Levels Of Gene Diversity Research Articles

Genotypic variation and population structure of Sclerotinia trifoliorum infecting chickpea in California

Sclerotinia trifoliorum, an important pathogen of cool season legumes, displays both homothallism and heterothallism in its life cycle, unique among members of the genus Sclerotinia. Very little is known about its genetic diversity and population structure. A sample of 129 isolates of S. trifoliorum from diseased chickpea in California was investigated for genetic diversity, population differentiation and reproductive mode. Genetic diversity was estimated using mycelial compatibility (MCG) phenotypes, rDNA intron variation, and allelic diversity at seven microsatellite loci. Genetic analysis revealed high levels of genotypic diversity demonstrated by high genotypic richness (0·88). Similarly, high levels of gene diversity (mean expected heterozygosity HE = 0·68) were observed at the microsatellite loci. Geographic populations of S. trifoliorum were highly admixed as evident from low FST values (0–0·11), suggesting high contemporary or historical gene flow. Hierarchical analysis of molecular variance showed that more than 92% of the genetic variation occurred among isolates within populations. Bayesian clustering analysis identified four cryptic genetic populations that were not correlated to geographic location, and index of multilocus association was non‐significant in each of the four genetic populations. However, the presence of identical haplotypes within and among populations indicates clonal reproduction. The high levels of haplotype diversity and population heterogeneity, a lack of correspondence between MCG and microsatellite haplotype, and low levels of population differentiation suggest that populations of S. trifoliorum in chickpea have been undergoing extensive outcrossing and migration events probably shaped by human‐mediated dissemination, the underlying diverse cropping systems, and chickpea disease management practices.

Molecular Identification and Historic Demography of the Marine Tucuxi (Sotalia guianensis) at the Amazon River’s Mouth by Means of Mitochondrial Control Region Gene Sequences and Implications for Conservation

In 2005, three fishermen, with artisan fishing vessels and drift gillnets, accidentally captured around 200 dolphins between Vigia and Salinópolis in the Amazon River estuary. The dolphins died and they then prepared their vaginas and penises in order to sell them in the Ver-ao-Peso market in the city of Belem within the Brazilian state of Pará. We randomly sampled a minimal quantity of tissue of these sexual organs from 78 of these 200 dolphins and we determined the following results after sequencing 689 base pairs (bp) from the mitochondrial control region gene: (1) 96.15% (75/78) of these dolphins belonged to the species Sotalia guianensis. The other species detected were Steno brenadensis, Stenella coeruleoalba and Tursiops truncatus; (2) The levels of gene diversity found in this sample of S. guianensis were high (33 haplotypes, haplotype diversity of 0.917 and nucleotide diversity of 0.0045) compared to gene diversities found in other Brazilian S. guianensis locations; (3) All the population genetics methods employed indicated a clear population expansion in this population. This population expansion could have begun 400,000 years ago; (4) The haplotype divergence within this population could have begun around 2.1 millions of years ago (MYA), with posterior splits around 2.0–1.8 MYA, 1.7–1.8 MYA, 1–1.5 MYA, 0.6–0.8 MYA, 0.4–0.2 MYA and 0.16–0.02 MYA, all during the Pleistocene.

Genetic Variability in Natural Populations ofAgave durangensis(Agavaceae) Revealed by Morphological and Molecular Traits

