New paper out: Parasitoid diversity reduces the variability in pest control services

My latest paper from the organic farms study in the UK has just come out. You can download from here or contact me for a copy.

Macfadyen, S., Craze, P., Polaszek, A., van Achterberg, K. & Memmott, J. (2011) Parasitoid diversity reduces the variability in pest control services across time on farms. Proceedings of the Royal Society B, 278: 3387-3394.


Recent declines in biodiversity have increased interest in the link between biodiversity and the provision and sustainability of ecosystem services across space and time. We mapped the complex network of interactions between herbivores and parasitoids to examine the relationship between parasitoid species richness, functional group diversity and the provision of natural pest control services. Quantitative food webs were constructed for 10 organic and 10 conventional farms. Parasitoid species richness varied from 26 to 58 species and we found a significant positive relationship between parasitoid species richness and temporal stability in parasitism rates. Higher species richness was associated with lower variation in parasitism rate. A functional group analysis showed significantly greater parasitoid species complementarity on organic farms, with on average more species in each functional group. We simulated parasitoid removal to predict whether organic farms experienced greater robustness of parasitism in the face of local extinctions. This analysis showed no consistent differences between the organic and conventional farm pairs in terms of loss of pest control service. Finally, it was found that the different habitats that make up each farm do not contribute equally to parasitoid species diversity, and that hedgerows produced more parasitoid species, significantly more so on organic farms.

Interesting paper – network analysis….a guide for community ecologists

I found this great ‘invited view’ paper in Basic and Applied Ecology that explains the problems and pitfalls of using a range of network metrics to describe network topology. Very useful for any ecologist involved with, or wishing to embark on, network analysis.

The full reference is:

Nico Blüthgen (2010) Why network analysis is often disconnected from community ecology: A critique and an ecologist’s guide. Basic and Applied Ecology 11:185-195.

Link to Journal website

Interesting paper

Compartments in a marine food web associated with phylogeny, body mass, and habitat structure
Ecology Letters (2009) 12(8), 779-788
Enrico L. Rezende, Eva M. Albert, Miguel A. Fortuna, Jordi Bascompte

doi: 10.1111/j.1461-0248.2009.01327.x

Rezende et al. examined network structure in a marine food web (containing 3313 interactions between 249 species/trophic groups!) and unequivocally showed the presence of compartments (or subunits) in this network. These are link-dense regions of the network where species interact more closely with other species within the module than between modules. Modules may may be important for the propagation of disturbance impacts throughout a network.  More importantly Rezende et al. identified some potential mechanisms behind this interesting network structure (body size, phylogeny and spatial structure).  Shark species played an important role in this network.