Molecular and morphological characterisation of two reproductively isolated species with mirror-image anatomy (Nematoda : Cephalobidae)

Detailed descriptions are given of the amphimictic nematode strains PS1158, PS2052 and PS2160, which are unusual in that they only differ in predomina nt body handedness. Although these strains are morphologically identical in all other respects, published reproductive data and new DNA sequence data of the D2/D3 region of the large subunit rRNA gene show that they do repres ent two separate species. On the basis of comparison with type material, th e left-handed strains PS1158 and PS2160 are identified as Acrobeloides bode nheimeri, and the right-handled strain PS2052 as A. camberenensis, which is re-instated as a valid species. A. bodenheimeri and its relatives exhibit various types of diagnostic and taxonomic problems at species level, and it is shown that D2/D3 sequence data provide an important new diagnostic tool for addressing these problems. Phylogenetic analysis shows that two right- handed parthenogenetic strains identified as A. maximus represent a third s pecies which is more closely related to A. camberenensis than to A. bodenhe imeri.