The effect of protective covers on pollinator health and pollination service delivery

Protective covers (i.e., glasshouses, netting enclosures, and polytunnels) are increasingly used in crop production to enhance crop quality, yield, and production efficiency. However, many protected crops require insect pollinators to achieve optimal pollination and there is no consensus about how best to manage pollinators and crop pollination in these environments. We conducted a systematic literature review to synthesise knowledge about the effect of protective covers on pollinator health and pollination services and identified 290 relevant studies. Bees were the dominant taxon used in protected systems (90%), represented by eusocial bees (e.g., bumble bees (Bombus spp.), honey bees (Apis spp.), stingless bees (Apidae: Meliponini)) and solitary bees (e.g., Amegilla spp., Megachile spp., and Osmia spp.). Flies represented 9% of taxa and included Calliphoridae, Muscidae, and Syrphidae. The remaining 1% of taxa was represented by Lepidoptera and Coleoptera. Of the studies that assessed pollination services, 96% indicate that pollinators were active on the crop and/or their visits resulted in improved fruit production compared with flowers not visited by insects (i.e., insect visits prevented, or flowers were self- or mechanically pollinated). Only 20% of studies evaluated pollinator health. Some taxa, such as mason or leafcutter bees, and bumble bees can function well in covered environments, but the effect of covers on pollinator health was negative in over 50% of the studies in which health was assessed. Negative effects included decreased reproduction, adult mortality, reduced forager activity, and increased disease prevalence. These effects may have occurred as a result of changes in temperature/humidity, light quality/quantity, pesticide exposure, and/or reduced access to food resources. Strategies reported to successfully enhance pollinator health and efficiency in covered systems include: careful selection of bee hive location to reduce heat stress and improve dispersal through the crop; increased floral diversity; deploying appropriate numbers of pollinators; and manipulation of flower physiology to increase attractiveness to pollinating insects. To improve and safeguard crop yields in pollinator dependent protected cropping systems, practitioners need to ensure that delivery of crop pollination services is compatible with suitable conditions for pollinator health

Blue and yellow vane traps differ in their sampling effectiveness for wild bees in both open and wooded habitats

Pan trapping is a common method for sampling wild bees, although the use of vane traps is growing globally. Despite this, few studies have tested the effectiveness of different coloured vane traps in attracting bees among different habitat types, and none exist in the southern hemisphere. The present study sampled 192 sites (108 in wooded habitats and 84 in open habitats) within an agricultural region of southern Australia. Pairs of coloured vane traps (one blue and one yellow) were placed at each site for a period of seven days. Combined, 16 348 individuals were collected from four families, comprising 13 genera (21 subgenera) and 55 species. Blue vane taps were most effective, sampling six times as many individuals as yellow vane traps and 96% of total species. Their effectiveness was consistent among open and wooded habitat types. The present study highlights the efficacy of vane traps as a passive sampling technique for wild bees. An added benefit of this technique is that vane traps do not require pheromones or lethal agents. A systematic sampling method best suited to the research question should be incorporated into studies of wild bees. For ecological census and population monitoring within multiple habitat types, the present study supports the use of blue vane traps as a major component of the sampling protocol

High sampling effectiveness for non-bee flower visitors using vane traps in both open and wooded habitats

Many non‐bee insects are important for pollination, yet few studies have assessed the effectiveness of sampling these taxa using low‐cost techniques, such as coloured vane traps, among different habitat types. This study sampled 192 sites – 108 in wooded and 84 in open habitats – within an agricultural region of southern Australia. Pairs of blue and yellow vane traps were placed at each site for a period of seven days during the austral spring. Overall, 3114 flies (Diptera) from 19 families and 528 wasps (non‐bee and non‐formicid Hymenoptera) from 16 families were collected during the study. This sampling was representative of the region, with vane traps equally or more likely to collect as many families from both taxa as those reported on the Atlas of Living Australia (ALA) database for the sampling area. Blue vane traps (BVTs) had greater average richness of both flies and wasps and greater activity density (abundance per 7‐day sampling period) of individuals than yellow vane traps (YVTs). BVTs were particularly favoured by fly and wasp families known to pollinate flowers (e.g. Syrphidae, Bombyliidae and Scoliidae), whilst YVTs sampled flower visitors that also provide additional ecosystem services, such as pest control and nutrient cycling. Here, vane traps were an effective sampling technique to capture non‐bee flower visitors, such as flies and wasps. This study supports the use of vane traps as a component of the sampling protocol for ecological census and population monitoring within multiple habitat types, where colour attraction will more effectively sample a comprehensive pollinator community

At the crossroads : does the configuration of roadside vegetation affect woodland bird communities in rural landscapes?

