Format: ORAL

Mansa Srivastav1, Amit Kumar2, Gopal Singh Rawat2, Michael J. Donoghue1

1 Department of Ecology & Evolutionary Biology, Yale University, USA 2 Department of Habitat Ecology, Wildlife Institute of India, India

The Himalayan-Tibetan-Hengduan region is one of the most important biodiversity hotspots for high-altitude plants. However, owing to the trans-boundary nature of this region and its remote peaks and valleys, many taxonomic problems remain unresolved. In turn, this has impeded our understanding of its evolutionary history. Here we resolve the phylogeny and delimit species in an endemic lineage of honeysuckles the Isoxylosteum clade of Lonicera using restriction-site associated DNA sequencing (RADSeq) combined with morphological and ecological data. These plants occupy almost the entire length and breadth of the Himalayan-Hengduan system, as well as the Tien Shan and Pamiro-Alai mountains to the north of the Tibetan Plateau. They also span an altitudinal range from ~2000-5000 m and occupy several major biomes, from wet and dry temperate forests to cold deserts and alpine areas. Phylogenetic and population structure analyses support the recognition of five species. One of the previously recognized varieties L. rupicola var. minuta was found to form a clade that is sister to L. spinosa. This is surprising because the geographic range of L. minuta is contiguous with the other varieties of L. rupicola in the northern Hengduan region and it is widely separated from L. spinosa whose range is confined mainly to the west of the Tibetan plateau. However, on close examination, several morphological and ecological traits also favour a closer relation of L. minuta to L. spinosa than to L. rupicola. This finding raises the possibility of ring speciation around the Tibetan Plateau. Our analyses demonstrate contrasting patterns of diversification between the predominantly lower-elevation L. angustifolia-L. tomentella clade and the higher-elevation L. spinosa-L. minuta-L. rupicola clade.We also found repeated parallel evolution into alpine habitats in L. angustifolia.