Micro- and macroclimate interactively shape diversity, niches, and traits of Orthoptera communities along elevational gradients

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.