Mate choice and hybridization in Lake Malawi cichlids, Sciaenochromis fryeri and Cynotilapia afra

Lake Malawi is home to hundreds of cichlid species, most of which are endemic to the lake. Several of these species exhibit a remarkably similar behavioural repertoire including territorial and reproductive behaviours. Despite their diverse anatomy and body colouration, hybridization among Malawi cichlids has been observed in captivity and has also been reported to occur in nature. Here, possible factors underlying hybridization between two species, Sciaenochromis fryeri, a large piscivore, and Cynotilapia afra (Jalo reef), a small planktivore biocover grazer, were investigated in captivity. In a series of experiments the size of the territory, the size of the males and the availability of conspecific mates were manipulated. It was found that mate selection in these two species under semi-natural conditions is dependent not only upon species-specific cues but also upon the status of the male. Larger male body size and larger territory size was generally preferred by females and when these attributes characterized a heterospecific male they also increased the probability of heterospecific courtship. Given that spawning between the above-mentioned species resulted in fertile offspring and that their geographical location and habitat overlap in nature, the effect of their mate-choice strategies on hybridization and speciation is considered.