Among-population Genetic Variation Research Articles

Unveiling a potential threat to forest ecosystems: molecular diagnosis of Alliaria petiolata, a newly introduced alien plant in Korea.

Identifying stages of a species invasion in a new habitat (i.e., colonization, establishment, and landscape spread) and their primary determinants in biological invasion warrants attention, as it provides vital insights for preventing non-native species from becoming pervasive invaders. However, delineating invasion stages and their associated factors can pose significant challenges due to the ambiguous distinctions between these stages. Alliaria petiolata, one of the most noxious weeds in woodland habitats, has recently been introduced to Korea and observed in a few distant locations. Although the plant's spread has been relatively slow thus far, rapid spread is highly likely in the future, given the high invasive potential reported elsewhere. We indirectly diagnose the current status of A. petiolata invasion in Korea through the assessment of genetic diversity and phylogenetic inferences using genome-wide molecular markers and cytological data. We analyzed 86 individual samples collected from two native and six introduced populations, employing 1,172 SNPs. Our analysis estimated within- and among-population genetic diversity and included two clustering analyses. Furthermore, we investigated potential gene flow and reticulation events among the sampled populations. Our data unraveled that Korean garlic mustard exhibits a hexaploid ploidy level with two distinct chromosome numbers, 2n = 36 and 42. The extent of genetic diversity measured in Korean populations was comparable to that of native populations. Using genome-wide SNP data, we identified three distinct clusters with minor gene flow, while failing to detect indications of reticulation among Korean populations. Based on the multifaceted analyses, our study provides valuable insights into the colonization process and stressed the importance of closely monitoring A. petiolata populations in Korea.

Too simple, too complex, or just right? Advantages, challenges, and guidance for indicators of genetic diversity

Abstract Measuring genetic diversity of wild species using DNA-based data remains resource intensive and time consuming for nearly all species. However, genetic assessments are needed for global conservation commitments, including the Convention on Biological Diversity, and for governments and managers to evaluate conservation progress, as well as prioritizing species and populations to preserve and recover genetic diversity (e.g., via genetic rescue). Recently, indicators were developed for tracking and reporting genetic diversity status and trends for hundreds of species. The indicators quantify two simple proxies of within-population and among-population genetic diversity and adaptive potential: small effective population size (Ne < 500) and the loss of genetically distinct populations. The indicators must balance scientific credibility, practicality, and simplicity. In the present article, we summarize the advantages of these pragmatic indicators, address critiques by scientists for simplifying assumptions and by policymakers for complexity, and propose potential solutions and next steps. We aim to support practitioners putting indicators into policy, action, legislation, and reporting.

Genetic structure of Trifolium pratense populations in a cityscape.

Urban grasslands provide numerous ecosystem services, and their maintenance should be based on naturally regenerating plant populations. However, the urban environment is challenging for preserving viable populations, mostly because of their high fragmentation and small size, which can lead to genetic drift. We examined red clover (Trifolium pratense) in a medium-size city in Central Europe to test the cityscape effect on within- and among-population genetic diversity. We used eight inter-simple sequence repeat markers to examine the genetic structure of 16 populations, each represented by eight individuals. The isolation by resistance was analysed using a least cost patch approach, focusing on gene flow via pollinators. We found great variation among T. pratense populations, with no discernible geographic pattern in genetic diversity. We linked the diversity to the long history of the city and high stochasticity of land use changes that occurred with city development. In particular, we did not find that the Odra River (ca. 100 m wide) was a strong barrier to gene transfer. However, notable isolation was present due to resistance and distance, indicating that the populations are threatened by genetic drift. Therefore, gene movement between populations should be increased by appropriate management of urban green areas. We also found that small urban grassland (UG) patches with small populations can still hold rare alleles which significantly contribute to the overall genetic variation of T. pratense in the city.

