Benefits and costs to pollinating,seed-eating insects: the effect of flower size and fruit abortion on larval performance |
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Authors: | Anne Burkhardt Lynda F Delph Giorgina Bernasconi |
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Institution: | (1) Department of Ecology and Evolution, University of Lausanne, Biophore, 1015 Lausanne, Switzerland;(2) Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405-3700, USA;(3) Present address: Institute of Biology, University of Neuchatel, Rue Emile-Argand 11, 2009 Neuchatel, Switzerland |
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Abstract: | Plant–pollinator interactions are well-known examples of mutualism, but are not free of antagonism. Antagonistic interactions
and defenses or counter-defenses are expected particularly in nursery pollination. In these systems, adult insects, while
pollinating, lay their eggs in flowers, and juveniles consume the seeds from one or several fruits, thereby substantially
reducing plant fitness. The outcome of such interactions will depend, for the plant, on the balance between pollination versus
seed predation and for the larvae on the balance between the food and shelter provided versus the costs imposed by plant defenses,
e.g., through abortion of infested fruits. Here, we examine the costs and benefits to the larvae in the nursery-pollination
system Silene latifolia/Hadena bicruris. Using selection lines that varied in flower size (large- vs. small-flowered plants), we investigated the effects of variation
in flower and fruit size and of a potential defense, fruit abortion, on larval performance. In this system, infested fruits
are significantly more likely to be aborted than non-infested fruits; however, it is unclear whether fruit abortion is effective
as a defense. Larger flowers gave rise to larger fruits with more seeds, and larvae that were heavier at emergence. Fruit
abortion was frequently observed (ca. 40% of the infested fruits). From aborted fruits, larvae emerged earlier and were substantially
lighter than larvae emerging from non-aborted fruits. The lower mass at emergence of larvae from aborted fruits indicates
that abortion is a resistance mechanism. Assuming that lower larval mass implies fewer resources invested in the frugivore,
these results also suggest that abortion is likely to benefit the plant as a defense mechanism, by limiting both resources
invested in attacked fruits, as well as the risk of secondary attack. This suggests that selective fruit abortion may contribute
to the stability of mutualism also in this non-obligate system. |
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Keywords: | Flower number Nursery pollination Pollination mutualism Pre-dispersal seed predation Silene alba |
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