Meta-analysis of urbanization effects on spider diversity

Urbanization has been shown to have broadly negative impacts on arthropod diversity and abundance. However, investigations of urbanization effects on spiders specifically have been relatively few and shown minimal clear patterns. We conducted a meta-analysis on the urbanization impacts of spiders globally, examining moderators including guild type, urbanization intensity, climate classification, habitat type, and dispersal ability. From 28 studies of 27 sites, we extracted data for 99 observations of abundance and 103 observations of richness of spider urban/natural comparisons. Overall, we found no significant effects of urbanization on spider abundance or richness. We also detected no modulation of dispersal ability, habitat type, or urbanization intensity on the urbanization effect of spider diversity. However, guild type emerged as a key moderator of urbanization impacts, as orb-weaver spiders had increased abundance and diversity in urban sites while sheet web weavers had reduced diversity. Our results highlight that not all arthropod groups respond to urbanization similarly, and that within spiders, variation in responses highlights the need to consider differential impacts of land-use change on spider guilds. Given the diversity of spiders globally and their crucial roles in ecosystems, how urbanization alters spider community compositions should constitute a priority for urban ecology and conservation.