Elevational species richness gradients in a hyperdiverse insect taxon: a global meta‐study on geometrid moths

Abstract

Aims We aim to document elevational richness patterns of geometrid moths in a globally replicated, multi‐gradient setting, and to test general hypotheses on environmental and spatial effects (i.e. productivity, temperature, precipitation, area, mid‐domain effect and human habitat disturbance) on these richness patterns. Location Twenty‐six elevational gradients world‐wide (latitudes 28° S to 51° N). Methods We compiled field datasets on elevational gradients for geometrid moths, a lepidopteran family, and documented richness patterns across each gradient while accounting for local undersampling of richness. Environmental and spatial predictor variables as well as habitat disturbance were used to test various hypotheses. Our analyses comprised two pathways: univariate correlations within gradients, and multivariate modelling on pooled data after correcting for overall variation in richness among different gradients. Results The majority of gradients showed midpeak patterns of richness, irrespective of climate and geographical location. The exclusion of human‐affected sampling plots did not change these patterns. Support for univariate main drivers of richness was generally low, although there was idiosyncratic support for particular predictors on single gradients. Multivariate models, in agreement with univariate results, provided the strongest support for an effect of area‐integrated productivity, or alternatively for an elevational area effect. Temperature and the mid‐domain effect received support as weaker, modulating covariates, while precipitation‐related variables had no explanatory potential. Main conclusions Despite the predicted decreasing diversity–temperature relationship in ectotherms, geometrid moths are similar to ants and salamanders as well as small mammals and ferns in having predominantly their highest diversity at mid‐elevations. As in those comparative analyses, single or clear sets of drivers are elusive, but both productivity and area appear to be influential. More comparative elevational studies for various insect taxa are necessary for a more comprehensive understanding of elevational diversity and productivity.

Seasonal shifts of biodiversity patterns and species’ elevation ranges of butterflies and moths along a complete rainforest elevational gradient on Mount Cameroon

“…In concordance with numerous studies of Lepidoptera and other organisms (e.g. Beck et al, ; Colwell et al, ), highest species richness of most studied lepidopteran groups was detected in lowlands (fruit‐feeding butterflies, Lymantriinae, Notodontidae, Lasiocampidae, Sphingidae) or mid‐elevations (fruit‐feeding moths, Arctiinae, Saturniidae, Eupterotidae). Such patterns are consistent with diversity patterns of dung beetles (mid‐elevation peak at 1,100 m a.s.l.…”

The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants

“…But no environmental variables emerged that would explain the decline in diversity at the lowest elevations. Beck et al (2017), in a large study of the distribution of geometrid moth diversity across many distinct elevational gradients, found that a mid-elevation diversity peak was most common, and yet they too found no clear explanation, other than a slight influence of area-integrated productivity.…”

Small mammal species richness is directly linked to regional productivity, but decoupled from food resources, abundance, or habitat complexity

“…Lastly, the elevational species–area relationship, which has been shown to be significantly related to insect elevational species richness patterns (e.g. Beck et al., ; Beck et al. unpub.…”