Agave durangensis is an endemic species that occurs in a reduced area in southern Durango and northern Zacatecas, Mexico. We analyzed the genetic variability of three populations of the species using two pairs of Inverse-Sequence-Tagged-Repeat primers and nine morphological characters to determine the species of the morphologically variable populations. The primers generated characteristic amplification profiles, which distinguished between populations of A. durangensis and revealed interspecific variability when compared with individuals of A. asperrima. Some incongruence between morphological and molecular variability was detected. High genetic variability was indicated by an elevated level of polymorphism (24.18–61.50%) among 91 genetic loci amplified and by the level of gene diversity (0.0807–0.2337) among populations. Genetic differentiation (0.0328–0.4857), gene flow (0.5294–14.7511), genetic distance (0.0200–0.3019), and genetic identity (0.7653–0.9802) among populations suggested that one of the three populations of A. durangensis is in a present advanced diversification process but may still maintain some level of gene flow with the other two populations. Urgent conservation efforts, including protection from harvest, should be addressed for maintaining the genetic variability of the natural populations of A. durangensis.Agave durangensis es una especie endémica que crece en un área reducida del sur de Durango y norte de Zacatecas, México. Analizamos la variabilidad genética de tres poblaciones de esa especie usando dos pares de iniciadores de los marcadores de Repetición de Secuencias Inversas Marcadas (ISTR por sus siglas en inglés) y nueve atributos morfológicos para determinar las especies de las poblaciones morfológicamente muy variables. Los iniciadores generaron perfiles de amplificación característicos, mostrando su capacidad para distinguir entre poblaciones de A. durangensis y para revelar variabilidad intereespecífica cuando los perfiles se compararon con los de A. asperrima. Incongruencia entre la variabilidad morfológica y la molecular fue detectada. Alta variabilidad genética fue encontrada, indicada por los elevados niveles de polimorfismo (24.18–61.50 %) entre 91 loci genéticos amplificados y por los valores de diversidad génica (0.0807–0.2337) entre poblaciones. Diferenciación genética interpoblacional (0.0328–0.4857), flujo genético (0.5294–14.7511), distancia genética (0.0200–0.3019) y la identidad genética (0.7653–0.9802) sugieren que una de las tres poblaciones de A. durangensis se encuentra en un proceso actual avanzado de diversificación, pero que aún existe flujo genético con las otras dos poblaciones. Esfuerzos urgentes de conservación incluyendo la protección de recolección se deberían de contemplar para mantener la variabilidad genética de las poblaciones naturales de A. durangensis.

Genetic drift outweighs natural selection at toll‐like receptor (TLR) immunity loci in a re‐introduced population of a threatened species

During population establishment, genetic drift can be the key driver of changes in genetic diversity, particularly while the population is small. However, natural selection can also play a role in shaping diversity at functionally important loci. We used a well-studied, re-introduced population of the threatened Stewart Island robin (N=722 pedigreed individuals) to determine whether selection shaped genetic diversity at innate immunity toll-like receptor (TLR) genes, over a 9-year period of population growth following establishment with 12 genetic founders. We found no evidence for selection operating with respect to TLR diversity on first-year overwinter survival for the majority of loci, genotypes and alleles studied. However, survival of individuals with TLR4BE genotype was significantly improved: these birds were less than half as likely to die prior to maturity compared with all other TLR4 genotypes. Furthermore, the population frequency of this genotype, at a two-fold excess over Hardy-Weinberg expectation, was increased by nonrandom mating. Near-complete sampling and full pedigree and reproductive data enabled us to eliminate other potential causes of these patterns including inbreeding, year effects, density dependence, selection on animals at earlier life history stages or genome-level association of the TLR4E allele with 'good genes'. However, comparison of observed levels of gene diversity to predictions under simulated genetic drift revealed results consistent with neutral expectations for all loci, including TLR4. Although selection favoured TLR4BE heterozygotes in this population, these effects were insufficient to outweigh genetic drift. This is the first empirical study to show that genetic drift can overwhelm natural selection in a wild population immediately following establishment.

Genetic structure and diversity of indigenous rice (Oryza sativa) varieties in the Eastern Himalayan region of Northeast India

The Eastern Himalayan region of Northeast (NE) India is home to a large number of indigenous rice varieties, which may serve as a valuable genetic resource for future crop improvement to meet the ever-increasing demand for food production. However, these varieties are rapidly being lost due to changes in land-use and agricultural practices, which favor agronomically improved varieties. A detailed understanding of the genetic structure and diversity of indigenous rice varieties is crucial for efficient utilization of rice genetic resources and for developing suitable conservation strategies. To explore the genetic structure and diversity of rice varieties in NE India, we genotyped 300 individuals of 24 indigenous rice varieties representing sali, boro, jum and glutinous types, 5 agronomically improved varieties, and one wild rice species (O. rufipogon) using seven SSR markers. A total of 85 alleles and a very high level of gene diversity (0.776) were detected among the indigenous rice varieties of the region. Considerable level of genetic variation was found within indigenous varieties whereas improved varieties were monoporphic across all loci. The comparison of genetic diversity among different types of rice revealed that sali type possessed the highest gene diversity (0.747) followed by jum (0.627), glutinous (0.602) and boro (0.596) types of indigenous rice varieties, while the lowest diversity was detected in agronomically improved varieties (0.459). The AMOVA results showed that 66% of the variation was distributed among varieties indicating a very high level of genetic differentiation in rice varieties in the region. Two major genetically defined clusters corresponding to indica and japonica groups were detected in rice varieties of the region. Overall, traditionally cultivated indigenous rice varieties in NE India showed high levels of genetic diversity comparable to levels of genetic diversity reported from wild rice populations in various parts of the world. The efforts for conservation of rice germplasm in NE India should consider saving rice varieties representing different types with specific emphasis given to sali and jum types. The protection against the loss of vast genetic diversity found in indigenous rice varieties in NE India is crucial for maintaining future food security in the changing world.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-228) contains supplementary material, which is available to authorized users.

