Genetic adaptation to polyploidy in animals: a case study in Australian burrowing frogs Neobatrachus

Whole-genome duplication can be adaptive in the long term but in the short term can impair chromosome segregation and fertility, obstacles polyploids must overcome to regain fitness. To investigate how animals adapt to polyploidy, we focused on Australian burrowing frogs (genus Neobatrachus), three species of which are polyploid: N. aquilonius, N. kunapalari and N. sudellae. We assembled a reference genome for diploid N. pictus and sequenced 96 individuals from all nine Neobatrachus species, finding tetraploid-specific selection on genes with meiotic roles in synaptonemal complex and crossover distribution (SYCE2, PRR19), or chromosome and spindle size (Condensin-2, KifC1). These changes may represent a genetic adaptation in vertebrate polyploids with tetrasomic and mixed inheritance that raises crossover interference and scales chromosome and spindle size to ensure successful chromosomal segregation. Finally, we show that adaptive alleles are shared between the tetraploids via interspecific introgression.