Structural heterogeneity in source-sink marine communities

Background/Question/Methods

Community ecology focuses on understanding the mechanisms that drive patterns of diversity, with emphasis on conservation efforts that maintain species abundance and distribution. As habitats become fragmented or destroyed, the spatial distribution and physical characteristics of habitats will play an important role in community dynamics. Source-sink relationships are controlled by mechanisms that change based on the dispersal strategies of the individual species. A habitat may become a source or sink population based on the combination of abiotic factors and coexisting species. However, a community does not necessarily behave as a source or a sink for all the species present. The occurrence of multiple dispersal strategies and life histories within a community creates the opportunity for heterogeneity to drive species’ abundance patterns and alter species distribution. In the northern Gulf of Mexico, we explored the effects of structural heterogeneity on the diversity of shallow-water benthic species. PVC tiles were used to form 10x10 cm² communities, and we used community age as a surrogate for the establishment of sources and sinks. Tiles were paired in close proximity at different levels of heterogeneity.

Results/Conclusions

Here, we report the response of populations’ sources and sinks to heterogeneity, and its effect on overall tile diversity. In systems with no heterogeneity or structure, communities showed a clear source and sink effect, however when structure was present, these effects disappeared.  Individual species were not using the similar levels of heterogeneity or structure, and differed in their source sink dynamics. Therefore, source-sink scenarios have to be tested at the species level and separately. Furthermore, heterogeneity can change the strength of the source or a sink.