The impact of climate change on parasite infection of bumblebees depends on mtDNA haplotypes of the host
Authors: Oliver Manlik 1, 2; Sunil Mundra 1; Regula Schmid-Hempel 3; Paul Schmid-Hempel 3
Affiliations: 1) United Arab Emirates University; 2) University of New South Wales; 3) ETH Zurich
Keywords: Ecological & conservation genetics
Climate change is predicted to affect host-parasite interactions. For instance, parasite infection prevalence is expected to increase with rising temperatures for some species. Global population declines of important pollinators have been attributed to fungal parasite (Nosema) infections, which, in turn, are influenced by environmental and climatic factors. However, the role of climate in driving parasite infection and the genetic basis for hosts to respond under variable climatic conditions remain obscure. In this study we investigated the association between climate and N. bombi infection of buffed-tailed bumblebees (Bombus terrestris), and whether this association is dependent on the host genotypes. For this we genotyped 876 wild bumblebee queens and screened N. bombi infection of those queens between 2000 and 2010. We also recorded seven climate parameters during those eleven years, and tested for correlations between climate and infection prevalence of specific host genotypes. Here we show that climatic factors drive N. bombi infection and that the impact of climate is dependent on mitochondrial DNA cytochrome oxidase I (COI) haplotypes of the host. Infection prevalence was correlated with climatic variables during the time period when queens emerge from hibernation. Remarkably, two host mtDNA COI haplotypes (‘A’ and ‘B’) best predict this association between climatic factors and infection. Both haplotypes displayed phenotypic plasticity, but in opposite direction: Haplotype A conferred greater resistance to parasite infection during hotter, wetter years, while haplotype B was more susceptible under those conditions. Our multivariate analysis further showed that the impact of interacting climatic variables on parasite infection is best explained by the two host haplotypes. To the best of our knowledge, this is the first study that identifies specific host genotypes that confer differential parasite resistance under variable climatic conditions. Our results demonstrate the importance of mitochondrial COI haplotypes to ward off parasites in a changing climate. More broadly, this also suggests that COI may play a pertinent role in climate change adaptations of insect pollinators.