Pollination and selection on an introduced island plant

Raw data (floral trait measurements, pollinator measurements, pollinator visits

Data from: A hurricane alters pollinator relationships and natural selection on an introduced island plant

Novel relationships between the floral morphology of introduced plants and the trophic morphology of native pollinators have been hypothesized to cause strong natural selection on both parties, but evidence for such selection is rare. We capitalized on a natural disturbance to examine selection on an introduced plant, Heliconia wagneriana, on the island of Dominica, before and after Hurricane Maria. Prior to the hurricane, female Anthracothorax jugularis hummingbirds, which have longer bills than males, were the main visitor to H. wagneriana, and directional selection on corolla length was insignificant. After the hurricane, shorter-billed male A. jugularis were the main visitor to H. wagneriana. The absence of trait-matching between a short-billed pollinator and a long-flowered plant resulted in directional selection for shorter flowers because males preferentially visited plants with shorter flowers. The amount of nectar removed by male A. jugularis was negatively associated with flower length, with flowers > 53 mm containing nearly five times the nectar than flowers < 53 mm. We estimate a roughly 75% decrease in the population size of A. jugularis, and results suggest the heaviest mortality occurred among short-billed male hummingbirds and larger-bodied individuals of both sexes, which would have higher nectar requirements and the most difficulty obtaining nectar. Our results indicate that hurricanes may alter relationships between plants and pollinators, and that lack of trait-matching resulting from such disturbances may lead to selection on both plant and pollinator

Temeles et al Heliconia Bihai Population Data

Temeles et al Heliconia bihai floral trait and seed set dat

Mate choice and mate competition by a tropical hummingbird at a floral resource

The influence of male territorial and foraging behaviours on female choice has received little attention in studies of resource-defence mating systems even though such male behaviours are thought to affect variation in their territory quality and mating success. Here we show that female purple-throated carib hummingbirds Eulampis jugularis preferred to mate with males that had high standing crops of nectar on their flower territories. A male's ability to maintain high nectar standing crops on his territory not only depended on the number of flowers in his territory, but also on his ability to enhance his territory through the prevention of nectar losses to intruders. We observed that males defended nectar supplies that were two to five times greater than their daily energy needs and consistently partitioned their territories in order to provide some resources to attract intruding females as potential mates. Such territorial behaviour resulted in males defending some flowers for their own food and other flowers as food for intruding females. Collectively, our results suggest that variation in mating success among males is driven primarily by variation in territory quality, which ultimately depends on a male's fighting ability and size

Pollinator Competition as a Driver of Floral Divergence: An Experimental Test.

Optimal foraging models of floral divergence predict that competition between two different types of pollinators will result in partitioning, increased assortative mating, and divergence of two floral phenotypes. We tested these predictions in a tropical plant-pollinator system using sexes of purple-throated carib hummingbirds (Anthracothorax jugularis) as the pollinators, red and yellow inflorescence morphs of Heliconia caribaea as the plants, and fluorescent dyes as pollen analogs in an enclosed outdoor garden. When foraging alone, males exhibited a significant preference for the yellow morph of H. caribaea, whereas females exhibited no preference. In competition, males maintained their preference for the yellow morph and through aggression caused females to over-visit the red morph, resulting in resource partitioning. Competition significantly increased within-morph dye transfer (assortative mating) relative to non-competitive environments. Competition and partitioning of color morphs by sexes of purple-throated caribs also resulted in selection for floral divergence as measured by dye deposition on stigmas. Red and yellow morphs did not differ significantly in dye deposition in the competition trials, but differences in dye deposition and preferences for morphs when sexes of purple-throated caribs foraged alone implied fixation of one or the other color morph in the absence of competition. Competition also resulted in selection for divergence in corolla length, with the red morph experiencing directional selection for longer corollas and the yellow morph experiencing stabilizing selection on corolla length. Our results thus support predictions of foraging models of floral divergence and indicate that pollinator competition is a viable mechanism for divergence in floral traits of plants