松科的核型和系统发育研究

STUDIES ON THE KARYOTYPE AND PHYLOGENY OF THE PINACEAE

松科通常主要依据长、短枝及叶等的形态特征分成冷杉亚科、落叶松亚科和松亚科。该科各属的核型可以划分成5个类型:(1)松型(24(22)m+0(2)sm);(2)冷杉型((22～14)m+(2～10)sm(st));(3)落叶松型(12m+12sm(st));(4)花旗松型(10m+12sm+4t);(5)金钱松型(4sm+40t(4SC))。本文根据核型资料的比较分析,各属从原始到进化的顺序可能是:松属(松型核型)→银杉属、云杉属、铁杉属、(雪松属)、油杉属、冷杉属(冷杉型核型)→黄杉属、落叶松属(花旗松型核型和落叶松型核型)→金钱松属(金钱松型核型)。这个顺序和亲缘关系在以核型的平均臂比为纵坐标、染色体长度比为横坐标的坐标图上得到清楚反映(不包括金钱松属)。核型为K(2n)=44=4sm+40t(4SC)的单型属金钱松属不仅在染色体数目和核型上与其他各属差异明显,而且具有独特的习性和一系列形态学和解剖学的特征,如落叶乔木(仅同落叶松属),短枝之叶簇状密生而辐射平展呈圆盘状,叶枕在落叶后密集成环节状,雄球花多数簇生短枝顶端,种鳞卵状披针形,成熟时与基部贴生的苞鳞连同崩解的球果中轴一起脱落,叶中3个树脂道及其分布,维管束帽缺如以及传输组织铁杉型(仅同铁杉属)等。因此,本文将金钱松属提升为一个新亚科Pseudolaricoideae L.C.Li。

Pinaceae is the largest family in gymnosperms, containing about 230 species in 10 genera. Based mainly on morphological characters of leaves, long and short branches, it is generally classified into three subfamilies, i. e. Abietoideae (Keteleeria, Abies, Pseudotsuga, Tsuga, Cathaya, Picea ) , Laricoideae (Larix, Pseudolarix, Cedrus ) and Pinoideae (Pinus). Five types of karyotypes was defined in this family. (1) Pines Type [24(22)m+ 0(2)sm, Pinus]; (2) Silver-Fir Type [(22 -14)m+ (2-10)sm(st), Cathaya, Picea, Tsuga, Cedrus, Keteleeria, Abies]; (3) Larches Type [12m+12sm(st), Pseudotsuga, Larix]; (4) Oregon-Douglas-Fir Type (10m + 12sm + 4t, Pseudotsuga menziesii); (5) Golden-Larch Type [4sm+40t(4SO , Pseudolarix]. In the light of comparative analysis of the karyotypic data, the evolutionary sequence of the genera may be as follows; Pinus (Pines Type)→ Cathaya, Picea, Tsuga, Cedrus, Keteleeria, Abies (Silver-Fir Type)→ Pseudotsuga, Larix (Larches Type, Oregon-Douglas-Fir Type)→Pseudolarix (Golden-Larch Type). This sequence and the relationships among the genera (excl. Pseudolarix) are clearly shown in Figure 1. The monotypic genus Pseudolarix with the karyotype K(2n) = 44 = 4sm+40t(4SC) is rather different from all the other genera (2n = 24) of the family not only in chromosome number and karyotype, but also in its peculiar habit, and a number of morphological and anatomical characters. Therefore, it seems reasonable to raise Pseudolarix to subfamily level, Pseudolaricoideae L. C. Li, and to reduce the three previously recognized subfamilies to three corresponding tribes (Abieteae, Lariceae and Pineae), which be- long to another subfamily Pinoideae. Pseudotsuga and Larix, having the karyotype K(2n) = 24 = 12m + 12sm(st), should constitute the Tribe Lariceae, and Cedrus [K(2n) = 24 = (20,18)m+(4,6)sm] be placed in Abieteae as its karyotype is similar to that of the tribe. Based on the karyotypic data, a new system of Pinaceae is proposed which is supported by data from morphology, anatomy, phytochemistry, immunology, biochemistry, embryology and paleobotany, etc. Meanwhile, the comments on the previous systems of the Pinaceae are made in this paper. Subfam. I Pinoideae Pilger 1926 Tribe 1 Pineae Parl. 1868 Firms Linn. 1753 2n = 24 Tribe 2 Abieteae Spach 1842 Cathaya Chen et Kuang 1958 2n = 24 Picea Dietr. 1824 2n = 24 Tsuga Carr. 1855 2n = 24 Cedrus Trew 1757 2n = 24 Keteleeria Carr. 1866 2n = 24 Abies Mill. 1754 2n = 24 Tribe 3 Lariceae Takhtajan 1956 Pseudotsuga Can. 1867 2n = 24(26) Larix Mill. 1754 2n = 24 Subfam. II Pseudolaricoideae L. C. Li Tribe 4 Pseudolariceae L. C. Li Pseudolarix Gord. 1858 2n = 44