A re-examination of the circumscription of Saxifraga mengtzeana (Saxifragaceae).

Abstract

In the Flora of China account of Saxifraga mengtzeana Engl. & Irmsch., eight synonyms were attributed to it and one variant, recognized as Saxifraga epiphylla Gornall & Ohba, was split from it. This study reevaluates the taxonomic status of some of the synonyms and of the segregated species in light of new evidence presented here. Morphological and molecular evidence demonstrate that collections from northwestern Yunnan and Sichuan are genetically differentiated from those in southeastern Yunnan and neighboring Guangxi. Observations in the field and in cultivation show that the peltate petiole attachment diagnostic of S.mengtzeana var. peltifolia Engl. & Irmsch. is developmentally labile. Similar observations combined with molecular data show that viviparous phenotypes, formerly treated as S.epiphylla, although largely under genetic control, occur sporadically throughout the ranges of both northern and southern taxa. Collections from northwestern Yunnan and Sichuan are best recognized as Saxifraga geifolia Balf.f., whereas those from southeastern Yunnan and neighboring Guangxi are S.mengtzeana. Peltate-leaved variants of the latter are given no status and are relegated to complete synonymy. Viviparous phenotypes of S.mengtzeana and S.geifolia are recognized at the rank of forma.