Islands: Stability, diversity, conservation
Islands: Stability, diversity, conservation
复制标题
DOI：
10.1023/a:1018372910025
复制
发表时间：
1997-03-01
影响因子：
3.4
通讯作者：
Cronk, QCB
中科院分区：
文献类型：
--
作者：
Cronk, QCB
岛屿呈现出多样性和稳定性的“悖论”。它们通常是高度物种贫乏的，但在非凡的特有属和分类学上孤立的群体方面具有相当大的生物学意义。它们似乎是稳定的，因为在某些情况下，这些生物已经持续了数百万年，并且具有海洋性气候，极端气候事件可能相对罕见。然而，当受到外来（人为）干扰时，它们似乎并不稳定，而是经常遭受灾难性的生态变化。当人们认识到所有这些特征都是同一岛屿特征的结果时，这些明显的矛盾就得到了解决：生物隔离和海洋性。由于这两个特点，远洋岛屿在生态过程的性质上与大陆系统有着数量上的不同，这似乎产生了一种极端间断的进化变化平衡模式。地方病可能是古老的残留地方病，表现出长期的停滞和持久性，或适应性辐射的产物，代表快速的间歇性事件。一个以过程为基础的残遗特有种（古特有种）的定义是其建立谱系（即最初的大陆来源分类单元）没有留下任何后代。这一定义的一个推论是，地方病与其大陆姐妹群之间的分歧时间应该早于现在的地方病谱系对岛屿的殖民化。一个例子是Dicksonia arborescens，它已经在圣赫勒拿岛至少有900万年的历史，不再出现在非洲的可能来源地区。这些在岛屿上频繁出现的地方性残遗，作为其他地方已经消失的生物多样性的最后残余，具有重要意义。岛屿养护战略需要综合了解多样性和稳定性矛盾的两个方面，以便岛屿进程和岛屿生物都能得到养护。
Islands present both a diversity and a stability 'paradox'. They are often highly species-poor but have considerable biological interest in terms of extraordinary endemic genera and taxonomically isolated groups. They appear to be stable, as in some cases these organisms have persisted for many millions of years, and having an oceanic climate, extreme climatic events may be comparatively rare. However, when subject to extrinsic (anthropogenic) disturbance they do not appear to be stable, but often suffer catastrophic ecological change. These apparent paradoxes are resolved when it is realized that all these features are consequences of the same island characteristics: biotic isolation and oceanicity. As a result of these two characteristics, far oceanic islands are quantitatively different from continental systems in the nature of their ecological processes, which appear to give rise to an extreme punctuated equilibrium model of evolutionary change. Endemics may be ancient relict endemics displaying prolonged stasis and persistence, or products of adaptive radiation representing rapid punctuational events. A process-based definition of a relict endemic (palaeoendemic) is one whose founding lineage (i.e. the original continental source taxon) has not left any descendents. A corollary of this definition is that the time of divergence between an endemic and its continental sister-group should predate the colonization of the island by the now endemic lineage. An example is Dicksonia arborescens which has been on St Helena for at least 9 Myrs and no longer occurs in the likely source area of Africa. These relict endemics, frequent on islands, are important as the last remnants of tranches of biodiversity that have vanished elsewhere. Island conservation strategies require an integrated understanding of both sides of the diversity and stability paradox so that both island processes and island organisms can be conserved.