Aim: Many mudskippers in the family Gobiidae are obligately amphibious, requiring both aquatic and terrestrial portions of their life cycle. The terrestrial phase involves restrictions to mudflat habitats during breeding, when adults build burrows in the mud to lay eggs. The effects of this restricted out-of-water phase might be reflected in the population structure of the species. However, dispersal during the aquatic larval phase could connect distant populations. We examine one such mudskipper, Periophthalmus modestus, to test whether populations separated by water are more differentiated than those connected along a coastline.

Location: South and East China Sea

Taxon: Periophthalmus modestus (family: Gobiidae, subfamily: Oxudercinae) (Cantor 1842)

Methods: We collected 236 individuals from ten locations around the East and South China Seas. We used a targeted capture sequencing method, RADcap, to call SNPs from 365 loci. We used multiple spatial and population genetics analyses and coalescent models to address the contemporary and historic biogeography of the species.

Results: Based on observed levels of genetic variation and population structure, populations of Ps. modestus are connected across large distances of continuous coastline and small spans of water. Restricted long-distance dispersal across deep water has resulted in fragmentation of populations. We recovered no signal of isolation by distance, but instead, found genetic differentiation associated with regional groupings separated by large expanses of water.

Main conclusions: These results are consistent with the hypothesis that a limited dispersal phase significantly affects population structure in fishes. The restrictive amphibious life history may be a key factor in the present-day distribution and population structure of Ps. modestus. Interactions between organismal life history and geography are critical for explaining the population genetic structure of a species.