Influence of the rate of introduction on the fitness of restored populations

Abstract

UMR 5173 MNHN-CNRS, 'Conservation des espe`ces restauration et suivi des populations', Muse´um National d ¢Histoire Naturelle, AbstractMost studies using demographic PVA models in a context of species restoration have concluded that rather than the rate of introduction, the total number of individuals released had the most important significant influence on the chance of success. In this article we use a genetic simulation model including deleterious and adaptive alleles to assess the impact of the method of release on the change in population mean fitness. We systematically compare a strategy that consists in releasing all individuals at the same time with a strategy that consists in staggering releases over a long period of time. Our results show that the former strategy is more beneficial for long-term fitness when considering advantageous genes only, while the latter is better when considering deleterious genes only. If deleterious and adaptive alleles are considered together, the best strategy depends then essentially on which of these types of alleles has the stronger influence on the change in total fitness. Although the relative contributions of the variance in total fitness due to adaptive and deleterious alleles may vary with the initial frequencies and the selective and dominance effects of these alleles, our results show that the optimal rate of release is mostly dependant on the expected long-term population size. Thus from a genetic view-point, the temporal release strategy of reintroduced populations should be considered with respect to their environment's carrying capacity.

Genotypic and phenotypic consequences of reintroduction history in the black-footed ferret (Mustela nigripes)

“…The addition of animals through time also appeared to obscure the signature of a population bottleneck in the Arizona population. In South Dakota, despite the maintenance of genetic diversity, we found evidence for a genetic signal of a population bottleneck, as predicted when founding animals are released over a short time frame (Robert and Couvet 2004).…”

Meteorological conditions influence short‐term survival and dispersal in a reinforced bird population

“…Finally, once relationships between mortality and meteorological conditions have been quantified, systematic use of long‐term weather forecast should be implemented to adapt release effort (McCarthy, Armstrong & Runge ). If conditions are unpredictable and highly variable among years, staggering releases over several years is the best strategy to buffer meteorological effects (Haccou & Iwasa ; Robert, Couvet & Sarrazin ). Given that observed variations in survival appear to be related to general processes (meteorological effects, interseasonal differences, role of experience to the release environment), it is likely that these results can be generalized to a large proportion of managed animal populations facing similar constraints, which make them useful to the discipline of reintroduction biology (Seddon, Armstrong & Maloney ) in providing stakeholders with information for reducing uncertainty associated with different release strategies and facilitating discrimination among competing models of post‐release performance (Nichols & Armstrong ).…”

Microsatellite and mitochondrial DNA variation defines island genetic reservoirs for reintroductions of an endangered Australian marsupial, Perameles bougainville

“…Examples from bridled nail-tail wallabies (Sigg 2006) and sea otters (Arrendal et al 2004) suggest that to avoid further erosion of genetic variability it is necessary to introduce supplementary individuals from the wild Dorre Island population. While this must be carefully balanced against the wild population's capacity to sustain continued removal of individuals (Todd et al 2002), only a small number of translocated individuals is needed to improve the genetic composition of the population as a whole (Robert and Couvet 2004;Theodorou and Couvet 2004).…”

“…Such evaluations, however, run the risk of failing to detect genetic changes that may occur in captivity or as founding effects, and which could jeopardise the long-term success of these conservation programs. Effects such as loss of genetic diversity, genetic adaptation to captivity, and accumulation of deleterious alleles have all been shown to detrimentally influence the outcome of translocation programs despite initial success in terms of population expansion (Arrendal et al 2004;Robert and Couvet 2004;Wang and Ryman 2001).…”