Periodic Reporting for period 4 - META-STRESS (Unravelling life-history responses and underlying mechanisms to environmental stress in wild populations)
Reporting period: 2019-10-01 to 2020-12-31
At the core of this project is the analyses of the weather in impacting the long-term (> 25 years) of population dynamics of the Glanville fritillary butterfly in the Åland islands over the 4,000 habitat patches and the changes we observe in the metapopulation synchrony. This completed analysis is accompanied with a detailed assessment of a set of local populations that have experienced contrasting environmental conditions in regards to environmental stress, drought, over several summers. These results indicated clear preference for drought prone microhabitat sites for egg oviposition, which benefit offspring survival on most years. However, in an extreme dry summer selection of these sites resulted in high mortality of larval families, which resulted in extreme decline in metapopulation occupancy.
We’ve successfully conducted several experiments to assess phenotypic responses of plants to drought and how this as well as other environmental stressors, alone and in combination, translate to larval performance. We find strong genotype-environment interactions in both plants and in larvae in these responses, and also some indication of the potential role of local adaptation. In the butterflies, we have revealed strong family and life-stage – specific responses, and trade-offs in regards to stress tolerance. The benefits of feeding on water stressed host plant diet during post diapause developmental stage further translate to adult performance.
We have performed a gene expression analyses on the larval responses to host plant drought, which have allowed us to to discover substantial inter-population variation in these stress response programmes but also identify genes underlying stress tolerance. We have used whole-genome resequencing of individuals from selected population across the Åland islands over few years to assess whether variation in neutral genetic diversity and/or in alleles related to stress response pathways show differential patterns between populations in bad (decrease in population occupancy), stable, or good (increase in populations occupancy and abundance) years. We find genetic diversity to be considerably high in the butterfly metapopulation despite the severe population declines. The habitat patches with high connectivity also had high heterozygosity indicating that connectivity could be contributing towards rescue of genetic diversity after a demographic bottleneck. This is in contrast with our studies on another, seasonally polyphenic species, where we observed reduced genetic variation for plasticity related genes, which is likely to limit adaptive potential under climate change, where the deteriorating accuracy of predictive cues will increase maladaptive phenotype-environment mismatches.
We’ve demonstrated that the butterfly larvae in the wild present a poor bacterial community structure at the family level with most of the variability observed at the individual level. The host plant microbiota is less variable and its variation is strongly correlated with the variation in the host plant metabolites. However, neither the plant microbiota nor the plant metabolites impacted the global composition of the larvae microbiota. We have also more experimentally tested the role of microbiota on individual performance across in different life stages.