Data from: Territorial males can sire more offspring in nests with smaller doors in the cichlid Lamprologus lemairii

To examine how territorial males counter reproductive parasites, we examined the paternity of broods guarded by territorial males using microsatellites and factors that determine siring success in a wild population of the Lake Tanganyika cichlid Lamprologus lemairii. Females enter rock holes (nests) and spawn inside, and territorial males release milt over the nest openings. Sneakers attempt to dart into the nests, but territorial males often interrupt the attempt. The body size of territorial males (territorial defence ability) and the size of nest opening (the ability to prevent sneakers from nest intrusions) are predicted to be factors that affect paternity at the pre-mating stage, while milt quality traits are factors that affect paternity at the post-mating stage. Parentage analyses revealed that most clutches have few or no cuckolders, and territorial males sired >80% of eggs in 7 of the 10 analysed clutches. Larger territorial males that spawned in nests with narrower openings had greater siring success. In contrast, none of the milt traits affected the siring success. These suggest that territorial male L. lemairii adopt pre-mating strategies whereby they effectively prevent reproductive parasitism.