作 者 ：Yü Te-Tsun, Lu Ling-Ti, Ku Tsue-Chih
期 刊 ：植物分类学报 1984年 22卷 5期 页码：351-359
Keywords:flora,
Abstract:
The Rosaceae is one of the five largest families of Xizang flora, consisting of
30 genera with 242 species, the total number of species is slightly less than those of
Compositae, Graminae, Leguminosae and Ericaceae in Xizang, amounting to 62.5% of
the total number of genera and 28% of the total number of species of the rosaceous flora
in China.
The four subfamilies of Rosaceae including primitive, intermediate and advanced
groups have been found in Xizang. These groups consist of 11 types of floristic ele-
ments, i.e. 4 genera belong to cosmopolitan, 9 genera belong to North Temperate, 3, E.
Asian-N. American, 3 Sino-Himalayan, 3 Sino-Japanesa, 2 Old World Temperate, 1
Temperate Asian, 2 Mediterranean-W. and O. Asian, 1 C. Asian, I Tropical Asian and 1
endemic to China. It is obvious that Rosaceae in Xizang comprises holarctic, Ancient Me-
diterranean and paleotropical elements, among which the temperate components are the
most dominant. The characteristics of the floristic composition of Rosaceae in Xizang
may be summarized as follows:
(1) Xizang abounds in both genera and species of the family which are diverse in
forms, including the primitive, intermediate and advanced groups, (2) The geographi-
cal elements are rather complex, mostly belonging to the temperate, among which the
Sino- Himalayan components and the elements endemic to China are dominant, (3) The
proportion of plants endemic to China and distributed in Xizang is much higher than
those endemic to Xizang itself, but there exist newly arisen species and infraspecific
forms or varieties which show that the speciation is apparently still active in Xizang.
The rosaceous flora of Xizang is a combination of old and new floristic elements, based
on the old floristic components, affected by the upheaval of the Himalayas, the differen-
tiation and speciation have been taking place in the long history.
The geographical distribution of Rosaceae in Xizang may be divided into 5 regions,
i.e. the northeastern, southeastern, southern, northwestern and northern. The rosaceous
plants are most abundant in the southeastern area, next in southern area, fewer in the
northeastern and very rare in the northwestern and northern regions. The general ten-
dency of the distribution of Rosaceae in Xizang is that the number of species gradually
decreases from the southeast to the northwest and the habit gradually changes from
trees, shrubs and herbaceous plants in the southeast to cushion-like scrubs and dwarf
perennial herbs in the northwest. These facts clearly show that the uplift of the Hi-
malayas has deeply affected the phytogeographical distribution of Xizang Rosaceae.
The rosaceous flora of Xizang has close relationships with those of the adjoring
regions, i.e. Yunnan and Sichuan. Besides, it is connected with floras of Nepal, Sikkim,
Bhutan nothern Buram and nothern India, but silghtly influenced by the Ancient Medi-
terranean flora.