Wahlund Effect Research Articles

Genetic tracing of the illegal trade of the white-bellied pangolin (Phataginus tricuspis) in western Central Africa

The white-bellied pangolin is subject to intense trafficking, feeding both local and international trade networks. In order to assess its population genetics and trace its domestic trade, we genotyped 562 pangolins from local to large bushmeat markets in western central Africa. We show that the two lineages described from the study region (WCA and Gab) were overlapping in ranges, with limited introgression in southern Cameroon. There was a lack of genetic differentiation across WCA and a significant signature of isolation-by-distance possibly due to unsuspected dispersal capacities involving a Wahlund effect. We detected a c. 74.1–82.5% decline in the effective population size of WCA during the Middle Holocene. Private allele frequency tracing approach indicated up to 600 km sourcing distance by large urban markets from Cameroon, including Equatorial Guinea. The 20 species-specific microsatellite loci provided individual-level genotyping resolution and should be considered as valuable resources for future forensic applications. Because admixture was detected between lineages, we recommend a multi-locus approach for tracing the pangolin trade. The Yaoundé market was the main hub of the trade in the region, and thus should receive specific monitoring to mitigate pangolins’ domestic trafficking. Our study also highlighted the weak implementation of CITES regulations at European borders.

Low-coverage sequencing and Wahlund effect severely bias estimates of inbreeding, heterozygosity and effective population size in North American wolves.

vonHoldt etal. ((2024), Molecular Ecology, 33, e17231) (vH24) used low-coverage (average ~ 7X read depth) restriction site-associated DNA sequence data to estimate individual inbreeding and heterozygosity, and recent effective population size (Ne), in Great Lakes (GL) and Northern Rocky Mountain (RM) wolves. They concluded that RM heterozygosity rapidly declined between 1991 and 2020, and that Ne declined substantially in GL and RM over the last 50 generations. Here, we evaluate the effects of low sequence coverage and sampling strategy on vH24's findings and provide general recommendations for using sequence data to evaluate inbreeding, heterozygosity and Ne. Low-coverage sequencing resulted in downwardly biased estimates of individual inbreeding and heterozygosity, and an erroneous large temporal decline in RM heterozygosity due to declining read depth through time. Additionally, vH24's sampling strategy-which combined individuals from several genetically differentiated populations and across at least eight wolf generations-is expected to have resulted in severe downward bias in estimates of recent Ne for RM. We recommend using high-coverage sequence data ( 15-20X) to estimate inbreeding and heterozygosity. Carefully filtering individuals, loci and genotypes, and using genotype imputation or likelihoods can help to minimise bias when low-coverage sequence data must be used. For estimation of contemporary Ne, the marginal benefits of using more than 103-104 loci are small, so aggressive filtering of loci with low average read depth potentially can retain most individuals without sacrificing much precision. Individuals are relatively more valuable than loci because analyses of contemporary Ne should focus on roughly single-generation samples from local breeding populations.

Structure and genetic variability of the Costa Rican Paso horse

The Costa Rican Paso Horse (CPC) is a breed developed in Costa Rica. The objectives were to estimate the genetic structure and evaluate the levels of genetic variability of the population. The genotypes of 14 microsatellites in 3654 records (2052 females and 1602 males) were analyzed. Expected (He) and observed (Ho) heterozygosity, polymorphic information content (CIP), fixation index (FIS), Shannon index, as well as Hardy-Weinberg disequilibrium (DHW) were evaluated. Kinship relationships (Rij) were estimated throughout the entire population. The effective population size (Ne) was calculated, alternating allele frequencies less than 0.05, 0.02 and 0.01. The Bayesian clustering study was carried out to infer how many lines are appropriate from the analysis of genotypes using multiple loci. The number of alleles per locus ranged from 7 to 17, with an average value of 9.6; nine loci presented DHW (P < 0.05); two loci presented negative FIS values, the same as Ho > He; the average of CIP, Ho and He was 0.254, 0.756 and 0.785, respectively. At the 12 loci where He > Ho, the differences ranged from 0.002 to 0.341 (0.036 on average). For Ne, the estimates were 201.9, 230.1, and 241.5. In the Rij, 54.86% of the estimates were in the interval of 0.01 to 77.7%. The number of lines that define the population corresponds to three, with an approximate composition of 33.1%, 32.4% and 34.5%, respectively. The CPC, as a subdivided population with DHW and a reduction in heterozygotes may be associated with possible Wahlund effects. Keywords: Wahlund effect, equines, genetic markers, synthetic breed, Hardy Weinberg.

