Extinction of canid populations by inbreeding depression under stochastic environments in Southwestern Goiás State: a simulation study

Abstract

A frequently addressed question in conservation biology is what is the chance of survival for a population for a given number of years under certain conditions of habitat loss and human activities. This can be estimated through an integrated analysis of genetic, demographic and landscape processes, which allows the prediction of more realistic and precise models of population persistence. In this study, we modeled extinction in stochastic environments under inbreeding depression for two canid species, the maned wolf (Chrysocyon brachiurus) and the crab-eating fox (Cerdocyon thous), in southwest Goiás State. Genetic parameters were obtained from six microsattelite loci (Short Tandem Repeats -STR), which allowed estimates of inbreeding levels and of the effective population size under a stepwise mutation model based on heterozygosis. The simulations included twelve alternative scenarios with varying rates of habitat loss, magnitude of population fluctuation and initial inbreeding levels. ANOVA analyses of the simulation results showed that times to extinction were better explained by demographic parameters. Times to extinction ranged from 352 to 844, in the worst and best scenario, respectively, for the large-bodied maned wolf. For the small-bodied crab-eating fox, these same estimates were 422 and 974 years. Simulations results are within the expectation based on knowledge about species' life history, genetics and demography. They suggest that populations can persist through a reasonable time (i.e., more than 200 years) even under the worst demographic scenario. Our analyses are a starting point for a more focused evaluation of persistence in these populations. Our results can be used in future research aiming at obtaining better estimates of parameters that may, in turn, be used to achieve more appropriate and realist population viability models at a regional scale.

Extinction of mammalian populations in conservation units of the Brazilian Cerrado by inbreeding depression in stochastic environments

“…Here, we extended previous results reported by Rodrigues and Diniz-Filho (2007) by evaluating spatial patterns of extinction in different body-size classes (hypothetical "species") of mammalian populations in conservation units of the Brazilian Cerrado. We started by assuming, under a pessimistic scenario of quick habitat loss and fragmentation in the Brazilian Cerrado (Klink and Machado 2005), that in these units isolation among local populations of hypothetical species exists.…”

“…On the other hand, despite methodological and theoretical advances provided by landscape genetics, data on genetic variation on broad regional spatial scales are still scarce, and therefore conservation planners can use overall and heuristic models which allow an integrated analysis of genetic, demographic and landscape parameters that, in turn, can provide data for an evaluation of biodiversity persistence and extinction risks (Henle et al, 2004). These models are usually parameterized by real-life history parameters of the target species or populations and by the environmental characteristics of the region in which the populations are conserved (Frankham et al, 2002;Morris and Doak, 2002;Rodrigues and Diniz-Filho, 2007).Here, we extended previous results reported by Rodrigues and Diniz-Filho (2007) by evaluating spatial patterns of extinction in different body-size classes (hypothetical "species") of mammalian populations in conservation units of the Brazilian Cerrado. We started by assuming, under a pessimistic scenario of quick habitat loss and fragmentation in the Brazilian Cerrado (Klink and Machado 2005), that in these units isolation among local populations of hypothetical species exists.…”

“…On the other hand, despite methodological and theoretical advances provided by landscape genetics, data on genetic variation on broad regional spatial scales are still scarce, and therefore conservation planners can use overall and heuristic models which allow an integrated analysis of genetic, demographic and landscape parameters that, in turn, can provide data for an evaluation of biodiversity persistence and extinction risks (Henle et al, 2004). These models are usually parameterized by real-life history parameters of the target species or populations and by the environmental characteristics of the region in which the populations are conserved (Frankham et al, 2002;Morris and Doak, 2002;Rodrigues and Diniz-Filho, 2007).…”

“…We started by assuming, under a pessimistic scenario of quick habitat loss and fragmentation in the Brazilian Cerrado (Klink and Machado 2005), that in these units isolation among local populations of hypothetical species exists. Our population dynamics simulations were based on Tanaka's (2000a) model of extinction by inbreeding depression under stochastic environ-ments (see also Tanaka, 1997Tanaka, , 1998Tanaka, , 2000b, as explained in detail in Rodrigues and Diniz-Filho (2007). This model is based on three dynamic recurrence equations for mean allele frequency q, inbreeding coefficient F and population size N. Unless otherwise specified, all parameters used here follow previous descriptions by Rodrigues and Diniz-Filho (2007).…”

Maned Wolves of Noel Kempff Mercado National Park

“…In rare events, they have been recorded crossing hundreds, even thousands, of kilometers of unsuitable habitat (Queirolo et al, 2011). Models, imperfect as they are, suggest that maned wolf populations have the potential to grow quickly (Paula et al, 2008) and that some populations are expected to persist for hundreds of years, even under worst-case scenarios (high inbreeding, high rates of habitat loss, and high population variability; Rodrigues and Diniz-Filho, 2007). Nonetheless, we should not diminish the evidence that in the past hundred years, MW have lost extensive habitat and geographic range, and the status of many subpopulations is desperate.…”