The loss of recombination on the Y chromosome is thought to limit the adaptive potential of this unique genomic region. Despite this, we describe an extraordinary case of Y chromosome adaptation in P. parae. This species contains five co-occurring male morphs, all of which are Y-linked, and which differ in reproductive strategy, body size, coloration, and mating behaviour. The five Y-linked male morphs of P. parae evolved after recombination was halted on the Y, resulting in five unique Y chromosomes within one species.
Our results reveal the surprising magnitude to which non-recombining regions can generate adaptive diversity and have important implications for the evolution of sex chromosomes and the genetic control of sex-linked diversity.