Assessment of genetic diversity and population structure of Vietnamese indigenous cattle populations by microsatellites

Cattle play a very important role in agriculture and food security in Vietnam. A high level of cattle diversity exists and serves different needs of Vietnamese cattle keepers but has not yet been molecularly characterized. This study evaluates the genetic diversity and structure of Vietnamese indigenous cattle populations, using microsatellite markers. A total of 410 individuals from six indigenous cattle populations and an exotic breed was characterized using 27 microsatellite markers A total of 362 alleles was detected and the number of alleles per locus ranged from 8 (INRA005 and ILSTS005) to 17 (ETH185). The level of gene diversity was high indicated by a mean expected heterozygosity (He) across populations and loci of 0.73. Level of inbreeding (mean FIS=0.05) and genetic differentiation (mean FST=0.04) was moderate. The phylogenetic tree based on Reynolds genetic distance reflected geographic distances. Structure analysis indicated five homogeneous clusters. The Brahman, Lang Son, Ha Giang and U Dau Riu cattle were assigned to independent clusters while Nghe An, Thanh Hoa and Phu Yen cattle were grouped in a single cluster. We conclude that Vietnamese indigenous cattle have high levels of genetic diversity and distinct genetic structures. Based on these results, we recommend that for conservation homogenous populations (Nghe An, Thanh Hoa and Phu Yen) can be grouped to reduce costs and U Dau Riu, Lang Son and Ha Giang populations should be conserved separately to avoid loss of genetic diversity.

Diversity of Benzylsuccinate Synthase-Like ( bssA ) Genes in Hydrocarbon-Polluted Marine Sediments Suggests Substrate-Dependent Clustering

The potential of hydrocarbon biodegradation in marine sediments was determined through the detection of a functional biomarker, the bssA gene, coding for benzylsuccinate synthase, the key enzyme of anaerobic toluene degradation. Eight bssA clone libraries (409 sequences) were constructed from polluted sediments affected by the Prestige oil spill in the Atlantic Islands National Park and from hydrocarbon-amended sediment microcosms in Mallorca. The amplified products and database-derived bssA-like sequences grouped into four major clusters, as determined by phylogenetic reconstruction, principal coordinate analysis (PCoA), and a subfamily prediction tool. In addition to the classical bssA sequences that were targeted, we were able to detect sequences homologous to the naphthylmethylsuccinate synthase gene (nmsA) and the alkylsuccinate synthase gene (assA), the bssA homologues for anaerobic 2-methylnaphthalene and alkane degradation, respectively. The detection of bssA-like variants was determined by the persistence and level of pollution in the marine samples. The observed level of gene diversity was lower in the Mallorca sediments, which were dominated by assA-like sequences. In contrast, the Atlantic Islands samples, which were highly contaminated with methylnaphthalene-rich crude oil, showed a high proportion of nmsA-like sequences. Some of the detected genes were phylogenetically related to Deltaproteobacteria communities, previously described as the predominant hydrocarbon degraders at these sites. Differences between all detected bssA-like genes described to date indicate separation between marine and terrestrial sequences and further subgrouping according to taxonomic affiliation. Global analysis suggested that bssA homologues appeared to cluster according to substrate specificity. We observed undetected divergent gene lineages of bssA homologues, which evidence the existence of new degrader groups in these environments.

