Monday, July 23, 2012

Charles Darwin's unpublished tree sketches, Part 3

In two previous blog posts I discussed those unpublished tree sketches housed among Charles Darwin's manuscript notes (Part 1) and those contained in his letters (Part 2). In this new post I point out that there is technically one other "unpublished" empirical phylogenetic tree.

In his Monograph on the Sub-class Cirripedia, published in two volumes (1851 and 1854) by the Ray Society, Darwin provided a comprehensive taxonomic revision and classification of the known species of barnacles. Since he had already developed his ideas about evolution, and the relationship between taxonomy and phylogeny, when he conducted the barnacle work, it has been assumed that the classification was produced within a modern phylogenetic context. So, when Darwin makes explicit comments in the Monograph about the relationships between the barnacle taxa it has been assumed that this refers to phylogenetic relationships. However, Darwin never published an explicit phylogenetic tree of this, or any other, taxonomic group.

Nevertheless, in 1973 Michael Ghiselin and Linda Jaffe did attempt to uncover Darwin's implicit phylogeny of the barnacles (Phylogenetic classification in Darwin's monograph on the sub-class Cirripedia. Systematic Zoology 22: 132-140). This was done by constructing the tree based on Darwin's written descriptions of relationships (ie. the words were turned into a picture). The resulting picture shows both the phylogeny of the genera and their classification.

This therefore counts as an unpublished empirical tree, but this time contained among Darwin's published works, rather than his notebooks and letters.

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