Genetic diversity of hyperiid amphipods along a meridional transect in the Atlantic Ocean

Detecting plankton community responses to a changing ocean environment requires knowledge of the diversity and distribution of species. Hyperiid amphipods are an important component of pelagic food webs as prey and as commensals and parasitoids of gelatinous zooplankton, but their species and genetic diversity remains incompletely known. Using mitochondrial cytochrome c oxidase subunit 1 (CO1) gene sequences, we assessed the genetic diversity of hyperiids collected along a meridional transect from 39 °N to 45 °S in the Atlantic Ocean in order to evaluate the congruence of genetic clades with morphologically-identified species, examine phylogeographic patterns within broadly-distributed species, and to contribute vouchered DNA barcodes into the public domain. CO1 sequences were obtained from 273 specimens representing 63 morphologically-identified hyperiid species belonging to 34 genera and 16 families, including sequences from 26 species with no prior reports in publicly-available databases. We recovered substantial amounts of genetic variation within nine nominal species, which were composed of two to four clades with 11–36% average sequence divergence between clades (range 10–45%). These are probably distinct or unrecognized biological species, however, additional sampling of morphological and/or genomic diversity is necessary to confirm this. Additionally, we examined the geographic distribution of genetic variation within Lycaea pulex, Phronimopsis spinifera, Phrosina semilunata, Tryphana malmii, and Vibilia armata, all species with broad or disjunct distributions across the Atlantic Ocean. We found that these species are composed of lineages with apparent geographic specializations to tropical, subtropical or temperate waters, suggesting more restricted biogeographic distributions than described for the inclusive morphospecies. This new collection of CO1 barcodes furthers our understanding of the diversity and distribution of hyperiids in the Atlantic Ocean and will support future research on this ecologically significant plankton group.