Unrivalled specialization in a pollination network from South Africa reveals that specialization increases with latitude only in the Southern Hemisphere

Abstract

AbstractAimWe aimed to produce the first complete pollination network for Africa to test (1) whether South African plants are unusually specialized in their interactions with pollinators, and (2) whether the South African data conform with global patterns of specialization.LocationCederberg, Cape Floristic Region, South Africa (32°04′31.52″ S, 19°04′ 48.42″ E; elevation 320 m).MethodsWe sampled all plant–pollinator interactions within a 1‐ha plot to assemble a network of 62 plant species linked to 217 pollinators species by 10,314 visits. We calculated the standardized Kullback–Leibler distance (d′) as an estimate of plant and animal specialization, and standardized two‐dimensional Shannon entropy (ΔH2′) as an estimate of network‐wide specialization. We compared these metrics with those calculated for 58 other networks from across the world.ResultsIn a global context, the South African plant species had an unusually high number of interaction partners (mean = 6.32) while the animal species had unusually few (mean = 1.81). Animal diversity was high relative to plant diversity (network asymmetry = 0.56). Nevertheless, the South African plants, pollinators and network overall were more specialized than any previously studied community (weighted mean d′ plants = 0.824 and animals = 0.807, community ΔH2′ = 0.834), suggesting functional specialization. Overall, specialization was found to increase sharply with latitude in the Southern Hemisphere, whereas no relationship was found in the Northern Hemisphere.Main conclusionsThe findings that South African plants have a high diversity of pollinators and that specialization of pollination networks increases with latitude in the Southern Hemisphere only are in contradiction to expectations derived from earlier literature. Long‐term climatic stability in the Southern Hemisphere might have allowed phenotypic and functional specialization to manifest and persist.