Temperature is one of the main drivers shaping species diversity and assembly processes. Yet, site-specific effects of the local microclimate on species and trait compositions of insect communities have rarely been assessed along macroclimatic temperature clines. Bavarian Alps, Germany Bayesian joint species distribution models were applied to investigate how ecological and morphological traits drive variation in the climatic niches of 32 Orthoptera species on 93 grassland sites with contrasting microclimatic conditions along a steep elevational macroclimatic gradient in an Alpine region in Central Europe. Species richness and abundance decreased along the elevational macroclimatic gradient, and both benefitted from warm microclimate. Interactive effects of elevation and microclimate on the abundance were, however, species-specific, and partly mediated by traits: Warm microclimatic conditions facilitated the occurrence of demanding xerophilic and late-hatching species, resulting in marked community dissimilarities at mid-elevations where colder sites harboured only a subset of the species. The latter mainly occurred at low elevations together with long-winged species. Abundance peaks of non-xerophilic species were further upslope when microclimate was warm. Intraspecifically, the body sizes and wing lengths of the larger females, but not the males, decreased with elevation akin the community mean, and brown colour morphs were more frequent at sites with warm microclimate. Our nuanced results reveal that trait-dependent responses of species to microclimate play a key role in the assembly and structuring of insect communities along macroclimatic gradients. Since microclimate preferences changed with elevation, we conclude that species temperature niches are narrower than the elevational range suggests and both macro- and microclimatic conditions must be considered when predicting species responses to climate change. Microclimatic contrasts among sites at similar elevations enhanced species turnover mediated by moisture preferences and phenology, highlighting the importance of mountains for conservation as climatic refugia where species with diverging niches can persist in proximity.

We assessed the abundances of Orthoptera species at 93 study sites (60x60m) located along elevational gradients (600 - 2.100 m a.s.l.) during surveys between May and October 2020.  To characterize the impact of microclimate, we measured microclimatic temperatures at 93 study sites in the Bavarian Alps with 3 temperature loggers per site. Those were regressed against modelled temperatures to measure the microclimatic deviation from macroclimatic temperatures.