Reproductive ecology of Elaeocarpus venustus Bedd.: an Endemic and Critically Endangered spiritually important tree of the Western Ghats

The critically endangered evergreen tree Elaeocarpus venustus is a specialist of submontane riparian swamps, where it exhibits a singular, synchronous annual phenological cycle driven by climatic cues. Research indicates that its flowering is positively correlated with rainfall but negatively influenced by rising temperatures. While a single individual in a nutrient-rich swamp habitat can command up to 31.8% of local reproductive resource allocation, the species overall suffers significant resource loss, including 18.33% bud drop and 16.02% flower wastage during periods of low humidity and heavy winds. Among thirteen observed floral visitors, the giant honeybee Apis dorsata is the most proficient pollinator, facilitating reproduction through a high visitation frequency of 8.7 visits per hour and a substantial stigmatic pollen load. Ultimately, E. venustus relies heavily on xenogamy, yielding a peak fruit set of 61%, highlighting the importance of specific pollination syndromes and stable hydrological conditions for the survival of this endemic species.