Abstract
The decorator worm Diopatra cuprea Bosc, 1802 (Annelid; Polycheate; Onuphidae) is an ecosystem engineer within high-salinity estuaries of the southern and eastern United States. A previous study revealed five relatively deep mitochondrial lineages across its wide geographic distribution. Here, we explore geographic distribution and mitonuclear concordance of these mitochondrial lineages with single nucleotide polymorphisms (SNPs) genotyped using RADseq. We genotyped 3,162 SNPs from 233 D. cuprea and detected four deep lineages in the nuclear genome: a northern US clade (Massachusetts), a single nuclear clade within mid-Atlantic populations (i.e., Virginia south through northeastern Florida), a southeastern Florida clade and a Gulf of Mexico clade. There was mitonuclear concordance within most individuals, with the notable exception of two mitochondrial clades within a single mid-Atlantic nuclear clade. Thus, there appear to be four cryptic lineages of D. cuprea that suggest four distinct species that rarely hybridize. Within the mid-Atlantic lineage, we detected increasing genetic isolation of populations with increasing geographic distance, a pattern consistent with low dispersal of D. cuprea larvae. Cryptic diversity within the D. cuprea complex is consistent with other common and geographically widespread annelid and Diopatra species that are now being revealed using high-throughput sequencing.