How do plants set the table for birds? Frugivorous birds as natural selection agents on fruit display traits

PALACIO, FACUNDO X.; ORDANO, MARIANO

Congreso; Joint Meeting of the Wilson Ornithological Society and the Association of Field Ornithologists; 2019

Since Darwin, a major challenge in evolutionary ecology has been to understand how mutualistic interactions between plants and animals drive the evolution of plant phenotype. The biological market between frugivorous birds and fleshy-fruited plants is no exception, and whether birds exert natural selection on phenotypic fruit traits has been long subject to debate. We assessed the role of birds as natural selection agents on fruit display traits in three plant populations from Argentina: Psychotria carthagenensis (n = 72 plants), Vassobia breviflora (n = 104 plants), and Celtis ehrenbergiana (n = 100 plants). We measured fruit and seed traits (mean and subindividual variation) and applied multivariate analyses of natural selection using the number of bird visits per hour as measure of relative fitness. We detected a positive directional selection on mean fruit diameter in P. carthagenensis, and a positive directional selection on fruit crop size and stabilizing selection on CV fruit diameter in V. breviflora. We also detected correlational selection on fruit trait combinations in C. ehrenbergiana (large crops with small fruits, and large fruits with low fruit size variation had higher plant fitness). Our results show that that birds act as natural selection agents on fruit display traits in nature. Overall, bird-mediated selection on fruit display traits may be more common than previously thought and, in the long term, might potentially drive microevolutionary changes on plant phenotype.