Formal description of Cladocopium proximale sp. nov. (Dinophyceae, Symbiodiniaceae), a coral photosymbiont from the C1 radiation

Formal description of Cladocopium proximale sp. nov. (Dinophyceae, Symbiodiniaceae), a coral photosymbiont from the C1 radiation | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 23 March 2026 V1 Latest version Share on Formal description of Cladocopium proximale sp. nov. (Dinophyceae, Symbiodiniaceae), a coral photosymbiont from the C1 radiation Authors : Giorgio Terzi 0009-0009-2686-0117 , Matthew Nitschke [email protected] , Madeleine J.H. van Oppen , and Davide Seveso Authors Info & Affiliations https://doi.org/10.22541/au.177425344.49246325/v1 130 views 72 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Coral reefs are among the most biodiverse ecosystems on Earth and rely on endosymbiosis with Symbiodiniaceae, a diverse family of dinoflagellates essential for coral nutrition and which also play an important role in thermal tolerance. Despite their ecological importance, resolving species boundaries within Symbiodiniaceae remains challenging, partly due to limited phylogenetic signal in commonly used genetic markers and the absence of broadly accepted criteria for species delimitation. Refining taxonomic resolution is therefore critical for understanding symbiont diversity, distributions, and evolutionary relationships. In this study, we delimit two closely related Cladocopium species using a meta-haplotype framework applied to two hypervariable loci—the ITS2 region and the psbA non-coding region (psbAncr). Slowly evolving markers fail to differentiate Cladocopium proximale (SCF049; described here) and its sister species C. proliferum, yet consistent and biologically meaningful variation is captured across both hypervariable regions. By integrating divergence across multiple organellar and nuclear regions, we demonstrate that C. proximale and C. proliferum represent distinct species. More broadly, closely related Symbiodiniaceae such as these provide important systems for examining speciation processes, including potential ecological differentiation and reproductive compatibility. Our results highlight the value of combining multiple hypervariable markers to improve taxonomic accuracy in Symbiodiniaceae and strengthen the basis for identifying and describing closely related species within this ecologically crucial group. Supplementary Material File (figures2.pdf) Download 2.27 MB File (figures3.pdf) Download 4.60 MB File (formal_description_of_cladocopium_proximale_sp._nov.,_a_coral_photosymbiont_from_the_c1_radiation_submit_gt.docx) Download 167.60 KB Information & Authors Information Version history V1 Version 1 23 March 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords comparative description evolutionary ecology marine microbial molecular genetics sequencing Authors Affiliations Giorgio Terzi 0009-0009-2686-0117 University of Milan-Bicocca View all articles by this author Matthew Nitschke [email protected] Australian Institute of Marine Science View all articles by this author Madeleine J.H. van Oppen The University of Melbourne View all articles by this author Davide Seveso University of Milan-Bicocca View all articles by this author Metrics & Citations Metrics Article Usage 130 views 72 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Giorgio Terzi, Matthew Nitschke, Madeleine J.H. van Oppen, et al. Formal description of Cladocopium proximale sp. nov. (Dinophyceae, Symbiodiniaceae), a coral photosymbiont from the C1 radiation. Authorea . 23 March 2026. DOI: https://doi.org/10.22541/au.177425344.49246325/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . Format Please select one from the list RIS (ProCite, Reference Manager) EndNote BibTex Medlars RefWorks Direct import Tips for downloading citations document.getElementById('citMgrHelpLink').addEventListener('click', function() { popupHelp(this.href); return false; }); $(".js__slcInclude").on("change", function(e){ if ($(this).val() == 'refworks') $('#direct').prop("checked", false); $('#direct').prop("disabled", ($(this).val() == 'refworks')); }); View Options View options PDF View PDF Figures Tables Media Share Share Share article link Copy Link Copied! Copying failed. 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