Gene conversion empowers natural selection in a clonal fish species.

Area of Science:

• Evolutionary Biology
• Genetics
• Molecular Biology

Background:

• Sexual reproduction is evolutionarily ancient and widespread, yet asexual reproduction persists in many species.
• Theory suggests asexual organisms accumulate deleterious mutations and face extinction due to lack of genetic reassortment.
• The Amazon molly (Poecilia formosa) is a long-existing asexual fish species that challenges these theoretical predictions.

Purpose of the Study:

• To investigate the mechanisms enabling long-term asexual reproduction in the Amazon molly.
• To understand how asexual lineages avoid mutational decay and maintain fitness.
• To explore the role of gene conversion in asexual adaptation and genetic stability.

Main Methods:

• Comparative genomic analysis of the Amazon molly and its sexual progenitor species.
• Investigation of mutation accumulation rates and patterns.
• Analysis of gene conversion activity and its impact on genetic variation.
• Examination of chromatin structure and its relation to asexual reproduction.

Main Results:

• The Amazon molly accumulates mutations at a higher rate than its sexual progenitors but does not exhibit functional mutational decay.
• Gene conversion actively facilitates both adaptive and purifying selection in asexual lineages.
• Gene conversion resolves hybrid incompatibilities and generates new clonal lineages with reverted or fixed mutations.
• Asexual reproduction altered chromatin structure, yet divergent mutational landscapes of progenitor species were maintained.

Conclusions:

• Asexual reproduction in the Amazon molly is supported by gene conversion, which counteracts theoretical predictions of mutational meltdown.
• Gene conversion provides a mechanism for adaptation and purging deleterious mutations in asexual organisms.
• The Amazon molly demonstrates that asexual lineages can overcome genetic challenges, offering new insights into the evolution of reproduction.