Print PageIn an effort to elucidate the role of bacteria in the connectivity of food webs, we added bacterial loops to existing food web matrices. We examined the influence of these modifications on indirect connectivity by performing a power series of 2, 5, and 10 on the adjacency matrices. We also calculated dominant eigenvalues. The dominant eigenvalues are interpreted as evidence of strongly connected components which lead to pathway proliferation. As a control we randomly added equal numbers of connections in 100 randomizations per web. We also examined the dominant eigenvectors for each web, and examined the impact of adding members of the transposes of the original matrices to the original matrices.
Results/Conclusions
Addition of microbial loops dramatically increased connectivity, pathway proliferation, and dominant eigenvalues. For example, in the Benguela matrix the addition of microbial loops increased the dominant eigenvalue from 3.0 to 8.9. The 100 randomizations in which an equal number of random connections were added produced a median dominant eigenvalue of 7.3. In our examination of the dominant eigenvectors of the matrices, we found that bacteria were the most important node. We believe that this is powerful evidence that bacteria can dramatically increase connectivity in ecosystems.
