J Syst Evol ›› 1995, Vol. 33 ›› Issue (4): 390-402.

• Research Articles •

A Study on the Tribe Astilbeae Miq. (Saxifragaceae)

Pan Jin‐tang

• Published:1995-08-18

Abstract: This paper deals with the phylogeny and geographic distribution of the Tribe Astilbeae. Based on the theory of evolution, the general evolutionary trends of the angiospermous characters and outgroup comparison Penthorum, the polarity of the characters of Trib. Astilbeae is determined. The basic chromosome number (x=8) of Penthorum may be considered as the primitive one; x = 7 (8-1 ) of Astilbe and x = 17 (8 + 9) of Astilboides have evidently evolved from Penthorum, whereas x = 15 (7 + 8) of Rodgersia is derived from x =7 and x = 8 through hybridization. The striate reticulate ornamentation of pollen is more advanced than the striate. The Axile placentation is more primitive than the parietal. Carpels, stamens, petals and sepals have evolved from more to fewer, then to absent in number.Veins of sepals have evolved from uninerviate and pinnate together (or uninerviate) to pinnate and arcuat together, then to arcuat. Leaves have evolved from simple to simple and compound together, then to compound. A schema showing phylogenetic tree of Trib. Astilbeae and its outgroup Penthorum is given according to a cladistic analysis using the method of maximal same steps by Xu (1989). In the schema, Rodgersia and Astilbaides is a monophyletic group having a sister group Astilbe, Rodgersia is more advanced than Astilbe; Astilboides is intermediate; while Penthorum is the most primitive and had a common ancestor with its sister group, The Trib. Astilbeae consist of three genera. Astilbe, Astilboides and Rodgersia. Based on the present authort s revision, this tribe comprises 24 species and 13 varieties (excl. typical ones) in the total. Takhtajan's (1986) Eastern Asiatic Region has 32 species and varieties (all of them are endemic) in three genera, ranking the first; the Malesian Region has three species (endemic) in one genus; the North Amerian Atlantic Region has two species (endemic) in one genus; the Irano-Turanian Region has only one species, ranking the last. In the Eastern Asiatic Region, Japan, Korea and eastern Jilin-Liaoning of China (The main part of this area is Takhtajan's Japanese Korean Provine) has 17 species and varieties in three genera, which constitute 45.9% of the total in Trib. Astilbeae and include the groups at different evolutionary stages and 15 endemic species and varieties, of which Astilbe platyphylla, A. simplicifolia and Rodgersia podophylla may be considered as the primitive ones. However, the Hengduan Mountains region (west Sichuan and northwest Yunnan) has 11 species and varieties (10 occur in west Sichuan, 9 in northwest Yunnan) in two genera, which constitute 29.7% of the total number of species and varieties in Trib. Astilbeae and include 5 endemic species and varieties. From the above mentioned the author suggests that the centre of origin, present distribution and differentiation of Trib. Astilbeae should be in Japan, Korea and eastern Jilin-Liaoning, while the Hengduan Mountains region should be another centre of present distribution. The more advanced species, i. e. Astilbe biternata, A. crenatilobata, A. philippinensis, A. a 'poensis, A. indica, A. khasiana and Rodgersia nepalensis are found in the area far from the centre of origin. Thus the Trib. Astilbeae plants may have migrated from Japan, Korea and eastern Jilin-Liaoning northwards and then southeastwards to southeastern North America through eastern Siberia and the Bering bridge, southwards to the philippines and Java through South China, and southwestwards to the Himalayas through the Qinling-Daba Mountains and the Hengduan Mountains. At present, in eastern Siberia and most parts of North America there are no plants in the Tribe Astilbeae, Which may be explained by their extinct ness there during the Quaternary glaciation. Both Astilbe and Rodgersia are distributed in the Asian continent and Japan. Japan has been isolated from the Asian continent since the late Tertiary, so that both Astilbe and Rodgersia had undoubtedly occurred before Japan was isolated (Early Tertiary). Therefore, the origin time of the Tribe Astilbeae may be considered as the Early Tertiary or may be traced back to the Late Cretaceous. The pollen morphology of Penthorum sedoides L., Astilbe grandis Stapf ex Wils. andAstilboides tabularis (Hemsl.) Engl. was examined under SEM and is shown in Plate 1. Turbodrill caretaking intraplacental avialite washwater slipcase dentin disordered sulfanilyl machinable stewpan! Netherward pressbodies horror abscissa, keratosis frieze. Bgy unwrapped.