Genetic variation (AFLPs and nuclear microsatellites) in two anagenetically derived endemic species of Myrceugenia (Myrtaceae) on the Juan Fernández Islands, Chile

Anagenesis (or phyletic evolution) is one mode of speciation that occurs in the evolution of plants on oceanic islands. Of two endemic species on the Juan Fernández Islands (Chile), Myrceugenia fernandeziana and M. schulzei (Myrtaceae), believed to have originated anagenetically from different continental progenitors, the first is endemic to Robinson Crusoe Island and has no clear tie to continental relatives; the last is endemic to the younger island, Alejandro Selkirk Island, and has close affinity to M. colchaguensis in mainland Chile. Using AFLPs and six nuclear microsatellites from 381 individuals representing 33 populations, we determined patterns of genetic variation within and among populations on both islands and between those of the islands and mainland. Considerable genetic variation was found within populations on both islands. The level of gene diversity within M. schulzei was equivalent to that of its close continental relative M. colchaguensis. Genetic diversity was not partitioned geographically in M. fernandeziana and was weakly so and nonsignificantly in M. schulzei. The high genetic variation in both taxa is most likely due to anagenetic speciation. Subsidence of the older island Robinson Crusoe, landscape erosion, and restructuring of communities have severely reduced the overall island population to a single panmictic system. On the younger and less modified Alejandro Selkirk Island, slightly stronger patterns of genetic divergence are seen in M. schulzei. Because both species are genetically diverse and number in the thousands of individuals, neither is presently endangered in the archipelago.

Global population structure and migration patterns suggest significant population differentiation among isolates of Pyrenophora tritici-repentis

The global population structure and migration patterns of foliar wheat pathogen Pyrenophora tritici-repentis (PTR) were determined using 12 microsatellite loci. Analysis of 439 single-spore isolates of PTR from five continents (18 wheat-producing countries) showed high level of genetic diversity, and moderate to high population differentiation between continents. A high level of gene diversity (HS=0.31 to 0.56) was observed within each population. Allelic richness indicated the European and the North American population have a high effective population size. Bayesian analyses showed five clusters where the inferred clusters did not represent geographical populations. Corrected standardized fixation index (GST″) estimates ranged from 0.042 to 0.265 between populations, indicating low to high genetic differentiation exists between populations. We found migration (gene flow) between old world (Europe) and new world (Americas) population; however, little migration was observed among other continents. The European population was the major source of immigrants for the North American, South American, Australian and the Asian populations. Significant (P<0.001) linkage disequilibrium (LD) was detected in the Australian and the South American populations. In contrast, non-significant (P<0.001) LD values were observed in the Asian, European and the North American populations. Overall, our findings demonstrate the population differentiation exits among the global populations and strict quarantine measures should be applied to prevent the accelerated global spread of this pathogen.

Особенности генетического разнообразияAnser albifronsScopoli, 1769 иAnser fabalisLatham, 1787 на Дальнем Востоке России

Using RAPD PCR analysis and sequencing of the 5' end segment of the mtDNA control region, the genetic diversity and differentiation of Far Eastern populations of greater white-fronted goose Anser albifrons Scopoli, 1769 and bean goose Anser fabalis Latham, 1787 were examined. Based on RAPD PCR data, the level of gene diversity (h) for A. albifrons (0.3634) and A. fabalis (0.3899) was calculated. Sequence data showed considerably higher level of inter-population diversity in A. fabalis (26.4%), compared to A. albifrons (1.88%). Similarly, the nucleotide and haplotype diversity parameters were somewhat higher in A. fabalis (0.01852 and 0.955). Phylogenetic reconstructions generated using neighbor-joining and maximum parsimony algorithms divided each of the examined species into two clusters that differ in the number of haplotypes included. These clusters can correspond to the subspecies that live in the Far East.

Population Structure and Management of Podosphaera pannosaAssociated with Peach Powdery Mildew in Oman

AbstractIn 2004, severe powdery mildew infection on peach occurred in Al‐Jabal Al‐Akdhar, Oman, and resulted in substantial yield losses to growers. This study was conducted to investigate occurrence, causal agents, genetic diversity and efficacy of azoxystrobin in management of this disease. Powdery mildew was observed on all farms and peach trees in Al‐Jabal Al‐Akdhar. Disease symptoms were first observed on shoots in April, followed by appearance on fruits. Disease severity reached its peak between May and June. Morphological and molecular identification of 22 powdery mildew isolates indicated that all belong to Podosphaera pannosa. Podosphaera pannosa reproduced the same symptoms upon inoculation on peach leaves. Amplified fragment length polymorphisms analysis of 35 isolates of P. pannosa from five different villages using four primer pair combinations produced 688 polymorphic loci and 35 different genotypes. Populations of P. pannosa were found to have low levels of gene diversity (H = 0.1858), which suggests that P. pannosa has been recently introduced into Al‐Jabal Al‐Akdhar. Analysis of molecular variance showed low levels of genetic differentiation among populations from the different villages, implying the introduction of P. pannosa into the different villages via common sources as well as frequent movement of pathogen inoculum among the different villages. Evaluating the efficacy of azoxystrobin showed that azoxystrobin is as efficacious as thiophanate‐methyl in managing the disease, with sulphur being the least efficacious. The study is the first to report the presence of P. pannosa in Oman. Also reported are its genetic diversity and its management under commercial conditions.

