ABSTRACT Plant-pollinator interactions and their reproductive implications are of central importance to the organization of plant populations and communities in restoration areas. We studied the breeding system and flower visitors of Pleroma trichopodum, a pioneer species of the Atlantic Forest. We attempted to answer three questions: (1) Is P. trichopodum dependent on pollinators and mates for reproduction? (2) What are the pollinators of P. trichopodum? (3) Do tree flower-density and flowering-tree density of P. trichopodum enhance the visitation rate of focal trees and their flowers? We tested the breeding system through pollination treatments. We performed focal observations on 10 trees and analyzed the relationship between tree and flower visitation rates, and the tree flower-density and flowering-tree density with Generalized Linear Mixed Models (GLMM). Pleroma trichopodum sets fruits by selfing and outcrossing, both of which occur only through pollinator visits. Bees visited P. trichopodum, and their visitation increased with tree flower-density. Thus, individuals with greater floral displays may function as magnet species, enhancing the pollination of nearby plant species. This characteristic, allied with the ability to reproduce without a mate (selfing) and a tolerance of soggy soils, make P. trichopodum a candidate for Atlantic Forest restoration.

The abundance and distribution of resources for pollinators modulate the reproduction of plants. This study attempted to determine whether and how the fruiting success of Tibouchina trichopoda flowers varies due to plant size, number of flowers produced, distance between individuals and cardinal orientation of the flowers. From July 2009 to February 2010, we conducted monthly evaluations of 21 plants in an area of regenerating forest within the Atlantic Forest biome, located near the municipality of Antonina, in southern Brazil. Floral density was monitored weekly. During the study period, the species bloomed twice: once during the cool, dry season, showing an extended flowering period with scattered flowering individuals; and once during the hot, rainy season, showing a brief flowering period with a high density of flowering individuals. Plant size was not found to influence fruiting success. There was greater production of flowers and fruits during the brief flowering period. The extent of the floral display positively affected the fruiting success of the flowers, the effect being greater when the density of flowers was low and tending to stabilize at higher densities. The northern-facing portions of tree crowns produced more flowers and therefore had greater fruiting success than did the southern-facing portions. However, the proportion of fruits produced per flower was the same.