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Pollination and floral ecology
Pollination and Floral Ecology is the most comprehensive single-volume reference to all aspects of pollination biology--and the first fully up-to-date resource of its kind to appear in decades. This beautifully illustrated book describes how flowers use colors, shapes, and scents to advertise themselves; how they offer pollen and nectar as rewards; and how they share complex interactions with beetles, birds, bats, bees, and other creatures. The ecology of these interactions is covered in depth, including the timing and patterning of flowering, competition among flowering plants to attract certain visitors and deter others, and the many ways plants and animals can cheat each other.
eBook
Nectar Theft and Floral Ant-Repellence: A Link between Nectar Volume and Ant-Repellent Traits?
As flower visitors, ants rarely benefit a plant. They are poor pollinators, and can also disrupt pollination by deterring other flower visitors, or by stealing nectar. Some plant species therefore possess floral ant-repelling traits. But why do particular species have such traits when others do not? In a dry forest in Costa Rica, of 49 plant species around a third were ant-repellent at very close proximity to a common generalist ant species, usually via repellent pollen. Repellence was positively correlated with the presence of large nectar volumes. Repellent traits affected ant species differently, some influencing the behaviour of just a few species and others producing more generalised ant-repellence. Our results suggest that ant-repellent floral traits may often not be pleiotropic, but instead could have been selected for as a defence against ant thieves in plant species that invest in large volumes of nectar. This conclusion highlights to the importance of research into the cost of nectar production in future studies into ant-flower interactions.
Journal Article
Floral volatiles controlling ant behaviour
1. Ants show complex interactions with plants, both facultative and mutualistic, ranging from grazers through seed predators and dispersers to herders of some herbivores and guards against others. But ants are rarely pollinators, and their visits to flowers may be detrimental to plant fitness. 2. Plants therefore have various strategies to control ant distributions, and restrict them to foliage rather than flowers. These 'filters' may involve physical barriers on or around flowers, or 'decoys and bribes' sited on the foliage (usually extrafloral nectaries - EFNs). Alternatively, volatile organic compounds (VOCs) are used as signals to control ant behaviour, attracting ants to leaves and/or deterring them from functional flowers. Some of the past evidence that flowers repel ants by VOCs has been equivocal and we describe the shortcomings of some experimental approaches, which involve behavioural tests in artificial conditions. 3. We review our previous study of myrmecophytic acacias, which used in situ experiments to show that volatiles derived from pollen can specifically and transiently deter ants during dehiscence, the effects being stronger in ant-guarded species and more effective on resident ants, both in African and Neotropical species. In these plants, repellence involves at least some volatiles that are known components of ant alarm pheromones, but are not repellent to beneficial bee visitors. 4. We also present new evidence of ant repellence by VOCs in temperate flowers, which is usually pollen-based and active on common European ants. We use these data to indicate that across a wide range of plants there is an apparent trade-off in ant-controlling filter strategies between the use of defensive floral volatiles and the alternatives of decoying EFNs or physical barriers.
Journal Article
Spatial Structuring and Floral Avoidance Behavior Prevent Ant-Pollinator Conflict in a Mexican Ant-Acacia
Ant-acacias represent a classic insect-plant mutualism: the ants defend the plant from attack by herbivores, and in return are provided with trophic rewards and living space within swollen thorns. A potential drawback of this and other ant-plant mutualisms is that ant-guards may drive away useful insects, particularly pollinators. We assess the potential for ant-pollinator conflict in a Mexican ant-acacia, Acacia hindsii. This Acacia is guarded by a highly aggressive ant (Pseudomyrmex veneficus), which resides entirely within the host plant canopy and is provided with extrafloral nectar and protein-rich Beltian bodies. Acacia hindsii flowers released their pollen from 0700 to 0830 hours, and were visited by pollinators from 0730 to 1300 hours. Over the same time period ants maintained high activity levels at extrafloral nectaries on young leaves. Although daily activity of ants and pollinators overlapped substantially in time, it was largely separated in space: resources exploited by the ants are predominantly concentrated within new growth, while inflorescences are present only on shoots from the previous year. Ants nevertheless visit extrafloral nectaries on older leaves near inflorescences, and there is thus potential for ant-pollinator conflict. Bioassays of ant behavior showed young A. hindsii inflorescences induce an avoidance response in its ant-guards, which reinforces spatial segregation between ants and pollinators. This effect is absent from buds or postreproductive flowers. Young flowers of two non-myrmecophilous Acacia species also induced significant (though less potent) repellent effects, suggesting a general role for ant-repellents in Acacia, with selective enhancement in myrmecophilous species.
