The role of pathogens in butterfly population declines – interactions with habitat fragmentation and climate change

In spring 2008, CEH began a three-year field study financed by the Environmental Change Integrating Fund to assess the prevalence and distribution of Lepidoptera pathogens (and parasitoids) across the UK and their interactions with habitat fragmentation and climate change.

Many species of Lepidoptera (butterfly and moth) have declined over the last few decades; habitat loss, fragmentation and climate change have been identified as major factors.

The way in which parasites, particularly insect diseases (entomopathogens), interact with Lepidoptera is rarely considered in life history studies, largely because pathogens are rarely "seen" in the field. Most reported studies refer only to predators and parasitoids when considering natural enemy guilds, even though naturally occurring entomopathogens are more diverse, widespread and anticipated to increase in importance as the climate gets warmer and wetter. In recent years, molecular techniques are revealing the prevalence and diversity of pathogens present in natural populations, enabling us to consider their true impact for the first time. 

Research questions

The overarching hypothesis of this project is that pathogens play a hitherto undetected role in regulating Lepidoptera populations, interacting with two key factors: habitat fragmentation and climate change. We plan to address these main questions:

The challenge ahead: living on the edge

Research will focus on Lepidoptera of chalk grassland habitat. We intend to monitor butterflies and moths for parasitoids and pathogen infection across transects in highly fragmented and unfragmented landscapes. In addition, we will study Lepidoptera populations both at the edge and centre of rapidly expanding ranges. 

How you could help

• What are insect diseases?
• Lepidoptera and pathogens
• Hitch-hiking pathogens and escaping hosts
• Background to the project