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. 2008 Jul;159(3):339-53.
doi: 10.1016/j.protis.2008.04.001. Epub 2008 Jun 9.

Molecular systematics and the diatom species

Andrew J Alverson

Molecular systematics and the diatom species

Andrew J Alverson. Protist. 2008 Jul.
No abstract available

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Figures

Figure 1
Figure 1
Conflicting evidence from two loci (M and N) about the monophyly of two species (A and B). In this example, each species has two different alleles (1 and 2) per locus. M and N might represent two unlinked autosomal loci, or one autosomal (N) and one organelle locus (M). In most cases, mitochondrial and chloroplast loci (e.g., M) will coalesce sooner than nuclear loci (e.g., N), which has important consequences for species delimitation from gene phylogenies. In this example, species A retains a single ancestral allelic lineage for both M and N, with all of the polymorphisms coalescing to a point that postdates the speciation event (marked by arrowheads). As a result, species A is monophyletic in both gene trees. The same scenario applies to the M locus for species B (also marked by arrowhead). Species B, however, retains two ancestral allelic lineages for N, one of which (NB1) shares a more recent common ancestor with alleles from species A (marked by a star). As a result, species B is paraphyletic in the N gene tree. Note that if allele NB1 was not sampled, species B would appear genetically distinct in both M and N gene trees. Figure concept adapted from Wendel and Doyle (1998) and Felsenstein (2004).
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References

    1. Alvarez I, Wendel JF. Ribosomal ITS sequences and plant phylogenetic inference. Mol Phylogenet Evol. 2003;29:417–434. - PubMed
    1. Alverson AJ. Strong purifying selection in the silicon transporters of marine and freshwater diatoms. Limnol Oceanogr. 2007;52:1420–1429.
    1. Alverson AJ, Kolnick L. Intragenomic nucleotide polymorphism among small subunit (18S) rDNA paralogs in the diatom genus Skeletonema (Bacillariophyta) J Phycol. 2005;41:1248–1257.
    1. Alverson AJ, Theriot EC. Comments on recent progress toward reconstructing the diatom phylogeny. J Nanosci Nanotechnol. 2005;5:57–62. - PubMed
    1. Alverson AJ, Cannone JJ, Gutell RR, Theriot EC. The evolution of elongate shape in diatoms. J Phycol. 2006;42:655–668.

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