Complex organism-environment feedbacks buffer diversity loss following habitat fragmentation

Background/Question/Methods

Understanding factors influencing the extent and rate of species extinction following habitat destruction are critical for effective conservation and management of ecological communities. One such factor may be various interactions between organisms and local environmental conditions, which can collectively influence the way species affect one another in fragmented habitats. However, this possibility has not received much attention. We investigated the effect of organism-environment feedbacks on extinction following fragmentation by using a stochastic, individual-based simulation model of competitive plant communities.  In this model, we included feedbacks between plants and the local environment, where each plant species affected their own and other species’ competitiveness by modifying local environmental conditions. We allowed the direction and strength of these organism-environment feedbacks to differ among pairs of species in order to mimic complex interactions that have been observed in plant-soil feedbacks. The simulation was conducted under several different assumptions regarding the spatial scale over which species dispersed and environmental heterogeneity is observed.

Results/Conclusions

We found that organism-environment feedbacks reduced both the extent and rate of diversity loss following habitat fragmentation. Our analysis suggested that this “buffering” effect of feedbacks operated via two mechanisms. First, organism-environment feedbacks shifted the scale at which species coexist from global to local, saving species from immediate extinction by fragmentation because they were more globally distributed. Second, feedbacks caused negative density dependence among species, saving species, particularly those that were rare at the time of fragmentation, from eventual extinction due to demographic stochasticity and other forces. In addition, we found that the magnitude of the buffering effect depended on the spatial scale at which species disperse and environmental conditions vary, with strongest buffering occurring when dispersal occurs locally and when environmental conditions vary globally. Overall, our results highlight how understanding factors structuring communities may reveal clues into the severity and rates of diversity loss from communities.