Rapid turnover of sex chromosomes is associated with speciation in Neotropical armored catfish Harttia (Siluriformes, Loricariidae)

The genus Harttia represents an important repository of multiple sex chromosomes, as they are found in more than a quarter of its valid species with distinct degrees of heteromorphism. We demonstrate that the recent and independent emergence of two distinct multiple sex chromosome systems (X1X2Y and XY1Y2) is associated with accelerated speciation rates. Using DArTseq data from 17 Harttia species, we investigate the sex chromosomes evolution and potential role in diversification. A time-calibrated phylogeny revealed main divergences occurring from 6 to 10 Mya, coinciding with Amazon River formation and other core river capture events in South America. Reconstruction of ancestral states (areas and chromosome number), combined with the identification of sex-linked markers, suggests the ancestor carried a karyotype of 2n=58 and homomorphic XY, occupying either the South and Southeast Atlantic drainages or the Eastern Amazon. These findings underscore the potential contribution of multiple sex chromosomes and turnovers in accelerating speciation.