Description of Divergence of Subpopulations in the Hierarchical System under the Analysis of Isonymy. II. Probabilities of Non-Isonymic Encounters

Metapopulations with typical for human populations hierarchical subdivision into parts (subpopulations) are considered, corresponding to classifications based on administrative-territorial division (say, village, village council, district, region, and so on) or on a genealogical approach based on ethnogenesis, as well as on other principles of biological classification. The purpose of this work is to analyze the general properties of the distribution of the surname concentration over subpopulations in their hierarchical structure. Attention is focused on the description of the surname divergence of subpopulations, as an indicator of which the total probability of two person with different surnames encounter is considered, which is understood as the probability of the encounter in a randomly chosen subpopulation, a unit of observation, from metapopulation with a hierarchical structure. Its decomposition by hierarchy levels is obtained, which generalizes the Wahlund effect in population genetics. The total probability of non-isonimic encounters in a hierarchically subdivided metapopulation is less than the probability of random encounters in it by the sum of the average surname concentration intragroup variances corresponding to separate levels. Such properties are purely statistical characteristics of the hierarchical structure, and not a feature of a particular population system, and are not derived from the regularities of one or another model of microevolution. They are computationally formulated in the same way for any hierarchical system, although in the general case they do not coincide quantitatively. The results obtained refer to rural and urban hierarchical metapopulations as separate components of the entire population.

Genetic Structure and Diversity of Dalbergia nigra from Brazilian Atlantic Forest Fragments

Dalbergia nigra is a long-living tree endemic to the Atlantic Rain Forest. Due to its high commercial value, this species has been widely exploited for timber production and is now endangered. It is widely known that understanding patterns of genetic structure is paramount for conserving threatened species. We analyzed the genetic diversity of 140 individuals from four different forest fragments in the southern region of Bahia, Brazil, to verify the possible effects of fragmentation on these populations and provide information for conservation initiatives. High polymorphism levels were detected from the genotyping of nine microsatellite loci (mean HE = 0.733). All populations showed high genetic diversity; however, a reduction of genetic diversity was detected in each population (HO &lt; HE). The average fixation index was high and significant (f = 0.167), which could be due to the occurrence of inbreeding, the Wahlund effect, reproductive system, or from null alleles. Genetic differentiation among populations was high (mean θP = 0.118), suggesting strong isolation, a pattern consistent with historically low gene flow. The Bayesian analysis revealed five different genetic groups, among which three groups correspond to three different forest fragments, and two groups showed the genetic subdivision of individuals from the other forest fragment. Based on our results, the suggested conservation strategy for D. nigra populations in the southern region of Bahia, Brazil, involves high environmental investments to protect all sampled forest fragments and individuals. Another strategy would be to collect seeds from all individuals from the sampled fragments and start a new population with human interference in its evolutive history inside a protection unit.

