The effect of summer drought on the predictability of local extinctions in a butterfly metapopulation.

Erik Van Bergen,Miska Luoto,Anniina L K Mattila,Aapo Kahilainen,Marjo Saastamoinen,Tad Dallas,Michelle F Dileo

doi:10.1111/cobi.13515

Abstract

The ecological impacts of extreme climatic events on population dynamics and community composition are profound and predominantly negative. Using extensive data of an ecological model system, we tested whether predictions from ecological models remain robust when environmental conditions are outside the bounds of observation. We observed a 10-fold demographic decline of the Glanville fritillary butterfly (Melitaea cinxia) metapopulation on the Åland islands, Finland in the summer of 2018 and used climatic and satellite data to demonstrate that this year was an anomaly with low climatic water balance values and low vegetation productivity indices across Åland. Population growth rates were strongly associated with spatiotemporal variation in climatic water balance. Covariates shown previously to affect the extinction probability of local populations in this metapopulation were less informative when populations were exposed to severe drought during the summer months. Our results highlight the unpredictable responses of natural populations to extreme climatic events.

Highlights

One of the major challenges in conservation science is to identify the species and populations that are most vulnerable to extinction
When populations are exposed to conditions that are beyond the normal range, such as in the case of extreme climatic events (ECEs), the factors underlying population dynamics may be less relevant and predictions relying on these factors less reliable
Owing to the profound impacts these ECEs can have on ecological functioning, the vulnerability of natural populations to the impacts of climate change may be severely underestimated (Anderson et al 2017; Ummenhofer & Meehl 2017)

Summary

Introduction

One of the major challenges in conservation science is to identify the species and populations that are most vulnerable to extinction. Ecological models aiming to improve understanding of population dynamics in temporally varying environments have been employed to shed light on which regions should receive priority for conservation and to predict which species and populations are most vulnerable (e.g., Franklin et al 2014; Oliver et al 2015). When populations are exposed to conditions that are beyond the normal range, such as in the case of extreme climatic events (ECEs), the factors underlying population dynamics may be less relevant and predictions relying on these factors less reliable. A pantropical episode of coral bleaching, triggered by a marine heatwave in 2016, eradicated over 60% of the coral communities in the Great Barrier Reef (Hughes et al 2017)

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Conclusion