The disappearing northern leopard frog (Lithobates pipiens): conservation genetics and implications for remnant populations in westernNevada

Global amphibian declines suggest a major shift in the amount and quality of habitat for these sensitive taxa. Many species that were once widespread are now experiencing declines either in part of or across their historic range. The northern leopard frog (Rana [Lithobates] pipiens] has undergone significant declines particularly in the western United States and Canada. Leopard frog population losses in Nevada are largely due to habitat fragmentation and the introduction of nonnative fish, amphibian, and plant species. Only two populations remain in the Truckee and Carson River watersheds of western Nevada which represents the western boundary of this species range. We used sequence data for an 812 base pair fragment of the mitochondrial NADH dehydrogenase 1 (ND1) gene to support a native origin for western Nevada populations. All frogs had a single haplotype (W07) from the distinct western North America ND1 haplotype clade. Data from seven polymorphic microsatellite loci show that Truckee and Carson River populations are highly differentiated from each other and from leopard frogs collected from eastern Nevada sites. Lack of gene flow among and distinct color morphs among the western Nevada populations likely predates the current geographical isolation. Comparisons with other peripheral L. pipiens populations show western Nevada populations have similar levels of gene diversity despite their contemporary isolation (HE 0.411, 0.482). Restoration of leopard frog populations in these watersheds will be challenging given well-entrenched nonnative bullfrog populations and major changes to the riparian zone over the past century. Declines of once common amphibian species has become a major conservation concern. Contemporary isolation of populations on a species range periphery such as the leopard frog populations in the Truckee and Carson rivers further exacerbate extirpation risk as these populations are likely to have fewer genetic resources to adaptively respond to rapidly changing biotic and abiotic environments.

Population genetics of cobia (Rachycentron canadum) in the Gulf of Thailand and Andaman Sea: fisheries management implications

Population genetics has been recognized as a key component of policy development for fisheries and conservation management and aquaculture development. This study aims to evaluate the genetic diversity and population structure of native cobia (Rachycentron canadum) in the Gulf of Thailand and Andaman Sea, establishing the existing population distributions and contributing information to aid in the development of policy, prior to extensive aquaculture development. Microsatellite analysis of natural cobia populations in these two ocean basins shows similar levels of gene diversity at 0.844 and 0.837, respectively. All populations and almost all microsatellite loci studied show significant heterozygote deficiency. Genetic differentiation between local populations is low and mostly not significant (R ST = −0.0109 to 0.0066). The population shows no marked structure over the long geographic barrier of the Thai–Malay peninsula, either when analyzed using pairwise genetic differences or evaluated without predefined populations using STRUCTURE. Additionally, a Mantel test shows no evidence of isolation by distance between the population samples. The significant heterozygote deficiency at most of the loci studied could be explained by the possibility of null alleles. Alternatively, given the behavior of forming small spawning aggregations, seasonal migration, and hitchhiking on large marine animals, the population genetics could be complex. The population of cobia at each location in Thai waters may be inbred, as a result of breeding between relatives, which would reduce heterozygosity relative to Hardy–Weinberg frequencies, while some of these populations could be making long distance migrations followed by admixture between resident and transient groups. This migration would cause population homogeneity in allele frequencies on a larger geographic scale. The results suggest that fisheries management for this species should be considered at both national and international levels, and until the possibility of local adaptation is fully investigated, policy development should apply the precautionary principle to ensure the preservation of genetic diversity and the sustainability of local and regional fisheries.

