Nevatte, Ryan J., Gillings, Michael R., Morejohn, Kirby, Ainley, Lara, Liggins, Libby, Pratchett, Morgan S., Hoey, Andrew S., Doll, Peter C., Pasisi, Brendon, and Williamson, Jane E. (2024) Of Clams and Clades: Genetic Diversity and Connectivity of Small Giant Clams (Tridacna maxima) in the Southern Pacific Ocean. Ecology and Evolution, 14 (10). e70474.

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Abstract

Giant clams (Tridacna and Hippopus) are large marine bivalves occupying tropical and subtropical reefs in the Indo-Pacific. Giant clam populations have declined in many areas of the Indo-Pacific and continue to be threatened by harvesting and environmental change. The small giant clam (Tridacna maxima) occurs throughout the Indo-Pacific and has been subject to several phylogeographic studies across its range. However, given its broad range, there are several areas where the genetic diversity and connectivity of T. maxima populations has not been characterised. Here, we analyse the mitochondrial marker cytochrome oxidase 1 (CO1) to examine the genetic diversity and connectivity of T. maxima in two regions: Australia's Coral Sea Marine Park and the Cook Islands. Samples were collected from 13 reefs within the Coral Sea Marine Park and ten islands within the Cook Islands archipelago. Tridacna maxima across the sampled region of the Coral Sea did not display any population structure, whereas significant population structure was detected for T. maxima within the Cook Islands. For the Cook Islands, most pairwise comparisons involving an island in the northern group (Manihiki) were significant, as were comparisons for Palmerston (a more centrally located island) and the southern islands, Rarotonga and Mangaia. Both regions displayed high haplotype diversities (> 0.90), indicating that they are important repositories of genetic diversity. Additional CO1 data from throughout T. maxima's distribution showed that the Coral Sea clams belonged to the clade occurring in the South-Western Pacific Ocean, whilst those from the Cook Islands belonged to a unique clade found in the Central Pacific Ocean. This clade extended from Fiji in the west to French Polynesia in the east and the atolls of Palmyra and Tarawa (Kiribati) in the north. Our assessment of genetic diversity and population structure in these regions will assist with management decisions for the species.

Item ID:	85060
Item Type:	Article (Research - C1)
ISSN:	2045-7758
Copyright Information:	© 2024 The Author(s). Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Date Deposited:	09 Apr 2025 01:36
FoR Codes:	31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 50% 31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310402 Biogeography and phylogeography @ 25% 31 BIOLOGICAL SCIENCES > 3105 Genetics > 310599 Genetics not elsewhere classified @ 25%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 60% 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180501 Assessment and management of benthic marine ecosystems @ 40%
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