Phylogeography of the Japanese scad, Decapterus maruadsi (Teleostei; Carangidae) across the Central Indo-West Pacific: evidence of strong regional structure and cryptic diversity

First Evidence of Cryptic Species Diversity and Population Structuring of Selaroides leptolepis in the Tropical Western Pacific

“…In such cases, individuals evolve into different haplotypes with minimal differences; and these haplotypes may either evolve directly or indirectly from an ancestral haplotype (Chanthran et al, 2020). This kind of genetic pattern has also been recorded in other TWP carangids (Rohfritsch and Borsa, 2005;Jamaludin et al, 2020;Mat Jaafar et al, 2020;Torres and Santos, 2020). The most recurrent and widespread haplotype is considered the oldest and most successful in traversing across sampling locations (Posada and Crandall, 2001;Mat Jaafar et al, 2012).…”

“…The high, significant genetic variations and correlation with geography supported an allopatric separation. The lineages' pairwise K2P divergences (COI = 6.77%; CytB = 6.64%) were higher than intraspecific variances on carangids with detected cryptic populations: Atule mate COI < 4.82%; S. crumenophthalmus COI < 4.66%; Seriolina nigrofasciata COI < 4.32% (Mat Jaafar et al, 2012); Decapterus maruadsi CytB < 5.0% (Jamaludin et al, 2020). These values were also more than 10× higher than the mean intraspecific divergences of barcoded fishes: COI = 0.39% (Ward et al, 2005); COI = 0.34% (Thu et al, 2019); COI = 0.32% (Zhang, 2011); COI = 0.59% and CytB = 0.57% (Kochzius et al, 2010); and CytB < 1.0% (Li et al, 2018).…”

Genetic diversity, population structure and historical demography of the two-spined yellowtail stargazer (Uranoscopus cognatus)

“…This is in concordance with the genetic break of the Indian-Pacific ocean-basin hypothesis 21 , and in accordance with earlier observations of several marine species including reef fish 29 – 32 , invertebrates 33 – 35 , seahorses 36 and pelagic fish 37 . Nevertheless, several findings on fish that showed low genetic differentiation within the IWP region were also reported and associated with the highly dispersive life history stages that contribute to high rates of gene flow among populations, for instance in moray eels 26 , Indian mackerel ( Rastrelliger kanagurta ) 27 , and Japanese scad ( Decapterus maruadsi ) 28 . To better comprehend the evolutionary history of U. cognatus and the level of structuration at the species level, collecting more samples from outside of the WCT and ECPM is therefore highly required.…”

“…Conservation measures are critical because the adult stargazer is strongly site-associated and has a limited capacity for dispersal and mobility, thus, it is vulnerable to site-specific benthic impacts such as trawling and dredging 4 . Nevertheless, low genetic diversity along the Andaman Sea has been recorded in commercially important species and is generally attributed to overharvesting, leading to population bottleneck and a subsequent genetic reduction in the total gene pool 28 , 34 , 36 . Ignoring such ecological or fishing pressures will likely cause adverse effects to marine resources, for instance, depletion of marine species along the WCT 56 – 58 .…”

“…Consequently, the terrestrial, freshwater, and marine taxa were affected by this historical geomorphological rearrangement, shaping the genetic distribution that is apparent today. Several hypotheses on molecular biogeography of multispecies within the IWP have been proposed 25 ; of these, several studies advocate genetic homogeneity or partial panmixia restricted within a particular area of the ocean, for example in moray eels 26 , Indian mackerel ( Rastrelliger kanagurta ) 27 and Japanese scad ( Decapterus maruadsi ) 28 , while others indicate extensive structuring, including in reef-fishes 29 – 32 , invertebrates 33 – 35 , seahorses 36 and pelagic fish 37 .…”