Flowering phenologies of hummingbird plants from the temperate forest of southern South America: is there evidence of competitive displacement?-

AIZEN, M.A. Y D.P. VÁZQUEZ

ECOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2006 vol. 29 p. 357 - 366

0906-7590

Plant species sharing pollinators may compete through pollination. This type ofcompetition may lead to overdispersed flowering phenologies. However, phenologicalsegregation is difficult to detect in seasonal climates. We compared patterns ofphenological overlap in assemblages of ornithophilous plants from three localities ofthe temperate forest of southern South America with those generated by four differentnull models. These species were all visited and presumably pollinated by a single species,the hummingbird Sephanoides sephaniodes, which makes this situation ideal to evaluatethe role of pollination-mediated competition. For one site, we compiled data onflowering phenologies for three different years. Three models considered the floweringperiod of the whole assemblage of ornithophilous plants as the phenological windowwithin which flowering phenologies were randomized, but made no furtherassumptions on how species should be distributed within that temporal frame. Thefourth model assigned differential probabilities to different time intervals based on theflowering onset of non-ornithophilous plant species. Observed mean pairwise overlapsfor all localities and years were well within the interval defined by the 2.5 and 97.5%percentiles of the randomized distribution of expected mean pairwise overlapsaccording to models 13. However, model 4 showed a consistent trend towardsoverdispersion of ornihophilous phenologies, which show a shift towards mid- to latesummerflowering. Thus, to the extent that the distribution of flowering of nonornithophilousspecies reflects the constraints imposed by a highly seasonal climate,our results provide support to the proposal that pollinator sharing may causeevolutionary displacement or ecological sorting of flowering phenologies. Otherfactors, such as phylogenetic inertia, could also contribute to explain extantphenological patterns in the highly endemic ornithophilous flora of the temperateforest of southern South America.