Weedy rice: An insight into genetic diversity and population structure for effective weed management

Weedy rice (Oryza sativa f. spontanea) is a conspecific weed that has invaded cultivated rice fields, effectively adapted to modern management practices, leading to substantial yield losses and reduced harvest quality. The understanding of weedy rice genetic diversity and population structure is critical in developing effective control measures. Twenty weedy rice populations were collected around the island and evaluated using 33 SSR markers. Our findings indicated that the genetic diversity (He) in a population of weedy rice was reasonably high (0.305 - 0.560). A high level of within-population (79%) and a low level of among-population (21%) genetic variation were found by analysis of molecular variance (AMOVA). There is no significant correlation across genetic and geographical distances (P>0.05). The unweighted pair group method with arithmetic mean (UPGMA) demonstrated that 20 populations were structured into two well-separated groups. Remarkably, many admixed individuals were evident according to the STRUCTURE. Weedy rice management strategies should focus on micromorphological monitoring to detect, group, and eliminate weedy rice in paddy fields, restricting the exchange of saved paddy seeds among geographical regions, increasing the production and distribution of certified seeds, the varietal recommendation for rice-growing regions to minimize mixing of varieties with different age classes, raising awareness are the recommendations to reduce the emergence of future weeds.

Gene Flow and Recruitment Patterns among Disjunct Populations of Allocasuarina verticillata (Lam.) L.A.S. Johnson

Allocasuarina verticillata (Lam.) L.A.S. Johnson is a widespread species in south-eastern Australia providing vegetation cover, protecting fragile soils and providing food for birds. Understanding the effects of gene flow on the recruitment patterns, genetic differentiation and structure of fragmented populations provides fundamental guidelines to underpin plant conservation strategies and activities. In this study, four spatially disjunct populations of A. verticillata were sampled to explore the effects of population size, reproductive patterns and pollen and seed dispersal on among-population genetic diversity, genetic differentiation and structure, using field survey and microsatellite marker techniques. It was found that stands of A. verticillata were predominantly sexually reproductive, but asexual reproduction through root suckering was an additional mode of reproduction. The reproductive success of A. verticillata is positively correlated with the effective population size rather than actual population size. The reduction in effective population size and increment of spatial isolation resulted in lower genetic diversity and higher inbreeding coefficient of progenies. Moderate pairwise genetic differentiation and weak genetic structure were identified. The results suggest that exogenous, wind-mediated pollen flow provides some maintenance of genetic diversity in the isolated stands. Seed dispersal appears mainly to be over short distances (i.e., within populations), but the infrequent transport of seeds between disjunct locations cannot be ruled out as another factor that may help maintain genetic diversity.

A review of intraspecific genetic diversity on wild plants in Korea estimated from varying nuclear DNA markers

Given the significant impact of molecular markers on the genetic diversity assessment, understanding genetic diversity pattern across diverse marker types in a comparative manner is of great importance. In Korea, within the last 10 years population genetics studies of wild plants have drawn much attention as varying DNA markers have developed. To investigate the pattern of among-population and within-population level genetic diversity of wild plants in Korea, we reviewed the extent of population genetic parameters across four DNA markers (RAPD, AFLP, ISSR, SSR). We compiled 73 data sets from research papers published between 2010 and 2019. ISSR markers were the most frequently used in population genetics studies conducted on Korean wild plants. Overall, genetic diversity patterns greatly varied across the different marker types. On average, endangered species exhibited low within-population genetic variation and high among-population genetic diversity. Species with wide geographic distribution showed greater within-population diversity values than the ones residing in a restricted area except for AFLP data. Populations were genetically less differentiated in long distance dispersal species with wide geographic ranges. Our review indicates that the studies on the genetic diversity of wild plants may be improved by expanding the scope and increasing the sample sizes.

