Influence of the North Equatorial Current on the population genetic structure of Tridacna crocea (Mollusca: Tridacnidae) along the eastern Philippine seaboard

Abstract

Tridacna crocea populations were sampled from 15 locations throughout the eastern Philippine seaboard and screened for allozyme variation at 7 polymorphic loci in order to examine the influence of the North Equatorial Current (NEC) bifurcation on population genetic structure. Significant genetic differentiation among all populations was detected (F ST = 0.065). Ordination methods and cluster analysis revealed 2 regional groups and a north-south spatial genetic structure broadly concordant with the bifurcation of the NEC into the Kuroshio and Mindanao current branches. Analysis of molecular variance (AMOVA) indicated greater partitioning of genetic variance among groups (F CT = 0.049) than among populations within groups (F SC = 0.029). An isolation-by-distance signal across the entire Philippine seaboard and marked geographical variation of allele frequencies between Kuroshio and Mindanao Current regions suggested that genetic differentiation is likely due to limited larval exchange and genetic drift. The Mindanao current populations are characterized by greater genetic diversity and differentiation (observed heterozygosity, H O = 0.298; F ST = 0.056) than the Kuroshio populations (H O = 0.152; F ST = 0.025), attributable to variable atmospheric and hydrographic regional conditions. Weaker connectivity among Mindanao current populations are attributed to complex patterns of hydrographic circulation south of the NEC bifurcation, which may translate to greater entrainment potential, in turn influencing dispersal and recruitment of planktonic propagules at varying spatial and temporal scales. Fine-scale genetic differentiation was also detected within Kuroshio and Mindanao current populations, indicating the influence of small-scale temporal and spatial physical processes that affect larval dispersal and recruitment along the eastern Philippine seaboard.

Oceanic currents drove population genetic connectivity of the brown alga Sargassum thunbergii in the north‐west Pacific

“…In other words, geographical isolation is not the factor in structuring biogeographical gradients of genetic diversity in S. thunbergii . As expected, homogeneous populations in the NWP driven by oceanic currents have also been reported in marine invertebrates from that area, such as the clam Tridacna crocea (Ravago‐Gotanco et al ., ), the crab Clistocoeloma sinense (Yuhara et al ., ) and the snail Batillaria attramentaria (Ho et al ., ). Sargassum thunbergii populations along the Japan‐Pacific side are characterized by extremely low genetic differentiation (ITS2: F ST = −0.04 to 0.01; cox 3: F ST = 0.00–0.06), which can be ascribed to the interactive coastal hydrodynamic systems (Fujikura et al ., ).…”

Recruitment constraints in Singapore's fluted giant clam (Tridacna squamosa) population—A dispersal model approach

“…Conversely, results from giant clam genetic studies have indicated restricted gene flow, suggesting lower levels of exchange [17], [18]. Ocean current patterns have been invoked to explain such genetic divergences among marine invertebrate populations [19], as they can influence temporal and spatial physical processes that potentially restrict larval dispersal and gene flow [20], [21].…”

Seascape genetics of Indo-Pacific reef organisms: methodologies and case studies for an emerging discipline

“…crocea throughout Wallacea using mitochondrial (mtDNA) markers [24][25][26], allozymes [27,28], and microsatellites [29]. Both T. crocea and T. maxima have been shown to contain distinct mtDNA clades associated with Sumatra (Sunda), Wallacea, and northwest New Guinea (Sahul, particularly in Cenderawasih Bay) [24][25][26].…”