In agricultural regions worldwide, linear networks of vegetation such as hedges, fencerows and live fences provide habitat for plant and animal species in heavily modified landscapes. In Australia, networks of remnant native vegetation along roadsides are a distinctive feature of many rural landscapes. Here, we investigated the richness and composition of woodland- dependent bird communities in networks of eucalypt woodland vegetation along roadsides, in an agricultural region in which >80% of native woodland and forest vegetation has been cleared. We stratified sites in a) cross sections and b) linear strips of roadside vegetation, to test the influence on woodland birds of site location and configuration in the linear network (the ‘intersection effect’). We also examined the influence of tree size at the site, the amount of wooded vegetation surrounding the site, and the abundance of an aggressive native species, the noisy miner Manorina melanocephala. Birds were surveyed at 26 pairs of sites (cross section or linear strip) on four occasions. A total of 66 species was recorded, including 35 woodland species. The richness of woodland bird species was influenced by site configuration, with more species present at cross sections, particularly those with larger trees (>30 cm diameter). However, the strongest influence on species richness was the relative abundance of the noisy miner. The richness of woodland birds at sites where noisy miners were abundant was ~20% of that where miners were absent. These results recognise the value of networks of roadside vegetation as habitat for woodland birds in depleted agricultural landscapes; but highlight that this value is not realised for much of this vast vegetation network because of the dominance of the noisy miner. Nevertheless, roadside vegetation is particularly important where the configuration of networks create nodes that facilitate movement. Globally, the protection, conservation and restoration of such linear networks has an important influence on the persistence of biota within human-dominated landscape

Linear habitats in rural landscapes have complementary roles in bird conservation

Linear strips of vegetation (e.g., hedges, roadsides) are characteristic of rural environments worldwide. Different types of linear features have distinct structure and landscape context, suggesting they each may offer unique opportunities for conservation in modified landscapes. We compared the avifauna of 76 streamside (riparian) sites and 33 sites in roadside vegetation—two distinctive types of linear features of rural landscapes in southern Australia. There was a marked difference in the composition of the avifauna between these linear features, reflecting their individual context within the landscape. For all response groups—woodland bird species, non-woodland species, waterbirds—riparian vegetation supported a greater species richness per site, and greater cumulative richness across multiple sites, than did roadside vegetation. For woodland species, the assemblage of greatest conservation concern, richness in both riparian and roadside sites increased with increasing width, and decreased with increasing abundance of an aggressive avian competitor. The ubiquity of linear features worldwide means that measures that enhance their conservation value will have widespread benefits. Our results demonstrate that: (1) linear features offer habitat for a broad range of species in rural environments; (2) by supporting distinct assemblages, different types of linear features have complementary roles in nature conservation; (3) wider linear features have a positive influence on species that require vegetated cover; and (4) the fauna of linear features are vulnerable to biotic influences, in this case a native avian competitor

Bee visitation and fruit quality in berries under protected cropping vary along the length of polytunnels

Wild and managed bees provide effective crop pollination services worldwide. Protected cropping conditions are thought to alter the ambient environmental conditions in which pollinators forage for flowers, yet few studies have compared conditions at the edges and center of growing tunnels. We measured environmental variables (temperature, relative humidity, wind speed, white light, and UV light) and surveyed activity of the managed honey bee, Apis mellifera L.; wild stingless bee, Tetragonula carbonaria Smith; and wild sweat bee, Homalictus urbanus Smith, along the length of 32 multiple open-ended polyethylene growing tunnels. These were spaced across 12 blocks at two commercial berry farms, in Coffs Harbour, New South Wales and Walkamin, North Queensland, Australia. Berry yield, fresh weight, and other quality metrics were recorded at discrete increments along the length of the tunnels. We found a higher abundance and greater number of flower visits by stingless bees and honey bees at the end of tunnels, and less frequent visits to flowers toward the middle of tunnels. The center of tunnels experienced higher temperatures and reduced wind speed. In raspberry, fruit shape was improved with greater pollinator abundance and was susceptible to higher temperatures. In blueberry, per plant yield and mean berry weight were positively associated with pollinator abundance and were lower at the center of tunnels than at the edge. Fruit quality (crumbliness) in raspberries was improved with a greater number of visits by sweat bees, who were not as susceptible to climatic conditions within tunnels. Understanding bee foraging behavior and changes to yield under protected cropping conditions is critical to inform the appropriate design of polytunnels, aid pollinator management within them, and increase economic gains in commercial berry crops

[In Press] Fire, drought and flooding rains : the effect of climatic extremes on bird species' responses to time since fire