Genetic diversity and gene-pool of Aegilops tauschii Coss. (Poaceae) based on retrotransposon-based markers

Genetic variation is an essential feature of biological variety for conservation methods, particularly for scarce and strictly endemic species. Iran's population genetic structure, genetic variation, and morphological variations are all unknown. Because of the therapeutic value of this species, six regional populations of Aegilops tauschii were studied for genetic diversity and population structure. To uncover within and among population genetic variation in this plant, we employed six inter-retrotransposon amplified polymorphism (IRAP) markers and 15 combined IRAP markers. The AMOVA test indicated a substantial genetic difference (PhiPT = 0.66, P = 0.010) among the tested populations, as well as the fact that 85 percent of overall genetic differences was related to within-population variety and 15 percent to genetic divergence across populations. The Mantel test revealed a substantial positive connection between genetic distance and geographical distance across the populations investigated. Based on (IRAP) markers, these findings suggested that regional populations of Aegilops tauschii are well separated.

Polygenic Selection within a Single Generation Leads to Subtle Divergence among Ecological NichesINc.

Selection on standing genetic variation may be effective enough to allow for adaptation to distinct niche environments within a single generation. Minor allele frequency changes at multiple, redundant loci of small effect can produce remarkable phenotypic shifts. Yet, demonstrating rapid adaptation via polygenic selection in the wild remains challenging. Here we harness natural replicate populations that experience similar selection pressures and harbor high within-, yet negligible among-population genetic variation. Such populations can be found among the teleost Fundulus heteroclitus that inhabits marine estuaries characterized by high environmental heterogeneity. We identify 10,861 single nucleotide polymorphisms in F. heteroclitus that belong to a single, panmictic population yet reside in environmentally distinct niches (one coastal basin and three replicate tidal ponds). By sampling at two time points within a single generation, we quantify both allele frequency change within as well as spatial divergence among niche subpopulations. We observe few individually significant allele frequency changes yet find that the “number” of moderate changes exceeds the neutral expectation by 10–100%. We find allele frequency changes to be significantly concordant in both direction and magnitude among all niche subpopulations, suggestive of parallel selection. In addition, within-generation allele frequency changes generate subtle but significant divergence among niches, indicative of local adaptation. Although we cannot distinguish between selection and genotype-dependent migration as drivers of within-generation allele frequency changes, the trait/s determining fitness and/or migration likelihood appear to be polygenic. In heterogeneous environments, polygenic selection and polygenic, genotype-dependent migration offer conceivable mechanisms for within-generation, local adaptation to distinct niches.

Selection patterns on early-life phenotypic traits in Pinus sylvestris are associated with precipitation and temperature along a climatic gradient in Europe.

Understanding the dynamics of selection is key to predicting the response of tree species to new environmental conditions in the current context of climate change. However, selection patterns acting on early recruitment stages and their climatic drivers remain largely unknown in most tree species, despite being a critical period of their life cycle. We measured phenotypic selection on Pinus sylvestris seed mass, emergence time and early growth rate over 2 yr in four common garden experiments established along the latitudinal gradient of the species in Europe. Significant phenotypic plasticity and among-population genetic variation were found for all measured phenotypic traits. Heat and drought negatively affected fitness in the southern sites, but heavy rainfalls also decreased early survival in middle latitudes. Climate-driven directional selection was found for higher seed mass and earlier emergence time, while the form of selection on seedling growth rates differed among sites and populations. Evidence of adaptive and maladaptive phenotypic plasticity was found for emergence time and early growth rate, respectively. Seed mass, emergence time and early growth rate have an adaptive role in the early stages of P. sylvestris and climate strongly influences the patterns of selection on these fitness-related traits.

Among-Population Genetic Diversity of Rice Blast Fungus Based on Fingerprinting of Virulence-related genes

