Body size mediates the role of insect seed predators as ecosystem engineers for arthropod communities

Abstract Arthropods that interact with host plants can function as allogenic ecosystem engineers by modifying plant structures, thereby influencing the availability of resources for other organisms. This study examined the role of insect seed predators as ecosystem engineers within arthropod communities and assessed how body size affects this facilitation process. We hypothesised that fruits with more and larger cavities would be more colonised, since they would increase the probability of colonisation and allow a wider range of sizes of arthropod species to access the fruits, respectively. We collected tamarind ( Tamarindus indica , Fabaceae) fruits infested by different seed predators. Following the emergence of these organisms, we categorised 200 fruits into five categories (40 per category) based on the number and size of entrance/emergence cavities: absent (fruits without cavities), small (one small cavity), medium (one medium cavity), large (one large cavity), and multiple (two or more cavities). The fruits were then taken back to the field for 2 and 4 months at the beginning of rainy season to allow colonisation by secondary arthropods. We recorded 5237 secondary colonisers from 50 morphospecies and 12 different orders. Ants were the most abundant group (4356 individuals) and utilised the fruits mainly as nesting sites (17 nests). Overall, tamarind fruits in the absent category had a lower species richness and abundance of arthropods compared to fruits with cavities present. Additionally, fruits with large cavities (medium and large categories) supported greater species richness and abundance than those in the small and absent categories. Finally, multiple cavities in fruits facilitate more arthropod species to colonise them compared with those with just one cavity. Our findings underscore the critical role of seed predators as ecosystem engineers, significantly shaping the structure of plant‐dwelling arthropod communities. We conclude that the cavity diameter and number of cavities in fruits are key factors influencing this facilitation process.