Molecular phylogeny of the sacoglossa, with a discussion of gain and loss of kleptoplasty in the evolution of the group.

摘要: Sacoglossan sea slugs retain the chloroplasts from food algae in their cells (kleptoplasty) and obtain photosynthetic products, but capability of kleptoplasty differs among species. One evolutionary hypothesis for is that family Volvatellidae ancestral sacoglossan lineage which arose, this based on ambiguous phylogenetic relationships. To test hypothesis, we analyzed phylogeny concat- enated sequences (approximately 4000 bp) nuclear (18S rRNA) mitochondrial (CO1, trnV, 16S genes 18 species, using neighbor-joining, maximum parsimony, likelihood, Bayesian methods. The resultant trees clearly revealed monophyly order Sacoglossa (including debatable genus Cylindrobulla), contained two sister clades: shelled group (Oxynoacea Cylindro- bulla) non-shelled (Plakobranchacea). was a derived position within Oxynoacea. most parsimonious rearrangement character states tree suggested (1) acquired at basal Cylindrobulla) as non-functional kleptoplasty, (2) functional gained Plakobranchacea clade, (3) lost Oxynoacea clade.