In this study, 189 strains of rice blast fungus isolated from rice-growing fields in five counties within the Jiangxi Province, China, were amplified with 16 pairs of virulence gene-specific primers. Fifteen pairs were able to amplify their target bands. The percentage of polymorphic sites was as high as 93.75%, and the frequency of amplification varied greatly. Cluster analysis classified the 189 strains, represented by 108 different haplotypes, into 21 genetic lineages at a genetic similarity level of 0.80. JXH16 was the dominant haplotype. The 21 genetic lineages included 1 dominant, 2 subdominant, 12 secondary, and 6 minor lineages. At the population level, rich genetic diversity was observed among the 189 strains from different geographic regions (H = 0.2890; I = 0.4398). At a genetic distance of 0.02, the five populations were clustered into three groups that were unrelated to geographical distribution. A certain level of genetic differentiation was found to exist within each blast fungus population (HT = 0.2842). Within-population genetic diversity was higher than that among populations (Hs = 0.2210; Dst = 0.0632), with 77.75% of the total genetic variation originates within populations (Gst = 0.2225). Some within-population gene flow were detected (Nm = 1.7473). The results of our study, which revealed the genetic structure and diversity of rice blast fungal strains in five major rice cultivation areas of Jiangxi Province and their relationship to geographical distribution, can serve as a basis for rice blast resistance breeding and the selection of suitable varieties for these regions, including Duchang County, Jinggangshan City, Fengcheng City, Wan ‘an County and Wuyuan County.

The Patterns and Puzzles of Genetic Diversity of Endangered Freshwater Mussel Unio crassus Philipsson, 1788 Populations from Vistula and Neman Drainages (Eastern Central Europe)

Mussels of the family Unionidae are important components of freshwater ecosystems. Alarmingly, the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species identifies almost 200 unionid species as extinct, endangered, or threatened. Their decline is the result of human impact on freshwater habitats, and the decrease of host fish populations. The Thick Shelled River Mussel Unio crassus Philipsson, 1788 is one of the examples that has been reported to show a dramatic decline of populations. Hierarchical organization of riverine systems is supposed to reflect the genetic structure of populations inhabiting them. The main goal of this study was an assessment of the U. crassus genetic diversity in river ecosystems using hierarchical analysis. Different molecular markers, the nuclear ribosomal internal transcribed spacer ITS region, and mitochondrial DNA genes (cox1 and ndh1), were used to examine the distribution of U. crassus among-population genetic variation at multiple spatial scales (within rivers, among rivers within drainages, and between drainages of the Neman and Vistula rivers). We found high genetic structure between both drainages suggesting that in the case of the analyzed U. crassus populations we were dealing with at least two different genetic units. Only about 4% of the mtDNA variation was due to differences among populations within drainages. However, comparison of population differentiation within drainages for mtDNA also showed some genetic structure among populations within the Vistula drainage. Only one haplotype was shared among all Polish populations whereas the remainder were unique for each population despite the hydrological connection. Interestingly, some haplotypes were present in both drainages. In the case of U. crassus populations under study, the Mantel test revealed a relatively strong relationship between genetic and geographical distances. However, in detail, the pattern of genetic diversity seems to be much more complicated. Therefore, we suggest that the observed pattern of U. crassus genetic diversity distribution is shaped by both historical and current factors i.e. different routes of post glacial colonization and history of drainage systems, historical gene flow, and more recent habitat fragmentation due to anthropogenic factors.

The genetically healthy terrestrial orchid <i>Liparis krameri</i> on southern Korean Peninsula

Neutral genetic diversity found in plant species usually leaves an indelible footprint of historical events. Korea’s main mountain range (referred to as the Baekdudaegan [BDDG]), is known to have served as a glacial refugium primarily for the boreal and temperate flora of northeastern Asia. In addition, life-history traits (life forms, geographic range, and breeding systems) influence the within- and among-population genetic diversity of seed plant species. For example, selfing species harbor significantly less within-population genetic variation than that of predominantly outcrossers. A previous study of two Liparis species (L. makinoana and L. kumokiri) emphasizes the role of the abovementioned factors shaping the levels of genetic diversity. Liparis makinoana, mainly occurring on the BDDG and self-incompatible, harbors high levels of within-population genetic diversity (expected heterozygosity, HeP = 0.319), whereas there is no allozyme variation (HeP = 0.000) in L. kumokiri, which is self-compatible and mainly occurs in lowland hilly areas. To determine if this trend is also found in other congeners, we sampled five populations of L. krameri from the southern part of the Korean Peninsula and investigated the allozyme-based genetic diversity at 15 putative loci. The somewhat intermediate levels of within-population genetic variation (HeP = 0.145) found in L. krameri are most likely due to its occurrence in mountainous areas that, despite being outside of the main ridge of the BDDG, still served as refugia, and a self-incompatible breeding system. Management strategies are suggested for L. krameri and L. makinoana based on the levels and distribution of genetic diversity and inbreeding.

