess truly peculiar distributions, being largely parapatric and restricted to narrow, small geographic areas with a strange distribution and there is a need to search for additional methods. We discuss the idiosyncrasy of the ENM-based approach when applied to organisms with subterranean habits.

Small mammals in Araucaria rain forest: linking vegetal components and the arthropod fauna with rodent community

The abundance of small mammal species is particularly influenced by vegetation and arthropods. Studies that focus on understanding these correlations between small mammals, habitat features and resource availability will provide insights into the ecological processes that drive mammal communities. We investigated the correlations of the abundance of terrestrial arthropod taxa and of the abundance of trees and treelets with the composition of a small mammal community in a patch of Araucaria rain forest in southern Brazil. We established 25 stratified plots in the sampling grid of small mammals and sampled the abundances of trees, treelets and the ground arthropods. Relatively poor small mammal richness, when compared with other formations of Atlantic forest, was registered for this area of Araucaria forest, but consistent with findings for other small mammal communities in the Araucaria forest of southern Brazil. The abundance of small mammal species of the local community was associated with the abundance of trees of two species and with the abundance of treelets of four species. Regarding the arthropods, the abundance of rodents was associated only with the abundance of coleopterans. Thus, these resources may be a mechanism allowing their coexistence in the same area.