Microsatellite variation in the Mexican rockfish <i>Sebastes macdonaldi</i>

Abstract

SUMMARY: The Mexican rockfish Sebastes macdonaldi is the Northeast Pacific rockfish with the southernmost distribution, featuring isolated populations in the Gulf of California. We analysed seven microsatellite loci in 111 organisms collected throughout most of its geographical range to test long-standing hypotheses regarding its disjunct distribution. One locus was fixed and the number of alleles in polymorphic loci ranged from 2 to 24 (average 13.5). We found very high levels of polymorphism (overall He = 0.75) comparable to other congeneric species but no significant differences in genetic diversity among localities or between Pacific and Gulf of California populations (p > 0.1). Significant shifts in allelic and genotypic frequencies were detected at three loci, which resulted in a small but significant partitioning of genetic variance among California, Baja California and Gulf of California populations (F ST = 0.007, p = 0.03) and between Gulf and Pacific populations (F ST = 0.01, p = 0.004). The latter but not the former result was corroborated by analyses of molecular variance (AMOVA) using the number of distinct alleles (F ST ) and the sum of square differences of allele sizes (R ST ) as Euclidean distances. The evidence argues against contemporary gene flow between the gulf and the Pacific ocean and against an ancient invasion of the gulf with a founder effect. The small level of divergence favours a recent dispersal but a larger data set including DNA sequences amenable to phylogenetic analyses will help to test alternative hypotheses of dispersal versus vicariance.Key words: Mexican rockfish, disjunct distribution, microsatellites, genetic structure, Baja California, México. RESUMEN: VARIACIÓN DE MICROSATÉLITES EN EL ROCKOT MEXICANO SEBASTES MACDONALDI. -El rockot mexicanoSebastes macdonaldi es la especie de Sebastes del Pacífico nororiental con la distribución geográfica más sureña e incluye poblaciones aisladas dentro del Golfo de California. Analizamos siete loci microsatelitales en 111 organismos que se colectaron a lo largo de gran parte de su distribución geográfica para probar hipótesis acerca de su distribución discontinua. Un locus se encontró fijado y el número de alelos en loci polimórficos varió entre 2 y 24 (media 13.5). Encontramos altos niveles de polimorfismo (en general He = 0.75) comparables con otras especies congenéricas, sin embargo no se encontraron diferencias en los niveles de diversidad entre las localidades ni entre las poblaciones del Pacífico y del Golfo de California (p > 0.1). Se detectaron cambios significativos en las frecuencias alélicas y genotípicas en tres loci, que resultaron en una división pequeña pero significativa de la variancia genética entre California, Baja California y el Golfo de California (F ST = 0.007, p = 0.03) y entre las poblaciones del golfo y del Pacífico (F ST = 0.01, p = 0.004). Solamente esta última diferenciación fue corroborada por un análisis de variancia molecular (AMOVA) en el que se utilizaron el número de alelos distintos (F ST ) y la su...

Population genetic structure of wild and hatchery black rockfish Sebastes inermis in Korea, assessed using cross-species microsatellite markers

“…We found no differentiation among wild S. inermis populations, despite different sea basin origins. The lack of significant genetic differentiation between the wild populations we sampled is consistent with the lack of genetic divergence found in wild S. inermis from mtDNA sequence variability studies (Higuchi and Kato, 2002), as well as that of other Sebastes species (Rocha-Olivares et al, 2003;Gilbert-Horvath et al, 2006). This could result from sufficient gene flow during the black rockfish pelagic phase.…”

“…In this study, the genetic variation of wild population samples of Korean S. inermis was low relative to that reported in other Sebastes species (Rocha-Olivares et al, 2003;Buonaccorsi et al, 2002Buonaccorsi et al, , 2004, as well as other marine fishery species (DeWoody and Avise, 2000). However, similar genetic variability was reported in S. maliger (Wimberger et al, 1999) and S. thompsoni (Sekino et al, 2001).…”

Tempo and mode of speciation in the Baja California disjunct fish species Anisotremus davidsonii

“…2003). For example, Sebastes macdonaldi , the Mexican rockfish, is the southernmost species of the northeast Pacific rockfishes (Rocha‐Olivares et al . 2003).…”

Genetic Diversity and Population Structure in the Heavily Exploited Korean Rockfish, Sebastes schlegeli, in Korea

“…Marine species generally possess significantly higher levels of genetic diversity (average H e = 0.79) than freshwater (average H e = 0.46) or anadromous (average H e = 0.68) species (DeWoody and Avise 2000). For example, other studies using microsatellite markers have demonstrated expected heterozygosities of 72–75% and averages of 17.3, 11.8, and 13.5 alleles per locus for Sebastes rastrelliger (six loci) (Buonaccorsi et al 2004), Sebastes caurinus (nine loci) (Buonaccorsi et al 2002), and Sebastes macdonaldi (seven loci) (Rocha‐Olivares et al 2003), respectively. Eight microsatellite loci described for four North Atlantic redfish ( Sebastes fasciatus , Sebastes mentella , Sebastes marinus , and Sebastes viviparus ) were also highly polymorphic (0.5 ≤ H e ≤ 0.96) and at least half the loci had H e > 0.8 in all species (Roques et al 1999).…”

“…Mexican rockfish, the southernmost of the northeastern Pacific rockfishes, also shows no evidence of genetic differentiation. Despite reasonable levels of polymorphism, population samples from throughout the Mexican rockfish's range were not distinct when analyzed using both mtDNA sequence information (Bernardi et al 2003) and seven microsatellite loci (Rocha‐Olivares et al 2003). With 16 microsatellite loci, kelp rockfish ( Sebastes atrovirens ) specimens collected from an 800‐km stretch along the central California coastline exhibited apparent genetic homogeneity (Gilbert‐Horvath et al 2006).…”