Morphological plasticity in scleractinian corals

Abstract

When describing coral shape and form the term phenotypic plasticity, i.e. environment-induced changes in morphology, is often used synonymously with intraspecific variation. Variation, however, may simply be due to genetic differentiation (polymorphism). Of the 1314 extant scleractinian coral species, less than 20 have been tested for plastic responses. Morphological plasticity has important implications for coral identification, as skeletal features used in coral systematics are directly affected by environment. Furthermore, plastic changes can indicate how corals acclimatise to environmental change. The studies that have examined phenotypic plasticity in corals experimentally can be divided into two groups, i.e. 'non-clonal'-those that have transplanted whole colonies or fragments of colonies (but not treated the fragments as clones) to new environments, and 'clonal'-those that have transplanted colony fragments and used them as clone-mates. The use of clone-mates is preferable as it facilitates the identification of among-genotype variation for plasticity. The heterogeneous nature of the reef environment makes identifying the parameters that affect coral morphology difficult in the field, but there are also many problems conducting suitable aquarium experiments. Nevertheless, evidence to date suggests light and water movement are the most important variables inducing change. As these factors are known to be axiomatic to coral growth, it is possible that associated plastic changes in corals are adaptive; however, this hypothesis is yet to be tested rigorously

Calcium Carbonate Production, Coral Cover and Diversity along a Distance Gradient from Stone Town: A Case Study from Zanzibar, Tanzania

“…We suspect that this coral species is highly resilient and therefore dominant in the reefs close to Stone Town. Presumably, corals adjust their skeletal shape to the main constraining environmental factors that control morphological specialization in corals, e.g., light intensity, water movement and sedimentation rates (Todd, 2008). Furthermore, our findings suggest that this mechanism drives beta diversity in our study sites as we found small scale (colony level) differences in the morphological strategies among sites (Figure 3).…”

“…All study sites are protected from swells (Shaghude et al, 2002) and tides have an equal effect on all the study sites. Tidal-induced currents although energetic (5 to 20 cm s −1 ), would not mechanically break corals, in contrast to wave-exposed coral reefs (Todd, 2008).…”

“…A number of physical parameters, such as wave exposure, currents and temperature, affect the development of coral reefs, its biodiversity (Roberts et al, 2002) and reef morphology (Mallela et al, 2004;Webb and Kench, 2010;Perry et al, 2013). For instance, platy coral morphologies are more successful on deep fore reef sites, due to their ability to harvest light (Todd, 2008), whereas more robust, boulder corals are generally found in the reef crest under moderate to high hydrodynamic regimes (Storlazzi et al, 2002).…”

The New Systematics of Scleractinia: Integrating Molecular and Morphological Evidence

“…As they are sessile or have restricted capacity for movement (e.g., free-living and/or solitary), corals are subjected to the environmental conditions at their place of settlement. Consequently, they exhibit considerable morphological plasticity, driven in part by various ecological factors (Foster 1979a(Foster , b, 1980Best et al 1984;Hoeksema 1991;Budd 1993;Todd 2008). According to Lowenstein (1985), taxonomic research based exclusively on morphology is plagued by two major limitations.…”

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“…Moreover, our work 395 suggests that surface area and volume, as well as the ratios between these variables 396 and PL TSA, are potential candidates as useful traits. This shift in focus would also 397 address the fact that corals can exhibit a high degree of morphological plasticity 398 within species (Todd 2008), with colonies of the same species fulfilling different 399 categories of morphotype. This level of plasticity suggests that when our equations 400 are used in the future they should be applied based on the morphotype observed in the 401 field, rather than one that is based on species identification.…”