Data from: Evolution of the immune system influences speciation rates in teleost fishes

Teleost fishes constitute the most species-rich vertebrate clade and
exhibit extensive genetic and phenotypic variation, including diverse
immune defense strategies. The genomic basis of a particularly aberrant
strategy is exemplified by Atlantic cod, in which a loss of major
histocompatibility complex (MHC) II functionality coincides with a marked
expansion of MHC I genes. Through low-coverage genome sequencing (9–39×),
assembly and comparative analyses for 66 teleost species, we show here
that MHC II is missing in the entire Gadiformes lineage and thus was lost
once in their common ancestor. In contrast, we find that MHC I gene
expansions have occurred multiple times, both inside and outside this
clade. Moreover, we identify an association between high MHC I copy number
and elevated speciation rates using trait-dependent diversification
models. Our results extend current understanding of the plasticity of the
adaptive immune system and suggest an important role for immune-related
genes in animal diversification.