A continent-wide high genetic load in African buffalo revealed by clines in the frequency of deleterious alleles, genetic hitchhiking and linkage disequilibrium

A high genetic load can negatively affect population viability and increase susceptibility to diseases and other environmental stressors. Prior microsatellite studies of two African buffalo (Syncerus caffer) populations in South Africa indicated substantial genome-wide genetic load due to high-frequency occurrence of deleterious alleles. The occurrence of these alleles, which negatively affect male body condition and bovine tuberculosis resistance, throughout most of the buffalo’s range were evaluated in this study. Using available microsatellite data (2–17 microsatellite loci) for 1676 animals from 34 localities (from 25°S to 5°N), we uncovered continent-wide frequency clines of microsatellite alleles associated with the aforementioned male traits. Frequencies decreased over a south-to-north latitude range (average per-locus Pearson r = -0.22). The frequency clines coincided with a multilocus-heterozygosity cline (adjusted R2 = 0.84), showing up to a 16% decrease in southern Africa compared to East Africa. Furthermore, continent-wide linkage disequilibrium (LD) at five linked locus pairs was detected, characterized by a high fraction of positive interlocus associations (0.66, 95% CI: 0.53, 0.77) between male-deleterious-trait-associated alleles. Our findings suggest continent-wide and genome-wide selection of male-deleterious alleles driven by an earlier observed sex-chromosomal meiotic drive system, resulting in frequency clines, reduced heterozygosity due to hitchhiking effects and extensive LD due to male-deleterious alleles co-occurring in haplotypes. The selection pressures involved must be high to prevent destruction of allele-frequency clines and haplotypes by LD decay. Since most buffalo populations are stable, these results indicate that natural mammal populations, depending on their genetic background, can withstand a high genetic load.

Genotype data not consistent with clonal transmission of sea turtle fibropapillomatosis or goldfish schwannoma

Recent discoveries of transmissible cancers in multiple bivalve species suggest that direct transmission of cancer cells within species may be more common than previously thought, particularly in aquatic environments. Fibropapillomatosis occurs with high prevalence in green sea turtles (Chelonia mydas) and the geographic range of disease has increased since fibropapillomatosis was first reported in this species. Widespread incidence of schwannomas, benign tumours of Schwann cell origin, reported in aquarium-bred goldfish (Carassius auratus), suggest an infectious aetiology. We investigated the hypothesis that cancers in these species arise by clonal transmission of cancer cells. Through analysis of polymorphic microsatellite alleles, we demonstrate concordance of host and tumour genotypes in diseased animals. These results imply that the tumours examined arose from independent oncogenic transformation of host tissue and were not clonally transmitted. Further, failure to experimentally transmit goldfish schwannoma via water exposure or inoculation suggest that this disease is unlikely to have an infectious aetiology.

Microsatellites to reveal genetic diversity and to distinguish four mangoes of Tegal District, Central Java, Indonesia

Hidayat A, Rahayu ES, Abdullah M, Retnoningsih A. 2021. Microsatellites to reveal genetic diversity and to distinguish four mangoes of Tegal District, Central Java, Indonesia. Biodiversitas 22: 3467-3473. The Wirasangka mango is Tegal District’s flora of identity, which requires recognition, and its existence deserves to be preserved. However, based on the morphology of the fruit, most of the people of Tegal still have difficulty distinguishing the wirasangka mango from other mangoes. Molecular markers are needed to ascertain the differences between these mango varieties. Microsatellite DNA is a repeating DNA of stable DNA markers with high repeatability and polymorphism. This study analyzes the level of genetic diversity and microsatellite alleles that can differentiate four mangoes from Tegal District, Central Java, Indonesia, i.e. wirasangka, tengkueh, golek, and okyong. Eleven accessions of six locations in Tegal District were analyzed using ten microsatellite loci. The microsatellite amplification result was separated using electrophoresis in 6% polyacrylamide gel and then visualized with silver dye. A total of 35 microsatellite alleles were found measuring 100-1000 bp, ranging from 1-7 alleles for each locus. The average polymorphism information content (PIC) of 0.54 indicates that genetic diversity is relatively high and informative. Therefore, the microsatellite alleles can be used to differentiate mango varieties. The specific allele characteristic of wirasangka mango accession is locus AJ63516, with an allele size of 600-700bp.

Population structure and genetic diversity of non-native aoudad populations

The aoudad (Ammotragus lervia Pallas 1777) is an ungulate species, native to the mountain ranges of North Africa. In the second half of the twentieth century, it was successfully introduced in some European countries, mainly for hunting purposes, i.e. in Croatia, the Czech Republic, Italy, and Spain. We used neutral genetic markers, the mitochondrial DNA control region sequence and microsatellite loci, to characterize and compare genetic diversity and spatial pattern of genetic structure on different timeframes among all European aoudad populations. Four distinct control region haplotypes found in European aoudad populations indicate that the aoudad has been introduced in Europe from multiple genetic sources, with the population in the Sierra Espuña as the only population in which more than one haplotype was detected. The number of detected microsatellite alleles within all populations (< 3.61) and mean proportion of shared alleles within all analysed populations (< 0.55) indicates relatively low genetic variability, as expected for new populations funded by a small number of individuals. In STRUCTURE results with K = 2–4, Croatian and Czech populations cluster in the same genetic cluster, indicating joined origin. Among three populations from Spain, Almeria population shows as genetically distinct from others in results, while other Spanish populations diverge at K = 4. Maintenance of genetic diversity should be included in the management of populations to sustain their viability, specially for small Czech population with high proportion of shared alleles (0.85) and Croatian population that had the smallest estimated effective population size (Ne = 5.4).

