求助GWD-RC一篇关于蜥蜴演化的文章 - ChaseDream

Anole lizard species that occur together (sympatrically) on certain Caribbean islands occupy different habitats: some live only in the grass, some only on tree trunks, and some only on twigs. These species also differ morphologically: grass dwellers are slender with long tails, tree dwellers are stocky with long legs, twig dwellers are slender but stubby-legged. What is striking about these lizards is not that coexisting species differ in morphology and habitat use (such differences are common among closely related sympatric species), but that the same three types of habitat specialists occur on each of four islands: Puerto Rico, Cuba, Hispaniola, and Jamaica. Moreover, the Puerto Rican twig species closely resembles the twig species of Cuba, Hispaniola, and Jamaica in morphology, habitat use, and behavior. Likewise, the specialists for other habitats are similar across the islands. The presence of similar species on different islands could be variously explained. An ancestral species might have adapted to exploit a particular ecological niche on one island and then traveled over water to colonize other islands. Or this ancestral species might have evolved at a time when the islands were connected, which some of these islands may once have been. After the islands separated, the isolated lizard populations would have become distinct species while also retaining their ancestors’ niche adaptations. Both of these scenarios imply that specialization to each niche occurred only once. Alternatively, each specialist could have arisen independently on each of the islands.

Anole lizard species 在不同岛上占领不同的栖息地：有的只住在草丛里，有的在树干上，有的在树枝上。这些种类从形态上也不同：grass dwellers are slender with long tails, tree dwellers are stocky with long legs, twig dwellers are slender but stubby-legged。但是最使人惊讶的不是同一岛上居住着形态各异和栖息地不同的蜥蜴，而是这三种栖息方式同时发生在四个不同的岛上：PR,C,H和J。同时，PR 栖息于twig的种族和同样栖息于twig的在C岛，H岛以及J岛上的蜥蜴种族在形态，习惯和行为上非常相似。同样的，其他栖息地的种群和其他岛的同样栖息地种群也相似。这种相似种群出现在不同岛上可以有多种解释：这些种群的祖先可能ai先在一个岛上开发了一个小生态境，然后穿过河水去占领了另一些岛。或者这些祖先在当陆地连接着的时候（有一些岛曾经是连着的）是一起进化的。但是当岛分开之后，孤立的蜥蜴种群就会变成和之前不同的种族，但是同时保留了祖先的适应性。这两种情况都表明了各个生态境的specialization只发生一次。如果不是这样，每个specialist 族群可能在不同的岛屿上是独立出现的。

If each type of specialist evolved just once, then similar specialists on different islands would be closely related. Conversely, if the specialists evolved independently on each island, then a specialist on one island would be more closely related to other types of anoles on the same island—regardless of their ecological niches— than it would be to a similar specialist on a different island. Biologists can infer how species are related evolutionarily by comparing DNA sequences for the same genes in different species. Species with similar DNA sequences for these genes are generally more closely related to each other than to species with less-similar DNA sequences. DNA evidence concerning the anoles led researchers to conclude that habitat specialists on one island are not closely related to the same habitat specialists elsewhere, indicating that specialists evolved independently on each island.

如果每种 specialist只进化一次，那么不同岛上的相似的specialists就是近亲。相反的，如果 specialists独立在不同岛上进化，那么一个岛上的某种specialist将会与本岛其他种群比在其他岛上的相似栖息地的specialist更相近。生物学家可以通过比对不同种族中的相同基因中的DNA序列来推测种族是否近亲关系。有相似DNA序列的种族之间比没有什么相似DNA序列的要近。关于 the anoles的DNA证据使得研究者得出结论：有相同栖息地，居住在不同岛上额 specialists并不是近亲，说明各岛 specialists独立演化。