Can floral repellents pre‐empt potential ant–plant conflicts?

Ants, by consuming floral nectar, are potential parasites of plant–pollinator mutualisms, the persistence of which depends on mechanisms preventing ants from visiting flowers. Here I report the existence of such a mechanism which, uniquely, appears general in its effects. I show that two acacia–ant mutualists are repelled by floral tissue chemicals from their own host-plants as well as those from 13 other plant genera, only one of which associates symbiotically with ants. Furthermore, 18 of 25 ant species, from several subfamilies representing degrees of ant–plant interaction, are repelled by acacia floral chemicals. Thus floral ant repellents are widespread among plants, repel most ant species, and can prevent ants from parasitizing plant–pollinator mutualisms.

[1]  D. Altshuler,et al.  Novel interactions of non-pollinating ants with pollinators and fruit consumers in a tropical forest , 1999, Oecologia.

[2]  M. Pfunder,et al.  Effects of ants on the reproductive success of Euphorbia cyparissias and associated pathogenic rust fungi , 2000 .

[3]  Markus Riederer,et al.  Slippery ant-plants and skilful climbers: selection and protection of specific ant partners by epicuticular wax blooms in Macaranga (Euphorbiaceae) , 1997, Oecologia.

[4]  L. McDade,et al.  THE IMPACT OF FLORAL PARASITISM IN TWO NEOTROPICAL HUMMINGBIRD‐POLLINATED PLANT SPECIES , 1980, Evolution; international journal of organic evolution.

[5]  H. G. Baker,et al.  Ants Like Flower Nectar , 1981 .

[6]  D. Schemske.  THE EVOLUTIONARY SIGNIFICANCE OF EXTRAFLORAL NECTAR PRODUCTION BY COSTUS WOODSONII (ZINGIBERACEAE): AN EXPERIMENTAL ANALYSIS OF ANT PROTECTION , 1980 .

[7]  R. Marquis,et al.  The role of ant-tended extrafloral nectaries in the protection and benefit of a Neotropical rainforest tree , 1999, Oecologia.

[8]  D. Janzen.  Why Don't Ants Visit Flowers? , 1977 .

[9]  J. García-Franco,et al.  Richness and Seasonal Variation of Ant-Plant Associations Mediated by Plant-Derived Food Resources in the Semiarid Zapotitlán Valley, México , 1998 .

[10]  D. Davidson,et al.  The evolutionary ecology of symbiotic ant-plant relationships , 1993 .

[11]  N. Pierce,et al.  A castration parasite of an ant–plant mutualism , 1998, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[12]  R. Buckley.  Ant-plant interactions: a world review , 1982 .

[13]  Rainer Wirth,et al.  Annual foraging of the leaf-cutting ant Atta colombica in a semideciduous rain forest in Panama , 1997, Journal of Tropical Ecology.

[14]  M. Puterbaugh,et al.  The roles of ants as flower visitors: experimental analysis in three alpine plant species , 1998 .

[15]  G. Stone,et al.  How aggressive ant-guards assist seed-set in Acacia flowers , 1997, Nature.

[16]  R. B. Knox,et al.  ANT INHIBITION OF POLLEN FUNCTION: A POSSIBLE REASON WHY ANT POLLINATION IS RARE , 1984 .

[17]  M. Ramsey.  Ant pollination of the perennial herb Blandfordia grandiflora (Liliaceae) , 1995 .

[18]  A. Beattie,et al.  THE VULNERABILITY OF POLLEN AND FUNGAL SPORES TO ANT SECRETIONS: EVIDENCE AND SOME EVOLUTIONARY IMPLICATIONS , 1985 .

[19]  D. Janzen.  COEVOLUTION OF MUTUALISM BETWEEN ANTS AND ACACIAS IN CENTRAL AMERICA , 1966, Evolution; international journal of organic evolution.

[20]  J. M. Gómez.  Effectiveness of ants as pollinators of Lobularia maritima: effects on main sequential fitness components of the host plant , 2000, Oecologia.

[21]  B. Bentley.  EXTRAFLORAL NECTARIES AND PROTECTION BY PUGNACIOUS BODYGUARDS , 1977 .

[22]  D. Janzen.  Swollen-thorn acacias of Central America , 1975 .

[23]  L. Jacobs,et al.  Specialized parasitoid attracted to a pheromone of ants , 1996, Animal Behaviour.

[24]  J. Bull,et al.  Distinguishing mechanisms for the evolution of co-operation. , 1991, Journal of theoretical biology.