Parasite intensity is driven by temperature in a wild bird

Adèle Mennerat,Anne Charmantier,Sylvie Hurtrez-Boussès,Marcel M Lambrechts,Philippe Perret

doi:10.24072/pcjournal.65

Abstract

Increasing awareness that parasitism is an essential component of nearly all aspects of ecosystem functioning, as well as a driver of biodiversity, has led to rising interest in the consequences of climate change in terms of parasitism and disease spread. Yet empirical knowledge on the extent and ways in which climatic factors affect parasite prevalence and intensities remains scarce. In an 18-year, multi-site, correlative study we investigated the contributions of weather variables and other factors to spatio-temporal variation in infestation by blowfly parasitic larvae (Protocalliphora spp.) in nests of Corsican blue tits (Cyanistes caeruleus). We found that ambient temperature during the nestling stage is strongly and positively related to parasite load (number of parasites per chick), both across broods when controlling for year, and across years. In addition, annual mean parasite load also increased with minimal spring temperature, and decreased with increasing average temperature in the previous summer. There was no indication of a dependence of parasite dynamics on host dynamics in this system, likely due in part to the wide host range of blowflies that do not solely rely on blue tit hosts. This suggests a major effect of temperature during the blowfly life cycle, with potential implications for blowfly host interactions across their geographical range as climate keeps warming up. Finally, given that ambient temperature increases throughout the breeding season and that blowflies negatively affect survival and recruitment of blue tits, these results also mean that parasites, along with caterpillar availability, can drive selection for breeding date in this system.

Highlights

As global climate is very likely to keep warming up, it is of growing importance to understand how populations and communities respond to variations in temperature and precipitation
Parasite load increased with mean ambient temperature, with some degree of saturation at higher temperatures
Parasite load was higher in nests surrounded by a cotton bag than in nests collected without a cotton bag (P = 0.02)

Summary

Introduction

As global climate is very likely to keep warming up, it is of growing importance to understand how populations and communities respond to variations in temperature and precipitation. Increasing awareness that parasitism is an essential component of most aspects of ecosystem functioning, as well as a driver of biodiversity (Hudson et al 2006), has led to a rising interest in the consequences of climate change in terms of parasitism and disease spread (Harvell et al 2002; Brooks & Hoberg 2007). Attempts were made to predict the direction of change in disease prevalence in response to climate warming (e.g. Møller et al 2013). It seems that no single scenario is to be expected given the dynamic nature of host-parasite interactions, the huge variation in parasite life histories, and the complexity of their effects at multiple levels within ecosystems (Mas-Coma et al 2009; Rohr et al 2011; Altizer et al 2013). Predictions of the effects of climate change on infectious diseases need to be supported by detailed empirical knowledge acquired regionally in well-studied host-parasite systems (Hernandez et al 2013; Roiz et al 2014)

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Conclusion