A Significant Genetic Admixture in Farmed Populations of the Noble Scallop Chlamys nobilis Revealed by Microsatellite DNA Analysis in Southern China

The noble scallop, Chlamys nobilis, is an important bivalve mollusk with high commercial value and is usually farmed in the waters of southern China. To date, very little is known about the genetic diversity and population structure of C. nobilis. In this study, 10 microsatellite loci of four farmed C. nobilis populations were compared with one another and compared wild population in southern China. A total of 83 alleles were found. Surprisingly, the level of genetic diversity of the farmed C. nobilis populations was higher than that of the wild population. Although the population genetic of wild population was completely in the Hardy–Weinberg equilibrium, due to heterozygote deficiency, significant deviations from the Hardy–Weinberg equilibrium were found in all farmed populations, suggesting a genetic admixture caused by the mixing of seeds from various hatcheries. The Fst and AMOVA values showed significant genetic differences between wild and farmed populations. The Bayesian assignment also confirmed that genetic admixture was significant and widespread in artificial breeding of C. nobilis. Furthermore, the UPGMA tree topology and PCA demonstrated that the genetic diversity of wild population can be clearly distinguished from farmed populations. In a nutshell, the findings of this study not only fill the knowledge gaps in genetic diversity of wild and farmed C. nobilis populations, but also serve as a guide for maintaining the genetic diversity of C. nobilis in both farmed and wild populations.

Distribution and hybridization of two sedentary gobies (Pomatoschistus microps and Pomatoschistus marmoratus) in the lagoons of southern France

Pomatoschistus marmoratus and Pomatoschistus microps are small sedentary gobies inhabiting the lagoons of European Mediterranean and Atlantic coasts. Along the French Mediterranean coast their respective geographical distribution is not precisely known, in part because they are cryptic species. In this study, 512 gobies of both species were caught as 17 samples in 12 lagoons of the Gulf of Lion on the French Mediterranean coast. They were genotyped at six microsatellite loci and investigated statistically using multidimensional analyses, Bayesian assignment (Structure) and NewHybrids classification. This allowed the contrasted distribution of each species (P. microps in the east, P. marmoratus in the west) to be described, with several exceptions. Neither geographic structure nor isolation by distance was detected among differentiated populations of each species. The suggested mechanism is a deep sedentary behaviour associated with foundations following extinctions. The two species are sympatric or even in syntopy in five or six sampled lagoons producing rare fertile hybrids.

Substantial hybridisation between wild boars (Sus scrofa scrofa) and East Balkan pigs (Sus scrofa f. domestica) in natural environment as a result of semi-wild rearing in Bulgaria

The East Balkan pig (EBP) is a traditional domestic pig breed in Bulgaria managed in semi-wild conditions and well-adapted to the continental climate and rearing on pastures. From the genetical and historical point of view it is important to preserve this ancient breed. However, over the last several years, a dramatic decline of EBP herds has been observed. Moreover, introgression between EBP and wild boar in Bulgaria (WBB) is very likely to have occurred. In this study we used a set of 10 microsatellites and the polymerase chain reaction–restriction fragment length polymorphism method on melanocortin-1 receptor (MC1R) polymorphisms to study the degree of hybridisation between WBB, EBP, and a commercial pig breed (CPB). MC1R results identified WBB-EBP hybrids and the analysis of the microsatellite data with a Bayesian assignment approach and the Discriminant Analysis of Principal Components revealed a low genetic differentiation between WBB and EBP and a high amount of introgression of WBB into EBP. A mentionable introgression of CPB into EBP was also revealed. It is apparent that the traditional rearing system of EBP, which is hundreds of years old, has led to a permanent hybridisation between WBB and EBP. In our opinion, the preservation of the semi-wild rearing system is a prerequisite for the conservation of this old, indigenous pig breed and its genetic composition, as the semi-wild rearing system allows the continuous introgression with WBB. Moreover, the introgression of commercial breeds into EBP or WBB should be prevented. Due to the bidirectional gene flow these hybridisation events would have negative consequences (i.e. loss of viability and adaptation) for the wild boars as well as for the indigenous pig breed.

Genetic Structure of Sympatric Sexually and Parthenogenetically Reproducing Population of Chara canescens (Charophyta)

Individuals that reproduce parthenogenetically do not have to produce males and can therefore produce twice as many female offspring. With this twofold reproduction advantage of asexual reproduction, the question of how sex persists in the short term remains unresolved. In the dioecious charophyte Chara canescens, both parthenogenetically reproducing females and sexually reproducing females and males occur sympatrically at only one site in Europe: Neusiedler See-Seewinkel (Austria). By means of four nuclear species-specific microsatellite loci, we examined the interaction between coexisting sexuals and parthenogens by analysing the population structure and gene flow between both reproduction systems. Using a Bayesian assignment method, we found that the sites encompassed two genetically distinct clusters of individuals. The first cluster included genotypes of sexual individuals, which are genetically distinct from a second cluster which included parthenogenetic individuals and few sexually reproducing males, which are genetically identical to the parthenogenetic individuals. However, an analysis of the population genetic structure found no differences with respect to genotypic variation, clonal diversity, and population differentiation between the sympatric parthenogenetically and the sexually reproducing populations. The results indicated that the parthenogenetic individuals cannot outcompete the sexually reproducing individuals.

The relic Criollo cacao in Belize – genetic diversity and relationship with Trinitario and other cacao clones held in the International Cocoa Genebank, Trinidad

Cacao (Theobroma cacao L.) was domesticated in Mesoamerica and is native to the South American rainforest. Belizean Criollo is a group of relic landraces that are thought to be similar to those used by the Olmecs and Mayans during early domestication. Knowledge of genetic diversity is essential for efficient conservation and use of these relic landraces. Using 30 microsatellite markers, we characterized genetic diversity in 77 Belize Criollo accessions collected from the Maya Mountains in Belize, and assessed their relationship with 62 cacao accessions including 25 Trinitario accessions. Genetic diversity and heterozygosity were low in Belizean Criollo germplasm. Eleven distinctive genotypes were identified among the Belizean germplasm. Results of ordination and cluster analysis supported their putative ancestral contribution to the Trinitario cacao. However, results of Bayesian assignment and parentage analysis both suggested that the contribution of Criollo cacao to the Imperial College Selections Trinitario is small. Our preferred hypothesis for the genesis of Trinitario cacao is that a limited population of Criollo × Forastero hybrids emanated from the introduced Forastero population of Trinidad. The present study provides new insights into the origin of the Trinitario cacao, which will be useful in the ex situ and in situ conservation of cacao landraces from Mesoamerica.