Floral characteristics and pollination of sonneratia Spp. (Lythraceae) in Southern Thailand

Abstract

Mangrove forests provide numerous ecosystem services. Despite their importance, they continue to be lost. Conserving a species requires knowledge about them. This study was conducted to find out about the reproductive biology of Sonneratia ovata and S. griffithii. Floral biology traits, including morphology, anthesis, nectar production, and pollen-ovule ratio, were determined from three S. ovata populations in southern Thailand and two S. griffithii populations in Satun Province. Flowers were used in a pollination experiment with five treatments (open pollination, insect pollination, hand-cross pollination, hand-self pollination, and spontaneous autogamy). Pollinators were also observed using camera traps. Results show that both species display xenogamous characteristics through herkogamy and protogyny. Their pollen-ovule ratio both indicate facultative xenogamy. Results from the pollination experiment showed that S. ovata is highly self-compatible but S. griffithii is largely self-incompatible. Moreover, the pollination experiments indicate that pollinators are critical for the reproduction of both species. Additionally, the lack of fruit set during the dry season of the El Niño year of 2016 appeared to indicate severe resource limitation for S. ovata. For S. griffithii, fruit set in the study site with strong vehicle-generated wind was lower. Macroglossus minimus was the only bat species netted near the S. ovata flowers, and is likely its most important pollinator. By contrast, M. minimus and Eonycteris spelaea were netted near S. griffithii flowers. However, bats were observed to avoid illuminated flowers. My findings reveal that pollinators increase the reproductive success of both mangrove species, indicating that conservation efforts should be directed towards both this mangrove species and its pollinators.