The Evolution of Annelids Reveals Two Adaptive Routes to the Interstitial Realm
The Evolution of Annelids Reveals Two Adaptive Routes to the Interstitial Realm
复制标题
DOI：
10.1016/j.cub.2015.06.007
复制
发表时间：
2015-08-03
期刊：
影响因子：
9.2
通讯作者：
Halanych, Kenneth Michael
中科院分区：
文献类型：
--
作者：
Struck, Torsten Hugo;Golombek, Anja;Halanych, Kenneth Michael
许多动物永久居住在海洋间质，即沙粒之间的空间[1,2]。不同的进化情景可以解释间质动物的存在[3,4]。这些假设包括：(1)间质界是双边动物的祖先栖息地[5,6],(2)间质分类群是由较大的祖先通过小型化进化而来的，或者(3)后代进化。第一种观点反映了前一种假设，即间质环节动物（称为archianelids）位于环节动物辐射带的底部。然而，根据形态学数据，现今间质环节动物普遍倾向于后代发生[3,4,8]。在此，我们的系统基因组方法显示，间质archianelids被稳稳地划分为嵌套在环节动物树中的两组。第一类恐龙的进化最好用后代来解释。相比之下，由原钻和多蛛科组成的第二组似乎是通过逐步小型化而进化的，从较粗的沉积物到较细的沉积物。因此，除了后代[3,4]外，被认为对间质环境适应过于缓慢的小型化是允许间质环境适应的重要第二途径。在研究间质类群的进化时，既要考虑后代性，也要考虑小型化[1,3]。
Many animals permanently inhabit the marine interstitium, the space between sand grains [1, 2]. Different evolutionary scenarios may explain the existence of interstitial animals [3, 4]. These scenarios include (1) that the interstitial realm is the ancestral habitat of bilaterians [5, 6], (2) that interstitial taxa evolved from larger ancestors by miniaturization, or (3) progenesis [3]. The first view mirrors the former hypothesis that interstitial annelids, called archiannelids, were at the base of the annelid radiation [7]. Based on morphological data, however, progenesis is generally favored for interstitial annelids today [3, 4, 8]. Herein, our phylogenomic approach revealed that interstitial archiannelids are robustly placed into two groups nested within the annelid tree. Evolution of the first group comprising among others Dinophilidae is best explained by progenesis. In contrast, the second group comprising Protodrilida and Polygordiidae appears to have evolved by stepwise miniaturization adapting from coarser to finer sediments. Thus, in addition to progenesis [3, 4], miniaturization, thought to be too slow for an adaptation to the interstitium [3], is an important second route allowing adaptation to interstitial environments. Both progenesis and miniaturization should be considered when investigating evolution of interstitial taxa [1, 3].