Allee effects and extinction debt
M. Labrum, "Allee effects and extinction debt". Ecological Modelling 222 (2011) 1205-1207, doi:10.1016/j.ecolmodel.2010.12.013
Habitat destruction may have profound negative impacts on the biodiversity of a given environment. The presence of Allee effects compounds these problems. A sound understanding of the interplay between habitat destruction, Allee effects, and subsequent extinctions is needed to better guide conversation efforts.
This study incorporates Allee effects into an extinction debt model, and the analyses provide upper bounds on the strength of those effects that are consistent with species persistence. These results differ from those of a previous study by up to four orders of magnitude assuming the same published parameter values. These new results suggest that if sufficiently strong Allee effects are present, efforts to prevent extinction through habitat restoration may be futile.
On the evolution of structure in ecological networks (.pdf)
M. Labrum, T. Soule, A. Blue, S.M. Krone, "On the evolution of structure in ecological networks". Proceedings of 5th International Conference on Complex Systems (ICCS '04), A. Minai, Y. Bar-Yam, Eds., Springer, Boston, Mass, USA, May 2004.
Previous research on simulated ecological networks has often focused on issues such as the distribution of the number of links between species, without generally categorizing the types of inter-species relationships that develop, unless those relationships are of some predesigned form (e.g., food webs). In this work we use a model system to examine general, dynamically-evolved ecological networks that are subject to occasional invasion by novel species. Keeping track of the specific types and numbers of interactions between species over time leads to insight on how these affect network stability, fragility and evolution. We discuss the role that assembly rules play on the evolutionary trajectories of randomly initialized communities. We also investigate the occurrence of certain types of interactions (e.g., cyclic) and quantify their destabilizing effect on the network. In particular, extinctions and secondary extinctions ("avalanches") are related to these issues.