Effects of climate on pine processionary moth fecundity and on its egg parasitoids.

Riziero Tiberi,Francesco Croci,Tiziana Panzavolta,Guido Tellini Florenzano,Matteo Bracalini

doi:10.1002/ece3.1664

Abstract

Climate change may be affecting the fecundity of phytophagous insects as well as impacting their natural enemies. However, temperature impacts these two insect groups differently, disrupting population regulation mechanisms, and ultimately, possibly culminating in an outbreak of the host. The pine processionary moth (PPM) is one of the most harmful insects of the Mediterranean basin. Not only are PPM larvae harmful to plants, but they are also dangerous to humans because of their urticating hairs. Although some information is available on climate change effects on the PPM, little is known about its potential effects on PPM egg parasitoids, especially on their distribution range or on their role in controlling PPM populations. The aim of this article was to verify the effects of climate on PPM fecundity and on its egg parasitoids. Our results show that climate warming may affect the PPM positively, but not its egg parasitoids. Specifically, during our study mild winters directly favored the PPM, while increasing summer temperatures (over 30°C) also favored the PPM indirectly, by decreasing parasitism rates. We predict that ever‐milder winters will not only favor PPM development, but also encourage it to spread in otherwise previously inhospitable environments.

Highlights

Climate change affects phytophagous insects, as demonstrated by several scientific papers on the main forest insect species (Battisti 2008)
pine processionary moth (PPM) fecundity was quite variable during the study period, with parasitism representing the main cause of egg mortality
As some PPM eggs parasitoids are negatively affected by high temperatures (Masutti 1964), we considered climate-independent variables (CIVs) which may affect parasitoids during the hottest period (July–August for the study area), which is when PPM eggs are usually exposed to parasitism (Dulaurent et al 2011)

Summary

Introduction

Climate change affects phytophagous insects, as demonstrated by several scientific papers on the main forest insect species (Battisti 2008). Effects of climate change on parasitoids and on their role in population regulation mechanisms are little known, parasitoids are presumably susceptible to environmental changes, as they depend on their hosts’ resilience (Hance et al 2007). Temperature flux affects phytophagous insects and their natural enemies differently, according to each one’s temperature preferences (Hance et al 2007). This disrupts population regulation mechanisms (Zovi et al 2006)

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Conclusion