Genetic diversity analysis of Katchaikatty Black – An endangered sheep breed from Tamil Nadu

The study presents the genetic diversity of Katchaikatty Black, an endangered and culturally significant sheep breed of Tamil Nadu. A panel of 25 microsatellite markers recommended for Indian sheep was used for genotyping. Considerable genetic variation in terms of allele diversity and heterozygosity was observed within the investigated breed. A total of 174 distinct alleles were detected across the analyzed microsatellite loci with an average of 6.96 alleles per locus. The average observed and expected heterozygosity values were 0.600 and 0.706, respectively. The positive heterozygote deficiency (FIS) value of 0.171, estimated for this breed may be due to the possibility of Wahlund effect resulting from sampling from different breeding flocks, i.e. different villages and flocks in the same area. A normal L-shaped curve suggested absence of genetic bottleneck in this breed. The information generated will be useful in guiding conservation and management programmes for Katchaikatty Black sheep.

Features of reproduction in an isolated island population of the feral horses of the Lake Manych-Gudilo (Rostov Region, Russia)

The article describes the results of a pilot study of the reproduction features of a small population of feral horses (Equus ferus) isolated for about 70 years on the Vodny Island in the Lake Manych-Gudilo (Rostov Nature Reserve, Rostov Region, Russia). The population was characterized by a fairly stable social structure for more than 10 years, including a constant composition of adult members of harem bands, though the scarce cases of mares being covered by ‘outsider’ stallions were recorded, which could be considered as one of the variants of sneak mating. The main purposes of the study were to confirm by molecular genetic methods the possible participation in the reproduction of ‘outsider’ stallions. The study was based on a combination of the direct ethological observations and genetic analyses of the individual animals. The ethological observations conducted during more than ten years revealed that the harem bands remained relatively stable throughout the period of the study. Both direct observations and genetic data revealed that the stallions heading neighboring harem bands actually participated in the fertilization of the mares. The subdominant stallions in the multi-male family bands also occasionally participated in the reproduction. No cases of participation of the bachelor stallions in the reproduction were recorded, which can be explained by their low social rank. The participation of the ‘outsider’ stallions in reproduction increases the overall genetic diversity in the population. With this, several instances of mating by close relatives were also observed that might result at random or forcibly under conditions of the complete isolation of a rather small population. The levels of observed and estimated heterozygosity (HO = 0.581 and HE = 0.606) were estimated for the first time. Such ratio of HO to HE corresponds to the provisions of the Wahlund effect and seems to indicate a small impact of the reproduction of the ‘outsider’ stallions on the level of genetic diversity in the studied local feral horse population.

New microsatellite loci for estimating genetic diversity and structure in Octopus hubbsorum from Nayarit, México.

Octopus hubbsorum Berry, 1953 is the most important species for commercial fishing in the Mexican Pacific. However, there is a lack of information regarding population structure that could have important management implications. We tested 44 microsatellite loci in O. hubbsorum by cross-amplification from O. bimaculatus. Genetic diversity and structure was tested over 30 octopus sampled from Santa Cruz de Miramar (Nayarit, México). A total of 11 loci were successfully amplified. All loci were polymorphic with the number of effective alleles ranging from 2.13 to 23.14, while three loci significantly deviated from Hardy-Weinberg equilibrium. No significant LD was observed between pairs of loci (P ≥ 0.05). The application of the new markers in a O. hubbsorum population from Santa Cruz de Miramar Nayarit, México, didnot showed Wahlund or isolate breaking effects due to the mixing of distinct populations. The loci were useful to estimate levels of pairwise relatedness and to discard the presence of recent demographic bottlenecks in the population. We consider that eight microsatellites are adequate from the 11 amplified loci.

Highly restricted dispersal in habitat-forming seaweed may impede natural recovery of disturbed populations

