Year-round temporal stability of a tropical, urban plant-pollinator network

Abstract

Plant-pollinator interactions are known to vary across time, both in terms of species composition and the associations between partner species. However, less is known about tropical pollination networks, and tropical urban parks provide a unique opportunity to study network stability in an environment where temperature and floral resources are relatively constant due to both the tropical climate as well as park horticulture. The objectives of this study were thus to examine the interactions between flowering plants and their potential pollinators in a large, tropical city (Bangkok, Thailand) across 12 consecutive months, and to assess the stability of network properties over time. We conducted monthly pollinator observations at 9 parks spaced throughout the city, and collected data on temperature, precipitation, floral abundance and floral species richness. We found that neither pollinator abundance nor richness varied significantly across months when all parks were pooled. However, pollinator abundance was significantly influenced by floral abundance, floral richness, and their interaction, and pollinator richness was significantly influenced by floral richness and precipitation. Finally, we found that network properties did not change across months, even as species composition did. We conclude that the year-round constancy of floral resources and climate conditions appear to create a network in dynamic equilibrium, where plant and pollinator species compositions change, but network properties remain stable. The results of this study provide useful information about how tropical pollinators respond to urban environments, which is particularly relevant given that most urban development is predicted to occur in the tropics.

A global review of urban pollinators and implications for maintaining pollination services in tropical cities

“…High floral abundance and diversity are the most important variables related to the maintenance of bees from different groups, offsetting the negative effects commonly associated with urbanization (Frankie et al 2013;Hülsmann et al 2015;Ayers and Rehan 2021). Such positive effects of floral resource availability have been described for cities in tropical countries such as Thailand (Tangtorwongsakul et al 2018;Stewart and Waitayachart 2020) and Costa Rica (Wojcik and McBride 2012), and is consistent with studies carried out in non-tropical regions (e.g., Ahrné et al 2009;Matteson and Langellotto 2010;Bates et al 2011;Hennig and Ghazoul 2011;Pardee and Philpott 2014;Hülsmann et al 2015).…”

“…Some recent studies on tropical urban environments, nevertheless, reinforce the importance of bees as pollinators. In Bangkok, Thailand, bees represent the majority of pollinator species found across urban green areas (Stewart et al 2018;Stewart and Waitayachart 2020), with stingless bees comprising 64.32 % of the pollinators recorded (Stewart et al 2018). Such a high proportion of stingless bees was also found in the city of Belo Horizonte, Brazil (Zanette et al 2005).…”

“…This review also reveals that the effects of urbanization on tropical pollinators are diverse, and they likely depend on the extent and type of urbanization, as well as the pollinator taxa studied. We have the most data on bees, and studies have revealed surprisingly high bee diversity and abundance in urban areas, which most studies (both non-tropical and tropical) attribute to the abundance of floral resources found in cities (Ahrné et al 2009;Matteson and Langellotto 2010;Bates et al 2011;Hennig and Ghazoul 2011;Wojcik and McBride 2012;Pardee and Philpott 2014;Hülsmann et al 2015;Stewart et al 2018;Tangtorwongsakul et al 2018;Stewart and Waitayachart 2020). However, it also appears that most of the bee diversity in cities is due to generalist bee species that have flexible diets and nesting habits, which stresses the importance of maintaining natural habitats for rare and specialist species.…”

Individual‐resource network between Xylocopa bees and plant resources: generalist species, specialist individuals?

“…For X. frontalis, modularity occurred regardless of the season and the low similarity between seasons indicates a temporal resource turnover. Although we did not evaluate resource availability over time, the stability of the network over the months was recorded before in a tropical plant-pollinator community, which was related to the floral constancy and climate conditions (Stewart & Waitayachart, 2020). Then, our results suggest that in an individual network, this stability could also occur.…”

Pollination in Agroecosystems: A Review of the Conceptual Framework with a View to Sound Monitoring

“…Records usually focus on the behavior of insects crossing plot borders. They include checking whether the visit promotes outcrossing, and recording the resource gathered (pollen and/or nectar) and the number of flowers visited in the patch [96,97]. It is customary to assign pollinators to functional groups, and to collect specimens for further identification in the laboratory.…”