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<dd>Power, E. F. and J. C. Stout. 2011. Organic dairy farming: impacts on
insect-flower interaction networks and pollination. Journal of Applied
Ecology <b>48</b>:561-569.<br><br>
</dl><h3><font face="Arial, Helvetica" size=4><b>Summary</b></font></h3>
<font face="Arial, Helvetica"><b>1.</b> Pollination interactions comprise
a network of connections between flowers and insect visitors. They are
crucial for reproductive success in many angiosperms but are threatened
by intensive agricultural practices. Although less intensive approaches,
including organic farming, could improve farmland biodiversity, it is not
clear whether or not these approaches enhance wild plant pollination and
the stability of insect–flower interaction networks.<br><br>
<b>2.</b> We investigated the effects of organic vs. conventional farming
on insect–flower interaction network size and structure, bee and hoverfly
diversity, and pollination in 10 pairs of organic and conventional dairy
farms in the Republic of Ireland.<br><br>
<b>3.</b> We found that insect–flower interaction networks on organic
farms were larger and more asymmetrically structured than networks on
conventional farms. Overall, however, networks contained fewer taxa and
niche overlap and plant/animal ratios were relatively low compared with
previously documented insect–flower interaction networks. Organic farms
did attract higher numbers of bees partly because of higher floral
abundances (mainly <i>Trifolium</i> sp.). Hoverfly evenness was greater
in organic farms but neither abundance, richness nor evenness was related
to floral abundance, suggesting organic farms provide additional
resources for hoverflies. Pollination of <i>Crataegus monogyna</i>
hawthorn was higher on organic farms, although pollen deposition was
limited.<br><br>
<b>4.</b> <i>Synthesis and applications</i>. Organic dairy farming can
increase the size and alter the structure of insect–flower interaction
networks. However, network stability was not improved and all networks
(organic and conventional) were vulnerable because of their small size,
low niche overlap and low plant/animal ratios. Nonetheless, organic
farming provided more flowers that attracted more flower visitors and
improved pollination of <i>C. monogyna</i>. We suggest that strategic
management of important flowers for pollinators in hedgerows and pastures
should be endorsed in agri-environmental schemes. Sowing <i>Trifolium</i>
spp., and allowing these plants to flower, could benefit bees, but more
research into hoverfly ecology is necessary before realistic conservation
recommendations can be made for this group. We conclude that organic
farming, although not the solution in its present form, can benefit
insect biodiversity, insect–flower interaction networks and
insect-mediated pollination.<br>
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