Warming-induced range expansion effects on the diversity and composition of the gut microbiome: a case study with two butterflies

Abstract

Species are the habitat of a diverse community of organisms, including bacteria, fungi and viruses - the microbiome. Evidence shows that many species shift and/or expand their geographical ranges following warming climate; yet, the response of host-associated microbiome communities to species range shifts has received less attention, especially in observational studies. Here, we use two British butterfly species for which detailed long-term distributional data is available, and document for the first time a variety of effects of warming-induced range expansion on the diversity and composition of their microbiome. Our results show similar diversity and species-specific responses in the evenness of the gut microbial communities in the two butterflies. However, butterflies at the expanded ranges showed (i) a larger variability in the microbiome diversity, and (ii) a smaller core community of bacteria that is to a large extent a subset of the bacterial core community in the original range. The microbiome is responsible for many aspects of the hosts physiology and growth, and for ecosystem function, so if the changes in the gut microbial communities reported here apply to other species and taxonomic groups, the potential impact to biodiversity and functioning after range expansion could be severe.