Implications of range overlap in the commercially important pan-tropical sea urchin genus Tripneustes (Echinoidea: Toxopneustidae)

Abstract

Sea urchins of the genus Tripneustes are among the most abundant and ecologically important pan-tropical marine invertebrates. Recognized as potent ecosystem engineers due to their intense grazing of macroalgae and sea grass and highly valued for their gonads, wild populations of Tripneustes are commercially exploited for fisheries and aquaculture. Recently, a new species, Tripneustes kermadecensis (Bronstein et al. 2017), was described from the southern Pacific Ocean, off the Kermadec Islands, near the tropical/sub-tropical transition zone. Here, we explore the range of Tripneustes and, in particular, T. kermadecensis by morphological and genetic tools to determine whether it also occurs in Australia. We report, for the first time, the presence of a second Tripneustes species, T. kermadecensis, from Australia. We show that T. kermadecensis is in fact highly abundant throughout most of sub-tropical eastern Australia, where it occurs in association with coral and temperate reefs and has been recognized for decades as the ‘lamington sea urchin’. As commercial exploitation and stock-release programs of Tripneustes are rapidly expanding, and as global warming causes tropicalization of eastern Australia, driving the southern expansion of its congener T. gratilla, we call for re-evaluation of the conservation vulnerability of T. kermadecensis along the Australian continent and action by the aquaculture industry to genetically confirm the species identity of stocks in their facilities.