Genetic diversity and genetic structure of natural populations in an extremely narrowly distributed perennial species Glycine tabacina (Labill.) Benth. on the southeast islands in China

In China, Glycine tabacina (Labill.) Benth. is only distributed in the southeast coast and islands. In this study, 28 natural populations of G. tabacina species were sampled from 13 islands using 22 SSR markers. The Chinese G. tabacina was characterized by higher outcrossing rate and within-population genetic variation, extensive migration, greater population genetic differences and geographically weak-associated genetic differentiation, with higher level of heterogeneity within the natural populations along the southeast islands of China even though this species is a self-pollinating plant. The number of alleles per locus averaged 5.77 and ranged from 2 to 16. The expected heterozygosity (He) per locus averaged a value of 0.51, varying from 0.08 to 0.80. As an autogamous species, the Chinese G. tabacina unexpectedly showed a relatively high mean outcrossing rate in single locus (ts = 6.52%) and multilocus (tm = 6.75%), higher mean gene flow (Nm = 0.315), lower mean gene differentiation index (Gst = 0.436), and particularly, relatively lower among-population genetic variation (43.55%) and higher within-population genetic variation (49.66%) revealed by analysis of molecular variance. Spatial autocorrelation analysis revealed that populations within a radius of approximately 14.7 km would have a positive and significant genetic relationship to one another. However, the event of long-distance genetic background dispersal was revealed by individual assignment test and haplotype analysis (> 200 km dispersal was inferred, but > 56 km dispersal was observed). The north and middle-north islands of Fujian Province seemed to be the center of genetic diversity.

Evolutionary Hotspots of Seed Plants in Subtropical China: A Comparison With Species Diversity Hotspots of Woody Seed Plants.

Genetic diversity is a fundamental level of biodiversity. However, it is frequently neglected in conservation prioritization because intraspecific genetic diversity is difficult to measure at large scales. In this study, we synthesized population genetic or phylogeographic datasets of 33 seed plants in subtropical China into multi-species genetic landscapes. The genetic landscapes identified 18 evolutionary hotspots with high within-population genetic diversity (WGD), and among-population genetic diversity (AGD), or both. The western subtropical China is rich in AGD (possessing four major AGD hotspots), deserving a high conservation priority. We found that WGD was positively correlated with longitude, with most WGD hotspots locating in east subtropical China. The results showed that the locations of 12 of 18 evolutionary hotspots corresponded approximately to those of previously identified species diversity (SD) hotspots, however, a positive and significant correlation existed only between AGD and SD, not between WGD and SD. Therefore, spatial patterns of species richness in plants in subtropical China cannot generally be used as surrogate for their intraspecific diversity. This study identified multi-species evolutionary hotspots and correlated multi-species genetic diversity with SD across subtropical China for the first time, providing profound implications for the conservation of biodiversity in this important ecoregion.

Differential invasion success in aquatic invasive species: the role of within- and among-population genetic diversity

