Charles Darwin University A Novel Widespread Cryptic Species and Phylogeographic Patterns within Several Giant Clam Species (Cardiidae: Tridacna) from the Indo-Pacific Ocean Huelsken,

Giant clams (genus Tridacna) are iconic coral reef animals of the Indian and Pacific Oceans, easily recognizable by their massive shells and vibrantly colored mantle tissue. Most Tridacna species are listed by CITES and the IUCN Redlist, as their populations have been extensively harvested and depleted in many regions. Here, we survey Tridacna crocea and Tridacna maxima from the eastern Indian and western Pacific Oceans for mitochondrial (COI and 16S) and nuclear (ITS) sequence variation and consolidate these data with previous published results using phylogenetic analyses. We find deep intraspecific differentiation within both T. crocea and T. maxima. In T. crocea we describe a previously undocumented phylogeographic division to the east of Cenderawasih Bay (northwest New Guinea), whereas for T. maxima the previously described, distinctive lineage of Cenderawasih Bay can be seen to also typify western Pacific populations. Furthermore, we find an undescribed, monophyletic group that is evolutionarily distinct from named Tridacna species at both mitochondrial and nuclear loci. This cryptic taxon is geographically widespread with a range extent that minimally includes much of the central Indo-Pacific region. Our results reinforce the emerging paradigm that cryptic species are common among marine invertebrates, even for conspicuous and culturally significant taxa. Additionally, our results add to identified locations of genetic differentiation across the central Indo-Pacific and highlight how phylogeographic patterns may differ even between closely related and co-distributed species. Citation: Huelsken T, Keyse J, Liggins L, Penny S, Treml EA, et al. (2013) A Novel Widespread Cryptic Species and Phylogeographic Patterns within Several Giant Clam Species (Cardiidae: Tridacna) from the Indo-Pacific Ocean. PLoS ONE 8(11): e80858. doi:10.1371/journal.pone. 0080858 Editor: Mikhail V. Matz, University of Texas, United States of America Received July 30, 2013; Accepted October 14, 2013; Published November 20, 2013 Copyright: 2013 Huelsken et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Funding for this work was provided by the Australian Research Council (www.arc.gov.au, DP0878306 to CR), the German Research Foundation (www. dfg.de/en, DFG, Hu 1806/1-1, Hu 1806/2-1 to TH), the World Wildlife Fund (worldwildlife.org/initiatives/fuller-science-for-nature-fund, Kathryn Fuller Post-doctoral Research Fellowship to EAT), the Malacological Society of Australasia (www.malsocaus.org, to TH), and the Joyce Vickery Fund (linneansocietynsw.org.au/ grants.html, to JK). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: c.riginos@uq.edu. au . These authors contributed equally to this work.