This study aimed at evaluating seed production and predispersal hazards in a sand dune population of P. polyanthus (Eriocaulaceae) in Southern Brazil. Bad development of flowering capitula was caused by the wind and by interference among umbels. A positive correlation between the proportion of atrophied capitula and the number of capitula/umbels also suggested resource limitation. A caterpillar of a Recurvaria Haworth (Lepidoptera: Gelechiidae) species that eats flowers and a boring caterpillar (Lepidoptera not identified) were the main herbivores. Plants reproducing during the flowering peak had a lower probability of being damaged by Recurvaria sp., suggesting an escape from herbivores by flowering synchronism. The proportion of capitula damaged by herbivores was low, causing a reduction of about 5% in the seed set/plant. The boring caterpillar may or may not cause umbel abortion. When the abortion occurs, seed production is reduced by 12%. Many capitula with no damage and individual flowers (up to 50%) did not produce seeds. Pollination failure could be related to this low rate of seed set. We discuss the fact that the low recruitment of seedlings reported for populations of P. polyanthus did not seem to be limited by seed rain, which was estimated at an average of 8000 seeds/plant even when herbivore damage occurred.
Paepalanthus polyanthus; herbivory; seed production; predispersal hazards; sand dune slack
