Differences among reciprocal hybrids of Labeotropheus

Area of Science:

• Evolutionary biology
• Ichthyology
• Genetics

Background:

• Hybridization is thought to be key in the early evolution of African cichlid species flocks.
• However, evidence for hybridization in extant cichlid populations is limited, suggesting it is rare today.
• This rarity may be due to natural or sexual selection against F1 hybrids.

Purpose of the Study:

• To investigate reciprocal hybridization between two sympatric cichlid species from Lake Malaŵi: *Labeotropheus fuelleborni* and *L. trewavasae*.
• To compare the body shape and coloration of reciprocal hybrid males.
• To assess the mate choice success of hybrid males in inter- and intrasexual interactions.

Main Methods:

• Performing reciprocal crosses between *L. fuelleborni* and *L. trewavasae*.
• Morphological and chromatic analysis of hybrid males.
• Conducting mate choice experiments to evaluate inter- and intrasexual interactions of hybrids.

Main Results:

• *L. trewavasae*-sired hybrid males exhibited intermediate morphology and coloration compared to parental species.
• *L. fuelleborni*-sired hybrid males displayed transgressive traits.
• Transgressive hybrid males performed poorly in mate choice experiments, being rejected by female *L. trewavasae*.

Conclusions:

• Selection against transgressive F1 hybrids may explain the rarity of contemporary hybridization in Lake Malaŵi cichlids.
• Reciprocal hybridization studies are crucial for a comprehensive understanding of hybrid fitness and evolutionary dynamics.
• The findings contribute to understanding the role of hybridization in cichlid diversification and speciation.