Title: ARE MESOPHOTIC CORALS AND OCTOCORALS REALLY THAT DIFFERENT? AN EVOLUTIONARY PERSPECTIVE FROM CARIBBEAN REEFS

Abstract: Mesophotic coral reef communities are usually below recreational SCUBA diving but too shallow for deep-sea vehicle exploration. This study aimed to provide a systematic exploration of the mesophotic zone (40-120 m) in an oceanic barrier reef complex in San Andrés Island and on banks along the Deep-sea Corals National Natural Park. Using CCR/Trimix, we wanted to determine whether the mesophotic corals and octocorals comprised unique evolutionary lineages carrying particular traits. We reconstructed molecular phylogenies for both coral (ITS2) and octocoral (mtMutS) species down to 120m and identified their symbiotic microalgae, if present. For both, we found an abrupt lineage/community replacement where zooxanthellate species disappear and azooxanthellate species dominate. We documented this replacement occurring shallower for octocorals (~60m) than corals (~90m). Some reef-building corals, notably Agaricia undata and Madracis senaria, distribute well into this zone (~80m) and are characterized by an increased presence of the endolithic algae Ostreobium, which is notable at the colony surface. Shallow coral communities are replaced by unrelated azooxanthellate cup corals also associated to Ostreobium. For octocorals, younger species lineages are replaced by older lineages characterized by phylogenetically dispersed species, which have thinner branches and smaller polyps than the shallow-water species. Our results suggest that the lower-mesophotic corals and octocorals (>60m) are old lineages related to deep-sea species, whereas upper-mesophotic (<60m) species are young species in response to deep-related ecological divergence.

Authors: Sánchez JA, González FL, Rivera G, Dueñas LF

Presentation: Oral

Session: 29

Date: 06/22/16

Time: 11:15

Location: 308 A/B

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