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Variation in predation costs with Chiastocheta egg number on Trollius europaeus : how many seeds to pay for pollination?
Author(s) -
Jaeger Nicolas,
Pompa François,
Després Laurence
Publication year - 2001
Publication title -
ecological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.865
H-Index - 81
eISSN - 1365-2311
pISSN - 0307-6946
DOI - 10.1046/j.1365-2311.2001.00298.x
Subject(s) - biology , predation , larva , population , seed predation , pollination , intraspecific competition , mutualism (biology) , pollinator , competition (biology) , germination , botany , horticulture , ecology , pollen , seed dispersal , biological dispersal , demography , sociology
Summary 1. In obligate plant/seed parasite–pollinator mutualisms, the plant is exclusively pollinated by an insect whose larvae are specific seed predators. Hence, outcomes of the interaction for the plant can vary with the number of eggs laid and the number of seeds eaten per larva. 2. In the work reported here, predation by Chiastocheta larvae on seeds of Trollius europaeus was analysed as a function of the number of eggs laid on the flower. Flowers with an increasing number of eggs were bagged in three populations and seeds were counted after the end of larval predation, in order to assess whether there was competition among larvae. 3. Seed predation on single‐egg flowers was high and variable (mean per population ranging from 15 to 40% of the developed seeds). Seed predation increased weakly with increasing egg load and was lower than gross seed production (always < 85%) whatever the number of eggs laid. This corresponds to a strong decrease in seed consumption per larva with increasing egg load, i.e. severe larval competition for resources. 4. The results suggest that both interference among Chiastocheta larvae and carpel dehiscence may protect T. europaeus seeds from total predation. Estimates of seed predation based on egg load observed in 20 natural populations in the French Alps typically ranged from 30 to 60%. The interaction was always beneficial for the plant and there was no risk of total seed destruction by Chiastocheta larvae, favouring stability of the mutualism.