Endozoochorous seed dispersal in urban ecosystems: a global review of patterns, interactions, and knowledge gaps

Urbanisation influences various aspects of species interactions, including animal-mediated endozoochorous seed dispersal – an essential mechanism that facilitates plant dispersal and establishment in urban environments. However, in-depth and systematic assessments of how urbanisation shape endozoochory interactions remain limited. To address this knowledge gap, we reviewed studies on endozoochory in urban ecosystems and examined the effects of urbanisation on endozoochorous seed dispersal. We also assessed whether urban endozoochorous networks exhibit high evenness and nestedness. Additionally, we analyzed trends in the abundance of the resulting plant functional diversity in urban ecosystems. Our review identified 34 studies on endozoochory in urban ecosystems across 17 countries, documenting 429 interactions involving 69 animal and 212 plant species. Most studies (26) focused on a single animal species as a seed disperser, while only two examined urbanisation rates. Furthermore, only 15 studies conducted germination tests on dispersed seeds, indicating limited attention to post-dispersal seed fate. We found substantial interaction evenness in urban endozoochory, alongside a reduction in the functional diversity of dispersed native plants compared to all dispersed plants, including non-native species. Among animal dispersers, only bats exhibited a positive response to urbanisation in terms of the number of plant species dispersed. Additionally, fleshy and dark-coloured fruits that often contain large seeds were positively correlated with urbanisation, suggesting that these traits may facilitate the dispersal of large-sized seeds in urban areas. Our findings highlight urbanisation as a key driver of endozoochorous interactions, emphasizing the need for future research to deepen our understanding of urban endozoochory and to enhance biodiversity conservation efforts.