Influence of landscape and connectivity on anuran conservation: population viability analyses to designate protected areas

Abstract

Threatened species with restricted ranges are at risk from habitat fragmentation and loss, which amplifies genetic bottleneck and impacts of small changes to their environments. Ecological models including population viability analyses (PVAs) can predict the trajectory of populations in a way that is not invasive or detrimental to the study species. They can therefore be a vital tool in modeling populations for conservation purposes. Although habitat suitability models have been used in studies to suggest areas for protected area designation, PVAs are generally not used in this regard. Dryophytes suweonensis and Dryophytes flaviventris are two threatened treefrog species endemic to the Korean Peninsula. The two species face threats of habitat loss and degradation and predation by invasive species among others. We used an integrated modeling approach combining ecological niche, connectivity, and PVAs in Vortex to determine the likelihood of extinction of each species under baseline and protected area designation scenarios. Designation scenarios were simulated in Vortex through halting future reduction in carrying capacity (halting future degradation to sites through protected area status), reducing effects of catastrophes (mitigating the effects of drought), and reducing mortality rates (controlling invasive predator populations and ex situ raising of tadpoles to maturity). We classified the combination of these management efforts as "active management" as opposed to "no management," which is currently being practiced. We additionally used a stepwise approach to determine designation priority of individual patches. Under current conditions (no management), the resulting effective metapopulations after 100 years were 167 +/- 325 individuals with an 86.5% extinction probability for D. suweonensis and 165 +/- 200 individuals with a 90.3% extinction probability for D. flaviventris. Under active management of all sites (93 sites covering 426.9 km(2)), the extinction probability was 0% for both species with significantly increased metapopulation sizes, 15 910 +/- 2855 for D. suweonensis, and 4400 +/- 874 for D. flaviventris. Determining designation priority can inform the regulatory bodies on which habitat to designate and whether active or passive management should be applied. Without intervention, these species will be likely to face imminent extinction. In addition to being useful for government-imposed conservation management, our study can be followed by future studies as a methodology for prioritizing sites for protected area designation.