轮藻居群的种内变异与生物地层对比

Intraspecies variation and biostratigraphic correlation in charophyte population

传统轮藻化石研究对中国白垩系古近系地层界线划分起到了重要的作用,但是轮藻属种的洲际对比却难以实现,究其原因,主要是中国与国际分类学方法未统一,属种名称不一致所导致。前人通过对现生轮藻藏卵器形态发育的观察发现,一个轮藻种的藏卵器钙化程度的不同,会导致其螺旋细胞呈现由凹到凸的变化。文章介绍了以居群为单位的轮藻化石研究思路,居群内不同的藏卵器个体在形态上存在一定的差异,但这些差异之间存在连续过渡的关系,并未出现明显的分异,我们将这些形态变化称为种内变异;种内形态分析可以对已建立的属种进行有效厘定,有助于中国与国际的轮藻化石居群进行对比。此外,轮藻生物地层学研究还需结合古生态学和古地理学分析,优先选择生态域广和地理分布范围广的分子进行生物带命名,有利于进行洲际地层对比。

Traditional charophyte fossil studies indicated that these fossils played a significant role in the stratigraphic division of the Cretaceous/Paleocene boundary.However,the continental correlation of charophyte species is hard to carry out due to lack of a united taxonomy standard.According to previous studies on modern charophytes,the spiral cells of gyrogonites in one species showed changes from concave to convex due to different degrees of calcification.Therefore,the identification of charophyte fossil taxa based on populations was introduced.Gyrogonite polymorphism is often found in the population of one of the species.If the changes in characteristics are transitional,these different morphologies are called intraspecific variations.Studies of intraspecific variations could provide evidence for species determination and further biostratigraphic correlation between Chinese and international charophyte populations.Palaeoecology and palaeogeography are also important for studying charophyte biostratigraphy.Eurytopic and widely distributed species can be used to denominate biozones,which are beneficial to intercontinental stratigraphic correlation.