鬼灯檠属的系统发育、分类和地理分布

PHYLOGENY CLASSIFICATION AND GEOGRAPHIC DISTRIBUTION OF RODGERSIA GRAY

本文对鬼灯檠属Rodgersia Gray的染色体数、花粉体积和纹饰、萼片数目、萼片脉序和脉型、萼片腹面毛被、花梗和花序轴毛被、叶的类型等关键性状进行了分析,确定了其进化顺序;依据性状的系统发生,绘制了鬼灯檠属的瓦格勒尔系统树;确认本属有5种和3变种,其中以R.podophylla为最原始, R.nepalensis为最进化,而R.aesculifolia,R.sambucifolia和R.pinnata则居于两者之间。本属分两组Sect.Rodgersia,仅含R.podophylla;Sect.Sambuclfolia J.T.Pan,含R.aesculifolia,R.sambucifolia,R.pinnata,R.nepalensis。依据种的主要分布区,划本属植物为4个分布类型,即:日本-朝鲜间断分布,秦岭-大巴山分布,横断山分布和东喜马拉雅分布。笔者认为,本属的起源地在日本-朝鲜一带,横断山地区是其现代分布中心和分化中心;本属的散布路线是自日本-朝鲜,经秦岭-大巴山,通过横断山地区而进入东喜马拉雅;本属的起源时间,当在晚第三纪以前(晚白垩世至早第三纪)。此外,还报道了鬼灯檠属植物的花粉形态。

This paper consists of three parts, i. e. the phylogeny, classification and geographic distribution of the genus Rodgersia. As a result of the character analysis, the evolutionary trends of the characters in Rodgersia are suggested. The tetraploid (2n = 60, x = 15) is evidently derived from the diploid (2n = 30) (Table 1). Pollen grains have evolved from small to medium-sized, then to large (Table 2). The reticulate ornamentation of pollen (Plate 1: 7-9^ Plate 2: 1-8) is more advanced than obscurely reticulate (Plate 1: 1-6). Sepals have evoved from 7-5 to (6-) 5, then to 5 in number,; from pinnate and arcuate together to arcuate, and from open to intermediate type, then to closed in vein type (Fig. 1: 1-5); from glabrous to both glabrous and sparsely covered with glandular hairs, then to covered with glandular hairs in ventral surface. The indumentum of pedicels and inflorescence axes has evolved from chaffy and subsessile-glandular mixed to long and glandular (Fig. 1: 6-7). Leaves have evolved from simple to digitate, then to subpinnate, and finally to pinnate. Based on the character evolution, a schema showing wagner's phylogenetic tree of Rodgersia is given (Fig. 2) , in which R. podophylla may be considered as the most primitive one, as some archaic characters are'preserved (e.g. diploid with 2n=30, small pollen grains, obscurely reticulate ornamentation of pollen, sepals 7-5 with open type of veins. etc. ) ; R. nepalensis having large pollen grains, distinctily reticulate ornamentation of pollen, sepals 5 with closed type of veins, pedicels and inflorescence axes coverd with mixed long hairs and glandular hairs, may be regarded as the most advanced one; while R. aesculifolia, R. sambucifolia and R. pinnata which are tetrapioid with 2n = 60 and are intermediate. A revised classification of Rodgersia is presented, in which 5 species and 3 varieties are recognized. This genus is divided into two sections; Sect. Rodgersia including only R. podophylla and Sect. Sambucifolia J. T. Pan consisting of R. aesculifolia, R. sambuci folia, R. pinnata and R. nepalensis. The genus Rodgersia is distributed in East Asia (Fig. 3). Four distribution patterns (Fig. 4) are recognized as follows; 1. Japan-Korea distribution The main part of this area is in Japan and Korea, but it extends westwards to China (a very little part of Jilin and Liaoning). This area has only one species, i. e. R. podophylla. As mentioned before, this species is the most primitive one in Rodgersia, and thus the author suggests that the centre of origin of Rodgersia be in this area. Japan is contiguous to the Asian continent not isolated before the late Tertiary. Therefore the origin of the genus must be at least before the late Tertiary (the late Cretaceous to the early Tertiary). 2. Qinling-Daba Mountains distribution The main part of this area is in the Qinling-Daba Mountains, but it extends southwest-ward to Wu's Hengduan Mountains region. Only one species, R. aesculifolia, is found in this area. 3. Hengduan Mountains distribution This area covers southwestern Sichuan and northern Yunnan. Most species in Rodgersia, i. e. R. aesculi folia i R. sambucifolia and R. pinnata are concentrated in this area. They constitute 3/5 of the total species number (including varieties) in Rodgersia. They are more advanced than R. podophylla and all endemic to China. This area is therefore both the distribution and differentiation centers. 4. E. Himalayas distribution The main part of this area is Wu's East Himalayan Region, but it extends westwards to Sikkim and Nepal. This area has two species, i. e. R. nepalensis and R. aesculifolia var. henricii. They constitute 2/5 of the total species number, and R. nepalensis is endemic to this area. The dispersal route of Rodgersia may well be the narrow area from Japan-Korea south-westwards to East Himalayas (Fig. 4) through Qinling-Daba Mountains and Hengduan Mountains. In addition, the pollen morphology of Rodgersia was examined under SEM and is shown in Plates 1-2.