The ecological niche and conservation value of Central European grassland orthopterans: A quantitative approach

The ongoing biodiversity decline across taxonomic groups, including insects, is tightly related to land-use changes and habitat degradation. To assess habitat quality, proper bioindicators that allow efficient monitoring of temporal changes in habitat properties and help to understand the role of anthropogenic activities in shaping habitat characteristics, are needed. Orthopterans have been previously proposed as promising bioindicators for grassland ecosystems; however, comprehensive quantitative information on their habitat preferences is lacking, which hinders full utilization of their bioindication potential. In this study, we surveyed orthopteran assemblages and quantified local environmental conditions at 476 grassland sites in Central Europe. To model orthopteran habitat preferences, the Maxent approach was employed, which allowed us to detect continuous species responses to particular habitat characteristics (moisture, vegetation cover, vegetation height, average seasonal temperature, and direct radiation). We calculated ecological niche indices describing niche widths, species optima, and the relative importance of particular environmental variables for a total of 38 analysed species. Evaluation of final Maxent models showed that their predictive power was high for the great majority of investigated species. Red-listed species had significantly narrower niches compared to unlisted orthopterans. In addition, application of the developed quantitative ecological niche indices for ecological and conservation studies was demonstrated on an independent, previously published dataset. The development of quantitative ecological niche indices coupled with the existing time- and cost-effective survey methods, also allowing adoption of citizen science approaches, makes orthopterans an optimal model insect group for assessment of grassland condition and conservation.