A Geographic Mosaic of Plant–Pollinator Interactions in the Eastern Caribbean Islands

Abstract

Abstract The interplay between generalized and specialized plant–animal interactions is a core concept in understanding the evolution of mutualisms. Within the E astern C aribbean, H eliconia bihai is a dominant forest species in the southern island of S t. V incent where H . caribaea is virtually absent. Heliconia caribaea is most common on the northern island of S t. K itts where H . bihai is restricted to the tops of the highest peaks. Both species are abundant on the central island of D ominica. We compared flowering patterns, nectar characteristics, and visitation frequency of hummingbirds in the two heliconias on the three islands to determine the extent of geographic variations in this plant–pollinator mutualism. The peak flowering season of the two heliconias was observed to be in A pril– M ay on all three islands with little within‐ and between‐island variations. Nectar production significantly varied between species and between islands. Visitation patterns by the principal hummingbird pollinators also varied between the islands: (1) on D ominica, only females of a single species of hummingbird pollinated the flowers of H . bihai (sexual specialization), whereas both sexes of the same hummingbird pollinated the flowers of H . caribaea (species specialization); (2) on S t. V incent, both sexes of the same hummingbird pollinated the flowers of H . bihai (species specialization); and (3) on S t. K itts, only females pollinated the flowers of H . bihai (sexual specialization), whereas several species of hummingbird visited the flowers of H . caribaea (species generalization). We propose that the H eliconia –hummingbird interactions in the E astern C aribbean represent a geographically variable coevolutionary mosaic of plant–pollinator interactions.