Chromosomes of Cruciferae. II. Cytogeography of Leavenworthia
Chromosomes of Cruciferae. II. Cytogeography of Leavenworthia
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DOI：
10.2307/2481536
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发表时间：
1945-01-01
期刊：
影响因子：
--
通讯作者：
Baldwin, J. T.
中科院分区：
文献类型：
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作者：
Baldwin, J. T.
利文沃西亚似乎由一个相当明确的种组成，并给出了其地理范围和特征。三个种子选手。被认为是六倍体2[图像]=30，[图像]=15，以及由四倍体衍生而来的非整倍体金针藻：2w=22，[图像]=11。并拥有最大的分布面积。柱花草是变异性最大的一种，这种情况可能与其自交不育有关，而其他种的自交不育程度较高，而且它有大而艳丽的花。Torulosa的分布范围最小，可能是最年轻的一种。可能与Stylosa有些交错，然而，更多的是与L.aurea混淆。由于其最南端的出现，分离的范围，和较低的染色体数量，金黄色葡萄球菌似乎是该属中最古老的成员，它可能包含二倍体和四倍体小种：它在德克萨斯州的代表与阿拉巴马州和田纳西州的代表有不同的方面。利文沃西亚的变异性中心在纳什维尔盆地，那里所有的物种。发生了什么，其中两个在很大程度上受到了限制。该属是“空地”植物区系的特征成分之一。对该植物区系中唯一的另一个复合体进行了详细的细胞地理学研究，该复合体具有二倍体、四倍体和六倍体小种：其种类范围和变异中心几乎与莱文沃西亚的相应。作者认为，十字花科和景天科的这些复合体所表现的基本格局反映了冰川的影响和纳什维尔盆地的地形，自中更新世以来，纳什维尔盆地的地形有利于建立许多大小不一的种群，在这些种群中，适应分化和漂移都可能有效地进行，并且由于植物的年代性，它们的速度很快。预计空地植物区系的其他成分也有类似的进化模式。|摘要作者：/.T·鲍德温，Jr
Leavenworthia seems to consist of A rather well-defined spp., of which the geographic ranges and characteris-tics are given. Three of the spp. are considered to be hexa-ploid 2[image] = 30, [image] = 15, and the 4th, L. aurea, an aneuploid derivative from tetraploidy: 2w = 22, [image] = 11. L. uniflora is the most clear-cut sp. and has the greatest distributional area. L. stylosa is the most variable sp., a condition probably correlated with its self-sterility as contrasted with a high degree of self-fertility in the others, and it has large and showy flowers. L. torulosa has the most limited range; it is probably the youngest sp. and perhaps intergrades somewhat with L. stylosa, which, however, is more often confused with L. aurea. Because of its southernmost occurrence, disjunct range, and lower chromosome number, L. aurea appears to be the oldest member of the genus, and it possibly harbors diploid and tetraploid races: its representatives in Texas have a different aspect from those in Alabama and Tennessee. The center of variability for Leavenworthia is in the Nashville Basin, where all the spp. occur and to which 2 of them are in large measure restricted. The genus is one of the characteristic elements of the "glade" flora. The only other complex of the flora that has been studied in cytogeographic detail is Sedum pulchellum, with diploid, tetraploid, and hexaploid races: the range of the species and the center of its variability are almost the counterparts of those of Leavenworthia. It is suggested that the basic pattern expressed by these complexes[long dash]one of the Cruciferae, the other of the Crassulaceae[long dash]is a reflection of glacial influence and of the topography of the Nashville Basin, which since mid-Pleistocene has been favorable for the establishment of many populations of vary-ing sizes within which both adaptive differentiation and drift might operate effectively and, because of the annuality of the plants, at a rapid rate. It is expected that other elements of the glade flora have comparable patterns of evolution. || ABSTRACT AUTHORS: /. T. Baldwin, Jr