Three New Cytotypes of Dryopteris chrysocoma Complex

Abstract

Abstract:

Two new species and one nataral hydrid close to Dryopteris chrysocoma

(Christ) C. Chr. are found by means of cytological study, which shows that D. chrysoco-

ma circumscribed in the past is not a single diploid in its range, but consists of seve-

ral cytotypes.

D. para-chrysocoma is a sexual diploid with narrowly lanceolate laminae that are

almost glandless. The scales on the rachis and pinna rachis are pale brown, longer in

length (4-7 mm) and denser. Indusium lacks glands too. The ultimate segments are

narrower and separated by arrow spaces. These characters distinguish it from D. chry-

socoma.

D. zinongii is a sexual tetraploid. It is recognised by its ovate laminae, sparse,

small and dark brown scales on the rachis and pinna rachis (1-2mm in length),

broad segments closely adjacent one another and membranous indusia.

D. × daliensis is shown to be an apomictic triploid which has rather irregular meio-

sis. There are some free chromosomes at the first metaphase, some lagging chromoso-

mes and bridges at the first anaphase and some micronuclei in young spores. Some un-

paired univalents can even be seen at diplotene. Approximately 14 univalents, 14 bi-

valents and 27 trivalents were observed at late diakinesis. Although a large number of

SMCs were counted, a definite chromosome number has so far proved impossible to be

obtained. This is possibly caused by variable pairing of the three genomes and diffe-

rent trivalent numbers formed in each SMC. As a result, generally less than 64 abor-

tive spores are formed in each sporangium, but the sporangium with 32 spores could

also be found rarely. All these show that this hybrid may be derived from the cross be-

tween a diploid and a tetraploid which have homoeologous genomes.

D. × daliensis is morphologically intermediate between D. zinongii and D. para-

Chrysocoma. in respect to characters such as ovate-lanceolate laminae, brown rachis sca-

les with a dark central stripe, 2-3 mm in length, and abortive spores in unequal size

and different shapes etc. In addition, they are often found growing together in Cang

Shan, Yunnan. It is therefore reasonable to consider that the latter two are probably

the parents of the former.

These new cytotypes show the presence of Dryopteris chry-socoma complex which

is generally characterized by shell-shaped indusia and glandular fronds. Accoding to

the morphology, D. woodsiisora Hayata, D. tenuissima Tagawa, D. alpicola Ching et Z.

R. Wang, D. fangii Ching, Fraser-Jenkins et Z. R. Wang and D. pseudochrysocoma

Ching etc. should be the members of this complex. In order to clarify the relation-

ships between all the members of D. chrysocoma complex, a great deal of further cy-

togenetic study, including artificial hybridization and analysis of meiosis in both wild

and synthesized hybrids, is required.

The author is grateful to Prof. R. C. Ching and Mr. C. R. Fraser-Jenkins of the

British Museum (Natural History) for their kind and helpful suggestion, and thank

Mr. Q. Xia and Mr. Y. L. Ma for their help in the field work.

Key words: Pteridophyta, Cytotaxonomy, Dryopteris, Dryopteris chrysocoma complex

Wang Zhong-Ren. Three New Cytotypes of Dryopteris chrysocoma Complex[J]. .

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Three New Cytotypes of Dryopteris chrysocoma Complex

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