Phylogeny Classification and Geographic Distribution of Rodgersia Gray

Abstract

Abstract:

This paper consists of three parts, i. e. the phylogeny, classification and geo-

graphic 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 tetraploid with 2n = 60 and are intermediate.

A revised classification of Rodgersia is presented, in which 5 species and 3 varleties 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. sambucifolia,

R. pinnata and R. nepalensis.

The genus Rodgersia is distributed in East Asia (Fig. 3). Four distribution patterns

(Fie. 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 au-

thor 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 Rodger-

sia, i. e. R. aesculifolia, 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 distri-

bution 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.

Key words: Rodgersia, phylogeny, classification, palynology, geographic distribution

Pan Jin-tang. Phylogeny Classification and Geographic Distribution of Rodgersia Gray[J]. .

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