Myrsine parvifolia (Primulaceae) in sandy coastal plains marginal to Atlantic rainforest: a case of pollination by wind or by both wind and insects?

Abstract

This study examined the pollination ecology of Myrsine parvifolia in an area of sandy coastal plain, namely restinga. Male and female plants were distributed in an aggregated form with sex ratio of 1.7♂:1♀. Flowers are open dish-shaped, greenish-white, odorless, and devoid of nectaries. The female flower has a well-exposed sessile stigma. The anthers of the male flower release pollen grains in a powdery cloud. The pollen grains are small, dry, prolate spheroidal, 3–5-colpate and have a scabrous exine. We concluded that M. parvifolia is wind pollinated by: the presence of pollen grains in the air; fruit production in inflorescences isolated from access by biotic pollinators, but not by wind; the female flowers were not visited by biotic agents. Our results reinforce the hypothesis that pollination by wind is the main pollination system in Myrsine. Pollen limitation has been recorded for M. parvifolia and also for other dioecious insect-pollinated species from restinga as Guapira opposita and Tapirira guianensis, but not for Coccoloba arborescens and Protium brasiliense. Natural and manual fruit set of all of them was low, suggesting that other factors, in addition to pollen limitation, are involved in the regulation of fruit production. Studies on floral biology may help to clarify the variable rates of pollen limitation found for the dioecious species from restinga. However, as they are woody and perennial, and therefore pass through several reproductive cycles throughout life, factors that influence female reproductive success may vary over the reproductive events, due to abiotic and biotic conditions.