Abstract
BackgroundPhenotypic plasticity, as a phenotypic response induced by the environment, has been proposed as a key factor in the evolutionary history of corals. A significant number of octocoral species show high phenotypic variation, exhibiting a strong overlap in intra- and inter-specific morphologic variation. This is the case of the gorgonian octocoral Antillogorgia bipinnata (Verrill 1864), which shows three polyphyletic morphotypes along a bathymetric gradient. This research tested the phenotypic plasticity of modular traits in A. bipinnata with a reciprocal transplant experiment involving 256 explants from two morphotypes in two locations and at two depths. Vertical and horizontal length and number of new branches were compared 13 weeks following transplant. The data were analysed with a linear mixed-effects model and a graphic approach by reaction norms.ResultsAt the end of the experiment, 91.8% of explants survived. Lower vertical and horizontal growth rates and lower branch promotion were found for deep environments compared to shallow environments. The overall variation behaved similarly to the performance of native transplants. In particular, promotion of new branches showed variance mainly due to a phenotypic plastic effect.ConclusionsGlobally, environmental and genotypic effects explain the variation of the assessed traits. Survival rates besides plastic responses suggest an intermediate scenario between adaptive plasticity and local adaptation that may drive a potential process of adaptive divergence along depth cline in A. bipinnata.
Highlights
Phenotypic plasticity, as a phenotypic response induced by the environment, has been proposed as a key factor in the evolutionary history of corals
Using reciprocal transplants of Seriatopora hystrix, a case of adaptive plasticity was detected in response to light conditions and adaptive divergence along the depth gradient [11, 12]
Sixty one of the initial 256 segments were lost during photo recovery or analysis
Summary
Phenotypic plasticity, as a phenotypic response induced by the environment, has been proposed as a key factor in the evolutionary history of corals. A significant number of octocoral species show high phenotypic variation, exhibiting a strong overlap in intra- and inter-specific morphologic variation This is the case of the gorgonian octocoral Antillogorgia bipinnata (Verrill 1864), which shows three polyphyletic morphotypes along a bathymetric gradient. Reciprocal transplant experiments consist of transferring phenotypic variants to the opposite environments and are a practical and cost-effective approach to testing phenotypic plasticity. One of the first experiments using a common garden approach on corals was done with Orbicella annularis and Siderastrea siderea, in four reef habitats and detected high phenotypic plasticity in response to the transplanted habitat [9]. Using reciprocal transplants of Seriatopora hystrix, a case of adaptive plasticity was detected in response to light conditions and adaptive divergence along the depth gradient [11, 12]
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