Phylogeographic Analysis Suggests a Recent Population Bottleneck in the Rare Red Sea Tridacna squamosina

Kah Kheng Lim,Susann Rossbach,Nathan R Geraldi,Ester A Serrão,Carlos M Duarte

doi:10.3389/fmars.2021.628142

Abstract

Giant clams are an important ecological component of coral reefs in the Red Sea, as they enhance the reef’s productivity and provide habitat that can increase diversity. Three species of giant clams, namely Tridacna maxima, T. squamosa, and T. squamosina have been described within the Red Sea. However, due to its scarcity, information about the distribution and ecology of T. squamosina in the Saudi Arabian Red Sea is still lacking. This study used DNA barcoding to confirm the identity of the rare T. squamosina in the Farasan Banks. Six mtCOI fragments (500 bp) of T. squamosina were successfully amplified using the SQUA-primers for the first time. We used our data along with 18 reference sequences (16S) from the online database to assess the genetic diversity and population structure of T. squamosina. Low genetic diversity among the T. squamosina populations inferred from the 16S sequences implies a recent bottleneck for this species, which is supported by their historically higher diversity based on the coalescent-based estimator. Given the small population abundance and limited genetic variation of T. squamosina, it may warrant immediate local protections such as biobanking and fertility preservation programs as well as effective integrated coastal zone management plans.

Highlights

The recognition of giant clams as a contributor to net primary productivity and biomass of Red Sea coral reefs is driving a growing research interest in their abundance, ecological roles and population genetic structure (Roa-Quiaoit, 2005; Richter et al, 2008; Pappas et al, 2017; Rossbach et al, 2019a,b; Fauvelot et al, 2020)
This study confirms the occurrence of Tridacna squamosina in the South-eastern Saudi Arabian Red Sea, based on DNA sequences
Our results combined with the finding of a single individual from Farasan Island by Fauvelot et al (2020), confirm that this species occurs in the warmer, productive waters of the southern Red Sea

Summary

Introduction

The recognition of giant clams (subfamily Tridacninae) as a contributor to net primary productivity and biomass of Red Sea coral reefs is driving a growing research interest in their abundance, ecological roles and population genetic structure (Roa-Quiaoit, 2005; Richter et al, 2008; Pappas et al, 2017; Rossbach et al, 2019a,b; Fauvelot et al, 2020) They are a common food source within the coral reef community, with 75 known predators, including fishes such as wrasses, triggerfishes, and emperor fishes (Neo et al, 2015). A recently published analysis using genome skimming has provided highly credible phylogenetic relationship between T. squamosina and the other Tridacninae (Tan et al, 2021), information about their population genetic structure across the Red Sea is still lacking

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Results

Conclusion