Browsing by Author "Potts, Simon G."
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Item Enhancing legume crop pollination and natural pest regulation for improved food security in changing African landscapes(Elsevier, 2020-09) Otieno, Mark; Dewentera, Ingolf S.; Potts, Simon G.; Kinuthia, Wanja; Kasina, Muo J.; Garrattb, Michael P.D.Legumes are important crops for food security, consumed by millions of people especially in Africa where they are an essential protein source and provide key vitamins and minerals. Most legumes depend on insect pollination and natural pest regulation for sufficient yields, however, there is emerging evidence that yield gaps caused by lack of pollination and/or pest pressure may be common. Here we review the literature reporting on pollinators and natural enemies contributing to legume crop yields, and the impact of land-use change on the services provided by these beneficial organisms. We identify strategies for enhancing the benefits of pollination and natural pest control in legumes and propose policy and practice interventions for better utilization of pollinators and natural enemies in legume cropping systems in Africa.Item A global quantitative synthesis of local and landscape effects on wild bee pollinators in agroecosystems(Blackwell Publishing Ltd, 2013) Kennedy, Christina M.; Lonsdorf, Erick; Neel, Maile C.; Williams, Neal M.; Ricketts, Taylor H.; Winfree, Rachael; Bommarco, Riccardo; Brittain, Claire; Burley, Alana L.; Cariveau, Daniel; Carvalheiro; Chacoff, Natacha P.; Cunningham, Saul A.; Danforth, Bryan N.; Dudenhoffer, Jan-Hendrick; Elle, Elizabeth; Gaines, Hanna R.; Garibaldi, Lucas A.; Gratton, Claudio; Holzschuh, Andrea; Isaacs, Rufus; Javorek, Steven K.; Jha, Shalene; Klein, Alexandra M.; Krewenka, Kristin; Mandelik, Yael; Mayfield, Margaret M.; Morandin, Lora; Neame, Lisa A.; Otieno, Mark; Park, Mia; Potts, Simon G.; Rundlof, Maj; Saez, Agustin; Steffan-Dewenter, Ingolf; Taki, Hisatomo; Viana, Blandina F.; Westphal, Catrin; Wilson, Julianna K.; Greenleaf, Sara S.; Kremen, Claire; Carvalheiro, Luisa G.Bees provide essential pollination services that are potentially affected both by local farm management and the surrounding landscape. To better understand these different factors, we modelled the relative effects of landscape composition (nesting and floral resources within foraging distances), landscape configuration (patch shape, interpatch connectivity and habitat aggregation) and farm management (organic vs. conventional and local-scale field diversity), and their interactions, on wild bee abundance and richness for 39 crop systems globally. Bee abundance and richness were higher in diversified and organic fields and in landscapes comprising more high-quality habitats; bee richness on conventional fields with low diversity benefited most from high-quality surrounding land cover. Landscape configuration effects were weak. Bee responses varied slightly by biome. Our synthesis reveals that pollinator persistence will depend on both the maintenance of high-quality habitats around farms and on local management practices that may offset impacts of intensive monoculture agriculture.Item Local and landscape effects on bee functional guilds in pigeon pea crops in Kenya(Springer, 2015-07) Otieno, Mark; Sidhu, Sheena C.; Woodcock, Ben A.; Wilby, A.; Ioannis, N.; Mauchline, Alice L.; Gikungu, Mary W.; Potts, Simon G.Pollinators face many challenges within agricultural systems due to landscape changes and intensification which can affect resource availability that can impact pollination services. This paper examines pigeon pea pollination and considers how landscape context and agricultural intensification in terms of pesticide use affects the abundance of bees characterized by species guilds on crops. The study was conducted on six paired farms across a gradient of habitat complexity based on the distance of each farm from adjacent semi-natural vegetation in Kibwezi Sub-county, Kenya. The study found that farms which do not use insecticides in farm management, but are in close proximity to natural habitat have greater bee guild abundance, but at further distances, overall abundance is reduced with or without insecticide use. At 1 km landscape radius, the complexity of habitats but not patch size had a positive impact on the abundance of cavity nesting bees and mason bees, which can be attributed to the interspersion of the small-holder farms with semi-natural habitats across the landscapes producing mosaics of heterogeneous habitats. The study revealed the strongest relationships between fruit set and bee abundance to be with the carpenter bee, social bee and solitary bee guilds, which are among the most abundant bees visiting pigeon pea flowers in this system. Our findings provide the foundation for conservation efforts by identifying which bee guilds pollinated pigeon peas. From this study, we suggest managing the floral and nesting resources that would best support the most abundant crop pollinators, and also reducing insecticide application to the crop.Item Local management and landscape drivers of pollination and biological control services in a Kenyan agro-ecosystem(Elsevier, 2011) Otieno, Mark; Woodcock, Ben A.; Wilby, Andrew; Vogiatzakis, Ioannis N.; Mauchline, Alice L.; Gikungu, Mary W.; Potts, Simon G.Arthropods that have a direct impact on crop production (i.e. pests, natural enemies and pollinators) can be influenced by both local farm management and the context within which the fields occur in the wider landscape. However, the contributions and spatial scales at which these drivers operate and interact are not fully understood, particularly in the developing world. The impact of both local management and landscape context on insect pollinators and natural enemy communities and on their capacity to deliver related ecosystem services to an economically important tropical crop, pigeonpea was investigated. The study was conducted in nine paired farms across a gradient of increasing distance to semi-native vegetation in Kibwezi, Kenya. Results show that proximity of fields to semi-native habitats negatively affected pollinator and chewing insect abundance. Within fields, pesticide use was a key negative predictor of pollinator, pest and foliar active predator abundance. On the contrary, fertilizer application significantly enhanced pollinator and both chewing and sucking insect pest abundance. At a 1 km spatial scale of fields, there were significant negative effects of the number of semi-native habitat patches within fields dominated by mass flowering pigeonpea on pollinators abundance. For service provision, a significant decline in fruit set when insects were excluded from flowers was recorded. This study reveals the interconnections of pollinators, predators and pests with pigeonpea crop. For sustainable yields and to conserve high densities of both pollinators and predators of pests within pigeonpea landscapes, it is crucial to target the adoption of less disruptive farm management practices such as reducing pesticide and fertilizer inputs.Item The Utility of Aerial Pan-Trapping for Assessing Insect Pollinators Across Vertical Strata(2011) Nuttman, Clive; Otieno, Mark; Kwapong, Peter K.; Combey, Rofela; Willmer, Pat; Potts, Simon G.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.