Management is more important than urban landscape parameters in shaping orthopteran assemblages across green infrastructure in a metropole

Abstract

Urbanisation significantly shapes species abundance, diversity, and community structure of invertebrate taxa but the impact on orthoptera remains widely understudied. We investigated the combined effects of spatial, urban landscape and management-related parameters. Additionally, we discussed different sampling strategies. We sampled orthopteran assemblages on green infrastructure associated with the public transport system of Vienna, Austria. Sampled areas include railroad embankments, recreational areas or fallows. Using LMs, (G)LMMs and nMDS, we compared quantitative sampling using transect counts and semi-quantitative sampling which also included observations made off-transects. We found that vegetation type was the most important parameter, whereby structure-rich fallows featured highest species diversities and, together with extensive meadows, highest abundances, while intensive lawns were less suitable habitats. The semi-quantitative data set revealed an underlying species-area-relationship (SAR). Other important but highly entangled parameters were the mowing intensity, vegetational heterogeneity and cover of built-up area in a 250 m radius. Most found species have high dispersal abilities. Urban assemblages are most significantly shaped by management-related parameters on the site itself, which highlights the potential of conservation efforts in urban areas through suitable management. Sites of different vegetation types differ greatly and need adjusted management measures. Urban landscape parameters, such as the degree of soil sealing, appeared less important, likely due to the high dispersal abilities of most observed orthoptera species. The indicated species-area-relationship could be used to prioritize sites for conservation measures.

Urbanization reduces Orthoptera diversity and changes community structure towards mobile species

“…Increasing habitat heterogeneity in urban habitats may therefore help to counteract to a certain extent the often‐described homogenization of urban species communities (Piano et al, 2020). Huchler et al (2022) have correctly stated that urban species communities are significantly shaped by management and its consequences for habitat structure. This becomes even more evident when not only diverse and multifaceted plant communities with high and dense cover are considered but also highly disturbed areas with open bare ground (Schwarz & Fartmann, 2022).…”

“…There are few studies examining the biological and functional diversity of grasshopper species in relation to urban habitat parameters and urban matrix variables. Most studies reported decreasing overall diversity of grasshopper species with increasing urbanization levels (Cherrill, 2015; Melliger et al, 2017; Penone et al, 2013; Piano et al, 2020), but some failed to establish these relationships (Huchler et al, 2022). Vegetation structure and its mowing regime have been shown to be important for urban grasshopper diversity (Eckert et al, 2017; Huchler et al, 2022), but this also applies to rural habitats (Ogan et al, 2022; Schirmel et al, 2019).…”

“…Most studies reported decreasing overall diversity of grasshopper species with increasing urbanization levels (Cherrill, 2015; Melliger et al, 2017; Penone et al, 2013; Piano et al, 2020), but some failed to establish these relationships (Huchler et al, 2022). Vegetation structure and its mowing regime have been shown to be important for urban grasshopper diversity (Eckert et al, 2017; Huchler et al, 2022), but this also applies to rural habitats (Ogan et al, 2022; Schirmel et al, 2019). Patch size is relevant for species richness (Huchler et al, 2022), suggesting that species–area relationships also exist in urban areas similar to rural landscape features (Melliger et al, 2017).…”

“…tat filter become much less clear andHuchler et al (2022) as well asOgan et al (2022) already postulated that urbanization cannot be the only driver of the urban habitat filter. Indeed, both grasshopper species diversity and abundance of most species as well as the species composition responded strongly to habitat characteristics at the local level, too Eckert et al (2017).…”

Functional traits drive the fate of Orthoptera in urban areas

“…Both dry grasslands and wetlands are habitats at high risk of replacement in urban areas, due to their association with geomorphological and edaphic conditions that are also favourable for agricultural/pastoral reclamation and urban development (Labadessa & Ancillotto, 2023). Both these habitats are mostly disappearing at faster rates than others, such as forests, in cities worldwide (Kingsford et al, 2016), and are highly affected by small‐scale management practices (e.g., mowing) that deeply affect the orthopteran assemblages they host (Huchler et al, 2022). In our specific case, the most recent development in Rome included both urban development/expansion at the expense of formerly agricultural areas and reclamation of abandoned sites (Filibeck et al, 2016), the latter resulting in deeply modified floral assemblages that show lower suitability to orthopterans associated with dry grasslands.…”