FLORAL SCENT IN A WHOLE-PLANT CONTEXT Floral volatiles controlling ant behaviour

Summary 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

Determinants of Contests in Ugandan Female Ground-Nesting Bees (Tetralonia sp. n.)

Many animals engage in contests with conspecifics for access to resources. Understanding which resources individuals are contesting for, and what influences the outcome is central to our understanding of contest behaviour. We initially observed female bees of the genus Tetralonia (sp. n.) aggressively competing for access to burrows in the ground, without any clear indication of exactly which resources were being contested, or what factors might predict the outcome.We then individually marked bees and assigned ownership of burrows to individuals, before observing over 100 aggressive interactions. After excavating burrows cast with molten wax, we concluded that burrows were nests for provisioning larvae. We found that ownership (as putatively designated by us) had no influence on contest outcome, but rather that the position of the bees in the burrow was decisive; whichever bee was already in the burrowwhenthe contest beganwonthe vast majority of interactions. Furthermore, bees that were designated ownership of a burrow did not engage in longer fights for possession of that specific burrow, indicating either that they were not committing any kind of 'Concorde fallacy' by basing decisions on past investment, or that the assignment of ownership was incorrect. Instead, fights were longer later in the day, presumably as the value of the burrow as a refuge from the cold and/or predation increased as night approached. Nest parasitism does not seem to be a common strategy in this species, as owners were not more likely to attempt ejecting an intruder than vice versa. This indicates that contest settlement may not always follow theoretical predictions, but rather that insights and inferences into a species' ecology can be made from observations of dyadic contests

The utility of aerial pan-trapping for assessing insect pollinators across vertical strata

Insect pollinators provide a critical ecosystem service by pollinating many wild flowers and crops. It is therefore essential to be able to effectively survey and monitor pollinator communities across a range of habitats, and in particular, sample the often stratified parts of the habitats where insects are found. To date, a wide array of sampling methods have been used to collect insect pollinators, but no single method has been used effectively to sample across habitat types and throughout the spatial structure of habitats. Here we present a method of ‘aerial pan-trapping’ that allows insect pollinators to be sampled across the vertical strata from the canopy of forests to agro-ecosystems. We surveyed and compared the species richness and abundance of a wide range of insect pollinators in agricultural, secondary regenerating forest and primary forest habitats in Ghana to evaluate the usefulness of this approach. In addition to confirming the efficacy of the method at heights of up to 30 metres and the effects of trap color on catch, we found greatest insect abundance in agricultural land and higher bee abundance and species richness in undisturbed forest compared to secondary forest