Reproductive conflicts ofPalicourea padifolia (Rubiaceae) a distylous shrub of a tropical cloud forest in Mexico

Abstract

We studied a population of the distylous Palicourea padifolia (Rubiaceae) in a cloud forest remnant near Xalapa City, Veracruz, M6xico to explore possible asymmetries between floral morphs in the attractiveness to pollinators, seed dispersers, nectar robbers, floral parasites, and herbivores, we first assessed heterostyly and reciprocal herkogamy by measuring floral attri- butes such as corolla length (buds and open flowers), style and anther heights, stigma and stamen lengths and the distance between the anther tip to the stigma lobe. We then estimated floral and fruit attributes such as flower size, anther height, number and size of pollen grains, fruit size, seed size, nectar production, and flower and fruit standing crops to assess differences between floral morphs in attracting and effectively using mutua- listic pollinators and seed dispersers. Also, floral parasitism and nectar robbing were assessed in this study as a measure of flower attractiveness to antagonists. The system seems to conform well to classical heterostyly (e.g. reciprocal stamen/style lengths, pollen and anther dimorphism, intramorph incompatibility) yet, there were several tantalizing differences observed between pin and thrum morphs. Thrum flowers have longer corollas and larger but fewer pollen grains than pin flowers. Both morphs produced the same total number of inflorescences, developed the same number of buds, and opened the same number of flowers per