Mitochondrial DNA analysis of North Pacific sword-fish Xiphias gladius population structure

Abstract

Restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA) was used to investigate population structure of the North Pacific swordfish X i p h~a s gladius. Sam:ples of X. gladius from the western (n = 47), central (n = 42), and eastern (n = 59) Pacific were examined for mtDNA variation using 17 six-base pair restriction endonucleases. A total of 27 composite mtDNA genotypes were revealed, and 50 % or more of individuals from each area shared the most common composite genotype. Pooled nucleon divers~ty and nucleotide diversity were 0.637 and 0.0019, respectively, and the mean nucleotide sequence divergence among genotypes was 0.88% (rank 0.11 to 2.80 %). Both nucleotide differences between populations and Gst analysis revealed low values. No significant geographic variation in genotypic frequencies was revealed by G-test and Monte Carlo randomization analysis with 1000 replicates. This suggests that there is sufficient gene flow across the North Pacific to prevent genetic differentiation, and is consistent with the interpretation that North Pacific swordfish represent a single genetic stock.

Nuclear and mitochondrial DNA analyses reveal four genetically separated breeding units of the swordfish

“…These studies show that mtDNA genotype frequency distributions are significantly different among samples derived from the Mediterranean, the Atlantic and Pacific Oceans. However, no heterogeneity of mtDNA genotype frequency has been reported within the Pacific or between the Indian and Pacific Oceans (Grijalva-Chon et al, 1994;Rosel & Block, 1996;Chow et al, 1997). In contrast, mtDNA genotype frequencies are significantly different between North and South Atlantic samples (Alvarado-Bremer et al, 1996;Chow et al, 1997).…”

Population structure and demographic history of Genypterus blacodes using microsatellite loci

“…A phenol-chloroform method followed by precipitation in ethanol was used, as described in Grijalva-Chon et al (1994). The quality and quantity were measured in an Eppendorf biophotometer ® and the template DNA was diluted to 20 ng for the PCR amplifications.…”

Mitochondrial diversity and genetic structure in allopatric populations of the Pacific red snapper Lutjanus peru

“…This observation is not without exceptions as hypervariable enzymes can sometimes be found, as in the case of MseI for the control region of L. peru. Generally speaking, the molecular diversity found in L. peru was larger than that observed in other fish using RFLPs of the entire mtDNA (Graves et al, 1992a(Graves et al, , 1992bGrijalva-Chon et al, 1994;Gold et al, 1997) (table 5). This can be explained by the higher rate of evolution of the mitochondrial control region compared to the average for the entire genome (Brown et al, 1993).…”

“…Grados de libertad Graves et al, 1992b Xiphias gladius 0.64 0.19 0.88 Grijalva-Chon et al, 1994 Pomatomus saltatrix 0.70 1.23 1.23 Graves et al, 1992a Pogonias cromis 0.78 0.48 Gold et al, 1994 Lutjanus campechanus 0.75 0.5 Gold et al, 1994 Lutjanus campechanus 0.81 Camper et al, 1994 Tetrapturus Gold et al, 1994 Mugil cephalus 1 1.5 Rocha-Olivares et al, 2000 diversidad para una misma región del genoma. En el caso de los RFLPs, los valores de diversidad aumentan con el número y el tipo de enzimas utilizadas (Graves et al, 1992a), aunque esta relación no siempre se verifica ya que pueden encontrarse enzimas hipervariables como MseI para la región de control de L. peru.…”