Reproduction of beetle-pollinated Anaxagorea dolichocarpa (Annonaceae) is resilient to habitat disturbance in rainforest fragments

Authors


M. Braun, Inst. of Systematic Botany and Ecology, Univ. of Ulm, DE-89081 Ulm, Germany. E-mail: marc.usbraun@web.de

Abstract

Strong evidence exists that fragmentation negatively affects pollination and plant reproduction, but little research has been conducted with regards to tropical trees. Specifically, effects of forest fragmentation on reproduction of plants with beetle-pollinated flowers are poorly understood, and there are no data on the impact of fragmentation on reproduction in the structurally important tropical family Annonaceae. We examined the relationship between fragment size, pollinator abundance and seed set of beetle-pollinated Anaxagorea dolichocarpa (Annonaceae) in a disturbed Brazilian Atlantic rainforest. Flower and fruit production and abundance of pollinators were quantified over ten months in three large (306–388 ha) and three small (6–14 ha) forest fragments. We recorded per flower pollinator abundance, resulting fruit set (fruits per flower) and seed set (monocarps per fruit) for a total of 209 individually marked flowers, and compared pollinator abundance in 186 flowers across all fragments. Flower and fruit production differed among fragments, but were similar for the combined large and small fragments. Between 64.8% (large fragments) and 66.3% (small fragments) of flowers received at least one pollinator. We found no significant difference in pollinator numbers between large and small fragments, and no correlation between pollinator abundance and fruit and seed set. A single visitor had a high probability of pollinating a flower. We conclude that 1) fragment size had no influence on pollinator number and plant reproductive success, and 2) generalist behavior of the pollinating beetles mitigate the risk of pollination failure for the reproductively specialized plant. However, further research may yet reveal genetic impoverishment of populations in small fragments due to restricted pollinator movements.

Ancillary