Genetic variability of Tehuelche scallop, Aequipecten tehuelchus, populations from the Patagonian coasts (Argentina)

Abstract

Genetic variation was investigated in ¢ve subtidal locations from the north of San Mat|¤ as Gulf (42823 0 S) to the north of San Jorge Gulf (45802 0 S). Fifteen loci were studied by means of vertical starch gel electrophoresis; ten loci were polymorphic. The percentages of polymorphic loci (P 0.99 and P 0.95 criteria) varied between 40% and 53.33% and between 33.33% and 46.67%, respectively. Expected mean heterozygosity per locus (He) ranged from 0.128 (Bajo Oliveira-El So¤ tano) to 0.160 (Puerto Madryn); this range is similar to those observed for other scallop species. All the loci were in Hardy^Weinberg equilibrium. The estimated genetic distances among populations were signi¢cantly lower than those reported for comparisons between populations of di¡erent pectinid species, suggesting that the ¢ve populations studied belong to the same species (Aequipecten tehuelchus). The absence of exclusive ¢xed alleles also supported that assumption. The results obtained suggest: (i) assignment of species or subspecies status to some morphological variants of the shells, like the 'madrynensis' form is not supported; (ii) the commercially exploited Tehuelche scallop from San Mat|¤ as and San Jose¤ Gulfs should be managed as distinct stocks.

Evolutionary relationships of the Tehuelche scallop Aequipecten tehuelchus (Bivalvia: Pectinidae) from the south-western Atlantic Ocean

“…The estimated interpopulational genetic distances obtained for the Tehuelche scallop were similar to the intraspecific variation expected for Pectinids (0.1% average, 1% threshold, Feng et al , 2011). Our results are consistent with those of Real et al (2004), who found no evidence of interspecific genetic differentiation using allozymes. Of their 10 loci, five had significant F ST values, averaging F ST = 0.032, suggesting some genetic differentiation along the Patagonian coast.…”

“…This southern geographic variant has been described as a separate species, Aequipecten madrynensis (Lahille 1906) (Castellanos, 1971) or as a subspecies, A. tehuelchus madrynensis (Bavay 1906) (Orensanz et al , 1991). The correlation between morphological and genetic differences of the two forms was explored by Real et al (2004), who found no evidence of interspecific genetic differentiation using allozymes. Another related species that lives in sympatry with tehuelchus and madrynensis is the non-commercial pectinid Flexopecten felipponei (Dall 1922) (Figure 1), which has rarely been recorded in the south-western Atlantic Ocean (Waller, 1991), distributed in rocky and sandy bottoms from 36°S to San Matías and Nuevo Gulfs (43°S) (Castellanos, 1970, 1971).…”

Towards a model of postglacial biogeography in shallow marine species along the Patagonian Province: lessons from the limpet Nacella magellanica (Gmelin, 1791)

“…Considering the migration estimation from the Atlantic to the Pacific and the prevailing direction of the oceanic fronts and winds, the hypothesis of postglacial recolonization from Atlantic Patagonia to the Pacific is most unlikely. Similar patterns of genetic discontinuities between Pacific and Atlantic localities in Patagonia have been found in Enteroctopus megalocyathus [116] and in the scallop Aequipecten tehuelchus [117]. Moreover, de Aranzamendi et al [49] found significant genetic differentiation between N. magellanica populations from Tierra del Fuego and northern localities such as Golfo San José and Golfo Nuevo.…”

Mitochondrial and nuclear markers reveal a lack of genetic structure in the entocommensal nemertean Malacobdella arrokeana in the Patagonian gulfs

“…For example, Real et al (2004) reported genetic variation between northern and southern San Matías populations of the scallop Aequipecten tehuelchus, estimating that genetic distances were higher between San Matías populations than between these populations and San José gulf population. Panopea abbreviata specimens from different populations of the San Matías gulf indicate different rates of individual growth between populations located on either side of the thermohaline front (Morsan et al 2010).…”