Trophic rewilding restructure the insect communities according to their functional traits: Insights from a multitaxa study

Abstract

Trophic rewilding, or returning vertebrate megaherbivores to defaunated ecosystems, is advocated for restoring ecosystems and biodiversity conservation. As many groups of modern insects radiated during the Neogene era into landscapes inhabited by abundant megafauna, they should be adapted to disturbances provided by megaherbivores' presence. In the Czech Republic, 11 fenced localities have been trophically rewilded by horse, the reconstructed ‘aurochs’, wisent and water buffalo, in various combinations, since 2016 onwards. At these localities, we established 1-ha plots in a rewilded/control design, characterised their vegetation and surveyed butterflies (passive monitoring since the rewilding onset), macro-moths, bees and wasps, ants and orthopterans (single-season rewilded/control surveys). We analysed the data using mixed linear models to compare insect species' richness and abundances and constrained ordinations with interpretation of ordination scores by the life history traits to investigate effects on species' composition. Trophically rewilded plots hosted more species and individuals of bees+wasps and orthopterans. They did not differ from controls in the other groups. Rewilding affected species' composition in all targeted groups, supporting smaller-sized, specialised and less mobile species; butterflies and moths developing on small forbs; and ant trait composition did not respond to rewilding. Synthesis and applications. Presence of large ungulates increased richness and abundance of some insect taxa. Across taxa, it supported life history traits declining in modern industrialised landscapes. Trophic rewilding thus represents a way to remedy undesirable effects of land use intensification, and to mimic conditions in which a substantial proportion of temperate insect biodiversity has evolved.