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.
Highlights
Scleractinian coral species identification is traditionally based on the classification of coral skeletal features, colony macro-morphology and corallite micro-structureHow to cite this article De Palmas et al (2018), Molecular assessment of Pocillopora verrucosa (Scleractinia; Pocilloporidae) distribution along a depth gradient in Ludao, Taiwan
The hist 3 Polymerase Chain Reaction (PCR)–restriction fragment length polymorphism (RFLP) revealed that all 15 samples (H1 and H2) belong to P. meandrina (Fig. S1)
As highlighted in previous studies, our results demonstrate the limitations of using morphology alone to identify Pocillopora in the field (Flot et al, 2008; Pinzón et al, 2013; Schmidt-Roach et al, 2012, 2014; Johnston, Forsman & Toonen, 2018) and emphasize the relevance of molecular taxonomy in supporting studies on the biology and ecology of Pocillopora species
Summary
Scleractinian coral species identification is traditionally based on the classification of coral skeletal features, colony macro-morphology and corallite micro-structureHow to cite this article De Palmas et al (2018), Molecular assessment of Pocillopora verrucosa (Scleractinia; Pocilloporidae) distribution along a depth gradient in Ludao, Taiwan. Some scleractinian species can exhibit environmentally correlated variations in morphology, i.e., ecomorphs (Veron & Pichon, 1976), which often makes species identification a challenge (Todd, 2008; Veron, 2013) This problem is exacerbated when attempting to identify coral species directly in the field; it highlights the need to redefine species boundaries in light of molecular approaches. A growing body of literature has focused on resolving the taxonomy of Pocillopora by assessing morphological traits in conjunction with genetic markers (Flot et al, 2008; Pinzón & LaJeunesse, 2011; Pinzón et al, 2013; Schmidt-Roach et al, 2012, 2014; Marti-Puig et al, 2014) These studies have identified the mitochondrial open reading frame (mtORF) as an efficient marker for delineating Pocillopora species. The mtORF marker has been recently used by Johnston et al (2017) in conjunction with a genus-wide genomic comparison of Pocillopora, which confirmed it as a suitable and fast tool for delineating most Pocillopora species
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