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Summary 1. Inbreeding and low genetic diversity can cause reductions in individual fitness and increase extinction risk in animal populations. Intentional introgression, achieved by releasing genetically diverse individuals into inbred populations, has been used as a conservation tool to improve demographic performance in endangered populations. 2. By the 1980s, Florida panthers ( Puma concolor coryi) had been reduced to a small, inbred population that appeared to be on the brink of extinction. In 1995, female pumas from Texas ( P. c. stanleyana) were released in occupied panther range as part of an intentional introgression programme to restore genetic variability and improve demographic performance of panthers. 3. We used 25 years (1981-2006) of continuous radiotelemetry and genetic data to estimate and model subadult and adult panther survival and cause-specific mortality to provide rigorous sex and age class-specific survival estimates and evaluate the effect of the introgression programme on these parameters. 4. Genetic ancestry influenced annual survival of subadults and adults after introgression, as F1 generation admixed panthers ( = 0·98) survived better than pre-introgression type panthers ( = 0·77) and other admixed individuals ( = 0·82). Furthermore, heterozygosity was higher for admixed panthers relative to pre-introgression type panthers and positively influenced survival. 5. Our results are consistent with hybrid vigour; however, extrinsic factors such as low density of males in some areas of panther range may also have contributed to higher survival of F1 panthers. Regardless, improved survival of F1 subadults and adults likely contributed to the numerical increase in panthers following introgression, and our results indicate that intentional admixture, achieved here by releasing individuals from another population, appears to have been successful in improving demographic performance in this highly endangered population. [ABSTRACT FROM AUTHOR]

The rediscovery of remnant Florida panthers (Puma concolor coryi) in southern Florida swamplands prompted a program to protect and stabilize the population. In 1995, conservation managers translocated eight female pumas (P. c. stanleyana) from Texas to increase depleted genetic diversity, improve population numbers, and reverse indications of inbreeding depression. We have assessed the demographic, population-genetic, and biomedical consequences of this restoration experiment and show that panther numbers increased threefold, genetic heterozygosity doubled, survival and fitness measures improved, and inbreeding correlates declined significantly. Although these results are encouraging, continued habitat loss, persistent inbreeding, infectious agents, and possible habitat saturation pose new dilemmas. This intensive management program illustrates the challenges of maintaining populations of large predators worldwide. [ABSTRACT FROM AUTHOR]

Genetic rescue-an increase in population fitness following the introduction of new alleles-has been proven to ameliorate inbreeding depression in small, isolated populations, yet is rarely applied as a conservation tool. A lingering question regarding genetic rescue in wildlife conservation is how long beneficial effects persist in admixed populations. Using data collected over 40 years from 1192 endangered Florida panthers (Puma concolor coryi) across nine generations, we show that the experimental genetic rescue implemented in 1995-via the release of eight female pumas from Texas-alleviated morphological, genetic, and demographic correlates of inbreeding depression, subsequently preventing extirpation of the population. We present unequivocal evidence, for the first time in any terrestrial vertebrate, that genetic and phenotypic benefits of genetic rescue remain in this population after five generations of admixture, which helped increase panther abundance (> fivefold) and genetic effective population size (> 20-fold). Additionally, even with extensive admixture, microsatellite allele frequencies in the population continue to support the distinctness of Florida panthers from other North American puma populations, including Texas. Although threats including habitat loss, human-wildlife conflict, and infectious diseases are challenges to many imperiled populations, our results suggest genetic rescue can serve as an effective, multi-generational tool for conservation of small, isolated populations facing extinction from inbreeding., (© 2024. The Author(s).)

Genetic introgression has been suggested as a management tool for mitigating detrimental effects of inbreeding depression, but the role of introgression in species conservation has been controversial, partly because population-level impacts of genetic introgressions are not well understood. Concerns about potential inbreeding depression in the endangered Florida panther (Puma concolor coryi) led to the release of eight female Texas pumas (P. c. stanleyana) into the Florida panther population in 1995. We used long-term reproductive data (1995-2008) collected from 61 female Florida panthers to estimate and model reproduction probability (probability of producing a litter) and litter size, and to investigate the influence of intentional genetic introgression on these parameters. Overall, 6-month probability of reproduction (±1SE) was 0.232 ± 0.021 and average litter size was 2.60 ± 0.09. Although F(1) admixed females had a lower reproduction probability than females with other ancestries, this was most likely because kittens born to F(1) females survive better; consequently, these females are unavailable for breeding until kittens are independent. There was no evidence for the effect of ancestry on litter size or of heterozygosity on probability of reproduction or litter size. In contrast, earlier studies have shown that genetic introgression positively affected Florida panther survival. Our results, along with those of earlier studies, clearly suggest that genetic introgression can have differential effects on components of fitness and highlight the importance of examining multiple demographic parameters when evaluating the effects of management actions.