Mangrove reproductive dynamics and the role of honeybee introduction in the vulnerable ecosystems of the Northwestern Arabian Peninsula

Abstract Mangrove forests are increasingly threatened worldwide and a growing number of regeneration initiatives have surged, aimed at reversing their decline. A critical factor influencing the effectiveness of these efforts is the reproductive success of mangrove plants. In this study, we documented patterns of pollen deposition and fruit set in Avicennia marina and Rhizophora mucronata at two sites at their northernmost range in the Arabian Peninsula. One of the sites hosted managed honeybees ( Apis mellifera carnica ) colonies as part of an ongoing beekeeping initiative. This setting provided an opportunity to document pollen deposition and fruit set under different pollination treatments and to obtain indications on how honeybee presence may relate to the reproductive dynamics of the two mangrove species. The local flower visitor community was surveyed using morphological and DNA barcoding approaches. During the period of honeybee presence, pollen deposition was higher at the coastal site, increasing approximately sixfold in A. marina and nearly threefold in R. mucronata , with a corresponding rise in fruit production indicators for both species. Self-pollination remained largely ineffective in both species. The survey of the flower visiting insects led to the collection of 153 specimens classified into 23 distinct taxonomic groups that include members of the orders Hymenoptera, Diptera, and Hemiptera. The results provide a descriptive baseline on mangrove reproductive dynamics and flower visitor communities, as well as preliminary field-based indications of the potential role of honeybees in supporting pollination and reproductive output in the two mangrove species.