The evolutionary history of the embiotocid surfperch radiation based on genome-wide RAD sequence data

- RAD seq data yields robust phylogenetic inference for Embiotocidae (surfperches).
- Inferred topology suggests family wide taxonomic revisions.
- Clades partitioned strongly with habitat, supporting adaptive radiation.
- Recent evolution of kelp forest in the North Pacific likely contributed to surfperch diversification.

The radiation of surfperches (Embiotocidae) in the temperate North Pacific has been suggested to be the product of ecological competition and niche partitioning. Surfperches are a family of viviparous marine fishes, which have been used to study multiple paternity, sperm competition, and population genetics. Phylogenetic inference is essential for interpreting the evolutionary context of embiotocid life history traits and testing alternative scenarios, yet previous studies have yielded phylogenies with low support and incongruent topologies. Here we constructed reduced representation genomic libraries using restriction-site associated DNA (RAD) sequence markers to infer phylogenetic relationships among all genera and 22 out of 24 embiotocid species. Orthologous markers retained across 91% of sampled species, corresponding to 523 loci, yielded trees with the highest support values. Our results support a scenario where embiotocids first diverged into clades associated with sandy and reef habitats during the middle Miocene (13-18 Mya) with subsequent invasions of novel habitats in the reef associated clade, and northern range expansion in the Northwest Pacific. The appearance of California kelp forests (Laminariales) in the late Miocene (8-15 Mya) correlates with further proliferation in the reef associated clade. In all cases, radiations occurred within specific habitats, a pattern consistent with niche partitioning. We infer fine scale species relationships among surfperches with confidence and corroborate the utility of RAD data for phylogenetic inference in young lineages.