  Community ecologists are principally occupied with the proposition that
natural assemblages of species exhibit orderliness and with identifying its
causes. Plant-pollinator networks exhibit a variety of orderly properties, one
of which is 'nestedness'. Nestedness has been attributed to various causes, but
we propose a further influence arising from the phylogenetic structure of the
biochemical constraints on the pollen diets of bees. We use an artificial
assemblage as an opportunity to isolate the action of this mechanism. The
properties of the network that we studied are consistent with the proposition
that nestedness is caused by the phylogeny of diet range in bees, but the claim
is preliminary and we propose that valuable progress in understanding
plant-pollinator systems may be made through applying the techniques of
chemical ecology at the community scale.
