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BMC Evolutionary Biology

, 7:122

First Online: 24 July 2007Received: 21 November 2006Accepted: 24 July 2007


BackgroundColonial invertebrates such as corals exhibit nested levels of modularity, imposing a challenge to the depiction of their morphological evolution. Comparisons among diverse Caribbean gorgonian corals suggest decoupling of evolution at the polyp vs. branch-internode levels. Thus, evolutionary change in polyp form or size the colonial module sensu stricto does not imply a change in colony form constructed of modular branches and other emergent features. This study examined the patterns of morphological integration at the intraspecific level. Pseudopterogorgia bipinnata Verrill Octocorallia: Gorgoniidae is a Caribbean shallow water gorgonian that can colonize most reef habitats shallow-exposed vs. deep-protected; 1–45 m and shows great morphological variation.

ResultsTo characterize the genotype-environment relationship and phenotypic plasticity in P. bipinnata, two microsatellite loci, mitochondrial MSH1 and nuclear ITS DNA sequences, and ITS2 DGGE banding patterns were initially compared among the populations present in the coral reefs of Belize Carrie Bow Cay, Panama Bocas del Toro, Colombia Cartagena and the Bahamas San Salvador. Despite the large and discrete differentiation of morphotypes, there was no concordant genetic variation DGGE banding patterns in the ITS2 genotypes from Belize, Panama and Colombia. ITS1–5.8S-ITS2 phylogenetic analysis afforded evidence for considering the species P. kallos Bielschowsky as the shallow-most morphotype of P. bipinnata from exposed environments. The population from Carrie Bow Cay, Belize 1–45 m was examined to determine the phenotypic integration of modular features such as branch thickness, polyp aperture, inter-polyp distance, internode length and branch length. Third-order partial correlation coefficients suggested significant integration between polypar and colonial traits. Some features did not change at all despite 10-fold differences in other integrated features. More importantly, some colonial features showed dependence on modular features.

ConclusionConsequently, module integration in gorgonian corals can be shifted, switched or canalized along lineages. Modular marine organisms such as corals are variations on a single theme: their modules can couple or decouple, allowing them to adapt to all marine benthic environments.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2148-7-122 contains supplementary material, which is available to authorized users.

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Autor: Juan A Sánchez - Catalina Aguilar - Daniel Dorado - Nelson Manrique


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