Response of omnivorous food web to the invasion of dual-role species: Reorganisation of food webs

To explore the mechanisms by which dual-role species invade stable food webs, we developed a patch dynamic model to describe species occupancy in an omnivorous food web. In this framework, a dual-role invader is introduced at different trophic levels, simultaneously acting as both predator and prey. We then examined how invasion influences species persistence under varying degrees of habitat loss and fragmentation. Our results show that: (1) When dual-role invasive species share the same prey but differ in their predators, the invasion outcomes for the invaders themselves are largely similar, with differences mainly reflected in the diversity of resulting food chain structures under habitat destruction. (3) When the dual-role invasive species preys on an intermediate consumer species, regardless of the trophic level of the invasive species' natural enemies in the food web, there will be a chain reaction of extinction in which the invasive species is exterminated first, followed by the intermediate consumer species and then a top predator species. (4) The degree of habitat loss, habitat fragmentation, and colonization rate impacts the invasion outcome under different roles and trophic levels.