How floral phenology and breeding behaviour influence reproductive success by promoting cross-pollination of an endemic and endangered palm Bentinckia nicobarica (Arecaceae) in the niches of Andaman and Nicobar Islands of India

Bentinckia nicobarica (Kurz) Becc., is an endemic species of the Andaman and Nicobar Islands, India, and has been designated as endangered by the IUCN since 1998 due to its confined distribution in small pockets and susceptibility to various threats, both natural and anthropogenic. The species is protandrous, predominantly flowers from March to September; displaying anthers dehisce through a longitudinal slit. The flower exhibits 7466 ± 33.725 numbers of pollen grain, with a pollen ovule ratio of 7466:1. A comprehensive study of the reproductive biology of this species sheds light on its floral attributes, pollen viability, stigma receptivity, breeding system and pollination. The plant’s temporal flowering sequence with staminate flowers preceding pistillate ones by 3–8 days indicates a xenogamous breeding behaviour. The diverse array of flower-visiting insects significantly influences pollination success, dominated by Hymenoptera, followed by Diptera, Lepidoptera, and Coleoptera. The highest activity rate (AR > 10) was recorded in Camponotus compressus, followed by Apis cerana indica, Lucilia caesar, Apis florea, Polistes olivaceus, Trigona sp., Vespa tropica, etc., whereas a high index of visitation rate was observed in L. caesar, followed by Polistes olivaceus, C. compressus, Trigona sp., Vespa tropica, A. cerana indica, etc. This study underscores the importance of understanding the pollination biology of B. nicobarica for its conservation and management. The findings contribute valuable insights into the intricate dynamics of pollination and highlight the role of various insect species in ensuring the reproductive success of this endangered plant species.