Lessons from the sea urchin genus Tripneustes: the importance of taxonomy and museum collections in understanding species distributions in a changing ocean

Emily McLaren

PhD Candidate, University of Sydney

Supervisors: Prof Maria Byrne (USyd), Dr Brigitte Sommer (UTS), Helen Stoddart (AM), Alex Hegedus (AM), Dr Stephen Keable (AM)

To understand the effect of climate change on biodiversity, accurate taxonomy is essential. Cryptic and uncharismatic species are often misidentified, and as a result the true ecological roles of these species are not understood. On the east coast of Australia, two species of the ecologically important echinoid genus Tripneustes co-occur, the tropical species T. gratilla and the subtropical specialist T. kermadecensis. Until recently Tripneustes kermadecensis was mistakenly identified as a range extension of the tropical species T. gratilla. Understanding how climate change is driving the redistribution of marine species is fundamental to conservation, however this must be underpinned by accurate species identification.

We reclassified museum specimens of Tripneustes from the east coast of Australia into T. gratilla and T. kermadecensis based on morphological traits and combined this with photographic transects from 6 sites along the east coast from 2010–2019 to determine the true distributions of these species. What was once thought to be the broad distribution of T. gratilla is now partitioned into the tropical distribution of T. gratilla and the limited subtropical/temperate distribution of T. kermadecensis in NSW.