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

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.