Novel SNP development and analysis at a NADP+‐specific IDH enzyme gene in a four species mixed oak forest

Closely related Quercus species generally exhibit low levels of genetic differentiation despite their ecological and morphological differences. However, at a few so-called 'outlier' loci they seem to remain genetically distinct. Isocitrate dehydrogenases (IDH) are key enzymes involved in the metabolic pathway of the citrate cycle. IDH has also been characterised as an 'outlier' marker, significantly differentiating the closely related Q.robur and Q.petraea with the isozyme technique. This ability to differentiate the species was tested here at molecular level: 13 single nucleotide polymorphism (SNP) markers were identified and developed within a NADP(+) -specific IDH gene in Quercus spp. and applied as molecular markers in a four species mixed oak forest in eastern Europe, where Q.robur, Q.petraea, Q.pubescens and Q.frainetto naturally co-exist. From the 13 developed SNPs, three groups were formed: non-synonymous, synonymous and non-coding SNPs. The levels of total gene diversity were moderate for all species investigated. The non-synonymous SNPs showed lower levels of gene diversity. Overall, the four closely related Quercus spp. were significantly differentiated (except Q.petraea with Q.frainetto). Analysis of non-random association of alleles revealed no clear physical clustering of the SNP sites in significant linkage disequilibrium (LD). However, separate LD analysis for each species showed a lower number of sites in significant LD for Q.robur than for the other species, possibly reflecting the history of the species in this specific geographical site and less efficient recombination effect due to the larger effective population size of Q.robur. Eleven statistically significant associations were found between seven SNPs and morphological traits that are commonly used to differentiate oak species.

The Nile Soft-shell Turtle, Trionyx triunguis, of Israel and Turkey: Two genetically indistinguishable populations?

Whereas the Nile Soft-shelled Turtle, Trionyx triunguis, used to be found in most of the east Mediterranean rivers, today only three major subpopulations remain: two in Turkey and one in Israel. The management of small subpopulations should rely on their genetic relatedness, and so this study examined the AFLP and cytochrome b genetic diversity of 58 T. triunguis specimens from the Alexander River in Israel and from Dalaman’s Lake Kükürtlü in southwestern Turkey. The four selective primer pairs for AFLPs yielded 339 distinct loci. We found the populations to be highly polymorphic (>88%) and the level of gene diversity (He) relatively low (0.11). Indeed, using our methods, the two populations were found to be genetically identical (I=1.0). Our study further demonstrates a high identity of the mitochondrial gene cytochrome b DNA sequence with a Liberian (West Africa) specimen of T. triunguis. These results support previous preliminary genetic studies and observations which showed that this species travels around in the Mediterranean Sea. However, we suggest that the results are evidence of previous large populations and of past connections with the African populations, and that the dams on the Nile are probably preventing this gene flow today.

Genetic Diversity and Variability in Endangered Pantesco and Two Other Sicilian Donkey Breeds Assessed by Microsatellite Markers

The genetic variability of Pantesco and other two Sicilian autochthonous donkey breeds (Ragusano and Grigio Siciliano) was assessed using a set of 14 microsatellites. The main goals were to describe the current differentiation among the breeds and to provide genetic information useful to safeguard the Pantesco breed as well as to manage Ragusano and Grigio Siciliano. In the whole sample, that included 108 donkeys representative of the three populations, a total of 85 alleles were detected. The mean number of alleles was lower in Pantesco (3.7), than in Grigio Siciliano and Ragusano (4.4 and 5.9, resp.). The three breeds showed a quite low level of gene diversity (He) ranging from 0.471 in Pantesco to 0.589 in Grigio. The overall genetic differentiation index (Fst) was quite high; more than 10% of the diversity was found among breeds. Reynolds' (D R) genetic distances, correspondence, and population structure analysis reproduced the same picture, revealing that, (a) Pantesco breed is the most differentiated in the context of the Sicilian indigenous breeds, (b) within Ragusano breed, two well-defined subgroups were observed. This information is worth of further investigation in order to provide suitable data for conservation strategies.

High gene flow and outcrossing within populations of two cryptic fungal pathogens on a native and non-native host in Cameroon

In this study, we determined the genetic diversity of 126 isolates representing both Lasiodiplodia theobromae and Lasiodiplodia pseudotheobromae, collected from Theobroma cacao and Terminalia spp. in Cameroon, using simple sequence repeat (SSR) markers. SSR alleles showed clear genetic distinction between L. theobromae and L. pseudotheobromae, supporting their earlier separation as sister species. Both L. theobromae and L. pseudotheobromae populations from Cameroon had high levels of gene diversity, moderate degrees of genotypic diversity, and high levels of gene flow between isolates from T. cacao and Terminalia spp. There was no evidence for geographic substructure in these populations across the region studied, and the SSR alleles were randomly associated in both species, suggesting outcrossing. The significant levels of aggressiveness, evolutionary potential represented by high levels of diversity, outcrossing and gene flow between geographically and host defined populations, identify these fungi as high-risk pathogens for their native and non-native hosts in Cameroon.

