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Applications to Food Webs

Applications to Food Webs

Nestedness and Reciprocal Specialization

(p.170) Chapter Ten Applications to Food Webs
Patterns In Nature
James G. SandersonStuart L. Pimm
University of Chicago Press

In this chapter, we move from biogeographical patterns to those describing food webs. We cover two ideas. The first asks whether trophic networks have a preponderance of reciprocal specialists. The famous example is the moth whose existence Darwin predicted from looking at a particular orchid that he speculated would pollinate it. We found no evidence that reciprocal specialization shapes ecological networks by creating an excess of reciprocally specialized trophic interactions between consumers and resources.The second idea involves nestedness—a pattern that likely applies to both biogeographic distributions and trophic networks. In the former, it would be hard to imagine that the pattern would not hold. For trophic networks, conventional wisdom rejects nestedness, arguing instead that species dietary preferences should be distinct and strung along some gradient like “beads on a string.” Despite textbooks’ predilection for this model, almost everyone who examines feeding relationships in the field rejects it. These results suggest that common processes and universal constraints might operate across such widely different networks, and lend support to the flower-petal model of network structure.

Keywords:   flower petal, food web, mutualism, nestedness, network, palimpsest, reciprocal specialization, string of beads, trophic network

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