Abstract:
The Costa Rican fig tree, Ficus pertusa, is pollinated by a species-specific wasp (Agaonidae) whose female offspring transfer pollen between trees. Pollination success (the proportion of inflorescences pollinated) ranged from 1-100% and averaged only 65%. Resource availability evidently was limiting to fruit set as well: every crop abscised many inflorescences at a predictable point during growth. This abscission period usually preceded the brief but variably timed period of pollinator arrivals; in most cases every pollinated, undamaged inflorescence set fruit. Fruit abortion would not be expected in plants that evolved under conditions of pollen limitation; although pollinators have been thought to be overabunadnt in highly coevolved pollination mutualisms, figs' unique flowering phenology may in fact make pollen limitation common. The fact that future pollen carriers as well as seeds mature within fruits may also help explain these unusual fruit maturation patterns. -from Author
Abstract:
A total of 26 species of birds in 10 families took F. pertusa fruit. Visitors' identity, abundance, and importance (estimated by an index of the number of fruits removed) all varied among trees and over time for individual trees. Compared with its obligate, species-specific pollination mutualism, F. pertusa's highly variable interactions with its present-day disperser assemblage are less likely to be products of coevolution. -from Authors
Abstract:
The natural history of Anidarnes bicolor (Ashmead) Boucek (Hymenoptera: Agaonidae: Sycophaginae), a host-specific galler of the Florida strangling fig (Ficus aurea, Moraceae), is described. A. bicolor females oviposit through the outside of the globular fig inflorescence; offspring feed on sterile tissue within galls induced on the inner wall of fig. Oviposition coincides with entry of the pollinators (Pegoscapus mexicanus; Hymenoptera: Agaonidae: Agaoninae) into the fig, and does not interfere with pollination. Pollinator presence is in fact crucial to A. bicolor success, because unpollinated, galled figs are aborted by the tree. However, A. bicolor may nevertheless reduce pollinator success: maturation of pollinator offspring appears to be negatively affected by the developing A. bicolor galls. Although the composition of the wasp community associated with the native Florida figs is relatively well-known, this is one of the first studies of the natural history of one of the non-pollinator species.
PMID: 19287014;PMCID: PMC2701751;Abstract:
BACKGROUND AND AIMS: A deeper understanding of mutualism can be reached by studying systems with measurable costs and benefits. Most studies of this type focus on an unusual class of obligate, species-specific pollination mutualisms. The interaction between Datura wrightii (Solanaceae) and the hawkmoth Manduca sexta offers similar advantages but greater generality. Adult moths both nectar at and deposit eggs on the same plant; larvae are herbivorous. The antagonistic component of this interaction has been well studied. Here the role of M. sexta as a pollinator of D. wrightii, particularly in the context of this moth's frequent nectaring visits to the bat-pollinated plant Agave palmeri, is documented. METHODS: Hand-pollinations were used to determine breeding system and the reproductive consequences of mixed loads of A. palmeri and D. wrightii pollen. Plants and moths were caged overnight to assess whether nectaring visits led to fruit and seed set. Finally, pollen deposited on field-collected stigmas was identified, with a particular focus on documenting the presence of D. wrightii and A. palmeri grains. KEY RESULTS: Datura wrightii is highly self-compatible, and a visit that deposits either outcross or self pollen almost doubles fruit and seed set compared with unvisited flowers. Manduca sexta transferred enough pollen to produce fruit and seed sets comparable to hand-pollination treatments. Agave palmeri did not interfere with D. wrightii success: in the field, stigmas received almost pure D. wrightii pollen, and hand-addition of large quantities of A. palmeri pollen had no measurable effect on fruit and seed set. CONCLUSIONS: The floral visitation component of the D. wrightii-M. sexta interaction is indeed mutualistic. This finding is essential background to future development of this interaction as a model system for studying mutualism's costs and benefits. It is already proving valuable for dissecting third-species effects on the outcome of mutualism. Results indicate that M. sexta's heavy visitation to A. palmeri has no negative effect on the benefits conferred to D. wrightii. However, it can be predicted to augment M. sexta populations to the point where the costs of the interaction begin to exceed its benefits.
