Eating the fruit of passion: bird functional traits and geography explains fruit removal by frugivorous birds in Blue Passionflower (Passiflora caerulea)

PALACIO, FACUNDO X.; CATAUDELA, FRANCISCO; ORDANO, MARIANO; MONTALTI, DIEGO

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

Geographic variation in bird-fruit interactions represents a complex ecological scenario which determines a mosaic of selection pressures between interactors. This mosaic may partly the result from geographic variation in bird assemblages, in which birds are expected to fulfil different ecological functions with strong consequences for seed dispersal patterns. However, the drivers of fruit removal by birds at a geographical scale are not fully understood. We described geographic variation in fruit removal and functional diversity (FD) of frugivorous bird assemblages among Blue Passionflower (Passiflora caerulea) populations, a bird-dispersed vine. We observed bird fruit consumption and frugivorous bird abundance in nine plant populations from northern and central Argentina (spanning 10° of latitude, 0-1250 masl, three biogeographical provinces). We quantified FD of frugivorous bird assemblages on the basis of body mass, fruit-handling behavior (gulper, pulp consumer or seed predator), and degree of frugivory. We recorded 14 bird species consuming passionflower fruits and detected a non-linear trend of higher frugivorous bird FD towards lower latitudes. Also, the number of birds consuming fruits (visits) per plant was negatively related to latitude, the proportion of gulper species, the degree of frugivory, and mean body mass. The Blue Passionflower shows functionally diverse frugivorous bird assemblages throughout its distribution range, which seems mainly driven by biogeographical factors at the geographical scale. At the population level, seed dispersal is presumably enhanced by small-sized generalist pulp consumers, whereas large birds may compensate lower visitation rates by increased fruit consumption.