Abstract

The spawning behaviour of male nest guarding sunbleak Leucaspius delineatus, a recent invasive species in southern England, was studied and quantified for the first time. In the absence of physical differences between territorial and nonterritorial males (i.e. colour, size, etc.), the reproductive behaviour of territorial males was analysed and related to reproductive success. The results showed that females preferred highcourting and highly aggressive males. The initial cue in female mate choice, however, was based on courtship, while aggression was the decisive behavioural trait in influencing mate choice, providing a direct signal of physical condition and 'paternal competence'. Some males picked nest sites which were subsequently preferred by other males taking over the nest of a previous male ('communal nest'), with the new territorial male adopting the eggs already present at the nest. It appears that either due to female preference for nests already containing eggs or lower rates of sired egg predation by dilution among unrelated eggs, sunbleak males have adopted the mating strategy of allopaternal care.