Comparison of reintroduction and enhancement effects on metapopulation viability

Abstract

Metapopulation viability depends upon a balance of extinction and colonization of local habitats by a species. Mechanisms that can affect this balance include physical characteristics related to natural processes (e.g. succession) as well as anthropogenic actions. Plant restorations can help to produce favorable metapopulation dynamics and consequently increase viability; however, to date no studies confirm this is true. Population viability analysis (PVA) allows for the use of empirical data to generate theoretical future projections in the form of median time to extinction and probability of extinction. In turn, PVAs can inform and aid the development of conservation, recovery, and management plans. Pitcher's thistle (Cirsium pitcheri) is a dune endemic that exhibited metapopulation dynamics. We projected viability of three natural and two restored populations with demographic data spanning 15-23 years to determine the degree the addition of reintroduced population affects metapopulation viability. The models were validated by comparing observed and projected abundances and adjusting parameters associated with demographic and environmental stochasticity to improve model performance. Our chosen model correctly predicted yearly population abundance for 60% of the population-years. Using that model, 50-year projections showed that the addition of reintroductions increases metapopulation viability. The reintroduction that simulated population performance in early-successional habitats had the maximum benefit. In situ enhancements of existing populations proved to be equally effective. This study shows that restorations can facilitate and improve metapopulation viability of species dependent on metapopulation dynamics for survival with long-term persistence of C. pitcheri in Indiana likely to depend on continued active management.

Life at the top: Long-term demography, microclimatic refugia, and responses to climate change for a high-elevation southern Appalachian endemic plant

“…Augmentation can be effective at increasing population viability (Halsey et al, 2015). Our modeling suggests that 20-70 seedlings would need be added each year to balance population growth.…”

Connectivity or isolation? Identifying reintroduction sites for multiple conservation objectives for wisents in Poland

“…New populations make an important conservation contribution by increasing the total number of individuals of threatened species. In addition, reintroductions increasingly take place within wider strategies to increase connectivity and genetic exchange among populations, and thus to establish larger metapopulations (Halsey et al , ; Peters et al , ). This requires identifying places where new populations would maximally contribute to linking existing but currently isolated herds (Kuemmerle et al , 2011 a ).…”

Population viability analysis and the effects of light availability and litter on populations of Cirsium pitcheri, a rare, monocarpic perennial of Great Lakes shorelines

“…Reintroduction may be a more immediate and reliable option. Successful reintroductions have established populations the southern end of the range and can enhance population viability (McEachern et al, 1994;Bell et al, 2003;Halsey et al, 2015). Recent work suggests that population sizes of reintroductions may have important genetic consequences (Fant et al, 2013(Fant et al, , 2014.…”

“…The effects of shade and litter accumulation on other stages are as yet unknown. Furthermore, this is but one population for a disturbancespecialist species which may function as a metapopulation (McEachern, 1992;Halsey et al, 2015).…”

“…Recent work suggests that population sizes of reintroductions may have important genetic consequences (Fant et al, 2013(Fant et al, , 2014. Suitable reintroduction sites should be selected based upon amount of cover and litter, successional stage, and probability of disturbance (Halsey et al, 2015) to increase availability of open sand habitat for future seedling recruitment and suitable effective population sizes.…”