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Summary. Geographic variations in the correspondence between diaspore phenotypes and disperser behavior are thought to determine the
evolution of plant-animal dispersal mutualisms. Helleborus foetidus is a widely distributed plant in Western Europe, which seeds bear a lipid rich elaiosome attracting ant dispersers. Laboratory
cross-tests were conducted to check the correspondence between diaspore phenotypes and ant preference in two localities of
the Iberian Peninsula, Caurel and Cazorla, separated by 750 km. Diaspores from Caurel were systematically preferred to those
from Cazorla by Formica lugubris (the major disperser at Caurel), and Aphaenogatser iberica and Camponotus cruentatus (both major dispersers at Cazorla). Further bioassays conducted on A. iberica only showed that differences in elaiosome traits were sufficient to explain ant preference. Separation of the lipid fractions
composing the elaiosome revealed that triglycerides, diglycerides and free fatty acids were all dominated by oleic acid. The
elaiosomes from Caurel contained relatively more free oleic acid but were less concentrated in linoleyl-containing triglycerides,
free palmitic acid and free linoleic acid than those from Cazorla. The three lipid fractions were attractive to ants but dummies
soaked with the free fatty acids extracted from Caurel were preferred to those from Cazorla. Taken together, these results
reinforce the idea that oleic acid is a major releaser of seed collection by ants and suggest that geographic variations in
free fatty acid composition affect the probability of diaspore removal by ants which in turn potentially determine plant demography. 相似文献
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