First Isolation and Genotyping of Toxoplasma Gondii Strains From Domestic Animals in Tunisia

The isolation and molecular typing of Toxoplasma gondii strains provides an essential basis for a better understanding of the distribution of genetic diversity and associated human health risks. In this context, we report, the molecular characterization of strains of T. gondii isolated from domestic animals infected with T. gondii in Southern and coastal area of Tunisia. This diversity is compared to that known for the Western European and Mediterranean sub-region.Blood, hearts and/or brains were collected from 766 domestic animals (630 sheep and 136 free-range chickens). Strain isolation from these samples were performed using mouse bioassay. The strains genotyping was carried out with a multiplex PCR technique using 15 microsatellite markers. Viable strains of T. gondii were isolated from 13.4% sheep and 33.3% chickens. Furthermore, the parasite was also detected in three DNA extracts from animal tissue digestates.This study showed a large predominance of type II strains (87.9%) from which two samples were type II variants for W35 locus. The other genotypes were three type III sheep isolates (9.1%) and, for the first time in Tunisia, an isolate of sheep origin of the Africa 4 genotype (3.0%). The comparison of microsatellite alleles of type II strains shows the recent migration of strains between Tunisia and other countries of the world.

Seascape Genomics of the Sugar Kelp Saccharina latissima Along the North Eastern Atlantic Latitudinal Gradient

Temperature is one of the most important range-limiting factors for many seaweeds. Driven by the recent climatic changes, rapid northward shifts of species’ distribution ranges can potentially modify the phylogeographic signature of Last Glacial Maximum such as increased genetic diversity at lower latitudes. To explore this question in detail in the kelp Saccharina latissima, we used microsatellites and double digest RAD-sequencing derived SNPs on S. latissima sporophytes sampled within 11 sites spanning the entire European Atlantic latitudinal range of this species. In addition, we checked for statistical correlation between genetic marker allele frequencies and three environmental proxies (sea surface temperature, salinity, and water turbidity). Our findings revealed that genetic diversity was significantly higher for the northern localities compared to the southern ones in contrast to the expected phylogeographic pattern. This suggests that the southernmost S. latissima populations are negatively affected by the recent climatic changes but also that the recolonization of S. latissima range following the LGM may have occurred from northerly refugia. Seven SNPs and 12 microsatellite alleles were found to be significantly associated with at least one of the three environmental variables. We discuss the potential adaptive functions of the genes associated with the outlier markers and the importance of these markers for successful conservation and aquaculture strategies for S. latissima in this age of rapid global change.

Painted black: Iguana melanoderma (Reptilia, Squamata, Iguanidae) a new melanistic endemic species from Saba and Montserrat islands (Lesser Antilles)

The Lesser Antilles, in the Eastern Caribbean, is inhabited by three Iguana species: the Lesser Antillean iguanaIguana delicatissima, which is endemic to the northernmost islands of the Lesser Antilles, the introduced common iguana from South America, Iguana iguana iguana, represented also by the two newly described endemic subspecies Iguana iguana sanctaluciae from Saint Lucia and Iguana iguana insularis from Saint Vincent and the Grenadines, and Grenada, and the introduced Iguana rhinolopha from Central America. Drawing on both morphological and genetic data, this paper describes the Iguana populations from Saba and Montserrat as a new species, Iguana melanoderma. This species is recognized on the basis of the following combination of characteristics: private microsatellite alleles, unique mitochondrial ND4 haplotypes, a distinctive black spot between the eye and tympanum, a dorsal carpet pattern on juveniles and young adults, a darkening of body coloration with aging (except for the anterior part of the snout), a black dewlap, pink on the jowl, the high number of large tubercular nape scales, fewer than ten medium sized–triangular dewlap spikes, high dorsal spikes, and lack of horns on the snout. This new melanistic taxon is threatened by unsustainable harvesting (including for the pet trade) and both competition and hybridization from escaped or released invasive alien iguanas (I. iguana iguana and I. rhinolopha) from South and Central America, respectively. The authors call for action to conserve Iguana melanoderma in Saba and Montserrat and for further research to investigate its relationship to other melanistic iguanas from the Virgin Islands and coastal islands of Venezuela.

Molecular Identification of the “Facciuta Della Valnerina” Local Goat Population Reared in the Umbria Region, Italy

Italy holds important genetic resources of small ruminant breeds. By distinguishing goat breeds at the DNA level, certification of products from specific breeds can be valorized. The aim of this study was to establish the genetic identity of Facciuta della Valnerina, a local goat population of Italy, compared with the cosmopolitan breeds, Saanen and Camosciata delle Alpi, reared in the same geographic area. A total of 116 microsatellite alleles ranging from 4 to 13 were detected at 16 loci in the three goat populations/breeds. A total of 23 private alleles with frequencies lower than 0.3 were detected in the Facciuta della Valnerina population. The mean numbers of alleles were 6.67, 4.58, and 4.92 in Facciuta della Valnerina, Camosciata delle Alpi, and Saanen, respectively. The expected heterozygosity ranged from 0.20 to 0.86. Most loci were highly polymorphic and informative (polymorphic information content ≥0.50). Factorial correspondence analysis and principal components analysis revealed very clear separation between Facciuta della Valnerina and the two reference goat breeds. Reducing the number of markers from 16 to 12 (on the basis of polymorphic information content and the number of alleles) still allowed us to distinguish the local population, indicating that microsatellite markers are capable of discriminating local livestock breeds at a low cost.