Female control of paternity in the internally fertilizing compound ascidian Diplosoma listerianum .2. Investigation of male mating success using RAPD markers

Randomly amplified polymorphic DNA paternity markers were used to assess male success during simultaneous, three-way mating opportunities between cultured clones of the hermaphroditic protochordate Diplosoma listerianum. The previously reported blockage of sperm movement in the oviduct, barring access to the site of fertilization in the ovary, was shown to prevent cross-fertilization between two particular clones. The same mechanism prevents selfing. Direct observation of pairings within a more extensive set of laboratory clones derived from the same natural population indicated that failure of one or both partners of a pair to produce brooded progeny was relatively common. A weak negative correlation was found between the mating success of pairs and their overall genetic similarity estimated from RAPD fingerprints from several primers. The data suggest the operation of a somatic-gametic incompatibility mechanism regulating mating in D. listerianum. This may involve differential phagocytic removal, in the oviduct, of sperm that share self-recognition markers with maternal tissue.