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Relationship between capitulum size and pre-dispersal seed predation by insect larvae in common Asteraceae

Relationship between capitulum size and pre-dispersal seed predation by insect larvae in common Asteraceae
Relationship between capitulum size and pre-dispersal seed predation by insect larvae in common Asteraceae
The evolution of a showy floral display as an advertisement to pollinators could simultaneously advertise the availability of resources to pre-dispersal seed-predators. The hypotheses tested here are that the incidence of seed predation by bud-infesting insect larvae in capitula of Asteraceae is positively related to (1) capitulum size among species, (2) capitulum size within species, (3) capitulum lifespan, and (4) the degree of flowering asynchrony on individual plants. Three populations of each of 20 common herbaceous species of Asteraceae from disturbed ground and grassland habitats were monitored for the presence of pre-dispersal, seed-eating insect larvae. Mean capitulum size (receptacle width) of each species was measured. In a sub-set of eight species, individual capitula were tagged to determine their flowering phenology and lifespan (from anthesis to seed shedding). From these data an index of flowering synchrony on individual plants was derived. Among species, the incidence of larval infestation increased with capitulum size. Small-flowered species such as Achillea millefolium were largely free of bud-infesting larvae, whilst large-flowered species such as Arctium minus were heavily infested. In three cases investigated in greater detail, bud infestation was found to increase with capitulum size within species, suggesting a potential for natural selection to favour smaller capitula. No relationship was found between infestation levels and either capitulum lifespan or degree of flowering synchrony, and there was no evidence that the relationship between capitulum size and infestation was confounded by correlations with these other features. The results support hypotheses I and 2, but not 3 and 4. It is suggested that the characteristic capitulum size of each species may represent a trade-off between the opposing selection pressures of pollinators and pre-dispersal seed predators.

bud-infesting larvae, flower lifespan, flower size, flowering synchrony, tephritidae
0029-8549
72-77
Fenner, M.
4de8d311-9bd9-4270-8634-113508ea988f
Cresswell, J.E.
22bd2cbf-bae5-4003-98f5-1a8f387574bc
Hurley, R.A.
3b93bc36-1fda-4bb0-abab-29baa0a0e5e3
Baldwin, T.
813a8f55-c7f3-4dff-b633-4eefc69fb2b0
Fenner, M.
4de8d311-9bd9-4270-8634-113508ea988f
Cresswell, J.E.
22bd2cbf-bae5-4003-98f5-1a8f387574bc
Hurley, R.A.
3b93bc36-1fda-4bb0-abab-29baa0a0e5e3
Baldwin, T.
813a8f55-c7f3-4dff-b633-4eefc69fb2b0

Fenner, M., Cresswell, J.E., Hurley, R.A. and Baldwin, T. (2001) Relationship between capitulum size and pre-dispersal seed predation by insect larvae in common Asteraceae. Oecologia, 130 (1), 72-77. (doi:10.1007/s004420100773).

Record type: Article

Abstract

The evolution of a showy floral display as an advertisement to pollinators could simultaneously advertise the availability of resources to pre-dispersal seed-predators. The hypotheses tested here are that the incidence of seed predation by bud-infesting insect larvae in capitula of Asteraceae is positively related to (1) capitulum size among species, (2) capitulum size within species, (3) capitulum lifespan, and (4) the degree of flowering asynchrony on individual plants. Three populations of each of 20 common herbaceous species of Asteraceae from disturbed ground and grassland habitats were monitored for the presence of pre-dispersal, seed-eating insect larvae. Mean capitulum size (receptacle width) of each species was measured. In a sub-set of eight species, individual capitula were tagged to determine their flowering phenology and lifespan (from anthesis to seed shedding). From these data an index of flowering synchrony on individual plants was derived. Among species, the incidence of larval infestation increased with capitulum size. Small-flowered species such as Achillea millefolium were largely free of bud-infesting larvae, whilst large-flowered species such as Arctium minus were heavily infested. In three cases investigated in greater detail, bud infestation was found to increase with capitulum size within species, suggesting a potential for natural selection to favour smaller capitula. No relationship was found between infestation levels and either capitulum lifespan or degree of flowering synchrony, and there was no evidence that the relationship between capitulum size and infestation was confounded by correlations with these other features. The results support hypotheses I and 2, but not 3 and 4. It is suggested that the characteristic capitulum size of each species may represent a trade-off between the opposing selection pressures of pollinators and pre-dispersal seed predators.

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Published date: 4 August 2001
Keywords: bud-infesting larvae, flower lifespan, flower size, flowering synchrony, tephritidae

Identifiers

Local EPrints ID: 24009
URI: http://eprints.soton.ac.uk/id/eprint/24009
ISSN: 0029-8549
PURE UUID: a8f3de7f-a587-411b-88dc-e2f8ff8e9abe

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Date deposited: 17 Mar 2006
Last modified: 15 Mar 2024 06:51

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Contributors

Author: M. Fenner
Author: J.E. Cresswell
Author: R.A. Hurley
Author: T. Baldwin

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