Cystoseira sensu lato (Class Phaeophyceae, Order Fucales, Family Sargassaceae) forests play a central role in marine Mediterranean ecosystems. Over the last decades, Cystoseira s.l. suffered from a severe loss as a result of multiple anthropogenic stressors. In particular, Gongolaria barbata has faced multiple human-induced threats, and, despite its ecological importance in structuring rocky communities and hosting a large number of species, the natural recovery of G. barbata depleted populations is uncertain. Here, we used nine microsatellite loci specifically developed for G. barbata to assess the genetic diversity of this species and its genetic connectivity among fifteen sites located in the Ionian, the Adriatic and the Black Seas. In line with strong and significant heterozygosity deficiencies across loci, likely explained by Wahlund effect, high genetic structure was observed among the three seas (ENA corrected FST = 0.355, IC = [0.283, 0.440]), with an estimated dispersal distance per generation smaller than 600 m, both in the Adriatic and Black Sea. This strong genetic structure likely results from restricted gene flow driven by geographic distances and limited dispersal abilities, along with genetic drift within isolated populations. The presence of genetically disconnected populations at small spatial scales (< 10 km) has important implications for the identification of relevant conservation and management measures for G. barbata: each population should be considered as separated evolutionary units with dedicated conservation efforts.

Genetic and mating system assessment of translocation success of the long‐lived perennial shrub Lambertia orbifolia (Proteaceae)

There is an increasing need to establish populations of threatened plants in threat‐free habitat to prevent species extinction. The amount of genetic diversity in founding plants will influence whether the new population has the capacity to persist and evolve over time, and factors that influence the maintenance of genetic diversity, such as the mating systems, will also play a role in population persistence. We developed 13 nuclear microsatellite markers and used these to evaluate genetic diversity and mating system parameters of three translocated populations of two subspecies of Lambertia orbifolia, and compared these parameters to seven wild populations. Genetic diversity was maintained in the translocated population of L. orbifolia subsp. Scott River Plains, established using a single source population (Nar = 3.270 and He = 0.478 in translocated population; Nar = 3.280 and He = 0.534 in wild populations), and maintained or increased in the two admixed translocated populations of L. orbifolia subsp. orbifolia (Nar = 3.115, 3.830 and He = 0.511, 0.635 in translocated populations; Nar = 2.708 and He = 0.438 in wild populations) compared to wild populations of each subspecies. Mating system parameters were comparable between translocated and wild populations of L. orbifolia subsp. Scott River Plains indicating the likelihood of genetic diversity being maintained in future generations. However, there was increased selfing in translocated populations of L. orbifolia subsp. orbifolia, suggesting suboptimal pollination and high values for the inbreeding coefficient in these admixed populations (Fis = 0.474, 0.275), which may be an artifact of the Wahlund effect or from less fit (inbred) seedlings surviving ex situ propagation and translocation.

Translocations and their effect on population genetics in an endangered and cryptic songbird, the Noisy Scrub-bird Atrichornis clamosus

ABSTRACT Best practice for conservation translocations dictates that large founder cohorts be used, in part to ensure that the maximum genetic variation from the source population is captured. Population bottlenecks caused by low founder numbers are understood to typically have a detrimental effect on genetic diversity and promote inbreeding. However, for some species, translocating large numbers of individuals may require an unfeasible allocation of resources or have a harmful effect on the source. The Noisy Scrub-bird (Atrichornis clamosus) is a cryptic and rarely observed passerine that was once believed extinct, and translocations to successfully establish new populations have been instrumental in securing its future. However, due to the inherent difficulties in capturing this elusive bird, these populations have been founded from only 11 to 31 individuals. We used 10 microsatellite markers to compare the genetics of the original source to the two extant translocated populations. Allelic diversity and heterozygosity were generally low but highest in the source population. Although translocations seem not to have conferred significant additional losses, relatedness, inbreeding and mean kinship were highest in the population founded with just 11 individuals. Despite historical evidence to the contrary, we found a bottleneck signature in just one population. The two translocated populations displayed significant differentiation from each other and there was evidence of spatial genetic structure between these populations. Additionally, there was some evidence of cryptic subdivision (Wahlund Effect). In light of these findings, we make recommendations for future management actions to help retain what genetic diversity remains.

