Genetic pool information reflects highly suitable areas: the case of two parapatric endangered species of Tuco-tucos (Rodentia: Ctenomiydae)

Abstract

Conservation of small mammals requires knowledge of the genetically and ecologically meaningful spatial scales at which species respond to habitat modifications. Conservation strategies can be improved through the use of ecological niche models and genetic data to classify areas of high environmental suitability. In this study, we applied a Maxent model integrated with genetic information (nucleotide diversity, haplotype diversity and Fu's Fs neutrality tests) to evaluate potential genetic pool populations with highly suitable areas for two parapatric endangered species of tuco-tucos (Ctenomys minutus and C. lami). Our results demonstrated that both species were largely influenced by vegetation and soil variables at a landscape scale and inhabit a highly specific niche. Ctenomys minutus was also influenced by the variable altitude; the species was associated with low altitudes (sea level). Our model of genetic data associated with environmental suitability indicate that the genetic pool data were associated with highly suitable areas for C. minutus. This pattern was not evident for C. lami, but this outcome could be a consequence of the restricted range of the species. The preservation of species requires not only detailed knowledge of their natural history and genetic structure but also information on the availability of suitable areas where species can survive, and such knowledge can aid significantly in conservation planning. This finding reinforces the use of these two techniques for planning conservation actions.

Figure 1. Coastal plain of southern Brazil with geographic details.

The most important lakes and rivers are shown. Points (•) represent geographical regions for which genetic data are available from Lopes and Freitas (2012) and Lopes et al. (2013). In the region of Coxilha das Lombas are displayed the four karyotypic blocks described by Freitas (2007) (A, B, C and D). Conservation areas within the distribution of each species are also displayed (a, b: Parque de Itapeva and Parque da Guarita; c: Parque de Itapuã; d: Refugio de Vida Silvestre Banhado dos Pachecos).

Figure 2. Suitable areas for (a) Ctenomys lami and (b) Ctenomys minutus, according to Maxent (maximum entropy) model in southern Brazilian coastal plain.

Darker regions indicate greater ecological suitability.

Figure 3. Jackknife analyses of the importance of environmental variables in maximum entropy modeling of C. lami (a) and C. minutus (b) occurrence.

A heuristic estimate of the relative contribution of each variable to the global model is given in parentheses, with variables listed in descending order of importance. Grey bars show the performance of the global model (known as test gain) without each variable, and black bars show the influence of each variable in isolation (derived from a univariate model only). The variables are the following: Mean T.C.Q.: mean temperature of coldest quarter; Min. T.C.M.: minimum temperature of coldest month; Max. T.W.M.: maximum temperature of warmest month; P.S.: precipitation seasonality; M.D.R.: mean diurnal range (mean of monthly (max temp - min temp)); Mean T.W.Q.: mean temperature of warmest quarter.

Figure 4. Geographical patterns of genetic parameters estimated within phylogeographic groups (C. minutus) and karyotype blocks (C. lami).

Nucleotide diversity, Π (a); Haplotype diversity, Hd (b); Fu's neutrality parameter, Fs (c), overlapping the potential distribution of C. lami (left column) and C. minutus (right column). Darker regions indicate greater ecological suitability.