Molecular analysis using the nuclear 18S and 28S rRNA genes, and the mitochondrial genecytochrome b, is based on 105 samples, including 87 recognized species from 47 genera (53% of living genera 47/88), and encompassing most of the major groups of living Lucinidae from around the world collected from a wide range of habitats at depths from 0 to 2050 m. The analysis includes longer sequences for 18S and 28S genes, and new cytochrome b data for many of the taxa previously analysed by Williams
et al. (2004). DNA extraction and amplification protocols were used to amplify
portions of three genes: the nuclear 18S and 28S rRNA genes, and the mitochondrial gene cytochrome
b (cytb).
The tree derived from 18S rRNA data shows Fimbriata fimbriata and Monitilora ramsayi
(Smith, 1885) form separate branches sister to the rest of the lucinid species that are resolved into two
large clades. One of these clades comprises species of Ctena, Codakia, and Lucinoma, and the second consists of a wide range of mainly shallow water lucinids. Within this latter clade, sequences for species were
highly conserved with little resolution of subclades.
Tree derived from 28S rRNA tree showed similar topology but with higher resolution of the major clades
and their internal structure. Like the 18S tree, there are two major clades of lucinids observed here to but the subclade and generic divisions are better resolved, for example the Codakia, Ctena and Lucinoma subclades. |