Range-wide population structure of three tropical deepwater Eteline snappers across the Indo-Pacific basin

Deep-sea habitats may drive unique dispersal and demographic patterns for
fishes, but population genetic analyses to address these questions have
rarely been conducted for fishes in these environments. This study
investigates the population structure of three tropical deepwater snappers
of the genus Etelis that reside at 100 – 400 m depth, with broad and
overlapping distributions in the Indo-Pacific. Previous studies showed
little population structure within the Hawaiian Archipelago for two of
these species: Etelis coruscans and E. carbunculus. Here we extend
sampling to the entire geographic range of each species to resolve the
population genetic architecture for these two species, as well as a
recently proposed cryptic species (Etelis sp.). One goal was to determine
whether deepwater snappers are more dispersive than shallow water fishes.
A second goal was to determine whether submesophotic fishes have older,
more stable populations than shallow reef denizens that are subject to
glacial sea-level fluctuations. Both goals are pertinent to management of
these valuable food fishes. A total of 1,153 specimens of E. coruscans
from 15 geographic regions were analyzed, along with 1,064 specimens of E.
carbunculus from 11 regions, and 590 specimens of E. sp. from 16 regions.
The first two species were analyzed with mtDNA and 9 – 11 microsatellite
loci, while E. sp. was analyzed with mtDNA only. Etelis coruscans had a
non-significant microsatellite global FST, but significant global mtDNA
FST= 0.010 (P=0.0007), with isolation of the Seychelles in the western
Indian Ocean, and intermittent signals of isolation for the Hawaiian
Archipelago. Etelis carbunculus had a non-significant microsatellite
global FST, and significant global mtDNA FST= 0.021 (P=0.0001), with low
but significant levels of isolation for Hawaiʻi, and divergence between
Tonga and Fiji. Etelis sp. had mtDNA FST= 0.018 (P=0.0005), with a strong
pattern of isolation for both Seychelles and Tonga. Overall, we observed
low population structure, shallow mtDNA coalescence, and isolation at the
fringes of the Indo-Pacific basin in Hawaiʻi and the western Indian Ocean.
While most shallow water species have population structure on the scale of
biogeographic provinces, deepwater snapper populations are structured on
the wider scale of ocean basins, more similar to pelagic fishes than to
shallow water species. This population structure indicates capacity for
widespread dispersal throughout the Indo-Pacific region.