Spatial variation in the morphological traits of Pocillopora verrucosa along a depth gradient in Taiwan

Abstract

Pocillopora verrucosa is a widely distributed depth-generalist coral that presents plasticity in its skeletal macro- and microstructure in response to environmental gradients. Light and water movement, which covary with depth, are the main environmental drivers of morphological plasticity in this genus; however, assessing environmentally-induced plasticity may be confounded by the extent of interspecific variation in Pocillopora. We examine the morphology of 8 typed P. verrucosa specimens collected along a depth gradient ranging from 7 to 45 meters and comprising 3 sites throughout Ludao, Taiwan. We measured 36 morphological characters, 14 which are novel, in 3 regions on the corallum—the apex, branch and base—in order to quantify their relationship to site and depth. We found significant correlation between depth and 19 morphological characters, notably branch verruca area, branch verruca height, base verruca spacing, base spinule length, and branch corallite area. 60% of microstructural characters and 25% of macrostructural characters showed a correlative relation to depth, suggesting that depth acclimatization is manifested primarily at the microstructural level. Canonical discriminant analysis of all morphometric characters by depth supports clustering into 3 groups: an overlapping 7m and 15m group, a 23-30m group, and a 38-45m group. Canonical discriminant analysis by site supports clustering into low- and high-current sites, differentiated primarily by branch septa width, base septa width, pre-terminal branch width, terminal branch maximum length, and terminal branch minimum length. We conclude that distinctive patterns of morphological variation in mesophotic specimens of P. verrucosa could reflect the effects of abiotic parameters such as light and water flow. Elucidating the mechanisms behind the morphological changes that occur in response to environmental gradients can help clarify the role that physiological plasticity plays in the acclimatization of corals to the unique environmental settings of mesophotic coral ecosystems.

Living on the edge: Assessing the diversity of South African Pocillopora on the margins of the Southwestern Indian Ocean

“…Thus, species assessment using the ORF marker was appropriate for delineation in South African Pocillopora and demonstrates the efficacy of this marker and suggests its use as a principal barcode marker. This data also corroborates and illustrates the reproducibility of our methods developed and employed by many studies over different regions [3,4,7,10,13,30,32–34,37].…”

“…Some studies [4,5,9] avoided primary morphometric species delineation and focussed on applying contemporary genetic algorithms without a priori species designations. These approaches have identified new cryptic lineages from different global biogeographic ocean provinces and linked conspecifics, primarily identified and grouped by morphology [3,7,9–13], though most of these studies were undertaken in isolation. In addition, the fast-paced identification and proposal of new species, the revival of junior synonyms and possible splitting of regional conspecifics, have all contributed to the knowledge about Pocillopora lineages and diversification.…”

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

“…However, facing a large spectrum of morphological variations at both the intra- and inter-species level, various studies have hypothesized that the actual number of species in this taxon could be overestimated ( Veron & Pichon, 1976 ; Veron, 2013 ). For example, Pocillopora colonies may display morphology corresponding to other ecomorphs when transplanted into different environmental conditions ( Lesser et al, 1994 ; Hoogenboom, Connolly & Anthony, 2008 ; Prada, Schizas & Yoshioka, 2008 ; Todd, 2008 ; Paz-García et al, 2015 ) or exhibit morphological plasticity along a depth gradient ( Soto et al, 2018 ). In the last decade, 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 ).…”

Phenotypic variation in two widespread Caribbean corals —Porites astreoidesandP. divaricata— between mangrove and lagoon habitats

“…One way to investigate how environmental variation affects coral phenotypes is to compare the same coral species across an environmental gradient. For example, in reef habitats, differences in depth (and associated differences in light and flow) have been shown to drive differences in microskeletal anatomy (Ow & Todd 2010, Soto et al 2018 and color (Gleason 1993). Presumably, this intraspecific variation is advantageous because a generalist that can live in a wide range of depths is at an advantage over a specialist that can only occur in a narrow range of depths.…”

“…Given that mangrove and lagoon habitats differ in key environmental parameters including temperature and light, we hypothesized that colonies from the two study locations would exhibit consistent and predictable differences in phenotype. Specifically, we expected that corals in the mangrove sites would exhibit traits associated with lower light levels, such as darker coloration (Gleason 1993) and distinct corallite architecture (Ow & Todd 2010, Soto et al 2018. We also expected colony morphology to differ because in the mangroves, colonies are attached to an approximately vertical substrate (prop roots of the red mangrove, Rhizophora mangle), while in the lagoon colonies are attached to an approximately horizontal substrate.…”