Genetic diversity and population differentiation of small giant clam Tridacna maxima in Comoros islands assessed by microsatellite markers

Abstract

Small giant clam, Tridacna maxima, widely distributed from French Polynesia to East Africa, has faced population declines due to over-exploitation. Comoros islands are an important biogeographic region due to potential richness of marine species, but no relevant information is available. In order to facilitate devising effective conservation management plan for T. maxima, nine microsatellite markers were used to survey genetic diversity and population differentiation of 72 specimens collected from three Comoros islands, Grande Comore, Moheli and Anjouan. A total of 51 alleles were detected ranged from 2 to 8 per locus. Observed and expected heterozygosity varied from 0.260 to 0.790 and from 0.542 to 0.830, respectively. All populations have high genetic diversity, especially the population in Moheli, a protected area, has higher genetic diversity than the others. Significant heterozygote deficiencies were recorded, and null alleles were probably the main factor leading to these deficits. F ST value indicated medium genetic differentiation among the populations. Although significant, AMOVA revealed 48.9 % of genetic variation within individuals and only a small variation of 8.9 % was found between populations. Gene flow was high (Nm = 12.40) between Grande Comore and Moheli, while lower (Nm = 1.80) between Grande Comore and Anjouan, explaining geographic barriers to genetic exchanges might exist in these two islands. Global gene flow analysis (Nm = 5.50) showed that larval dispersal is enough to move between the islands. The high genetic diversity and medium population differentiation revealed in the present study offer useful information on genetic conservation of small giant clams.

Phylogeographical patterns and a cryptic species provide new insights into Western Indian Ocean giant clams phylogenetic relationships and colonization history

“…The high genetic distinctiveness of the Red Sea lineages, especially in T. squamosa , suggest possible cryptic species (Hui et al, ). In the southern part of the WIO, apart from a single genetic study on the connectivity of T. maxima populations from the Comoros Islands (Mohamed et al, ), and two ecological studies on T. maxima and T. squamosa around Mauritius (Ramah, Taleb‐Hossenkhan, & Bhagooli, ; Ramah, Taleb‐Hossenkhan, Todd, Neo & Bhagooli, ), little attention has been paid to giant clams of this least known biogeographical province (Wafar, Venkataraman, Ingole, Ajmal Khan, & LokaBharathi, ) despite its high species richness (Costello et al, ; Hoareau, Boissin, Paulay, & Bruggemann, ). Cryptic species and/or highly genetically divergent peripheral populations have been revealed in the Red Sea and the WIO provinces in many groups (Berumen et al, and references therein), which contributed to the view that these provinces are marine biodiversity and evolutionary hotspots (Borsa et al, ; Hoareau et al, ; Obura, ; Ramírez, Afán, Davis, & Chiaradia, ; Roberts et al, ).…”

Population status and genetic diversity of two endangered giant clams (Tridacna squamosa and Tridacna maxima) on the fringing reefs of Perhentian Islands, Malaysia

“…Most studies of giant clam species have measured the genetic diversity at large spatial scales across the Indo‐Pacific region (Nuryanto & Kochzius, 2009; Neo & Todd, 2012; DeBoer et al, 2014; Hui et al, 2016; Hui, Nuryanto & Kochzius, 2017; Keyse et al, 2018); however, genetic differentiation can be detected at local scales; for example, Comoros Islands (Mohamed et al, 2016), oceanic New Caledonia islands and Vanuatu archipelago (Van Wynsberge et al, 2017b). Interestingly, this study demonstrated that both giant clam species exhibited low but significant genetic differentiation, with different patterns of genetic structure at the local‐scale scenario of PMP and Rhu Island.…”

KERAGAMAN GENETIK KIMA KECIL (Tridacna maxima) DI PULAU KUR, PULAU BIAK, DAN MANADO SERTA IMPLIKASINYA UNTUK KONSERVASI

“…Semua spesies Tridacna mengalam i tahap larva planktotrophic pada siklus hidupnya sebelum menjadi spesies bentik (Lucas, 1988). Larva dispersal Tridacna dapat menghabiskan waktu hingga 9-19 hari (Jameson, 1976;Mies & Sumida, 2012;Triandiza & Kusnadi, 2013;Mohamed et al, 2016) melayang mengikuti arus sebelum menetap di substrat yang keras. Aliran genetik yang dibawa pada tahap kehidupan planktonik ini berpotensi untuk terdistribusi ke populasi yang jauh dan melakukan percampuran genetik antar populasi melalui perkawinan acak.…”