Species richness has been shown to decrease, and elevational range increase (the Rapoport effect), with elevation as a consequence of biotic and abiotic factors, but patterns are inconsistent across taxonomic groups. Despite being an important indicator taxon and component of local communities, Orthoptera distributions at higher elevations in Europe remain unclear. We investigated the relationship of Orthoptera species richness and elevational range with elevation by conducting field studies at 28 sites across three study areas in the Pyrenees mountains, Europe. We found that species richness declined with elevation. Study area and the site-specific factors of sampling effort, topography (slope) and vegetation structure (density and cover) were also important predictors of species richness. We did not observe a Rapoport effect, with elevational range peaking at mid-elevation instead. Smaller elevational ranges found at high elevations may be due to a combination of sampling over a restricted elevational range and the presence of specialist high-elevation species. We also explored the composition of Orthoptera assemblages using multivariate methods, finding no clear effect of elevation, slope or vegetation structure on these communities, although study area somewhat influenced assemblages. To our knowledge, this is the first study of the Rapoport effect along an elevational gradient using insects as a study system in Europe. We argue that our findings are useful for understanding species distributions with elevation at the interface between local and regional scales. Clarifying the biotic and abiotic predictors of species distribution is important for informing conservation efforts and predicting consequences of climate change.

Species richness has been shown to decrease, and elevational range increase (the Rapoport effect), with elevation as a consequence of biotic and abiotic factors, but patterns are inconsistent across taxonomic groups. Despite being an important indicator taxon and component of local communities, Orthoptera distributions at higher elevations in Europe remain unclear. We investigated the relationship of Orthoptera species richness and elevational range with elevation by conducting field studies at 28 sites across three study areas in the Pyrenees mountains, Europe. We found that species richness declined with elevation. Study area and the site-specific factors of sampling effort, topography (slope) and vegetation structure (density and cover) were also important predictors of species richness. We did not observe a Rapoport effect, with elevational range peaking at mid-elevation instead. Smaller elevational ranges found at high elevations may be due to a combination of sampling over a restricted elevational range and the presence of specialist high-elevation species. We also explored the composition of Orthoptera assemblages using multivariate methods, finding no clear effect of elevation, slope or vegetation structure on these communities, although study area somewhat influenced assemblages. To our knowledge, this is the first study of the Rapoport effect along an elevational gradient using insects as a study system in Europe. We argue that our findings are useful for understanding species distributions with elevation at the interface between local and regional scales. Clarifying the biotic and abiotic predictors of species distribution is important for informing conservation efforts and predicting consequences of climate change.

1. The Millennium Ecosystem Assessment assessed ecosystem change, human well-being and scientific evidence for sustainable use of biological systems. Despite intergovernmental acknowledgement of the problem, global ecological decline has continued, including declines in insect biodiversity, which has received much media attention in recent years. 2. Several roadmaps to averting biological declines have failed, due to various economic and political factors, and so biodiversity loss continues, driven by several interacting human pressures. Humans are innately linked with nature but tend to take it for granted. The benefits we gain from the insect world are broad, yet aversion or phobias of invertebrates are common, and stand firmly in the path of their successful conservation. 3. Providing an integrated synthesis for policy teams, conservation NGOs, academic researchers and those interested in public engagement, this article considers: (1) the lack of progress to preserve and protect insects. (2) Examples relating to insect decline and contributions insects make to people worldwide, and consequently what we stand to lose. (3) How to engage the public, governmental organisations and researchers through “insect contributions to people” to better address insect declines. 4. International political will has consistently acknowledged the existence of biodiversity decline, but apart from a few narrow cases of charismatic megafauna, little meaningful change has been achieved. Public values are reflected in political willpower, the progress being made across the world changing views on insects in the public should initiate a much-needed political sea-change, but only if we as entomologists enormously expand our engagement efforts.

Barriers to gene-flow within populations, typically in response to divergent selection, are often mediated via third-party interactions. Under these conditions speciation is inextricably linked to ecological context. We present a novel framework for studying arthropod speciation as mediated by Wolbachia, a microbial endosymbiont capable of causing host cytoplasmic incompatibility (CI) via alternative strain associations. Building on empirical findings, our model predicts that sympatric host sister-species harbour paraphyletic strains that provide CI, while well-defined congeners in ecological contact and recently diverged noninteracting congeners are uninfected due to Wolbachia redundancy. We argue that Wolbachia may provide an adaptive advantage when coupled with reduced hybrid fitness (via trait mismatching), by facilitating assortative mating between co-occurring divergent phenotypes – the contact contingency hypothesis. To test this, we applied a custom-built predictive algorithm to empirical data from host-specific pollinating fig wasps, achieving ≤88.46% accuracy. We then considered post-zygotic offspring mortality during CI matings by developing a model featuring fitness clines across oviposition resources. This oviposition trade-off model, tested through simulation, favoured CI at realistic conspecific mating frequencies despite fecundity losses. We demonstrate that a rules-based algorithm accurately predicts Wolbachia infection status. This has implications among other systems where closely-related sympatric species encounter adaptive disadvantage through hybridisation.