Human activities and dispersal capacity: key drivers of dung beetle colonization in Mediterranean and Macaronesian islands

Abstract This study examines how geography, environmental factors, and human history shape the composition of dung beetle assemblages on Mediterranean and Macaronesian islands. We analysed 146 islands (27 in Macaronesia and 119 in the Mediterranean), compiling species inventories from extensive literature. Various environmental factors and species traits, such as body size, geographical range, and nesting behaviours, were evaluated using statistical methods, including Simple Matching Coefficient and k-means clustering, to assess species colonization capacities and biogeographical patterns. Our results show that dung beetle assemblages on these islands are more similar to those of the European mainland than to those inhabiting North Africa or the Middle East, particularly on larger and more populated islands. Human-driven processes, including historical colonization, significantly shape the observed trait distributions, diminishing the impact of geographical isolation. Species with traits such as broader geographical ranges, larger body sizes, and paracoprid nesting behaviour exhibited higher colonization success, indicating that species with better dispersal ability and adaptability are more likely to thrive in insular environments. These findings emphasize the complex interplay between natural and human-mediated factors in shaping island biodiversity. Traditional biogeographical theories prioritize isolation as a key driver of species diversity, whereas our study highlights the pivotal role of human activity in facilitating species establishment and persistence. This human influence can override classical island biogeography effects, such as isolation and island size. Our study underscores the need to integrate both ecological and anthropogenic factors when studying island biodiversity and calls for further research into how these forces interact in insular ecosystems.