Ontogenetic divergence generates novel phenotypes in hybrid cichlids

Area of Science:

• Evolutionary biology
• Ichthyology
• Ecomorphology

Background:

• Hybridization is a key driver of evolutionary diversification in lacustrine East African cichlids.
• Hybridization influences genetic diversity and phenotypic differentiation in closely related species.
• Little is known about how hybrid ontogeny establishes trait differentiation related to trophic and locomotor specializations.

Purpose of the Study:

• To compare body shape ontogeny in a Lake Victoria cichlid hybrid with its parental species.
• To investigate the emergence of transgressive traits and their relation to functional specializations during hybrid development.

Main Methods:

• Comparative analysis of body shape changes throughout post-hatch ontogeny.
• Between-group principal component analysis (PCA) on body shapes across size categories.

Main Results:

• Hybrids occupy a distinct, intermediate morphological space with transgressive traits.
• Unique axes of shape variation, exclusive to hybrids, were identified in early developmental stages.
• Hybrid shape differences involve traits linked to trophic and locomotor specializations in parental species.

Conclusions:

• Phenotypic divergence in hybrids can lead to functional differences, potentially reducing competition with parental species.
• Hybridization may play a significant role in the rapid diversification of the Lake Victoria cichlid species flock.