Floral traits predict pollination syndrome in Syzygium species: a study on four endemic species of the Western Ghats, India

Abstract

Pollination ecology and the breeding system of four endemic species of Syzygium (S. heyneanum, S. travancoricum, S. laetum and S. mundagam) of the Western Ghats, India are investigated. The floral traits are used for ordination analysis to understand if the species form any cryptic groups and whether this grouping predicts the pollination syndrome and the breeding system. Pollinators were distinguished from frequent visitors by studying their efficiency to transfer pollen to the stigma or induce fruit set following their exclusive visit to virgin flowers. The species formed two groups in the ordination map: the S. heyneanum and S. travancoricum group and the S. laetum and S. mundagam group. The flowers of studied species attracted 3–23 species of animals during the day, but none were encountered during the night. Flowers of S. heyneanum and S. travancoricum were visited by a large number of insect species of which only a limited number turned out to be the pollinators. S. laetum and S. mundagam attracted two bird species apart from a few insect species. In S. laetum, although birds did not bring about pollination directly, their visits facilitated anemophily by releasing pollen to the air by causing physical disturbance to the flowers. In S. mundagam, both birds and wind were involved in pollination. S. heyeanum and S. travancoricum were fully self-compatible, whereas S. laetum and S. mundagam were partially self-compatible.