INTRODUCTION

Urban areas are expanding at alarming rates all over the world (Yang et al., 2018), with well-recognised adverse effects on biodiversity due to habitat deterioration and direct replacement with deeply modified cover, for example, the impervious surfaces of buildings and infrastructures (Piano et al., 2020). Such replacement has profound impacts on wildlife, which may be classified according to their response by urban ecologists as either exploiters/tolerant or avoiders of urban areas (Callaghan et al., 2021; Fischer et al., 2015; Santini et al., 2019; Tryjanowski et al., 2020). Such responses in turn lead to persistence or local extinction of species within cities, a process that—together with colonisation and introduction events—determines the structure of urban wildlife assemblages (Aronson et al., 2016).

Despite that urbanisation per se mostly implies the disappearance of natural habitats, many cities around the world are characterised by a set of green spaces derived by different processes, for example, specific urban development planning or unintentional abandonment (Gandy, 2016). Cities may thus still feature relatively species-rich wildlife assemblages, particularly in the case of highly mobile taxa such as birds and butterflies (Hall et al., 2017; MacGregor-Fors et al., 2016). Yet, the high unpredictability of urban areas due to, for example, renovation and development, jointly with the implicit higher risk of stochastic events of small areas and populations living therein, poses a serious challenge to wildlife, with high rates of local extinction being recorded, in comparison to more natural areas (Aronson et al., 2017; Grimm et al., 2008). The urban environment is known to selectively filter species from the surrounding natural habitats according to specific traits—or sets of traits—that play major roles in allowing species to persist in such highly modified areas (Aronson et al., 2016; Grilo et al., 2022; Planchuelo et al., 2020). Specific key traits are well known and relatively conserved among vertebrates, with species characterised by high behavioural plasticity, reproductive outputs and dispersal capabilities being more likely to adapt and persist to life in the city. Conversely, very little is known on comparable traits among invertebrates (Diamond et al., 2023; but see: Piano et al., 2017).

Within the scientific literature on urban wildlife, insects have been in fact mostly neglected as targets, with higher attention being posed to vertebrates (Di Pietro et al., 2021). Nonetheless, insects represent a significant portion of wild species occurring within cities worldwide, beside playing key roles in trophic and pollination networks, that is, sustaining functioning ecosystems and their associated services (Losey & Vaughan, 2006; Steffan-Dewenter & Westphal, 2008). Moreover, the peculiar conditions found in many artificial (recreational) urban green spaces, such as the occurrence of large or senescent trees in historical parks and villas, may also provide unexpected profitable habitats even to highly specialised insects, as in the case of saproxylic beetles (Fattorini & Galassi, 2016; Horák, 2018). Conversely, species more strongly associated with habitat types that are rarely featured within anthropogenic green spaces, for example, natural or semi-natural grasslands and wetlands, may be at higher risk to become locally extinct following urbanisation (New, 2015).

Here we focus on Orthoptera, that is, crickets, grasshoppers and bush crickets, as a model group to test hypotheses on the relationship between species' traits and adaptability to urban environments, using the city of Rome, in Italy, as study area. European orthopterans are excellent models to study the long-term effects of land use changes, since they feature subtle and usually highly specific relationships with vegetation structure (Labadessa et al., 2015; Whiles & Charlton, 2006), are sensitive to anthropogenic modifications at several scales (Báldi & Kisbenedek, 1997; Labadessa & Ancillotto, 2022; Rácz et al., 2013) and their diversity includes species with diverging ecological needs and functional traits, for example, in terms of size, mobility, diet and habitat preferences (Moretti et al., 2013). Here we compare two Orthoptera faunal checklists from the urban area of Rome in the last decades, and predict that urban orthopterans' probability of persistence within urban areas will be biased according to specific sets of physiological, morphological and life-history traits. More specifically, and based on studies on other taxa—such as butterflies, birds and mammals (Callaghan et al., 2021; Fraissinet et al. 2023, Santini et al., 2019)—we predict that higher values of traits related to reproductive output and dispersal abilities may foster species' persistence in urban areas through time, while we conversely expect a negative effect of specialisation degree.