Pollination service delivery is complex: Urban garden crop yields are best explained by local canopy cover and garden scale plant species richness

Abstract

1. Pollination is an important ecosystem service to agriculture, however, the factors influencing pollination in urban food gardens are poorly understood.2. We investigated how features within urban environments, including floral resources and canopy cover, impacted (a) flower visitation and seed production of a model plant (Brassica rapa) and (b) total yields of produce from urban gardens in Sydney, Australia. Floral visitation to model plants was dominated by a few common species, withhoneybees responsible for 53.4% of visitation and native stingless bees and two hoverfly species accounting for another 37.1% of visitors; 28 other species were collectively responsible for less than 10% of visitation. 4. While insect pollinators were abundant, the relationship between floral visitation and model plant reproductive output was weak and not always positive.The pollination success of model plants was only marginally impacted by environmental features, while pollinator visitation had a small negative impact. However, total crop yields across urban gardens were strongly influenced by local canopy cover and garden scale plant species richness. Synthesis and applications.The factors influencing pollination service delivery to urban gardens are complex; pollinator visitation, richness and/or floral resource availability may not always reflect positive, plant reproductive outcomes. Yields of garden crops, whether pollinator dependent or not, were more strongly influenced by surrounding environmental variables, including broad scale measures of canopy cover and local plant diversity, than pollination-related metrics. This implies policies to support pollinator richness will likely differ to those supporting crop yields in urban gardens and will require assessment and management of

Artificial flowers as a tool for investigating multimodal flower choice in wild insects

“…It is possible that our artificial flower design is biased towards attracting some taxa over others. While honeybees made up the majority of flower visitors in our study, we note that multiple studies have found honeybees to be the most abundant flower visitors in the Sydney area (Y. Hanusch & T. Latty, unpublihsed data; McDougall et al., 2022; Tasker et al., 2020), and in Australia more generally (e.g. Nacko et al., 2022; Prendergast & Ollerton, 2021; Tierney et al., 2023; Yates et al., 2005).…”

“…Nacko et al., 2022; Prendergast & Ollerton, 2021; Tierney et al., 2023; Yates et al., 2005). For example, previous studies in the Sydney region have found that honeybees make up 44% of flower visitors in community gardens (Tasker et al., 2020), 53% of visitors in urban gardens (McDougall et al., 2022) and 85% of visitors in market gardens (Hanusch et al., in preparation). We suggest that the high visitation rates of honeybees to our artificial flowers reflects their high abundance in the environment, although we cannot entirely rule out the possibility that our artificial flowers were particularly attractive to honeybees.…”

“…Prendergast & Ollerton, 2021;Tierney et al, 2023;Yates et al, 2005). For example, previous studies in the Sydney region have found that honeybees make up 44% of flower visitors in community gardens(Tasker et al, 2020), 53% of visitors in urban gardens(McDougall et al, 2022) and 85% of visitors in market gardens(Hanusch et al, in preparation). We suggest that the high…”

Promoting Beneficial Arthropods in Urban Agroecosystems: Focus on Flowers, Maybe Not Native Plants

“…Within urban gardens, ecosystem services, such as pollination and pest control, may be provided by both native and non-native species. While native bee abundance and richness may be important for pollination in urban gardens [79,115,116], honeybees (Apis mellifera) are still the most abundant bees in our study sites, account for large numbers of floral visits in gardens [117] and likely provide pollination services to crop and non-crop plants therein. Moreover, Argentine ants are by far the most efficient predators of some species of sentinel prey within gardens [118], and non-native ladybeetles can still provide effective pest control in agroecosystems including in gardens [119].…”

Insect-Mediated Pollination of Strawberries in an Urban Environment

“…Urban food production, from allotments or private gardens, provides local and sustainable fruits and vegetables for the increasing human urban population, which represents over half of the world population [33]. A few recent studies have demonstrated the importance of taxonomically diverse pollinator communities, supported by florally diverse and dense gardens, for the urban production of various crops [34][35][36]. Indeed, pollinator species complement each other [5], and they can have synergistic effects on crop production, meaning that the service provided by the multi-species community is greater than the addition of the individual contributions of each species [6,37,38].…”