Journal Article
Linking Bees and Flowers: How Do Floral Communities Structure Pollinator Communities?
Pollinators provide essential ecosystem services, and declines in some pollinator communities around the world have been reported. Understanding the fundamental components defining these communities is essential if conservation and restoration are to be successful. We examined the structure of plant-pollinator communities in a dynamic Mediterranean landscape, comprising a mosaic of post-fire regenerating habitats, and which is a recognized global hotspot for bee diversity. Each community was characterized by a highly skewed species abundance distribution, with a few dominant and many rare bee species, and was consistent with a log series model indicating that a few environmental factors govern the community. Floral community composition, the quantity and quality of forage resources present, and the geographic locality organized bee communities at various levels: (1) The overall structure of the bee community (116 species), as revealed through ordination, was dependent upon nectar resource diversity (defined as the variety of nectar volume-concentration combinations available), the ratio of pollen to nectar energy, floral diversity, floral abundance, and post-fire age. (2) Bee diversity, measured as species richness, was closely linked to floral diversity (especially of annuals), nectar resource diversity, and post-fire age of the habitat. (3) The abundance of the most common species was primarily related to post-fire age, grazing intensity, and nesting substrate availability. Ordination models based on age-characteristic post-fire floral community structure explained 39-50% of overall variation observed in bee community structure. Cluster analysis showed that all the communities shared a high degree of similarity in their species composition (27-59%); however, the geographical location of sites also contributed a smaller but significant component to bee community structure. We conclude that floral resources act in specific and previously unexplored ways to modulate the diversity of the local geographic species pool, with specific disturbance factors, superimposed upon these patterns, mainly affecting the dominant species.
Journal Article
Daily Partitioning of Pollinators in an African Acacia Community
Many studies have shown sympatric plants with similar floral structures to have flowering periods separated in time, and this is usually interpreted as a selective response to competition for pollination. In highly seasonal habitats, however, the time available for flowering may be highly constrained, and many species often flower together. Under such conditions, one alternative to temporal partitioning on a seasonal scale is for species to flower simultaneously, but with pollen release (dehiscence) structured on a diurnal timescale. Here we provide evidence for such diurnal partitioning of both floral resources and pollinator visitation in an African Acacia community. Temporal separation is enhanced by differences in the rewards offered by Acacia species to their pollinators: species producing nectar as well as pollen receive flower visits from insect groups absent from acacias offering only pollen. In contrast to competition for pollination, this situation may promote mutualistic maintenance of shared pollinators by the Acacia species.
Journal Article
Entomology: The bee-all and end-all
Seven scientists give their opinions on the biggest challenges faced by bees and bee researchers.
Journal Article
Pollination and floral ecology / Pat Willmer
This beautifully illustrated book describes how flowers use colors, shapes, and scents to advertise themselves; how they offer pollen and nectar as rewards; and how they share complex interactions with beetles, birds, bats, bees, and other creatures. The ecology of these interactions is covered in depth, including the timing and patterning of flowering, competition among flowering plants to attract certain visitors and deter others, and the many ways plants and animals can cheat each other. --from publisher description.
eBook
A dual function for 4-methoxybenzaldehyde in Petasites fragrans? Pollinator-attractant and ant-repellent
Ant-repellent floral volatiles offer one method through which plants can mediate the detrimental effects of ants on flowers. Although the repellence itself is well documented, the volatiles involved are less well explored. Here, we investigated the floral bouquet of ant-repellent male flowers of
Petasites fragrans
, identifying 4-methoxybenzaldehyde as the main component. 4-methoxybenzaldehyde significantly repelled ants when presented in isolation in an olfactometer and thus is the likely source of the repellent effect. As 4-methoxybenzaldehyde has previously been shown to attract pollinators, it may therefore have a dual function in
P. fragrans
, pollinator-attractant and ant-repellent. Additionally, 4-methoxybenzaldehyde is particularly interesting as an ant-repellent as it has been observed in the bouquets of other plant species with specific ant interactions.
Journal Article