The Karyotype Analysis of Arthrotaxis (Taxodiaceae) and Its Systematic Position

Abstract

Abstract:

The present paper deals for the first time with an analysis of the

karyotypes of Athrotaxis cupressoides Don and A. selaginoides Don endemic to

Tasmania (Australia). Their morphology of somatic chromosomes in seed root-tip

cells, chromosome measurements, and diagrams are shown in Plate 1, Table 1

and Fig. 1 respectively, The karyotypic formulas of the two species are

2n = 22 = 22m (2SAT) and 2n = 22 = 20m(2SAT ) + 2sm according to of terminolo-

gy Lexvan et al (1964). They all belong to IB type of Stebbins’(1971)karyotypic

asymmetry which was reported for the first time in the higher plants by

Li(1987b). Their chromosome complements are 22 = 2L + 10M₂+ 8M₁+ 2S and 22

=2L+ 10M₂+ 6M₁+ 4S respectively according to the standard defined by Kuo et

al. (1972) based on relative length. The karyotype of A. selaginoides is more ad-

vanced than that of A. cupressoides.

In the light of karyotypic data, the sequence of the taxo-diaceous genera (excl.

Sciadopitys) from primitive to advanced may be in the following order:

Cryptomeria, Glyptostrobus, Taxodium, Metasequoia, Sequoiadendron, Sequoia,

Athrotaxis, Cunninghamia and Taiwania. The genus Athrotaxis is closely related

to Sequoia (Sequoiadendron) and Cunninghamia The peculiarity of the karyotype

of Athrotaxis deserves the establishment of a new status Arthrotaxoideae (Wettste-

in) L. C. Li This suggestion is also supported by the data from morphology,

embryology, palynology and geography. The family Taxodiaceae is divided into

six subfamilies and nine genera, as shown in the following table:
—————————————————————————————————————————————————

1. Cryptomerioideae Hida Cryptomeria D. Don 4. Arthrotaxoideae (Wettstein) L. C. Li

2. Taxodioideae Pilger Glyptostrobus Endl. Taxodim Richard Athrotaxis D. Don

3. Sequoideae Saxton metasequoia Miki ex Hu et 5. Cunninghamioideae Hida Cunninghamia

Cheng Sequoiadebron Buch. Sequoia Endl. R.Brown

6. Taiwanioideae (Hayata)L. C. Li

Taiwanta Hayata
—————————————————————————————————————————————————

The systematic positions of Athrotaxis in the systems of other authors are dis-

cussed too.

Key words: Athrotaxis cupressoides, Athrotaxis selaginoides, Taxodiaceae, Karyotype, Systematics

Li Lin-Chu. The Karyotype Analysis of Arthrotaxis (Taxodiaceae) and Its Systematic Position[J]. .

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The Karyotype Analysis of Arthrotaxis (Taxodiaceae) and Its Systematic Position

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