Pollinator interactions of native and introduced plants in smallholder tropical orchards across a gradient of anthropogenic landscapes

Abstract

Anthropogenic habitats commonly favor introduced species. However, there is little information regarding the responses of pollinators to native and introduced plants across anthropogenic landscapes. The main goal of the study is to investigate pollinator interactions of native and introduced plants across smallholder tropical orchards in Thailand, as these plantations are essential to local food security. We compiled data from four recent studies on plant-pollinator networks in 65 smallholder tropical orchards across Thailand. Using network analyses, we compared species degree (i.e., the number of pollinator species visiting a plant) and specialization (d′) between native and introduced plant species, with the latter further categorized into non-naturalized, naturalized, and invasive groups. Analyses were conducted using linear mixed-effects models, treating individual plant species as the unit of analysis and incorporating orchard identity nested within study as a random effect. Additionally, we examined whether variation in surrounding anthropogenic landscapes (i.e., the proportion of agricultural and urbanized areas) and the proportional representation of introduced plant species influenced the structure of plant–pollinator networks. Overall, specialization (d′) of the native plants was significantly greater than that of the introduced plants, while pollinators exhibited no preference towards naturalized or invasive plants over non-naturalized ones. We found a decrease in species degree of native plants as well as connectance and linkage density with increasing proportion of anthropogenic areas, likely due to limited floral resources and nesting availability. However, we also found an increase in network specialization (H2′) with a higher proportion of urban area. Understanding the impact of land-use changes with the presence of introduced plant species is important for predicting community stability of plant-pollinator interactions as well as for habitat management strategies. Surrounding natural habitats and important food plants should be preserved and promoted to maintain pollinator interactions in human-dominated areas.