Department of Biology, Duke University, Durham, North Carolina 27708-0338 USA.
Am J Bot. 2005 Nov;92(11):1774-83. doi: 10.3732/ajb.92.11.1774.
Species are the most common currency by which biodiversity is measured, but species are not equivalent in "biodiversity value" because of differences in phylogenetic history and current population processes. Morphologically defined species in Sphagnum section Acutifolia (Bryophyta) were compared with regard to how phylogenetically distinct each is from its sister species and how much nucleotide variation each encompasses. Comparisons were based on sequence variation at seven nuclear and chloroplast loci. Assignment of collections to morphospecies accounted for about 57-75% of the overall nucleotide variation at the seven loci, but morphospecies differed greatly in how much nucleotide diversity they encompass. In addition, morphospecies varied widely in their genetic distinctiveness, estimated as the length of the stem branch from the most recent common ancestor and numbers of differentially fixed and shared polymorphic nucleotides among taxa. Levels of molecular diversity within morphospecies were not correlated with their degree of isolation. Factors that affected the biodiversity value of species include age, mode of origin, demographic history, and reproductive biology.
物种是衡量生物多样性最常用的单位，但由于系统发育历史和当前种群过程的差异，物种在“生物多样性价值”上并不等同。本文比较了石松科 Acutifolia （苔藓植物）形态定义的物种，从每个物种与其姊妹种的系统发育差异程度以及每个物种包含的核苷酸变异程度两个方面进行比较。比较是基于七个核和叶绿体基因座的序列变异。基于形态种的收集物分配占七个基因座的总核苷酸变异的约 57-75％，但形态种在包含的核苷酸多样性方面差异很大。此外，形态种在遗传独特性方面差异很大，估计为从最近共同祖先的茎分支长度以及分类群之间不同固定和共享的多态核苷酸数量。形态种内的分子多样性水平与它们的隔离程度无关。影响物种生物多样性价值的因素包括年龄、起源模式、种群历史和繁殖生物学。
