Phosphoglucose isomerase (<Emphasis Type="Italic">Pgi</Emphasis>) performance and fitness effects among Arthropods and its potential role as an adaptive marker in conservation genetics

The development of conservation genomics will be greatly aided by the use of neutral as well as adaptive molecular markers. Identifying novel adaptive molecular markers that have general application across diverse taxa is challenging, especially in Arthropods where few if any examples of balanced polymorphisms exist that are shared across species. A review of literature on the Pgi gene provides strong evidence for population level fitness consequences of genetic variation in this gene, across very diverse lineages of Arthropods. While these observations demonstrate the potential of using Pgi as an adaptive molecular marker, this gene is fundamentally different from the adaptive markers MHC and SI. Rather than providing insights into individual genetic health, Pgi appears to have a role in conservation genetics by providing insights into gene by environment interactions, local adaptation and evolutionary significant units, and potentially even morphologically cryptic dispersal phenotypes. These findings argue for studying Pgi variation in more species, as it appears central to the goals of conservation genomics.     

Isolation and characterization of polymorphic microsatellite loci in the grand jackknife clam Solen grandis (Bivalvia: Veneroida)

The grand jackknife clam Solen grandis (Dunker, 1861) is an overexploited bivalve species. In order to promote a conservation program for this species, it is necessary to evaluate its genetic diversity and population genetics. For this purpose, we isolated the first set of 18 polymorphic microsatellite markers and examined their allelic variation using a total of 30 wild individuals collected from one locality. The number of alleles per locus ranged from 5 to 24, and the observed and expected heterozygosity varied from 0.300 to 0.967 and from 0.721 to 0.952, respectively. The high variabilities at these loci indicated that they would be useful tool for exploring the population genetics of S. grandis.     

Isolation and characterization of twelve novel microsatellite loci in the ark shell <Emphasis Type="Italic">Scapharca broughtonii</Emphasis>

Scapharca broughtonii is an over-exploited bivalve in China. In order to promote a conservation program for this species, it is necessary to evaluate its genetic diversity and population genetics. For this purpose, we isolated twelve novel polymorphic microsatellite markers and examined their allelic variation using 40 wild individuals collected from one locality along the Chinese coast. The number of alleles ranged from 2 to 22 per locus with the expected heterozygosities ranging from 0.444 to 0.944. These markers will be useful for the assessment of genetic variation for this species.     

Identifying genetic signatures of selection in a non-model species, alpine gentian (Gentiana nivalis L.), using a landscape genetic approach

It is generally accepted that most plant populations are locally adapted. Yet, understanding how environmental forces give rise to adaptive genetic variation is a challenge in conservation genetics and crucial to the preservation of species under rapidly changing climatic conditions. Environmental variation, phylogeographic history, and population demographic processes all contribute to spatially structured genetic variation, however few current models attempt to separate these confounding effects. To illustrate the benefits of using a spatially-explicit model for identifying potentially adaptive loci, we compared outlier locus detection methods with a recently-developed landscape genetic approach. We analyzed 157 loci from samples of the alpine herb Gentiana nivalis collected across the European Alps. Principle coordinates of neighbor matrices (PCNM), eigenvectors that quantify multi-scale spatial variation present in a data set, were incorporated into a landscape genetic approach relating AFLP frequencies with 23 environmental variables. Four major findings emerged. 1) Fifteen loci were significantly correlated with at least one predictor variable (R _adj ²  > 0.5). 2) Models including PCNM variables identified eight more potentially adaptive loci than models run without spatial variables. 3) When compared to outlier detection methods, the landscape genetic approach detected four of the same loci plus 11 additional loci. 4) Temperature, precipitation, and solar radiation were the three major environmental factors driving potentially adaptive genetic variation in G. nivalis. Techniques presented in this paper offer an efficient method for identifying potentially adaptive genetic variation and associated environmental forces of selection, providing an important step forward for the conservation of non-model species under global change.     

Isolation and characterization of microsatellite DNA loci for endangered fish,Japanese huchen (Hucho perryi)

Japanese huchen, Hucho perryi, is an endangered fish in Japan. In order to promote a conservation program for this species, it is necessary to evaluate its genetic diversity and population genetics. For this purpose, we designed 15 primers containing dinucleotide microsatellite regions and examined their allelic variation using a total of 23 wild individuals collected from two different localities. Eight loci showed moderate allelic variation ranging from two to four alleles, with expected heterozygosities from 0.043 to 0.548. These markers will be useful for the assessment of genetic variation for this species.     

Evaluation of Genetic Diversity and Development of a Core Collection of Wild Rice (Oryza rufipogon Griff.) Populations in China

Common wild rice (Oryza rufipogon Griff.), the progenitor of Asian cultivated rice (O. sativa L.), is endangered due to habitat loss. The objectives of this research were to evaluate the genetic diversity of wild rice species in isolated populations and to develop a core collection of representative genotypes for ex situ conservation. We collected 885 wild rice accessions from eight geographically distinct regions and transplanted these accessions in a protected conservation garden over a period of almost two decades. We evaluated these accessions for 13 morphological or phenological traits and genotyped them for 36 DNA markers evenly distributed on the 12 chromosomes. The coefficient of variation of quantitative traits was 0.56 and ranged from 0.37 to 1.06. SSR markers detected 206 different alleles with an average of 6 alleles per locus. The mean polymorphism information content (PIC) was 0.64 in all populations, indicating that the marker loci have a high level of polymorphism and genetic diversity in all populations. Phylogenetic analyses based on morphological and molecular data revealed remarkable differences in the genetic diversity of common wild rice populations. The results showed that the Zengcheng, Gaozhou, and Suixi populations possess higher levels of genetic diversity, whereas the Huilai and Boluo populations have lower levels of genetic diversity than do the other populations. Based on their genetic distance, 130 accessions were selected as a core collection that retained over 90% of the alleles at the 36 marker loci. This genetically diverse core collection will be a useful resource for genomic studies of rice and for initiatives aimed at developing rice with improved agronomic traits.     

