Abstract Detail

Systematics

Srivastav, Mansa [1], Kumar, Amit [2], Rawat, GS [3], Clement, Wendy [4], Donoghue, Michael [5].

Character evolution, geography, ecology, and taxonomy of the Himalayan-Tibetan-Hengduan lineage Isoxylosteum (Lonicera, Caprifoliaceae).

Isoxylosteum is a small clade within Lonicera (the honeysuckles) that stands out from the rest owing to its derived radially symmetrical flowers. It contains four species complexes and ~4-11 species that are endemic to the Himalayan-Tibetan-Hengduan region. Even though it is a small group with a restricted distribution, it shows remarkable morphological and ecological diversity. Its species occupy a wide elevational range from 2000 to more than 5000 metres, and they grow in a wide range of habitats, from dry and wet temperate forests to cold deserts and wet alpine regions. Morphologically, Isoxylosteum exhibits exceptional variation between as well as within the species complexes. In fact, it provides a microcosm of the morphological diversity found across Lonicera and hence provides an excellent system for studying variation in the lineage as a whole. For example, within Isoxylosteum, the ovaries may be completely free or fused partially or fully; two bracteoles of adjacent flowers may fuse at the base of the flower pair or all four bracteoles may fuse completely to form a partial cupule around the two ovaries; plants may or may not bear thorns; and fruits may be blue, orange, or red in colour. Isoxylosteum species also exhibit some apomorphies not found in other Lonicera species, such as whorled leaves, complete fusion between adjacent flowers, and a style/stigma deeply embedded within the corolla tube. Some of the species complexes show dramatic morphological variation. For example, within L. angustifolia, extreme height variation can be found within a distance of several kilometres: some plants of L. angustifolia var. myrtillus are less than five cm tall, while those of L. angustifolia var. angustifolia can exceed a meter in height. Likewise, L. rupicola subsps. rupicola, which is found from Central Himalaya to Hengduan, has white lanate, evergreen leaves, whereas the Hengduan endemic, L. rupicola subsps. syringantha has glabrous, deciduous leaves. Here we provide a detailed taxonomic history of the clade, and give an account of the morphological, ecological and geographical variation in Isoxylosteum that reflects new information obtained in our recent field studies.

1 - Yale University, Ecology And Evolutionary Biology, 21 Sachem Street, New Haven, Connecticut, 06511, USA
2 - Wildlife Institute of India, Department of Habitat Ecology, Wildlife Institute Road, Chandrabani, Dehradun, Uttarakhand, 248001, India
3 - Wildlife Institute of India, Wildlife Institute Road, Chandrabani, Dehradun, Uttarakhand, 248001, India
4 - The College of New Jersey, Department of Biology, 2000 Pennington Road, Ewing, NJ, 08628, USA
5 - Yale University, Department Of Ecology And Evolutionary Biology, 21 Sachem St., New Haven, CT, 06511, United States

Keywords:
Lonicera
honeysuckle
Caprifoliaceae
Himalaya-Tibet-Hengduan
species complex
Taxonomy 
ecology
trait evolution
Isoxylosteum
Fieldwork
alpine
cold desert.

Presentation Type: Oral Paper
Number:
Abstract ID:922
Candidate for Awards:None