Abstract
Argopecten nucleus is a functional hermaphroditic pectinid species that exhibits self‐fertilization, whose natural populations have usually very low densities. In the present study, the genetic diversity of a wild population from Neguanje Bay, Santa Marta (Colombia), was estimated using microsatellite markers, and the effect of the presence of null alleles on this estimation was assessed. A total of 8 microsatellite markers were developed, the first described for this species, and their amplification conditions were standardized. They were used to determine the genotype of 48 wild individuals from Naguanje Bay, and 1,010 individuals derived from the offspring of 38 directed crosses. For each locus, the frequencies of the identified alleles, including null alleles, were estimated using the statistical package Micro‐Checker, and the parental genotypes were confirmed using segregation analysis. Three to 8 alleles per locus with frequencies from 0.001 to 0.632 were detected. The frequencies of null alleles ranged from 0.10 to 0.45, with Ho from 0.0 to 0.79, and He from 0.53 to 0.80. All loci were in H‐W disequilibrium. The null allele frequencies values were high, with lower estimations using segregation analysis than estimated using Micro‐Checker. The present results show high levels of population genetic diversity and indicate that null alleles were not the only cause of deviation from H‐W equilibrium in all loci, suggesting that the wild population under study presents signs of inbreeding and Wahlund effect.
Highlights
Argopecten nucleus is a pectinid species endemic of the Caribbean Sea that forms very sparse populations in nature, to the extent that no natural beds have been described in literature (Díaz & Puyana, 1994; Lodeiros, Freites, Núñez, & Himmelman, 1993)
Studies on population genetic structure of marine species attract considerable interest, since they allow us to assess the state of conservation of natural populations (Piñero, CaballeroMellado, Cabrera-Toledo, & Zúñiga, 2008; Smith, 1996), to adopt proper management practices in their fisheries, and to develop aquaculture strategies to reduce the risk of inbreeding depression and fitness loss (Gjedrem & Baranski, 2009), contributing to sustainable production over time (Petersen, Baerwald, Ibarra, & May, 2012; Wang, Fu, & Xia, 2013)
There is no information about the genetic structure of wild populations of A. nucleus, but the low population densities usually found for this species suggest the existence of high levels of genetic drift and inbreeding, as previously reported for other mollusks such as Haliotis iris (Smith & Conroy, 1992)
Summary
Argopecten nucleus is a pectinid species endemic of the Caribbean Sea that forms very sparse populations in nature, to the extent that no natural beds have been described in literature (Díaz & Puyana, 1994; Lodeiros, Freites, Núñez, & Himmelman, 1993). The presence of null alleles has been observed in different aquatic species, such as the bivalves Donax trunculus (Rico et al, 2017), Pinna nobilis (González-Wangüemert et al, 2015), Pinctada margaritifera (Lemer, Rochel, & Planes, 2011) and C rassostrea gigas (Hedgecock et al, 2004), and the flatfish Scophthalmus maximus (Borrell et al, 2004), among others These estimations, do not allow to correct the index of genetic diversity, and the precision and confidence interval of the estimations can be very variable depending on the real frequency of the null alleles and other factors such as the sample size, the number of sampled generations, the level and duration of the genetic bottlenecks of the population, nonrandom mating, changes of density or migration rates (Dabrowski et al, 2014). The purpose of the present study is to identify and characterize the first set of primers for microsatellite loci in A. nucleus and use them to estimate the genetic diversity in a wild population from Bahía Neguanje, Santa Marta (Colombia), as well as to assess the effect of the presence of null alleles on the estimations of genetic diversity in a species with self-fertilization and very low population densities in the wild
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