Broom and Honeybees in Australia: An Alien Liaison

Facilitative interactions between non-indigenous species are gaining recognition as a major driver of invasion success. 'Cytisus scoparius' (L.) Link (Fabaceae), or Scotch broom, is a cosmopolitan invasive shrub that lacks the capacity for vegetative reproduction and is a good model to study facilitative interactions. Its success in pioneer environments is determined by constraints on its reproduction. We determined whether pollinators were required for seed set in 'C. scoparius' at Barrington Tops, NSW, Australia, where the species has infested ca. 14 000 ha across the plateau. Field and laboratory experiments showed that 'C. scoparius' is an obligate outcrossing species at Barrington Tops. Monitoring of plants (10.7 h) showed that the flowers of 'C. scoparius' have to be tripped to effect seed set and the only pollinator to do this was the introduced honeybee, 'Apis mellifera L.' Most floral visits by honeybees result in fruit set (84 %) and because fruits have many ovules (10 - 18 per ovary) a single bee on an average foraging day can effect the production of over 6000 seeds. A review of 'C. scoparius' pollination across four continents revealed major differences in pollen quantity, which may explain differences in the efficiencies of honeybees as pollinators of 'C. scoparius'. The incorporation of pollinator management in an integrated approach for the control of 'C. scoparius' is discussed

Importance of native vegetation to beneficial insects and its role in reducing insect pest damage in cotton

Conservation biological control is one of the strategies in integrated pest management (IPM.) Its aim is to conserve naturally occurring predators within the agricultural landscape. Modifying the landscape to enhance predator efficiency, referred to as habitat management, is one of the methods used in conservation biological control. Habitat management, until recently has largely been ignored within many IPM programs. Area wide management of pests has changed this perception and there is now a realisation that events outside the crop impacts on events within the crop

Pollen grains as markers to track the movements of generalist predatory insects in agroecosystems

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Fine scale genetic structure and fire-created habitat patchiness in the Australian allodapine bee, Exoneura nigrescens (Hymenoptera: Apidae)

Fire promotes an abundance of nest sites for the stem nesting bee Exoneura nigrescens, which remain viable for approximately 10 years. The finite duration of nesting substrate and localized fire events suggest that migration should minimize genetic structure among suitable habitat patches. Exoneura nigrescens was sampled from 7 localities with a known fire history in southwestern Victoria, Australia. Individual bees were genotyped at 8 microsatellite loci and genic and genotypic analyses applied to examine genetic structure among burn patch localities, within burn patches, and within colonies. Despite relatively short-term availability of nesting substrates, remarkably fine-scale genetic structure was observed both among burn patches and within burn patches. The spatial distribution of relatedness shows a strong pattern of isolation-by-distance at geographic distances to 35 km, suggesting that genetic partitioning among burn patches is, at least in part, a result of dispersal ability. Genetic structure within burn patches includes colonies consisting of close kin with genic partitioning among nests. Relatedness structure within colonies suggests that polygamy, multiple breeding pairs, and a lack of inbreeding typifies the mating system.7 page(s

Pollen grains as markers to track the movements of generalist predatory insects in agroecosystems

This special issue provides ample evidence why it is becoming increasingly important to be able to track the movement of predatory insects in agroecosystems through space and time. Tracking predatory insects presents a considerable challenge as they are often small, cryptic and highly mobile organisms. Using insect-borne pollen present either on the exoskeleton or within the gut, presents a useful technique by which the movements (spatial displacements) of insects can be determined, based on the distribution of flowering plants in the area, an appropriate pollen key or atlas, and an understanding of pollination ecology. Pollen has successfully been used to track the movement of bees and moths, but has rarely been used to track predatory insects. Since many predators are likely to encounter pollen as they forage on flowers, they are good candidates for this technique. In this review we examine two types of study that use pollen to track the movements of predatory insects: (a) those in which pollen from the surrounding landscape is used to assess habitat usage and short-term movement of generalist predators from a range of insect orders, and (b) those in which pollen from a known point-source is used to assess the movement and dispersal distance of the insects. We discuss the benefits and limitations of using pollen to determine the movement of predatory insects, and explain how the information derived can contribute to optimising the use of predatory insects within the agricultural landscape in integrated pest management programmes

Differential antimicrobial activity in response to the entomopathogenic fungus Cordyceps in six Australian bee species

Microbial pathogens were important in the evolution of insect societies and remain a major cause of colony death. The differential effects are reported of antimicrobial compounds extracted from six species of Australian native bees on the spores and hyphae of the entomopathogenic fungus Cordyceps bassiana. The bee species were: Amegilla bombiformis, A. asserta, Exoneura robusta, E. nigrescens, Exoneurella tridentata and Trigona carbonaria. The fungus was isolated from E. robusta and it was this species that showed the greatest activity against both Cordyceps spore germination and hyphal growth. One explanation is that anti-Cordyceps activity may have been under greatest selection in this bee species, but its congener, E. nigrescens, showed only slightly weaker activity against the pathogen. In contrast, A. bombiformis, A. asserta, E. tridentata and T. carbonaria showed considerable variation in anti-Cordyceps activity. Nevertheless, there was a trend of greater activity against Cordyceps spore germination than hyphal growth. On the basis of this result, a mechanism whereby fungal pathogens may have been important drivers of social evolution is suggested