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A Temperate Region Plant‐Ant‐Seed Predator System: Consequences of Extra Floral Nectar Secretion by Helianthella Quinquenervis
Author(s) -
Inouye David W.,
Taylor Orley R.
Publication year - 1979
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936460
Subject(s) - biology , nectar , predation , predator , herbivore , seed predation , bract , pollination , botany , insect , hymenoptera , lepidoptera genitalia , mutualism (biology) , ecology , seed dispersal , population , pollen , biological dispersal , demography , inflorescence , sociology
Helianthella quinquenervis (Asteraceae), the aspen sunflower, secretes sugar and amino acid rich nectar from involucral bracts during bud and flowering stages. The nectar is usually collected by ants as fast as it is secreted. H. quinquenervis is subject to predispersal seed predation by larvae of several insect species, primarily tephritid flies, an agromyzid fly, and 3 Lepidoptera. When present, ants interrupt oviposition efforts by the female flies but do not appear to be effective against lepidopteran or mammalian herbivores. The degree of protection by ants conferred upon plants was investigated by excluding ants from some plants and by correlating ant density with subsequent damage to ovules and developing seeds. At higher elevations (2896 and 3091 m) damage to plants with ants was significantly reduced compared with plants without ants. At a lower elevation (2734 m) where seed predator and ant densities were highest, the ants were less effective as deterrents and predation on ovules and seeds usually exceeded 60%. Flowers of some other composite species in the same habitats appear to be more effectively protected from predation by chemical deterrents, raising questions of the relative benefits of chemical deterrents compared to ants as a means of protection.