This is a set of morphological variants corresponding to the common cauliflower, slowly selected by early farmers during domestication, to create modified inflorescence structures corresponding to multiple varieties, characterized by distinct shapes, colors, geometries, dimensions and even tastes.
Well, this is Pocillopora damicornis sensu Linnaeus, 1758. Each ecomorph is the result of local natural selection forces dictated by environmental variables, bathymetric gradients, symbiotic bacteria or any other type of cue capable of apparently manipulating epigenetic mechanisms in this coral. Everybody knows Pocillopora damicornis as the experimental “guinea pig”, the “poster child”, the “reef builder” or simply in Aquariology, the “cauliflower coral”!
Ranging morphologically from a filiform, pointed, branching colony to a compact and stunted posture, depending on whether it is growing in wave-exposed or protected environments, this species is unquestionably an important component of the reef.
But is this really a single coral species?
Well, not exactly. For decades, hidden genetic variants corresponding to several socalled ecomorphs, five to be precise, coexisted in sympatry. These genetic groups can be delineated by mitochondrial DNA analysis and most importantly, for the super-trained eye, by morphology. If nuclear markers are used, the five morphs correspond to at least 3 biologically distinct species.
And so what?
Well, hidden biological diversity matters, particularly when occurs within species of the reefs threatened by climate change; the knowledge on hidden biological diversity is essential for correct biodiversity estimates, forecasting and management. And this knowledge is particularly important in the post-genomic era, when “morphologically invisible” taxa are erroneously pooled together into the same research project, only because they reassemble the morphology of the so-called type specimen.
Abstract
The incredible range of morphological plasticity present in scleractinian corals has confused the taxonomy of the group, prompting to the introduction of "ecomorphs" to explain the observed correlation between local environmental conditions and phenotypic variation. Pocillopora damicornis (Linnaeus, 1758) represents one of the best known examples of eco-phenotypic variation in scleractinian corals with a variety of forms and reproductive strategies reported across its global distribution range. Here we reconstruct genealogical relationships of P. damicornis colonies collected from thirteen locations along the East Australian coast to examine the relationship between genetic and phenotypic diversity in this species. Haplotype networks computed from two mitochondrial DNA regions (CR, ORF) indicate that the range of morphotypes observed within this taxon fall into at least five genetically distinct mitochondrial lineages. Nuclear (HSP70, ITS2) haplowebs on the other hand recovered sharp genetic discontinuities amongst three of the morphological groups. We conclude that P. damicornis from Eastern Australia constitutes a cryptic species complex. The misinterpretation of taxonomical units within P. damicornis may well explain the perceived variation in the ecology, biology and life history across its range.
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