Abstract:

A taxonomic revision of Rhododendron tsoi (Ericaceae) was made in this paper, based on literature survey, field investigation, specimen examination, and evaluation of taxonomical significance of the major morphological characters. The size and shape of leaves, leaf apex and indumentum on lower surfaces were found to be reliable diagnostic characters for the circumscription of R. tsoi and its related taxa. However stamen length and its relative length in comparison with the style were so variable that they could not be used to circumscribe R. tsoi at species and sub-species level. Based on the leaf characters the previous R. tsoi and its related taxa were circumscribed as one species, that is R. tsoi,and four varieties, I.e. R. tsoi　var. hypoblematosum (Tam) X. F. Jin & B. Y. Ding,R. tsoi var. nudistylum (Tam) X. F. Jin & B. Y. Ding,R. tsoi var. huiyangense (Fang & M. Y. He) X. F. Jin & B. Y. Ding , and R. tsoi var. polyraphidoideum (Tam) X. F. Jin & B. Y. Ding. In addition, R. crassimedium and R. crassistylum were reduced to the synonyms of R. tsoi var. hypoblematosum, and R. tingwuense and R. unciferum were synonymized into R. tsoi var. nudistylum. The geographic distribution of R. tsoi and these intraspecific taxa were described as well.

Key words: I>Rhododendron tsoi, statistical analysis;morphological variation of leaf;taxonomic revision;new combination;new synonym