Body mass dependent dispersal and feeding constraints drive food web assembly

Background/Question/Methods

Food webs are often described as static networks of interacting species and little attention has been devoted to research of food web assembly and temporal dynamics. On the other hand, studies of community assembly have usually avoided complex food web structure and assumed random species-invariant dispersal and discrete trophic levels. We built a simulation framework to address this situation, modeling food web assembly which incorporates realistic food web structure, body mass dependent dispersal and random extinctions. We study the interactive effects of dispersal-body mass scaling and feeding constraints on food web assembly. We model food web assembly in a system of one source patch and one new empty patch which is colonized from the source patch. The source patch contains a rich community of species characterized by body mass and feeding interactions prescribed by a topological food web model with body mass dependent feeding interactions.

Results/Conclusions

We find that colonization success, food web structure and body mass distribution vary systematically during the assembly process and among different dispersal scenarios. First, the assembly process is slowed down when small and even more when large species have relative dispersal advantage. Food web structure (connectance, proportion of top vs. basal species etc.) and body mass distribution also vary systematically during the assembly process and among different dispersal scenarios. At the level of individual species, time until successful establishment depends on dispersal and feeding constraints related to body mass. Our results demonstrate that the scaling of dispersal rate with body mass fundamentally affects food web assembly with potential implications for community stability during early stages of food web development in newly colonized environments, such as islands or restored habitats. In conclusion, we suggest that the theory of community assembly could greatly benefit from a synthesis of the research on dispersal and extinction-colonization processes with food web models.