Pollinators, pests, and predators: Recognizing ecological trade-offs in agroecosystems
Ecological interactions between crops and wild animals frequently result in increases or declines in crop yield. Yet, positive and negative interactions have mostly been treated independently, owing partly to disciplinary silos in ecological and agricultural sciences. We advocate a new integrated research paradigm that explicitly recognizes cost-benefit trade-offs among animal activities and acknowledges that these activities occur within social-ecological contexts. Support for this paradigm is presented in an evidence-based conceptual model structured around five evidence statements highlighting emerging trends applicable to sustainable agriculture. The full range of benefits and costs associated with animal activities in agroecosystems cannot be quantified by focusing on single species groups, crops, or systems. Management of productive agroecosystems should sustain cycles of ecological interactions between crops and wild animals, not isolate these cycles from the system. Advancing this paradigm will therefore require integrated studies that determine net returns of animal activity in agroecosystems.
Interactions between almond plantations and native ecosystems: Lessons learned from north-western Victoria
Five years of research on interrelationships between fauna use of almond plantations and native vegetation in north-western Victoria shows that almond plantations have a strong influence on fauna dynamics and in some cases may provide important habitat for threatened species.
Pan trap catches of pollinator insects vary with habitat
Coloured pan trapping is a simple and efficient method for collecting flying insects, yet there is still discussion over the most effective bowl colour to use for particular target groups (e.g. pollinator insects). The success of particular colours can vary across bioregions and habitats. Most published pan trap studies have been conducted in the northern hemisphere, and very few investigated the effects of habitat on pan trap catches. Our study is one of the first to (1) sample for potential pollinators in Australian mallee vegetation and almond orchards and (2) investigate whether habitat interacts with trap colour to influence pan trap catches. We sampled Hymenoptera and Diptera using yellow, white and blue pan traps in native mallee vegetation and two types of managed almond orchards (monoculture and plant-diverse) in the Murray Mallee bioregion of north-western Victoria, Australia. Yellow traps caught the most insects across all habitats, although catches in each colour trap varied with habitat. For all insect groups combined, blue traps caught more individuals in mallee habitats than in almond orchards. For native hymenopterans, yellow traps caught more individuals in plant-diverse orchards than in native sites, while blue traps caught more individuals in native sites. Our results highlight the importance of considering the habitat of individual pan trapping surveys, as no one trap colour is likely to be suitable for trapping target insects across all habitats.
A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes
Agricultural intensification is a leading cause of global biodiversity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant diversification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect biodiversity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant diversification on abundance, local diversity (communities within fields), and regional diversity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in-field plant diversity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in-field plant diversification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant diversification promote diverse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving diverse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes.
Bees visiting unopened flowers: bumbling burglars or sneaky pollinators?
Most studies of angiosperm pollination have been conducted on fully opened flowers, while interactions between animal pollinators and unopened flowers are less well-known. In December 2015, I observed aggregations of small-bodied hylaeine bees swarming between inflexed stamens of unopened blossoms of pink and red flowering gums ('Corymbia' spp.) planted as municipal street trees in southern New South Wales, Australia (Albury: 36.0737° S, 146.9135° E) (Fig. 1a). The bees appeared to be predominantly 'Hylaeus (Prosopisteron) perhumilis' Cockerell 1914 (expert identification provided via high resolution photographs), but there were also occasionally other small bees from the Halictidae and Colletidae families. All bee visitors appeared to be feeding on pollen-laden anthers. I saw this behavior on more than 15 individual flowers across five trees at various stages of opening between the initial split of the operculum and full extension of stamens. Individual bees were constantly arriving and departing, but a single bud had between 3-7 individuals visiting at any one time. 'Corymbia ficifolia' is native to southwestern Australia, but the species and its hybrids are popular as street trees in urban areas around the country. There is little published empirical work on animal pollination in 'Corymbia' spp., but its pollinators are traditionally assumed to be birds or large-bodied insects (Phillips et al. 2010).
Interaction effects between local flower richness and distance to natural woodland on pest and beneficial insects in apple orchards
1 Local and landscape factors interact to influence animal populations and, ultimately, crop yields in agroecosystems. Yet few studies have considered interactions and trade-offs between these factors within a single agroecosystem. 2 We sampled insect communities (fruit-damaging pests and Diptera and Hymenoptera pollinator and natural enemy taxa) associated with focal apple trees in south-eastern Australian orchards across a single growing season.We also measured marketable fruit yields on netted (preventing access to vertebrates) and open branches on each focal tree. We focused on relationships with local (ground cover attributes) and landscape (proximity to natural woodland) factors. 3 Importantly, we found that local flower richness in orchard understoreys may buffer the negative effects that isolation from natural woodland has on wild bee and natural enemy communities and the ecosystem services they provide. 4 The results of the present study suggest that floral diversity may be more effective in supporting beneficial insects in crop interiors, rather than at edges near natural vegetation. 5 More studies are needed that identify how local and landscape vegetation structure interact to influence communities of pest and beneficial taxa, and relevant ecosystem functions, in agroecosystems.
Insect pollinators collect pollen from wind-pollinated plants: implications for pollination ecology and sustainable agriculture
Current research, management and outreach programmes relevant to insect pollinator conservation are strongly focused on relationships between pollinators and insect-pollinated crops and wild plants. Pollinators also visit wind-pollinated plants to collect pollen, or for nest sites and materials, but these interactions are largely overlooked. I review documented records of bee and syrphid fly species collecting pollen from wind-pollinated plant taxa, including economically important crops, and provide the most comprehensive collation of peer-reviewed records of pollinators visiting wind-pollinated plants to date. I argue for more basic research into functional relationships between insect pollinators and wind-pollinated plants. I found over 200 visitation records for 101 wind-pollinated plant genera in 25 families, including 4 of the 12 gymnosperm families. Almost half the records (49%) were for grasses and sedges (Poales). I also identified records of bees and/or syrphid flies visiting 10 economically important wind-pollinated crop plant species, including three major grain crops (rice, corn, and sorghum). Most records (70%) were from indirect pollen analysis from hives, nest cells or insect bodies, highlighting the need for more direct observational studies of plant-pollinator interactions. Insect pollinator communities require resource diversity to persist in a landscape. Hence, researchers and land managers aiming to identify links between pollinators and ecosystem function should also consider broader interactions beyond the standard traits of the entomophily syndrome.