Spatial ecological communities often exist in patchy and irregular arrangements. Ecological theory predicts that more isolated and distant communities should promote regional diversity, by harboring rare and endemic species due to dispersal limitations and environmental heterogeneity (Shurin et al. 2004; Scheffer et al. 2006). However, most studies on community assembly have focused on the assembly of species from a single trophic level and generally focused on how local communities assemble from a static species pool, despite ideas that suggest regional food webs are dynamic and communities are made up of multiple trophic levels forming complex ecological networks (Mittelbach and Schemske 2015). Field studies have shown that colonization and extinction rates influence the assembly of food webs from a static regional species pool (Holt 2010; Fahimipour and Anderson 2015; Fahimipour and Hein 2014; Piechnik et all. 2008). What is not known is how varying the regional food web and spatial structure interacts with colonization rates and local species interactions to assemble local food webs. Research thus far has focused on species specific dispersal rates of protists with the goal of looking at how whole food webs assemble under different spatial connectivity. Measuring dispersal rates involves setting up two nalgene bottles connected via a dispersal tube at varying lengths, where protists are placed in one bottle and allowed to disperse to the empty bottle. Mechanistic modeling and maximum likelihood analyses of species dispersal and growth were used to quantify relationships between growth, dispersal rate, and distance.
Results/Conclusions
Preliminary laboratory results suggest that the dispersal ability of Colpidium colpoda decreases as a function of increasing distance from the source region (growth rate= 0.299; dispersal rates: 7cm= 0.494, 13.5cm=0.190, 23cm=0.108). Dispersal trials with other protist bacterivores show similar results, although with greater variance. These results support ideas from the Theory of Island Biogeography, that distance from the regional species pool has a strong effect on local community structure, by influencing the rate of colonization and extinction (MacArthur and Wilson 1967). Ongoing experiments with a mainland-island experimental setup and complex regional food webs are providing insight into how food webs assemble as a function of bacteria productivity, spatial arrangements from the source pool, and the effects of regional food web structure on local communities.