van Dis, N. E. | Search bioRxiv

bioRxiv2026

The microbiota of a wild butterfly species over three decades of climate change

Thermal stress can disturb microbial communities associated with host species. As microbes can support essential functions related to host metabolism, physiology, nutrition and immunity, changes in microbial communities can have severe fitness consequences for the host. Although the effects of thermal conditions on host-associated microbiomes have been demonstrated in controlled laboratory settings, how climate change might affect the structure and functionality of microbial communities in wild populations remain poorly understood. Here, we took advantage of the well-characterized long-term field survey of the Glanville fritillary butterfly (Melitaea cinxia) metapopulation on the [A]land islands, in the Baltic Sea, to fill this gap. We investigated whether bacterial communities associated with larvae show signs of gradual temporal change in response to slow environmental warming across a 28-year period, or whether these communities responded through abrupt change following a sudden drought event that triggered bottlenecks in their butterfly host population. Using a combination of 16S rRNA metabarcoding and metagenomic sequencing, we first showed that M. cinxia harbours a set of stable resident bacteria, including Pseudomonas, Telluria, and Enterobacteriaceae bacteria. But we also characterized a gradual shift in the M. cinxia associated bacterial community over three decades of increasing temperatures and decreasing precipitations. This shift was not unidirectional for all bacterial taxa, as the dominant Telluria and Pseudomonas showed opposing responses to environmental trends. Additionally, the 2018 extreme drought, which triggered acute host population bottlenecks, was associated with a severe disruption of M. cinxia microbiota, and the loss of key Enterobacteriaceae taxa. However, the M. cinxia bacterial community seemed to be able to recover towards pre-drought structure in subsequent years, suggesting a degree of resilience to acute climatic perturbations in this microbial system.

microbiology↗

bioRxiv2021

Timing of increased temperature sensitivity coincides with nervous system development in winter moth embryos

Climate change is rapidly altering the environment and many species will need to genetically adapt their seasonal timing to keep up with these changes. Insect development rate is largely influenced by temperature, but we know little about the mechanisms underlying temperature sensitivity of development. Here we investigate seasonal timing of egg hatching in the winter moth, one of the few species which has been found to genetically adapt to climate change, likely through selection on temperature sensitivity of egg development rate. To study when during development winter moth embryos are most sensitive to changes in ambient temperature, we gave eggs an increase or decrease in temperature at different moments during their development. We measured their developmental progression and timing of egg hatching, and used fluorescence microscopy to construct a timeline of embryonic development for the winter moth. We found that egg development rate responded more strongly to temperature once embryos were in the fully extended germband stage. This is the phylotypic stage at which all insect embryos have developed a rudimentary nervous system. Furthermore, at this stage timing of ecdysone signaling determines developmental progression, which could act as an environment dependent gateway. Intriguingly, this may suggest that, from the phylotypic stage onward, insect embryos can start to integrate internal and environmental stimuli to actively regulate important developmental processes. As we found evidence that there is genetic variation for temperature sensitivity of egg development rate in our study population, such regulation could be a target of selection imposed by climate change.

evolutionary biology↗