Aim: Climatic extremes and fire affect ecosystems across the globe, yet our understanding of how species are influenced by the interaction of these broadscale ecological drivers is poorly understood. Using a ten-year dataset, we tested how extreme drought and rainfall interacted with time since fire (TSF) to shape bird species’ distributions. Location: Semi-arid mallee woodlands of south-eastern Australia. Methods: We quantified the effects of climatic extremes on bird species’ occurrence, species richness and incidence at 180 sites across three climatic periods—an El Niñoassociated drought (the “Big Dry”), immediately after La Niña drought-breaking rainfall (“Big Wet”) and three years following the La Niña event (“Post-Big Wet”). We then compared species’ responses with TSF across the three climatic periods using a chronosequence of sites from 1 to 117 years post-fire. Results: La Niña rainfall had sustained impacts on species’ occurrence. Over half of species increased significantly during the Big Wet. Despite three intervening years of below-average rainfall, three quarters of these species remained comparably high, Post-Big Wet. By contrast, less than half of threatened and declining species benefited from high rainfall. Responses of species to TSF were found to differ contingent on climatic conditions: almost twice as many species responded to TSF during the Big Wet and almost three times as many Post-Big Wet, compared with the Big Dry. Across climatic periods, a majority of species showed preference for mid to older post-fire vegetation. Main conclusions: Variation in responses to TSF is likely due to the effect of climatic variation on resources. We suggest that, at sites of different post-fire age, interactions between TSF and climate may differentially influence both the availability and longevity of resources. Given climatic extremes are predicted to become increasingly severe with climate change, accounting for their influence on fauna–fire dynamics will require careful management of fire

Riparian tree cover enhances the resistance and stability of woodland bird communities during an extreme climatic event

1. Ecosystems world-wide increasingly are subject to multiple interacting disturbances. Biodiversity in anthropogenic landscapes can be enhanced by manipulating landscape patterns, but could such landscape management also assist biota to cope with the effects of extreme climatic events, such as drought? 2. We surveyed woodland bird communities in 24 ‘whole’ landscapes (each 100 km2) in an agricultural region of south-eastern Australia near the beginning (2002–2003), middle (2006– 2007) and after (2011–2012) an extreme drought (the ‘Millennium Drought’). We quantified the resistance, resilience and stability of the avifauna to the decade of drought and related these measures to properties of the study landscapes: the extent of wooded habitat, configuration of habitat, land-use composition, landscape productivity and geographic context. 3. Landscape productivity, represented by the extent of riparian tree cover in the landscape, was the strongest driver of the resistance, resilience and stability of avifaunal richness to severe drought. Woodland bird communities in landscapes with larger areas of riparian tree cover retained a larger proportion of their species richness during the Millennium Drought and consequently had greater stability over the drought’s duration. 4. Synthesis and applications. Landscape properties can influence the resistance, resilience and stability of faunal communities to an extreme climatic event. By protecting, restoring and enhancing native vegetation in productive areas of landscapes along stream systems, drainage lines and floodplains, land managers can effectively build climatic refugia and thereby enhance the resistance of biota to climatic extremes. However, a net decline over the entire study period suggests this will not, by itself, arrest decline during periods of extreme drought

Scientific note on small hive beetle infestation of stingless bee (Tetragonula carbonaria) colony following a heat wave

We present the first study of infestation by the small hive beetle, Aethina tumida , in a queenright colony of the stingless bee Tetragonula carbonaria , a species used for pollination services. Nine managed hives were deployed outside the bee’s endemic range. After 2 months, including a heat wave of four consecutive days above 40 °C, one colony was visibly weakened with fewer foragers. This hive was removed from the site for the colony to recover. After a second heat wave, another colony was found weakened and infested with small hive beetle (SHB). Inside the hive, 14 adults and 133 larvae of SHB were discovered. Extreme daily maximum temperatures and low humidity appear to have weakened this colony. Our study highlights the need for careful placement of managed hives, as the SHB has potential to be a significant pest of stingless bees under adverse conditions

Cucurbit crops in temperate Australia are visited more by native solitary bees than by stingless bees

The propagation and management of stingless bees for pollination services is a growing industry in Australia, but we need to better understand in which crops and environments these pollinators are most useful. We investigated the potential of two Australian stingless bee species, Tetragonula carbonaria and Tetragonula hockingsi, to pollinate cucumber and watermelon crops in both field and protected cropping (greenhouse or polytunnel) environments. We recorded floral visitation rates and fruit yield in cucumber and watermelon and characterized the assemblage of wild pollinators visiting both field-grown crops. Of 229 surveys of cucumber flowers and 144 surveys of watermelon flowers in field experiments where T. carbonaria colonies were deployed, no stingless bees were recorded visiting cucumber flowers, and only one was recorded visiting watermelon flowers. Visitor assemblages in both crops were dominated by the introduced Apis mellifera, with a high number of native solitary halictid bees also visiting watermelon flowers. In a no-choice experiment, stingless bee (T. carbonaria and T. hockingsi) visits to watermelon flowers in a polytunnel occurred after four days but were low in number at first, compared to a greenhouse experiment where visits to cucumber flowers occurred only after 22 days and resulted in poor fruit set. In fact, T. hockingsi more readily collected fungal spores than pollen from cucumbers. Our results indicate that T. carbonaria and T. hockingsi do not make major contributions to the pollination of cucumber and watermelon, but other native flower visitors, including halictid bees, may be important pollinators of these crops