Genetic diversity and population structure of wild and domesticated black tiger shrimp (Penaeus monodon) broodstocks in the Indo-Pacific regions using consolidated mtDNA and microsatellite markers

Black tiger shrimp (Penaeus monodon) is one of the most important internationally traded fishery species, and the commercial success of their aquafarming primarily depends on the high quality broodstock for seed production. Therefore, identifications of genetically diverse broodstocks of P. monodon are essential to eliminate inbreeding effects, ensure sustainable seed supply, and facilitate genetic upgrading for selective breeding and restocking programs. The present study used a combination of mtDNA control region sequences and ten microsatellite markers to evaluate the genetic diversity, demographic history and population structure of P. monodon broodstocks collected from five sampling locations across the Indo-Pacific regions. The domesticated P. monodon broodstock populations were collected from Hawaii, USA (MMO), Thailand (MT) and Madagascar (MD), while the wild broodstock populations were collected from Japan (MJ) and Malaysia (MS). Clustering analyses based on the Principle Component Analysis (PCA), Canonical Variate Analysis (CVA), STRUCTURE, and Neighbour-Joining (NJ) phylogenetic analysis revealed that the domesticated populations were unequivocally diverged from the wild-caught populations. Haplotype networks, neutrality testing, and mismatch distribution analysis indicated a complex population expansion pattern involving Wahlund effect based on human translocation, and continental drift during the paleogeographic event in Pleistocene glacial age. Both mtDNA and microsatellite data detected relatively high levels of genetic diversity among all populations, but higher levels of nucleotide diversity in the wild populations, given that the artificial selection in aquaculture practice could reduce the genetic heterogeneity of the domesticated populations. The negative correlation of isolation by distance (IBD) results further supported the findings from neutrality test, indicating that founder stocks for genetic improvement program which were established from several geographic origins may have caused admixture in the domesticated populations. The genetic information obtained from this study could help to establish appropriate breeding strategies and genetic improvement program, and would provide essential data for genetic management and conservation of P. monodon wild populations.

Population genomics of selectively neutral genetic structure and herbicide resistance in UK populations of Alopecurus myosuroides.

Alopecurus myosuroides (blackgrass) is a major weed in Europe with known resistance to multiple herbicide modes of action. In the UK, there is evidence that blackgrass has undergone a range expansion. In this paper, genotyping-by-sequencing and population-level herbicide resistance phenotypes are used to explore spatial patterns of selectively neutral genetic variation and resistance. We also perform a preliminary genome-wide association study (GWAS) and genomic prediction analysis to evaluate the potential of these approaches for investigating nontarget site herbicide resistance. Blackgrass was collected from 47 fields across the British Isles and up to eight plants per field population (n = 369) were genotyped by Restriction site-associated DNA (RAD)-sequencing. A total of 20 426 polymorphic loci were identified and used for population genetic analyses. Phenotypic assays revealed significant variation in herbicide resistance between populations. Population structure was weak (FST = 0.024-0.048), but spatial patterns were consistent with an ongoing westward and northward range expansion. We detected strong and consistent Wahlund effects (FIS = 0.30). There were no spatial patterns of herbicide resistance or evidence for confounding with population structure. Using a combination of population-level GWAS and genomic prediction we found that the top 20, 200, and 2000 GWAS loci had higher predictive abilities for fenoxaprop resistance compared to all markers. There is likely extensive human-mediated gene flow between field populations of the weed blackgrass at a national scale. The lack of confounding of adaptive and neutral genetic variation can enable future, more extensive GWAS analyses to identify the genetic architecture of evolved herbicide resistance. © 2020 Society of Chemical Industry.

