Abstract
The number of valid species in the genus Echinometra (Echinodermata, Echinoidea) and their associated identification keys have been debated in the scientific literature for more than 180 years. As the phylogeny and dispersal patterns of these species have been widely used as a prominent model for marine speciation, new insights into their taxonomy have the potential to deepen our understanding of marine speciation processes. In this study we examine Echinometra taxonomy, combining morphology and molecular tools. We present the taxonomy and phylogeny of Red Sea and Western Indian Ocean Echinometra. The currently available morphological keys were found to be limited in their ability to delineate all species within this genus. Nonetheless, morphological similarities between the Red Sea and Western Indian Ocean populations were high, and delimited them from the other species. These latter populations together formed a monophyletic clade, genetically distant from any of the other Echinometra species by more than 3%. Combining both traditional taxonomy and molecular evidence, we found that these populations were neither Echinometra mathaei nor E. oblonga, as previously considered. The morphological discrepancies of these populations, and their genetic divergence from the other Echinometra species, suggest that they should be considered as a new Echinometra species.
Highlights
The genus Echinometra currently comprises eight species, two of them still undescribed, with species-level taxonomy of this genus yet to be completed [1,2,3,4,5]
Though early studies of Echinometra suggested that only one species of this genus, E. mathaei, occurred in the Indo West Pacific (IWP) [8,9], later studies revealed the presence of four independent Echinometra species in that region [3,4,6,10,11,12,13,14,15]
It is clear that spine color alone is insufficient to determine species affiliation in most Okinawan Echinometra, since all but one species share spine colors
Summary
The genus Echinometra currently comprises eight species, two of them still undescribed, with species-level taxonomy of this genus yet to be completed [1,2,3,4,5]. Though early studies of Echinometra suggested that only one species of this genus, E. mathaei, occurred in the Indo West Pacific (IWP) [8,9], later studies revealed the presence of four independent Echinometra species in that region [3,4,6,10,11,12,13,14,15] These four closely-related IWP species occur sympatrically in Okinawa [6,11,14,16], and were originally referred to as Echinometra species A, B, C, and D [3]. One of these four species, E. mathaei, has been called the world’s most abundant sea urchin [6], with distribution that spans from Hawaii and Tahiti throughout the
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