Seed Dispersal of the Mistletoe Psittacanthus schiedeanus by Birds in Central Veracruz, Mexico1

Abstract

Mistletoes are hemiparasitic plants that frequently depend on frugivores for seed dispersal; yet their seed dispersal ecology is still poorly known. The mistletoe Psittacanthus schiedeanus (Loranthaceae) was studied for a five-month period in cloud forest remnants in central Veracruz, Mexico, to determine its seed dispersal ecology. We hypothesized that dispersal ecology of this mistletoe species is directly affected by the fruit-eating bird abundance, and asked if this species is following the high-investment strategy as suggested by Godschalk (1983). To evaluate this, we determined the morphological and nutritional characteristics of mistletoe fruit, the availability of ripe fruits along the mistletoe fruiting phenology, and the abundance of fruit-eating birds. Because P. schiedeanus is dispersed by generalist rather than specialist birds, we asked if this mistletoe species is ripening fruits during the fruit scarcity time (with highest possibilities of being consumed and dispersed by birds). We compared P. schiedeanus ripe fruit production to the cloud forest tree leaf fall and fruit production. Psittacanthus schiedeanus matures its nutritious fruits from November to April, with a peak of abundance in January and February. We found a synchrony between the abundance of P. schiedeanus ripe fruits and the abundance of Gray Silky-flycatchers (Ptilogonys cinereus) and Social Flycatchers (Myiozetetes similis); however, this was not the case with Cedar Waxwings (Bombycilla cedrorum), although these birds play an important role in the mistletoe dispersal. The fruiting pattern of P. schiedeanus, together with the fact that it is an important food resource for generalist rather than specialist frugivorous birds, suggest that this mistletoe is using the nutrient investment strategy to attract dispersers during a time of fruit scarcity.