Genetic Characterization of the Yugoslavian Shepherd Dog – Sharplanina, a Livestock Guard Dog from the Western Balkans

Abstract Yugoslavian Shepherd Dog - Sharplanina (YSD) is a livestock guard dog from the Western Balkans present in this region over a long time, but recognized by the Fédération Cynologique Internationale as a distinct breed as late as 1957. However, the information regarding the origin and the size of the breed’s foundation stock is still lacking. In order to contribute towards better understanding of the genetic make-up of the YSD and its foundation stock, we re-analyzed previously generated genetic profiles of 94 registered YSD dogs assessed with nine nuclear microsatellites. Studied individuals comprised 90 unrelated dogs and two pairs of full-sibs, sampled at four sampling sites: three dog shows and at a military training centre for dogs in Serbia. We supported earlier findings on high levels of genetic diversity in YSD (HE =0.728±0.027) and lack of inbreeding, and revealed substructure of the breed because we found two distinct gene pools in the Bayesian clustering analysis, indicated also by the excess of homozygotes (i.e., Wahlund effect) and outcomes of other analyses: linkage disequilibrium tests, Neighbour-Joining tree, principal coordinates and two-dimensional scaling analyses. The two gene pools were almost equally represented at each sampling site. One gene pool was composed of individuals with high genetic integrity, while the other gene pool was characterized with admixed ancestry, developed possibly via hybridization with native breeding stock outside the registry system, other breeds, such as the Caucasian Shepherd, and/or individuals admixed with wolves. Thus, we demonstrate rather complex and diverse ancestry implying a genetically heterogeneous foundation stock of the YSD.

Mediterranean swordfish (Xiphias gladius Linnaeus, 1758) population structure revealed by microsatellite DNA: genetic diversity masked by population mixing in shared areas.

BackgroundThe Mediterranean swordfish stock is overfished and considered not correctly managed. Elucidating the patterns of the Mediterranean swordfish population structure constitutes an essential prerequisite for effective management of this fishery resource. To date, few studies have investigated intra-Mediterranean swordfish population structure, and their conclusions are controversial.MethodsA panel of 20 microsatellites DNA was used to investigate fine-scale population structuring of swordfish from six main fishing areas of the Mediterranean Sea.ResultsThis study provides evidence to reject the hypothesis of a single swordfish population within the Mediterranean Sea. DAPC analysis revealed the presence of three genetic clusters and a high level of admixture within the Mediterranean Sea. Genetic structure was supported by significant FST values while mixing was endorsed by the heterozygosity deficit observed in sampling localities indicative of a possible Wahlund effect, by sampling admixture individuals. Overall, our tests reject the hypothesis of a single swordfish population within the Mediterranean Sea. Homing towards the Mediterranean breeding areas may have generated a weak degree of genetic differentiation between populations even at the intra-basin scale.

Assessing the genetic diversity in Argopecten nucleus (Bivalvia: Pectinidae), a functional hermaphrodite species with extremely low population density and self-fertilization: Effect of null alleles.

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.

Assortative Mating in Hybrid Zones between Chromosomal Races of the Common Shrew Sorex araneus L. (Soricidae, Soricomorpha)

The article is devoted to quantitative characteristics of assortative mating (R) as indicator of “reinforcement” in 12 hybrid zones between chromosomal races of the common shrew, Sorexaraneus L. The Wahlund effect in hybrid population and its potential reduction are examined. In hybrid zones with heterozygotes CIV, CV, and RIV, the R index varies within 0.23–0.59. In hybrid zones with more complex heterozygotes (RVI, CIX–CXI), it exceeds 0.82. Gene flow in the hybrid zone is interrupted at R > 0.99. Assortative mating reduces gene flow and also maintains genotype stability in hybrid populations.

Is there a host-associated molecular and morphological differentiation between sympatrically occurring individuals of the invasive leaf miner Cameraria ohridella?

