Metacommunity robustness of plant–fly–wasp tripartite networks with specialization to habitat loss

Recent observations have found plant‐species‐specific fly‐host selection (i.e., specialization) of wasp parasitoids (wasps) in plant–fly–wasp (P–F–W) tripartite networks, yet no study has explored the dynamical implications of such high‐order specialization for the persistence of this network. Here we develop a patch‐dynamic framework for a unique P–F–W tripartite network with specialization observed in eastern Tibetan Plateau and explore its metacommunity robustness to habitat loss. We show that specialization in parasitoidism promotes fly species diversity, while the richness of both plant and wasp decreases. Compared to other two null models, real network structure favors plant species coexistence but increases the extinction risk for both flies and wasps. However, these effects of specialization and network structure would be weakened and ultimately disappear with increasing habitat loss. Interestingly, intermediate levels of habitat loss can maximize the diversity of flies and wasps, while increasing or decreasing habitat loss results in more species losses, supporting intermediate disturbance hypothesis. Finally, we observe that high levels of habitat loss initiate a bottom‐up cascade of species extinction from plants to both flies and wasps, resulting in a rapid collapse of the whole tripartite networks. Overall, this theoretical framework is the first attempt to characterize the dynamics of whole tripartite metacommunities interacting in realistic high‐order ways, offering new insights into complex multipartite networks

Use of structural identifiability analysis to inform experimental design for enzyme kinetics

Objective: The study of enzyme kinetics invariably combines mathematics, chemistry and biology. Experimental techniques allow the concentrations of species in an in vitro reaction to be measured in real time. Numerical fitting algorithms can then be used to estimate unknown parameters for a given mathematical model. Structural identifiability analysis of the model is essential to discover whether the parameters could be uniquely determined (or otherwise) from a perfect noise-free form of the data collected. By analysing models corresponding to changes of experimental technique it is possible to design experiments which produce data appropriate for robust numerical fitting. Result: Three experimental approaches to studying a simple two substrate enzyme catalysed reaction were considered. The first case, using quasi-steady state assumptions and measurement of reaction product only, proved unidentifiable using a variant of the Taylor series approach. Of the four unknown parameters only one was identifiable. The second case, an experiment measuring reaction product and an intermediate for a complete time series, was found to be identifiable using the Taylor series approach. The third case, an alternative experiment for the second case without the measurement of an intermediate, proved intractable using the same approach. However use of a novel input/output relationship approach showed this model to be identifiable. Conclusions: Typical experimental procedure for enzyme kinetics measures steady state concentrations of reaction product. A single time course of such measurements are insufficient for numerical fitting to uniquely estimate the unknown parameters for the relatively simple model considered. These results suggest that a change of experimental technique to measure pre-steady state concentrations is necessary to allow accurate parameter estimation. Additionally a new input/output relationship approach to structural identifiability analysis has been developed which proves effective in cases where the Taylor series approach is unable to produce a result

Reinfection with hookworm after chemotherapy in Papua New Guinea

Reinfection with hookworm (Necator americanus) following chemotherapy was studied over 2 years in a rural village in Madang Province, Papua New Guinea. The prevalence of hookworm infection had returned to pre-treatment levels after 2 years, and the geometric mean hookworm burden had returned to 58% of the pre-treatment value. The rate of acquisition of adult worms was independent of host age, and was estimated as a geometric mean of 2.9-3.3 worms/host/year (arithmetic mean 7.9-8.9 worms/host/year). There was significant predisposition to hookworm infection; the strength of this predisposition did not vary significantly between age or sex classes