The Morphological Variation of the Genus Rhododendron (Ericaceae) in Himalayan Ranges of Bhutan
Bhutan Himalayan ranges harbor 46 species of Rhododendron and contributes four percent of the genus in the world. The genus Rhododendron is associated with morphologically diverse, complex vegetative and floral traits. The variation of floral traits of rhododendrons might have attributed due to the pollinators and adaptive preference resulting in the evolution of floral complexity. However, there is a paucity of scientific studies concerning the vegetative and reproductive morphology of rhododendrons and pollinators. A comparative morphological study was investigated on 30 species of Rhododendron from different geographical locations of Bhutan. We studied the interspecific variation of seed and pollen morphology among the selected species. Casual pollinator observations were also examined to identify the potential pollinators and visitors through in-person and binocular. Eight different floral types and two seed types were identified from the present study. We suggest that the floral morphology and distribution of Rhododendron floral types over the landscape may reflect their adaptive value of the plant-pollinator interactions. Additionally, seed traits might have influenced the dispersal ability and colonization of species. Further in-depth explorations on floral development, pollination ecology, and seed developmental allometry may offer a broader understanding of the floral evolution, specialization in plant-pollinator interaction in angiosperm, and their adaptation to the unique environmental cline of the Himalayas.
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