The leaf-miner moth Cameraria ohridella, a pest in Central Europe, causes severe damage to trees. Host-associated differentiation (HAD) for this species has been suggested previously based on the occurrence of a specific mitochondrial haplotype. We assessed genetic diversity and population structure for sympatrically occurring individuals collected in association with two host species, Ohio buckeye (Aesculus glabra) and horse chestnut (Ae. hippocastanum), using six microsatellite loci (SSR) and mtDNA sequences that encode parts of cytochrome oxidase I and II. To infer population structure and assign individuals to clusters, we employed Bayesian clustering. We further characterized the relationships between genetic distance and geographical distance (IBD) in analyzed samples. Although our results derived from the SSR loci analyses demonstrating that there was no population substructuring caused by the hosts, we found evidence of differences in wing size, which might be attributed to the quality of food resources available to larvae. The population structure with K = 2 cannot be interpreted as the result of IBD; rather, it reflects a population differentiation due to demographic or genetic processes (e.g., an origin of invaders). Although genetic diversity was relatively high (He> 0.5), the population had a deficiency of heterozygotes (FIS > 0), which was most likely due to nonrandom mating and, possibly, a Wahlund effect. A star-like haplotype network and negative Tajima’s D support the genetic effect of bottleneck followed by population expansion. Based on presumably neutral markers, we conclude that C. ohridella appeared to be a good model for studying evolution toward a generalist invasive species, rather than HAD.

Bayesian quantification of ecological determinants of outcrossing in natural plant populations: Computer simulations and the case study of biparental inbreeding in English yew.

The mating system is a central parameter of plant biology because it shapes their ecological and evolutionary properties. Therefore, determining ecological variables that influence the mating system is important for a deeper understanding of the functioning of plant populations. Here, using old concepts and recent statistical developments, we propose a new statistical tool to make inferences about ecological determinants of outcrossing in natural plant populations. The method requires codominant genotypes of seeds collected from maternal plants within different locations. Using extensive computer simulations, we demonstrated that the method is robust to the issues expected for real-world data, including the Wahlund effect, inbreeding and genotyping errors such as allele dropout and allele misclassification. Furthermore, we showed that the estimates of ecological effects and outcrossing rates can be severely biased if genotyping errors and genetic differentiation are not treated explicitly. Application of the new method to the case study of a dioecious tree (Taxus baccata) allowed revealing that female trees that grow in lower local densities have a greater tendency towards mating with relatives. Moreover, we also demonstrated that biparental inbreeding is higher in populations that are characterized by a longer mean distance between trees and a smaller mean trunk perimeter. We found these results to agree with both the theoretical predictions and the history of English yew.

Microsatellite Polymorphism Suggests High Genetic Diversity But Disrupted Gene Flow in the Two-Spot Ladybird Adalia bipunctata (Linnaeus, 1758) (Coleoptera: Coccinellidae) Populations from Diverse Environments

The two-spot ladybird Adalia bipunctata (Linnaeus, 1758) (Coleoptera: Coccinellidae) is a widely distributed generalist, feeding preferably on aphids. The species inhabits various environments, including anthropogenic landscape, where pollution and microclimate enables to attain very high numbers of favorite prey. Recently, the abundance of the two-spot ladybird has declined, mainly as an after-effect of invasion of the competing species — the harlequin ladybird Harmonia axyridis (Pallas, 1773). High phenotypic polymorphisms made the two-spot ladybird classic model for population genetic studies of Coccinellidea. However, studies investigating diversity of the species at DNA level have Coccinellidae been scarce. In our investigation we used microsatellite markers to characterize genetic diversity in the two-spot ladybird populations from different environments. We made an attempt to amplify 13 loci, identified previously in the genome of the species, however due to lack of amplification, monomorphisms and presence of the null alleles, the final set of six markers useful for analysis on a population level was obtained. Analyzing genotypes of 124 individuals, we confirmed high genetic diversity of the species, suggested previously by studies, applying allozymes and mitochondrial DNA. Also, microsatellites revealed weakly pronounced genetic structure in a large scale (localities separated by a distance of 500 kilometers). However, we found some indications (signs of the Wahlund effect) that gene flow could be disturbed among sites in diverse environments (rural, suburban and urban). Our data suggested that invasion of the harlequin ladybird has not yet affected populations of the two-spot in such extent to alter genetic diversity or genetic structure.