Nuclear sequences reveal mid‐range isolation of an imperilled deep‐water coral population

Abstract

The mitochondrial DNA of corals and their anthozoan kin evolves slowly, with substitution rates about two orders of magnitude lower than in typical bilateral animals. This has impeded the delineation of closely related species and isolated populations in corals, compounding problems caused by high morphological plasticity. Here we characterize rates of divergence and levels of variation for three nuclear gene regions, then use these nuclear sequences as markers to test for population structure in Oculina, a taxonomically confused genus of corals. Rates of sequence divergence (obtained by comparison to Solenastrea hyades) were at least five (and sometimes over 10) times faster for the three nuclear markers than for a mitochondrial reference sequence. Nuclear sequence variation was also high within populations, although it tended to decline north of Cape Canaveral. Significant subdivision was evident among samples from 10 locations from between North Carolina and the Florida Panhandle, but neither nominal species designation nor population depth explained much of this variation. Instead, a single population from the unique deep (> 70 m) water reefs at the Oculina Banks off central Florida was a strong genetic outlier: all pairwise measures of subdivision involving this population were greater than those involving all other populations, and multilocus clustering recognized the Oculina Banks as distinct from other populations, despite its close proximity (< or = 36 km) to populations from shallower waters nearby and its location at the centre of the sampled range. Genetic isolation of the Oculina Banks population suggests that focused efforts will be needed to conserve the foundation species of these monotypic reefs and that depth may play a role in isolating marine populations and perhaps facilitating initial steps towards speciation.

Morphological variation and different branch modularity across contrasting flow conditions in dominant Pocillopora reef-building corals

“…Incongruence between morphology and genetics has been reported in a number of Pocillopora (Flot et al 2010;Pinzón and LaJeunesse 2011;Forsman et al 2013) and other scleractinian corals (Eytan et al 2009;Stat et al 2012), while mitochondrial lineages have been found to coincide with some eco-morphs of P. damicornis and with corallite features (Souter 2010;Schmidt-Roach et al 2013;Marti-Puig et al 2014). These results emphasize the need to use molecular markers in combination with morphological analysis to understand morphological variation in genetic lineages in each region.…”

Possible involvement of Tachylectin-2-like lectin from Acropora tenuis in the process of Symbiodinium acquisition

“…Tachylectin-2 homologues have been found in the corals Montastrea feveolata, Oculina diffusa, O. robusta, O. varicosa, Acropora palmata, A. digitifera, and A. millepora [57][58][59][60], but the function of Tachylectin-2 homologues in corals remains unknown. Our study revealed that AtTL-2, a Tachylectin-2 homologue, plays a role in the acquisition of Symbiodinium.…”

Genetic discontinuity among regional populations of Lophelia pertusa in the North Atlantic Ocean

“…Due to climatically driven changes in sea levels and temperature during the last glacial maximum, the GOM and Atlantic marine faunas have a complex history structured by repeated episodes of vicariance and dispersal (Avise 1994). These historical vicariant events, along with present-day currents and latitudinal selection gradients, have lead to varying degrees of genetic discontinuities (such as sharp changes in allele frequencies) for many marine organisms in the Cape Canaveral region (reviewed by Avise 1994;Cunningham and Collins 1998;Avise 2000;Eytan et al 2009). Although L. pertusa occurs much deeper than marine taxa with known phylogeographic breaks in the Cape Canaveral region, our data suggest the presence of a transition from GOM to Atlantic genotypes in this same area.…”