The origin of urban communities: From the regional species pool to community assemblages in city

Abstract

Aim Cities worldwide are characterized by unique human stressors that filter species based on their traits, potentially leading to biodiversity loss. The knowledge of which species are filtered and at which scale is important to gain a more mechanistic understanding of urban community assembly and to develop strategies to manage human impact on urban ecosystems. We investigate the ecological mechanisms shaping urban community assembly, taking into account changes across scales, taxa and urban green space types. Location City of Zurich, Switzerland. Taxon Carabid beetles and wild bees. Methods We use a large species occurrence and trait dataset with a high spatial resolution to assess the filtering effect of a medium‐sized city on a regional pool of potential colonists. We then assess the filtering from the urban pool to five widely distributed types of urban green spaces. Results We found that our model city selects for functionally similar but taxonomically diverse bee and carabid beetle species from the regional species pool. Within the city, community assembly processes vary among green space types and taxa resulting in important changes in community taxonomic and functional composition. Main conclusions Our findings suggest that urban community assembly is a multi‐scale process dominated by the strong environmental filtering from a regional to an urban species pool. This leads to the selection of species pre‐adapted to urban conditions. Spatial habitat heterogeneity within and among UGS types can maintain an important taxonomic diversity within cities. However, increasing urban functional diversity would require stronger management efforts that consider regional ecological processes.

Indigenous plants promote insect biodiversity in urban greenspaces

“…Finally, we are also aware that our study was conducted at a single scale, focusing exclusively at the plant level. Although beyond the scope of this paper, to fully understand the mechanisms structuring insect communities in urban environments it would be necessary to analyze the patterns driving their diversity and distribution across multiple spatial and temporal scales (Estes et al 2018, Fournier et al 2020, Piano et al 2020). For example, in a follow‐up study, we are using a multi‐scale occupancy model (Kéry and Royle 2016, Szewczyk and McCain 2019) to assess the species‐specific responses of insects at the site, plot, plant, and detection levels.…”

Only habitat specialists become smaller with advancing urbanization

“…Changes during urbanization in habitat structure and configuration intensify the warming and drying effects of urban habitats, and, therefore, have serious negative effects on body size and condition of organisms (Dahirel, De Cock, Vantieghem, & Bonte, 2019; Meillère, Brischoux, Parenteau, & Angelier, 2015) although this can be modulated by the particular features of urban habitats (Fournier, Frey, & Moretti, 2020). Urbanization and associated anthropogenic activities are also major sources of environmental pollution.…”

Managing gardens for wildlife: Features that predict mammal presence and abundance in gardens vary seasonally

“…Although we highlight numerous garden features that are important for mammal wildlife and that these vary seasonally, we did not consider the influence of landscape‐scale features in our study which may explain why no garden features influenced the presence or abundance of mammals in some seasons (e.g., in autumn for southern brown bandicoot presence and western ringtail possum abundance). While there is promising evidence that wildlife‐friendly gardening can be beneficial regardless of landscape‐scale factors (e.g., level of surrounding urbanization; Fontaine et al 2016), it is important to recognize that the occurrence of wildlife in gardens likely also depends on broader landscape factors (such as city size and intensity of urbanization), the biological and ecological traits of species (e.g., mobility, behavior, resource requirements), and complex interactions among all of these (Fournier et al 2020). How local‐scale features (including the seasonal importance of features), landscape‐scale factors, and the biological traits of animals interact to determine the occurrence of wildlife in gardens is worthy of further investigation.…”