Using interaction profile to measure species uniqueness in food webs

Species are embedded in an intricate network of trophic interactions, it is therefore natural to examine species importance from a network perspective. In addition to measuring species importance by considering the centrality of their network positions in a food web (implying to be well connected to interaction partners), recent years have seen the emergence of species uniqueness (implying to be functionally harder to replace) as another facet of species importance. Existing network or food web-based uniqueness measurements are based on how species affect others and how their trophic fields may overlap. In this short communication paper, we demonstrate that it is also important to consider information on how species can be affected by others, and how this can be incorporated into species uniqueness measurement. We demonstrate our approach by analyzing in detail the Great Barrier Reef food web, and show how the inclusion of new information on species interaction pattern can change the uniqueness ranking of species. We further analyze 92 aquatic food webs to test the generality of our findings. For very few food webs, the correlation between species uniqueness rankings derived from the old and the new approaches is almost perfect. For the remaining food webs such a correlation varies, with many showing a medium level of correlation. Thus, including new information on species interaction pattern can offer new information on network or food web-based species uniqueness measurement.