Niche segregation in three crab spider species (Araneae: Thomisidae)

Understanding ecological niches makes it possible to assess how species respond to alterations of environmental conditions and trophic interactions caused by climate change. However, integrating abiotic and biotic niche axes remains challenging. Citizen Science platforms provide large-scale and multi-taxa data to support those efforts, but spiders are frequently underrepresented due to public aversion. Thomisidae, being colourful and frequently observed on flowers with prey, are promising models for studying ecological niches using Citizen Science data. In this study, we analysed 627 iNaturalist Italian records of three Thomisidae species, Misumena vatia, Thomisus onustus and Synema globosum, photographed with prey on flowers to assess their ecological niches in terms of environmental and trophic preferences. We first assessed the affinity of each species with the Italian Köppen’s climatic regions by analysing niche overlap, equivalency and similarity, unfilling, expansion, and stability. Misumena vatia emerged as a more Alpine-Temperate spider, while the other two species were more Mediterranean Temperate. The same parameters were used to assess overlap in environmental niches between the species, showing the highest overlap between T. onustus and S. globosum. Finally, bipartite networks highlighted that all the three species primarily hunted on Asteraceae flowers, and their prey mainly belonged to the Apidae family, although network structure, dietary overlap, and specialisation varied slightly across climatic regions. This study highlights Citizen Science data’s value in capturing multidimensional niches and shows how climate influences spider-prey-plant networks. Such insights are crucial for understanding how climate change may disrupt trophic dynamics involving these underappreciated arachnids.