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Photo: Two male guppies from Venezuela showing the effect of the many colouration genes associated with sexual selection and sex chromosomes in these species.

Choosey female guppies select for more colourful males with bigger Y chromosomes 

The motivationHumans (and most mammals) have a small Y chromosome; as a poor cousin to the others, it carries the gene that turns on maleness, but has very few other functional genes.  For almost 100 years, evolutionary biologists have thought they had answers to the question of how the evolution of such diminutive Y chromosomes with few functional genes comes about.  For most species, however, sex chromosomes evolved a long time ago, and thus it is difficult to test ideas of how sex chromosomes evolve.

The discovery – The Breden group at SFU, along with an international team of researchers, have worked with guppy populations to show that guppy sex chromosomes have evolved very recently.  They used this finding to show that when sexual selection and female choice is very important, the guppy Y chromosome expands and probably contains more functional genes, just as would be predicted by the models for the evolution of sex chromosomes.  This is one of the first studies to confirm these ideas on how sex chromosomes evolved in natural populations.

Its significance – This work promises to help us to understand the molecular mechanisms underlying differentiation in males or females and how these mechanisms have evolved.  Such insights can help us understand the control of gender and all of the disease syndromes associated with sex and sex determination.

Read the paper“Convergent recombination suppression suggests role of sexual selection in guppy sex chromosome formation” by Alison E. Wright, Iulia Darolti, Natasha I. Bloch, Vicencio Oostra, Ben Sandkam, Severine D. Buechel, Niclas Kolm, Felix Breden, Beatriz Vicoso & Judith E. Mank. Nature Communications 8:14251 (2017). doi:10.1038/ncomms14251

Website article compiled by Jacqueline Watson with Theresa Kitos