Tag Archive | ecological networks

Interesting Paper: Impact of Fragmentation on Plant-Frugivore networks redundancy

Jörg Albrecht, my former co-supervisor at the University of Marburg finally published his first results from his PhD. I was eagerly waiting for this publication as i also helped to raise a lot of data as a volunteer ornithologist while working on my bachelor thesis. Looking back i remember many nice beautiful moments web_DSC_0003like sitting in a camouflaged tent early in the morning counting frugivorous birds in the very core zone of Bialowieza forest. Bisons, Mooses, wildcats, the sound of howling wolfs in the morning were among the nice experiences i took with me. It was definitely a nice period of my life and i congratulate Jörg for publishing this nice paper! Published in the renown Journal of Ecology you can now access the paper in early-view:

Albrecht  et al. 2013 – Logging and forest edges reduce redundancy in plant–frugivore networks in an old-growth European forest

For those of you who want a little appetizer of what the paper is about. The paper itself incorporates information gained from many recently developed techniques for ecological network analysis to draw conclusions using general ecological theory (Optimal Foraging Theory). The optimal Foraging Theory developed by MacArthur (1955) hasn’t yet much appeared in the ecological network literature, which is a shame as it allows predictions about changing plant/animal specialization patterns in the light of habitat perturbations.  Here is a little summary, but i still recommend to read the full paper as both methods and conclusions are quite sophisticated 🙂

  • 2 years of recorded plant-frugivorous interactions in Europe’s last old-growth lowland forest (Białowieza, Eastern Poland)
  • Hypothesis (Summarized from the 3 expectations in the paper): Increased competition at Forest edges (caused by logging) compared to the interior forest leads to higher, respectively lower, redundancy in plant-frugivore networks. (But better read the paper!)
  • To fully understand the extent of this study you need to dive deep into the study design and purpose. It uses state of the art statistical network-analysis techniques to calculate network redundancy and interaction specialization. Two and a half pages alone explain the data gathering and analysis, while the results sections is nearly half a page long 🙂
  • Despite the small sample size (which was/is a major critical point) the results show that the networks redundancy was reduced at forest edges due to shifting dietary specialization of the interacting partners. As i remember from the data collection Black-caps and Blackbirds dominated in most of the assessed trees, which leads to an asymmetry in the interaction network. As shown in the paper this might be due to forest fragmentation.
  • Possible Critic:The sampling effort of 10 studysites, which were sampled over 2 years might not be enough to detect real properties of ecological networks. However so far every study investigating ecological networks worked with incomplete data. I also don’t really trust the whole separation of species in specialist and generalists based on available literature. Although much is known up to now, both foraging and behavioral patterns of birds might change due to forest fragmentation and therefore such classification might be inaccurate depending on the study sites properties.
  • Why is the study of interest?  Up to now not much is known about how temperate Plant-frugivore interactions change in the face of habitat perturbation. Most of the available literature was conducted in the tropics or didn’t incorporated whole interaction networks. Probably due to the geographical bias, most of the available literature furthermore failed to detect an effect on network stability as this study shows.

So, enough advertising 😉

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