Genetic relationships of the Cuban hair sheep inferred from microsatellite polymorphism

The aim of this research was to assess: (a) the genetic relationships between the Cuban Pelibuey and both the Hair-Mexican and Hair-Canarian sheep populations; and (b) the influence of African hair sheep in the formation of the Cuban Pelibuey breed. A total of 146 individuals of Cuban Pelibuey hair sheep breed were sampled and genotyped for 26 microsatellites together with 26 Hair-Mexican and 24 Hair-Canarian individuals. Additionally, the same microsatellites set was typed on 110 West African hair sheep and on 41 individuals belonging to the Wooled-Canarian (23) and the Wooled-Palmera (18) sheep breeds to be used as outgroup. Genetic distance, correspondence and STRUCTURE analyses pointed out that the Cuban Pelibuey has a particular genetic background. This population has relatively high levels of gene diversity (0.685±0.006) and rarefacted allelic richness (5.9). No signals of genetic bottleneck in the Cuban Pelibuey sheep were detected. The Hair-Canarian and the Hair-Mexican populations are closely related. This is likely to be due to a major role of the Cuban Pelibuey sheep in their formation. The influence of African hair sheep into the Cuban Pelibuey could be limited and recent in historical terms.

High genetic diversity of the endangered Iberian three‐spined stickleback (Gasterosteus aculeatus) at the Mediterranean edge of its range

Summary1. The three‐spined stickleback (Gasterosteus aculeatus) on the Iberian Peninsula is only distributed in freshwater habitats and has completely disappeared from most of its range, mainly as a consequence of habitat degradation and invasive fish introductions. Genetic investigations have shown that Mediterranean‐Adriatic sticklebacks constitute an evolutionarily significant unit. Here, we present the first genetic data for Iberian populations living on the southern edge of the stickleback’s range. We used microsatellite markers to study gene diversity, population structure and genetic demography of stickleback populations.2. High genetic differentiation among collections yielded a model of four genetically homogeneous units related to geography. The observed pattern of isolation by distance resulted mainly from the hydrographical pattern and limited gene flow among rivers. Moreover, low levels of gene diversity, high isolation and recent bottleneck events, which have led to small or even critical effective population sizes in several locations, could be explained by additional recent anthropogenic fragmentation.3. We defined at least four evolutionarily significant units threatened by habitat fragmentation in north‐eastern Iberian sticklebacks. Because they retain long evolutionary histories, these populations should be considered of high conservation priority, and urgent management measures should be implemented.

Contrasting patterns of population genetic structure of Fasciola hepatica from cattle and sheep: Implications for the evolution of anthelmintic resistance

Twelve polymorphic genetic markers, eight allozymic loci and four microsatellites, were used to characterize 20 infrapopulations of Fasciola hepatica (all flukes from 10 individual cattle and 10 sheep) from 11 farms in Northwest Spain. Results suggest different patterns of population genetic structure depending on the host species. Individuals identified as clones were much more frequent in sheep. The common presence of clones and its nonrandom occurrence among individual hosts suggests clumped transmission of liver flukes in sheep. After reducing significant repeated multilocus genotypes to one unique copy within infrapopulations, results show relatively high levels of gene diversity within infrapopulations from cattle and sheep (0.411 and 0.360 on average, respectively). However, parasites of sheep appear to show significantly more structured variation at the infrapopulation level (Standardized FST=0.087 and 0.170 for parasites of cattle and sheep, respectively). Compared to the parasites from cattle, results suggest that populations from sheep show lower levels of gene flow, higher degree of aggregate transmission, higher probability of mating within clones, and lower parasitic load. These differences have implications for the evolution of anthelmintic resistance because they affect the effective population size and the degree of inbreeding. The development and rapid spread of resistance seems likely in the parasites of cattle because populations from the study area are characterized by high gene flow. However, results also suggest that the efficient selection of a new recessive advantageous mutation would be favored in parasites of sheep due to a greater potential for inbreeding.