MEPS 583:163-178 (2017)  -  DOI: https://doi.org/10.3354/meps12348

ABSTRACT: Sea urchins from the genus Diadema are some of the most widespread and ecologically important species in tropical marine environments. Two distinct clades of Diadema setosum have been previously recognized based on DNA sequence data: the widespread clade a (distributed throughout the Indo-West Pacific) and clade b (native to the Arabian Peninsula). We use published and novel molecular data to assert the distribution of the 2 D. setosum clades and compile a comprehensive, georeferenced occurrence list for both clades throughout their range. These data are then used to model the global distribution of D. setosum with respect to the 2 molecularly inferred clades and evaluate their invasive potential throughout the Mediterranean. We combine morphological with molecular data to assert the taxonomic identification of the single Mediterranean Diadema recovered to date and provide an updated phylogenetic analysis of this genus. Species distribution modeling predicts suitable habitats for the 2 clades, including some along the Egyptian and Israeli coasts of the Levantine Basin, and in restricted areas in the Aegean and Adriatic Seas. Genetic data show that the Mediterranean Diadema derives from mitochondrial clade b of D. setosum. The spatio-temporal pattern of D. setosum’s Mediterranean invasion does not follow a gradual succession of directional population expansion as may be expected from an unmediated larval transport through the Suez Canal, indicating potential anthropogenic involvement. Without intervention, further spread of D. setosum in the Mediterranean seems likely, elevating the risk of a population outbreak that may have far-reaching anthropogenic and environmental consequences.

KEY WORDS: Alien species · Environmental niche modeling · Molecular diagnostics · Mediterranean Sea · MaxEnt · Diadema setosum