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Pollination systems in which the host plant provides breeding sites for pollinators, invariably within flowers, are usually
highly specialized mutualisms. We found that the pollinating bee Braunsapis puangensis breeds within the caulinary domatia of the semi-myrmecophyte Humboldtia brunonis (Fabaceae), an unusual ant-plant that is polymorphic for the presence of domatia and harbours a diverse invertebrate fauna
including protective and non-protective ants in its domatia. B. puangensis is the most common flower visitor that carries the highest proportion of H. brunonis pollen. This myrmecophyte is pollen limited and cross-pollinated by bees in the daytime. Hence, the symbiotic pollinator
could provide a benefit to trees bearing domatia by alleviating this limitation. We therefore report for the first time an
unspecialised mutualism in which a pollinator is housed in a plant structure other than flowers. Here, the cost to the plant
is lower than for conventional brood-site pollination mutualisms where the pollinator develops at the expense of plant reproductive
structures. Myrmecophytes housing resident pollinators are unusual, as ants are known to be enemies of pollinators, and housing
them together may decrease the benefits that these residents could individually provide to the host plant. 相似文献
2.
Plant defense against herbivores often involves constitutive and inducible mechanisms of resistance. Obligate ant-plants,
which provide food and housing for ants, are thought to primarily rely on ants for defense against herbivores. This form of
plant defense has largely been viewed as static. We have been investigating the dynamic nature of Azteca ants as an inducible defense of Cecropia trees. Ants rapidly recruit to and patrol sites of foliar damage. We propose that Azteca ants can be viewed as an inducible defense for Cecropia trees because of their sensitivity to cues associated with herbivory, their rapid and aggressive recruiting ability, and
their reclaimable and redeployable nature as a plant defense. In this study, we examine ant behavior following plant damage,
and the potential cues that indude ant recruitment. We found that ants present on leaves when the plant is damaged leave the
damaged leaf and recruit other ants to it, presumably by laying recruitment trails. Volatile leaf cues associated with herbivory
were important in eliciting an induced response in two experiments. However, we found that cues associated with a congeneric
plant elicited a much stronger ant response than conspecific cues. Although the type of leaf damage (gaping wounds versus
leaf edge wounds) did not affect the level of ant recruitment, the extent of damage did. Leaves with one hole punched showed
a 50% increase in ants, while leaves with five holes punched in them elicited a 100% increase in ant numbers. In sum, it appears
that multiple plant-related cues associated with herbivory are involved in induction of ant recruitment in the Cecropia-Azteca system. We discuss the generality of ant responses to herbivory in obligate ant-plant systems, and in facultative ant-plant
associations, which may be more common.
Received: 23 March 1998 / Accepted after revision: 5 July 1998 相似文献
3.
Tolerating castration by hiding flowers in plain sight 总被引:1,自引:0,他引:1
A key challenge in the study of inter-specific cooperation, or mutualisms, is to understand the mechanisms that prevent cheating.
However, many mutualisms are still invaded by parasites, and we propose that plant ‘tolerance strategies’, which allow an
individual to re-grow and/or reproduce after damage, might have evolved to recover some of the fitness lost to parasitism.
We focus on the ant plant Cordia nodosa and its protecting ant symbionts Allomerus octoarticulatus and Azteca spp. Allomerus is a castration parasite, destroying host flowers. However, some flowers are produced on new branch shoots, where they escape
castration. Here, we ask whether C. nodosa tolerates castration by directing floral growth to new shoots. We find that C. nodosa produces four times more floral buds on the new shoots of Allomerus-inhabited plants, compared to Azteca-inhabited plants. Additionally, on Allomerus-inhabited plants, the production of floral buds is three times greater on new than on mature shoots, and more floral buds
are grown on plants with new shoots than on those without. We conclude therefore that C. nodosa tolerates castration by re-allocating floral resources to new shoots. We also test whether tolerance exploits behavioural
differences between the brood-tending ‘nurse’ ant worker caste, which is active on mature shoots, and the new shoot-protecting
‘patroller’ caste. Behavioural assay experiments reveal that nurse ants are strongly attracted to extracts of flowers, whereas
patrollers are not, suggesting that nurses are the primary castrating caste. Thus, producing flowers on new shoots avoids
the castrating caste. We finish by proposing that tolerance strategies can promote the evolution and maintenance of mutualism. 相似文献
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