摘要
大灭绝后生物的幸免实质上是对灾变恶化环境的忍耐和适应生存。幸存分子能提供大灭绝规模和残存机制的部分信息。历次大灭绝后的残存与复苏有不同的形式,不同生物类群和同一类群中的不同生物对大灭绝事件更有不同的应对策略。在识别奥陶纪末大灭绝后3种幸存类型(“扩增幸存型”、“减缩幸存型”和“复活型”)的基础上,文中进一步指出,“减缩幸存型”的研究有助于理解“复活型”的含义。复活效应的识别应建筑在较高质量的化石记录基础上,但实践中寻找真正的复活生物却非易事。复活分类单元并不一定反映大灭绝的强度,其数量是受许多条件限制的;不同的大灭绝事件对不同门类(或类群)的冲击程度不一样,其复活表现形式也各不相同;并非每次大灭绝、每种生物类别都发育复活分子的。因此,复活效应和复活生物在大灭绝过程中的意义比过去想象的小得多。分析复活现象须掌握全球、而非局部地区的资料。在灾变时期,典型、常见分子是识别一个动物群的标志,而稀有分子更有助于复活效应的研究。史前避难所包含古地理、古生态、古环境和宏演化四方面因素,其识别和确定需寻找尽可能多的证据。史前“减缩幸存型”研究可能会给当今生物界研究一个有益的启示,即“濒危种”不一定完全陷入“穷途末路”之境地,而是仍有续生(或复活)的可能。
Survivors from mass extinction are important for the study of the survival since they are sources of biotic recovery. Based on dynamic change of brachiopods through the Ordovician and Silurian transition, increaslng-survlvors, decreasing survivors, and Lazarus taxa are discussed in this paper. New investigations on a global scale indicate that the more work on the Lazarus type, the smaller number of these taxa survived. Examination has reduced the number of Lazarus taxa but has indicated that a number of brachlopod groups had restricted distributions in the crisis and its subsequent interval. The rare occurrence of fossils following mass extinction may be related to several factors, such as biological factors （e. g. reduction of population size）, incompleteness of fossil record （e. g. an extended period of poor preservation）, stratigraphlc factors （e. g. development of facies）, artificial factors （e. g. collection bias, sampling failure）, and a combination of all these factors. Collecting bias is heavily involved in the evaluation of the fossil record. Many fossil collections are too small to obtain rare and uncommon forms. Our results suggest that a single, common refugium for the end Ordovician brachiopods probably did not exist. The scattered pattern of distribution of the relicts in the Hirnantian also helps us achieve a better understanding of the problems of Lazarus taxa. It seems to the authors that Lazarus taxa and refugia may have been less significant than what was previously thought.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2006年第6期187-198,共12页
Earth Science Frontiers
基金
中国科学院创新工程方向性项目(KZCX3-SW-149)
国家重点基础研究发展计划"973"项目(2006CB806400)