Despite a well-developed theoretical basis for the role of genetic diversity in the colonization process, contemporary investigations of genetic diversity in biological invasions have downplayed its importance. Observed reductions in genetic diversity have been argued to have a limited effect on the success of establishment and impact based on empirical studies; however, those studies rarely include assessment of failed or comparatively less-successful biological invasions. We address this gap by comparing genetic diversity at microsatellite loci for taxonomically and geographically paired aquatic invasive species. Our four species pairs contain one highly successful and one less-successful invasive species (Gobies: Neogobius melanostomus, Proterorhinus semilunaris; waterfleas: Bythotrephes longimanus, Cercopagis pengoi; oysters: Crassostrea gigas, Crassostrea virginica; tunicates: Bortylloides violaceous, Botryllus schlosseri). We genotyped 2717 individuals across all species from multiple locations in multiple years and explicitly test whether genetic diversity is lower for less-successful biological invaders within each species pair. We demonstrate that, for gobies and tunicates, reduced allelic diversity is associated with lower success of invasion. We also found that less-successful invasive species tend to have greater divergence among populations. This suggests that intraspecific hybridization may be acting to convert among-population variation to within-population variation for highly successful invasive species and buffering any loss of diversity. While our findings highlight the species-specific nature of the effects of genetic diversity on invasion success, they do support the use of genetic diversity information in the management of current species invasions and in the risk assessment of potential future invaders.

Molecular characterization of genetic variation in somaclones of durum wheat (Triticum durum Desf) using SSR markers

This study is a continuation of a previous work; the main objective is to characterize the induced somaclonal variation in the first generation of durum wheat plants. In a previous experiment, in vitro plants of three genotypes of durum wheat were obtained following treatment with PEG6000 (0%, 10% and 20%). First generation offspring was produced. Five microsatellite markers were used for genotyping 26 durum wheat somaclones obtained under stressful and non-stressful conditions from 3 durum wheat cultivars. Amplifiable and reproducible alleles were obtained in three of the tested loci. These loci provided in total 78 monomorphic alleles of which 69 were detected in somaclones while the remaining 9 in the mother plants. High values of among-population genetic diversity were found, which accounted for 71 % of the total genetic variation. The number of alleles per locus varied from three to six. Estimated genetic distances varied from 0.83 to 1.67 between populations. The somaclonal variation was identified with 2 SSR markers. Five new alleles were identified in somaclonal variants DKR1-S1, DKR1-S2, OZR1-S2, WR1-C3 and WR1-S1at loci gmw131 and gwm427. Genetic variation rate was 21.74%. Eighty % of the genetic variation was identified in plants obtained from callus undergoing high osmotic pressure. The presence of selective agent in the medium could explain the observed genetic variations. Somaclonal variation cannot always be detected at the gross morphological level. The selected SSR markers could be used to study the uniformity of plants obtained from tissue culture and varietal identification.

Mitochondrial DNA reveals evolutionary status and population genetics of two closely related fish (Misgurnus bipartitus and Misgurnus mohoity) in northeast China

To provide valuable insights into the taxonomic relationship and germplasm resource of Misgurnus mohoity and Misgurnus bipartitus, phylogenetic and population structure analysis were performed based on mitochondrial DNA. The phylogenetic tree reconstructed from genera Misgurnus and Paramisgurnus revealed the species in genus Misgurnus were not in a monophyletic group and divided into two divergent clades; M. bipartitus and Misgurnus anguillicaudatus were clustered into a monophyletic group; M. mohoity was embedded in the Paramisgurnus dabryanus lineage. Totally, 19 and 21 haplotypes were identified from the individuals of M. bipartitus and M. mohoity based on COI gene, respectively. High haplotype diversity and low nucleotide diversity were found within the populations of M. bipartitus, and the populations of M. mohoity exhibited both high levels of haplotype diversity and nucleotide diversity. Meanwhile, high levels of genetic differentiation and genetic variation between populations in Liao River basin (PAJ, FUS and HUR) and populations in Songhua river basin (MDJ, FUY and FUJ) were observed in M. bipartitus; the populations of M. mohoity also revealed high genetic differentiation and high among-population genetic variation. The results of this study can be potentially exploited to conservation and management strategies of wild loach resources.

Genetic diversity of two Daphnia-infecting microsporidian parasites, based on sequence variation in the internal transcribed spacer region.

