ACCLIMATORY CAPACITY OF THE GORGONIAN ISIS HIPPURIS LINNAEUS 1758 TO ENVIRONMENTAL CHANGE IN SE SULAWESI, INDONESIA
Coral reefs within the Indonesian archipelago are some of the most biodiverse yet anthropogenically compromised marine ecosystems. In the Wakatobi Marine National Park, Indonesia, two distinct morphotypes of the protected zooxanthellate gorgonian octocoral Isis hippuris partition across environmental clines: long-branched bushy colonies on turbid, degraded reefs, and short-branched multi/planar colonies on healthy reefs. To test if local adaptation has lead to divergent selection through the action of environmental perturbation, a one-year reciprocal transplant experiment assessing multiple traits (45: morphological, physiological, environmental) was conducted. After one year, reduced survivorship of healthy reef morphotypes on degraded reefs implied the onset of lineage segregation through immigrant inviability. Phenotypic traits in healthy source colonies showed significant trait plasticity, whereas residents from the impacted site were insensitive to environmental change. Interestingly, photoacclimatory responses were integrated at the morphological and bio-optical levels, with host skeletal articulation maximizing the internal light field in healthy clones on degraded reefs. Variable optical responses were not, however, attributed to endosymbiont type, as all test colonies possessed a novel Symbiodinium Clade D1a. In sum, patterns of phenotypic variability within the I. hippuris holobiont likely represent incipient ecological divergence, with a high capacity for plasticity that has become fixed through on-going anthropogenic disturbance on degraded reefs.
Rowley, S. J., University of Hawai'i at Manoa, USA, email@example.com
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