Losses of specialist and expansion of thermophilic generalist macro-moths in nature reserves of Central Europe

Ongoing environmental change has caused significant modifications in the diversity, abundance and community composition of insects across Central Europe. Nocturnal insects, such as macro-moths, are species rich and represent a large part of insect biomass, but are underrepresented in scientific studies. In this study, we analysed long-term changes of macro-moth diversity and community composition across south-western Germany, using records from two time periods: 1970–2000 and 2001–2020 obtained at identical study sites, almost all nature reserves. Total species richness remained constant, while local species composition changed significantly. Endangered and specialized open landscape species, and those adapted to bogs and coniferous forests became less common. Thermophilic species adapted to dry mixed forests became more abundant. The macro-moth communities became considerably more uniform and are increasingly dominated by common habitat generalist species. The decline in specialized open-landscape species seems to be due to losses of formerly extensively used grassland and agricultural intensification. Species with Mediterranean core areas increased in abundance. Likely, climate and land-use change will strengthen the observed trends and continue to reshape macro-moth communities, with the potential for continued compositional homogenisation. Species respond differently to environmental changes depending on their performance and biogeographic history. Long-term observations on macro-moths (1970–2000 vs 2001–2020) indicate winners and losers across a study region in Central Europe. Proportions (a) of species (Δπ) with Mediterranean (gains) or Central European (losses) distribution and (b) of 2024 IUCN endangerment categories with changes in record numbers in 2020 compared to the random sample prediction in the earlier period (1970–2000). Error bars denote two standard deviations. (c) Numbers of species in each IUCN category during the past (period I) and present (period II).