BackgroundMicrosporidia are spore-forming obligate intracellular parasites that include both emerging pathogens and economically important disease agents. However, little is known about the genetic diversity of microsporidia. Here, we investigated patterns of geographic population structure, intraspecific genetic variation, and recombination in two microsporidian taxa that commonly infect cladocerans of the Daphnia longispina complex in central Europe. Taken together, this information helps elucidate the reproductive mode and life-cycles of these parasite species.MethodsMicrosporidia-infected Daphnia were sampled from seven drinking water reservoirs in the Czech Republic. Two microsporidia species (Berwaldia schaefernai and microsporidium lineage MIC1) were sequenced at the internal transcribed spacer (ITS) region, using the 454 pyrosequencing platform. Geographical structure analyses were performed applying Fisher’s exact tests, analyses of molecular variance, and permutational MANOVA. To evaluate the genetic diversity of the ITS region, the number of polymorphic sites and Tajima’s and Watterson’s estimators of theta were calculated. Tajima’s D was also used to determine if the ITS in these taxa evolved neutrally. Finally, neighbour similarity score and pairwise homology index tests were performed to detect recombination events.ResultsWhile there was little variation among Berwaldia parasite strains infecting different host populations, the among-population genetic variation of MIC1 was significant. Likewise, ITS genetic diversity was lower in Berwaldia than in MIC1. Recombination signals were detected only in Berwaldia.ConclusionGenetic tests showed that parasite populations could have expanded recently after a bottleneck or that the ITS could be under negative selection in both microsporidia species. Recombination analyses might indicate cryptic sex in Berwaldia and pure asexuality in MIC1. The differences observed between the two microsporidian species present an exciting opportunity to study the genetic basis of microsporidia-Daphnia coevolution in natural populations, and to better understand reproduction in these parasites.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1584-4) contains supplementary material, which is available to authorized users.

Assessment of Chosen Reproductive Cycle Processes and Genetic Diversity ofSalix myrtilloidesL. in Wetlands of Polesie Lubelskie: The Prospects of Its Survival in the Region

ABSTRACT Salix myrtilloides L. is an endangered species whose western limit of range runs through Poland. The main aim of the study was to increase the knowledge on the ecology and biology of S. myrtilloides populations in the Polesie Lubelskie region (Eastern Poland) in order to create an effective protection program. An 80% decrease in its population was found in this area. Our study was conducted to identify the mechanisms responsible for the process of withdrawal of this species from its natural stands by determining whether the processes of generative reproduction (pollen viability and germinability, seed germination ability and dynamics) in the populations occur properly and by characterizing within- and among-population genetic diversity of S. myrtilloides, using ISSR (Inter-Simple Sequence Repeat) primers. The results confirmed that S. myrtilloides pollen viability was high (84.17±8.67), and so were the seed germination ability (76% of the total number of sown seeds/24 h) and dynamics. The within-...

Contemporary and historic factors influence differently genetic differentiation and diversity in a tropical palm

Population genetics theory predicts loss in genetic variability because of drift and inbreeding in isolated plant populations; however, it has been argued that long-distance pollination and seed dispersal may be able to maintain gene flow, even in highly fragmented landscapes. We tested how historical effective population size, historical migration and contemporary landscape structure, such as forest cover, patch isolation and matrix resistance, affect genetic variability and differentiation of seedlings in a tropical palm (Euterpe edulis) in a human-modified rainforest. We sampled 16 sites within five landscapes in the Brazilian Atlantic forest and assessed genetic variability and differentiation using eight microsatellite loci. Using a model selection approach, none of the covariates explained the variation observed in inbreeding coefficients among populations. The variation in genetic diversity among sites was best explained by historical effective population size. Allelic richness was best explained by historical effective population size and matrix resistance, whereas genetic differentiation was explained by matrix resistance. Coalescence analysis revealed high historical migration between sites within landscapes and constant historical population sizes, showing that the genetic differentiation is most likely due to recent changes caused by habitat loss and fragmentation. Overall, recent landscape changes have a greater influence on among-population genetic variation than historical gene flow process. As immediate restoration actions in landscapes with low forest amount, the development of more permeable matrices to allow the movement of pollinators and seed dispersers may be an effective strategy to maintain microevolutionary processes.