The Disconnect Between Short- and Long-Term Population Projections for Plant Reintroductions

Lalasia Bialic-Murphy,Orou G Gaoue,Kapua Kawelo,Tiffany M Knight

doi:10.3389/fcosc.2021.814863

Abstract

The reintroduction of rare species in natural preserves is a commonly used restoration strategy to prevent species extinction. An essential first step in planning successful reintroductions is identifying which life stages (e.g., seeds or large adults) should be used to establish these new populations. Following this initial establishment phase, it is necessary to determine the level of survival, growth, and recruitment needed to maintain population persistence over time and identify management actions that will achieve these goals. In this 5-year study, we projected the short- and long-term population growth rates of a critically endangered long-lived shrub, Delissea waianaeensis. Using this model system, we show that reintroductions established with mature individuals have the lowest probability of quasi-population extinction (10 individuals) and the highest increase in population abundance. However, our results also demonstrate that short-term increases in population abundances are overly optimistic of long-term outcomes. Using long-term stochastic model simulations, we identified the level of natural seedling regeneration needed to maintain a positive population growth rate over time. These findings are relevant for planning future reintroduction efforts for long-lived species and illustrate the need to forecast short- and long-term population responses when evaluating restoration success.

Highlights

The reintroduction of rare plants is a commonly used restoration strategy to prevent species extinction (Maschinski and Haskins, 2012; Soorae, 2013)
Those studies used long-term population projection models to examine if the reintroduction of rare species will likely result in the desired outcome
Consistent with our long-term population growth rate projects, we found that scenario F1 had the highest probability of quasi extinction within a 50-year timeframe (0.19 probability of dropping below 10 individuals), followed by scenario F2 (0.09 probability) and scenarios F3–F6 (0 probability) respectively (Figure 2)

Summary

INTRODUCTION

The reintroduction of rare plants is a commonly used restoration strategy to prevent species extinction (Maschinski and Haskins, 2012; Soorae, 2013). Within the population ecology literature, there are a small but growing number of studies that have moved beyond evaluating initial benchmarks of reintroduction success, such as initial establishment, reproductive maturity, and recruitment (Bell et al, 2003; Maschinski and Duquesnel, 2007; Colas et al, 2008) Those studies used long-term population projection models to examine if the reintroduction of rare species will likely result in the desired outcome (i.e., establishing new populations that will persist over time). We focused on setting biologically meaningful benchmark goals for seedling recruitment because it was the only life stage that could be improved by management

METHODS

RESULTS

DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT