麻黄属的起源时间讨论

摘要

利用分子钟对麻黄属起源时间的估测和基于带有生殖特征的大化石标定的最小起源时间有很大的差距,分子钟估测麻黄属起源于古近纪的渐新世,而大化石则标定麻黄属起源不晚于早白垩世巴列姆期.麻黄属化石和分子钟结果之间的冲突至少有三种不同的解释:即古近纪瓶颈、古老支系缓慢绝灭和频繁的基因交流减缓了分子进化速率.本文的分析表明古老支系缓慢绝灭、频繁的基因交流以及rbc L基因不稳定的进化速率一起可以解释分子钟和化石证据之间的冲突.麻黄属现代类型不足以重建该属的系统发育和生物地理过程.%Molecular clock and megafossil bearing reproductive features indicate remarkable discrepancy on minimum age of Ephedra L. Three different explanations at least are present on the conflicts: Paleogene bottleneck, extinction of ancient lineages, and frequent gene exchanges in the genus.This study indicates that extinction of ancient lineages together with frequent gene exchanges may account for the conflict between molecular and megafossil assessments. Modern species alone are inadequate to phylogenetic reconstruction of the genus.