Sympatric speciation by sexual selection alone is unlikely

Area of Science:

• Evolutionary Biology
• Speciation Research

Background:

• Sympatric speciation, the evolution of new species from a single ancestral species while inhabiting the same geographic region, is traditionally attributed to disruptive natural selection.
• Recent hypotheses suggest disruptive sexual selection may also drive sympatric speciation, particularly in species like African cichlids with distinct mate choice behaviors.

Purpose of the Study:

• To investigate the conditions under which disruptive sexual selection can lead to sympatric speciation using theoretical models.
• To compare the potential of extreme-phenotype preference versus similarity-based preference in driving sympatric speciation.

Main Methods:

• Utilized hypergeometric phenotypic and individual-based genotypic models to simulate sympatric speciation.
• Explored a wide range of conditions, focusing on the genetic architecture of preference and display traits.

Main Results:

• Sympatric speciation via extreme-phenotype preference requires strong sexual selection and symmetric initial trait distributions; otherwise, genetic variability is lost.
• Similarity-based female preferences, which do not impose strong sexual selection, are less disruptive and can facilitate sympatric speciation under broader conditions.
• The genetic basis of reproductive isolation, involving multiple loci, influences the likelihood of speciation.

Conclusions:

• Female preferences for extreme male phenotypes are unlikely to drive sympatric speciation unless genetic variation is limited to very few loci.
• Similarity-based mate choice presents a more robust mechanism for sympatric speciation across diverse initial conditions.
• Disruptive natural selection remains a more probable driver for the evolution of reproductive isolation in species like African cichlids, given their complex genetic basis for mate choice.