Molecular assessment ofPocillopora verrucosa(Scleractinia; Pocilloporidae) distribution along a depth gradient in Ludao, Taiwan

Abstract

It can be challenging to identify scleractinian corals from the genus Pocillopora Lamarck 1816 in the field because of their large range of inter- and intra-specific morphological variation that co-occur with changes in the physical environment. This task is made more arduous in the context of a depth gradient, where light and water current could greatly affect the morphology of the corallum. Pocillopora verrucosa (Ellis & Solander 1786) in Taiwan was previously reported exclusively from shallow waters (<10 m in depth), but a recent observation of this species in the mesophotic zone (>40 m in depth) questions this bathymetric distribution. We used the mitochondrial open reading frame and the histone 3 molecular markers to investigate the vertical and horizontal spatial distribution of P. verrucosa around Ludao (Green Island), Taiwan. We genotyped 101 P. verrucosa-like colonies collected from four depth zones, ranging from 7 to 45 m, at three sites around the island. Of the 101 colonies sampled, 85 were genotyped as P. verrucosa, 15 as P. meandrina, and one specimen as an undescribed Pocillopora species. P. verrucosa was found at all depths, while P. meandrina and the undescribed Pocillopora specimen were limited to 15 m depth. P. verrucosa has a large bathymetric distribution around Ludao and could benefit from the refuge that the mesophotic zone offers. This study illustrates the difficulty of identifying Pocillopora corals in the field and emphasizes the relevance of molecular taxonomy as an important and complementary tool to traditional taxonomy for clarifying vertical and horizontal species distribution. Our results also illustrate the need in conservation biology to target species genetic diversity rather than just species diversity.

The Genome of the Cauliflower Coral Pocillopora verrucosa

“…P. verrucosa is widely distributed and is prevalent in the Red Sea, across the Indian Ocean, and across the Pacific Ocean, up to the Eastern Tropical Pacific, colonizing an extensive range of depths that cover shallow to mesophotic settings ( Schmidt-Roach et al. 2014 ; De Palmas et al. 2018 ; Soto et al.…”

Strong horizontal and vertical connectivity in the coral Pocillopora verrucosa from Ludao, Taiwan, a small oceanic island

“…Effective ecological connectivity between shallow and deep zonations is achieved under three prerequisite criteria: 1) suitable habitats supporting robust populations, 2) habitats that are physically connected via water or propagule movements, and 3) organisms with life-history traits that enable successful replenishment of both their own populations and those connected to them [ 45 ]. In Ludao, Denis et al [ 48 ] and De Palmas et al [ 50 ] reported that P . verrucosa is one of the dominant species found across the depth gradient.…”

“…Eighty-five colonies originating from three depth ranges—Shallow (7–15 m, hereafter “S”), Mid-depth (23–30 m, hereafter “M”), and Deep (38–45 m, hereafter “D”)—were previously confirmed to be Pocillopora verrucosa by mtORF sequencing [ 50 ]. Nine locations were defined accordingly: Gongguan S, Gongguan M, Gongguan D, Guiwan S, Guiwan M, Guiwan D, Dabaisha S, Dabaisha M, and Dabaisha D. Locations are separated by vertical distances (i.e., depth) and horizontal distances (i.e., perpendicular to the depth axis) so that the frontal distances between locations from the same site are < 100 m.…”

“…DNA extraction process followed De Palmas et al [ 50 ]. Additionally, DNA extracts were purified and concentrated using a sodium acetate (3M, pH 5) precipitation method.…”

“…Along the bathymetric gradient, Pocillopora verrucosa is one of the most dominant scleractinian hard corals, distributed from the near-surface to as deep as 55 m [ 48 ]. Despite variation in corallum micro and macro morphologies with depth [ 49 ], sequencing of the mitochondrial Open Reading Frame marker (mtORF, from a gene with unknown function) has confirmed this species’ distribution across a large bathymetric gradient in Ludao [ 50 ]. Several microsatellite markers (also called Simple Sequence Repeats, SSRs) have been developed for Pocillopora species [ 51 – 54 ] and were used to investigate species diversity and population connectivity across their biogeographic distribution [ 55 – 58 ].…”