Data for: Microclimate structures communities, predation and herbivory in the High Arctic

In a warming world, changes in climate may result in
species-level responses as well as changes in community structure through
knock-on effects on ecological interactions such as predation and
herbivory. Yet, the links between these responses at different levels are
still inadequately understood. Assessing how microclimatic conditions
affect each of them at local scales provides information essential for
understanding the consequences of macroclimatic changes projected in the
future.  Focusing on the rapidly changing High Arctic, we examine
how a community based on a common resource species (avens, Dryas
spp.), a specialist insect herbivore (Sympistis zetterstedtii), and
natural enemies of lepidopteran herbivores (parasitoids) varies along a
multidimensional microclimatic gradient. We ask (1) how parasitoid
community composition varies with local abiotic conditions, (2) how the
community-level response of parasitoids is linked to species-specific
traits (koino- or idiobiont life cycle strategy and phenology) and (3)
whether the effects of varying abiotic conditions extend to interaction
outcomes (parasitism rates on the focal herbivore and realized herbivory
rates).  We recorded the local communities of parasitoids,
herbivory rates on Dryas flowers and parasitism rates
in Sympistis larvae at 20 sites along a mountain slope.
For linking community-level responses to microclimatic conditions with
parasitoid traits, we used joint species distribution modelling. We then
assessed whether the same abiotic variables also affect parasitism and
herbivory rates, by applying generalized linear and additive mixed models.
We find that parasitism strategy and phenology explain local variation in
parasitoid community structure. Parasitoids with a koinobiont strategy
preferred high-elevation sites with higher summer temperatures or sites
with earlier snowmelt and lower humidity. Species of earlier phenology
occurred with higher incidence at sites with cooler summer temperatures or
later snowmelt. Microclimatic effects also extend to parasitism and
herbivory, with an increase in the parasitism rates of the main
herbivore S. zetterstedtii with higher temperature and
lower humidity, and a matching increase in herbivory rates.  Our
results show that microclimatic variation is a strong driver of local
community structure, species interactions and interaction outcomes in
Arctic ecosystems. In view of ongoing climate change, these results
predict that macroclimatic changes will profoundly affect arctic
communities.