Variation in "biodiversity value" of peatmoss species in Sphagnum section Acutifolia

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 accounts for about 57-75% of the overall nucleotide variation at the seven loci (Table 1), but morphospecies differ greatly in how much nucleotide diversity they encompass. In addition, morphospecies vary 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 are not correlated with how isolated they are (Fig. 1). Factors that affect the biodiversity value of species include age, mode of origin, demographic history, and reproductive biology.

Table 1. Partitioning of nucleotide variation among and within morphospecies of Sphagnum section Acutifolia revealed by separate single-gene AMOVAs. * = FST > zero at P < 0.00001.

Reference:

Shaw, A. J. & C. J. Cox. 2005. Variation in "biodiversity value" of peatmoss species in Sphagnum section Acutifolia (Sphagnaceae). American Journal of Botany 92: 1774-1783. reprint

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