Temperature preferences drive additive biotic homogenization of Orthoptera assemblages

Abstract

The degradation of natural habitats is causing ongoing homogenization of biological communities and declines in terrestrial insect biodiversity, particularly in agricultural landscapes. Orthoptera are focal species of nature conservation and experienced significant diversity losses over the past decades. However, the causes underlying these changes are not yet fully understood. We analysed changes in Orthoptera assemblages surveyed in 1988, 2004 and 2019 on 198 plots distributed across four major grassland types in Central Europe. We demonstrated compositional differences in Orthoptera assemblages found in wet, dry and mesic grasslands, as well as ruderal habitats decreased, indicating biotic homogenization. However, mean α-diversity of Orthoptera assemblages increased over the study period. We detected increasing numbers of species with preferences for higher temperatures in mesic and wet grasslands. By analysing the temperature, moisture and vegetation preferences of Orthoptera, we found that additive homogenization was driven by a loss of species adapted to extremely dry and nitrogen-poor habitats and a parallel spread of species preferring warmer macroclimates.

Less overall, but more of the same: drivers of insect population trends lead to community homogenization

“…Concerning species-specific climate-sensitivity traits, this was found in tiger moths in the field [ 14 ], but also in a warming experiment with ants [ 15 ], both in a Panamanian rainforest. In the temperate zone, similarly positive effects on thermophilous species were observed for orthopterans [ 7 ] and for stream-dwelling mayflies, stoneflies and caddisflies [ 16 ]. The shift to warm-adapted species thus appears as a more general global phenomenon confirmed by many other studies on individual species trends [ 17 ] and likely will result in an overall thermophilization of communities across many taxa [ 18 , 19 ].…”

“…In the same time span, average and frequency of precipitation had increased. The opposite effect was observed for two Orthoptera species in Germany, which severely decreased in wet and mesic grasslands over the study period (1988, 2004 and 2019), possibly due to summer droughts and increased evaporation [ 7 ].…”

“…In forest ecosystems, increased monocultures of coniferous plantations caused population declines in three species, while one species benefited from this change [ 6 ]. In German grasslands, fertilization contributed to species loss and an additive homogenization of grasshopper communities [ 7 ]. In Brazilian freshwater ecosystems, dam and hydroelectric power plant construction was pointed out as the main driver of abundance and richness declines in freshwater insects due to lower water turbidity and nitrogen increase [ 29 ].…”

“…Winning species were usually warm-adapted or moderately heat-tolerant [ 7 , 14 – 16 ], tolerant to pesticides and disturbances [ 6 , 16 ], had invasive traits [ 15 ] and/or a broad dietary spectrum [ 16 , 43 ]. Decreasing species, in contrast, preferred dry, nitrogen-poor habitats [ 7 ] and open forests [ 6 ] or had a protein-rich diet [ 6 ]. This matches previous studies, which additionally identified high rates of dispersal and habitat recolonization after disturbance as traits associated with winners (e.g.…”

How can an intensively used agricultural landscape preserve diversity of Orthoptera assemblages?

“…The role of linear ruderal habitats (roadsides, ditch banks and other linear landscape elements) in preserving Orthoptera diversity is well studied (Berggren et al 2001(Berggren et al , 2002Vadkerti and Szövényi 2005;Eriksson et al 2013;Torma et al 2018). Studies mostly focused on the wildlife of natural and semi-natural patches nested within intensively cultivated arable lands (Duelli and Obrist 2003;Rand et al 2006;Braschler et al 2009;Jauker et al 2009;Marini et al 2010;Badenhausser and Cordeau 2012;Bátory et al 2016;Hall et al 2022;Martínez-Núñez et al 2022;Thorn et al 2022). The distribution of sites a priori categorized as linear ruderal habitats (country roadsides, dirt roads) between cluster groups showed that the naturalness and diversity of these habitats and their assemblages may be affected by various factors e.g.…”