AMPHITROPICAL RELATIONSHIPS IN THE FLORAS OF NORTH AND SOUTH AMERICA
AMPHITROPICAL RELATIONSHIPS IN THE FLORAS OF NORTH AND SOUTH AMERICA
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DOI：
10.1086/403797
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发表时间：
1963-01-01
影响因子：
6.5
通讯作者：
RAVEN, PH
中科院分区：
文献类型：
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作者：
RAVEN, PH
在西半球，维管植物的两亲性分布可分为三类：两极或高纬度，约有30种;温带，约有130种;沙漠，数量可观。这种密切的亲缘关系可以解释为从一个共同的热带祖先分化而来，也可以解释为起源于热带的一边，随后迁移到另一边。对于所讨论的绝大多数群体来说，后者是真实的。它们可能通过一次跳跃或直接迁徙穿越热带。所涉及的植物群落起源相对较晚。双翅目间断种来自相对较少的科，大多数是在开放的栖息地，如海岸或季节性潮湿的地方，建立相对容易的植物。木本植物，甚至是封闭群落的草本植物几乎没有代表。一般来说，动物并没有类似的两栖动物分布，因为如果植物通过陆桥或山脉直接穿过热带迁移，那么它们就会被期望。几乎所有的植物都是自交亲和的;一粒种子到达一个合适的栖息地就足以开始一个新的间断种群。动物，主要是两性的，不太可能建立殖民地在新的地区，他们很少分散，是自花受精的植物。许多分离的模式与鸟类的迁徙路线相对应，鸟类必须偶尔在一个半球和另一个半球之间携带种子。热带以外的北美洲和南美洲的植物区系至少从白垩纪中期开始就截然不同，而且至今仍有很大差异;少数共同或非常相似的物种是叠加在这种格局上的不协调因素。尽管如此，在至少200个物种和物种群的植物中，北美和南美种群之间的关系非常密切。其中许多是一年生草本植物的迅速演变的群体，其中染色体差异往往积累迅速。尽管如此，在几个群体中，北美和南美植物之间的杂交已经证明了相对较高的染色体配对程度和一定的育性。两极物种大多来自北方半球;他们最有可能的传播时间似乎是更新世。大约85%的温带物种可能同样来自北方，可能是在上新世晚期和更新世。大多数沙漠物种可能来自南方，在某些情况下可能是更新世后期。零星的远距离跨热带扩散似乎是解释所有这些事实的最佳假设。
Amphitropical distributions of vascular plants in the Western Hemisphere are divided into three groups: bipolar or high-latitude, with about 30 species; temperate, with about 130 species; and desert, with a substantial number. Close relationships of this sort can be explained either by divergence from a common tropical ancestor or by origin on one side of the tropics and subsequent migration to the other. The latter is true for the great majority of groups discussed. These may have crossed the tropics in a single jump or by direct migration. The plant communities involved are relatively recent in origin. The amphitropical disjuncts are drawn from relatively few families and mostly are plants that occur in open habitats such as sea-coast or seasonally moist places where establishment would be relatively easy. Woody plants and even herbs of closed communities are scarcely represented. Animals by and large do not have analogous amphitropical distributions as they would be expected to if the plants migrated by a land bridge or mountain chain that took them directly through the tropics. Nearly all of the plants are self-compatible; the arrival of a single seed in a suitable habitat is sufficient for the start of a new disjunct population. Animals, being predominantly bisexual, are not as likely to establish colonies in new areas to which they are rarely dispersed as are autogamous plants. Many of the disjunct patterns correspond with the migration routes of birds, which must occasionally carry seeds between one hemisphere and the other. The floras of extratropical North and South America have been distinct since at least the middle Cretaceous and are still very different at present; the few common or closely similar species are discordant elements superimposed on this pattern. Despite this, in at least 200 species and species-groups of plants, the relationships between North and South American populations are very close. Many of these are annual herbs of rapidly evolving groups in which chromosomal differences often accumulate quickly. Nevertheless, crosses between North and South American plants in several groups have demonstrated a relatively high degree of chromosome pairing and some fertility. The bipolar species mostly come from the Northern Hemisphere; their most likely time of dispersal seems to have been the Pleistocene. About 85 per cent of the temperate species may likewise have come from the north, possibly in the late Pliocene and Pleistocene. A majority of the desert species may have come from the south, possibly as recently as post-Pleistocene time in some cases. Sporadic longdistance transtropical dispersal seems to be the best hypothesis to account for all these facts.