Development of robust genomic simple sequence repeat markers for estimation of genetic diversity within and among bulb onion (Allium cepa L.) populations

Improved understanding of genetic diversity in onion and shallot (Allium cepa L.) is required to inform breeding and genetic resource conservation, and to enable development of association genetics and seed quality assurance methods. To develop quantitative estimates of diversity we estimated within- and among-population heterozygosity in a set of onion populations using genomic simple sequence repeat (SSR) markers developed by genomic skim sequencing. Primer sets (166) designed to flank SSR motifs identified were evaluated in a diverse set of lines, with 80 (48?%) being polymorphic. The 20 most robust single copy markers were scored in 12 individuals from 24 populations representing short-day to long-day adapted material from diverse environments. The average genetic diversity estimate (H _e) per population was 0.3 (SD 0.08) and the average per marker was 0.49 (SD 0.2). The onion populations assessed in this survey were distinct with moderate to large population differentiation but also had high within-population variation (F _st?=?0.26). There was evidence of inbreeding (F _is?=?0.22) with observed heterozygosities lower than the expected. This marker resource will be applicable for DNA fingerprinting, measuring levels of inbreeding in breeding lines, assessing population structure for association mapping and expanding linkage maps that are principally based on expressed sequence tag-based markers. A Galaxy workflow was developed to facilitate bulk SSR marker design from next-generation sequence data. This study provides one of the first quantitative views of population genetic variation in onion and a practical toolset for further genetics.     

Progeny-testing of full-sibs IBD in a SSC2 QTL region highlights epistatic interactions for fatness traits in pigs

Background

Tetraena mongolica (Zygophyllaceae), an endangered endemic species in western Inner Mongolia, China. For endemic species with a limited geographical range and declining populations, historical patterns of demography and hierarchical genetic structure are important for determining population structure, and also provide information for developing effective and sustainable management plans. In this study, we assess genetic variation, population structure, and phylogeography of T. mongolica from eight populations. Furthermore, we evaluate the conservation and management units to provide the information for conservation.

Results

Sequence variation and spatial apportionment of the atp B- rbc L noncoding spacer region of the chloroplast DNA were used to reconstruct the phylogeography of T. mongolica. A total of 880 bp was sequenced from eight extant populations throughout the whole range of its distribution. At the cpDNA locus, high levels of genetic differentiation among populations and low levels of genetic variation within populations were detected, indicating that most seed dispersal was restricted within populations.

Conclusions

Demographic fluctuations, which led to random losses of genetic polymorphisms from populations, due to frequent flooding of the Yellow River and human disturbance were indicated by the analysis of BEAST skyline plot. Nested clade analysis revealed that restricted gene flow with isolation by distance plus occasional long distance dispersal is the main evolutionary factor affecting the phylogeography and population structure of T. mongolica. For setting a conservation management plan, each population of T. mongolica should be recognized as a conservation unit.     

Fitness differences associated with Pgi SNP genotypes in the Glanville fritillary butterfly (Melitaea cinxia)

Allozyme variation at the phosphoglucose isomerase (PGI) locus in the Glanville fritillary butterfly (Melitaea cinxia) is associated with variation in flight metabolic rate, dispersal rate, fecundity and local population growth rate. To map allozyme to DNA variation and to survey putative functional variation in genomic DNA, we cloned the coding sequence of Pgi and identified nonsynonymous variable sites that determine the most common allozyme alleles. We show that these single‐nucleotide polymorphisms (SNPs) exhibit significant excess of heterozygotes in field‐collected population samples as well as in laboratory crosses. This is in contrast to previous results for the same species in which other allozymes and SNPs were in Hardy–Weinberg equilibrium or exhibited an excess of homozygotes. Our results suggest that viability selection favours Pgi heterozygotes. Although this is consistent with direct overdominance at Pgi, we cannot exclude the possibility that heterozygote advantage is caused by the presence of one or more deleterious alleles at linked loci.     

Genetic variation and cultivar identification in Cymbidium ensifolium

As a popular flowering species with many cultivars, Cymbidium ensifolium (L.) is commercially important in horticulture. However, so far little has been known about genetic diversity and conservation genetics of this species. Understanding of the genetic variation and relationships in cultivars of C.?ensifolium is a prerequisite for development of future germplasm conservation and cultivar improvement. Here we report assessment of genetic variations in C.?ensifolium cultivars using the DNA fingerprinting technique of inter-simple sequence repeats (ISSR). A total of 239 ISSR loci were identified and used for evaluation of genetic variation with a selection of 19 ISSR primers. Among these ISSR loci, 99.16% were polymorphic with wide genetic variation as shown by Nei??s gene diversity (H?=?0.2431) among 85 tested cultivars. ISSR fingerprinting profiles showed that each cultivar had its characteristic DNA pattern, indicating unequivocal cultivar identification at molecular level. Eighteen cultivar-specific ISSR markers were identified in seven cultivars. The cultivar Sijiwenhan was confirmed as hybrid by four ISSR primers. Several cultivars with same name but different geographical origins were distinguished based on their ISSR profiles. A dendrogram generated with ISSR markers could group 73 of 85 cultivars into four major clusters. Further analysis of ISSR variation revealed that about 69% of total genetic variation in this species is due to genetic divergence inside geographical groups. Our results suggest that both germplasm collection and in?situ conservation are important for future planning of C.?ensifolium species conservation.     

Isolation and characterization of 18 polymorphic microsatellite markers for the “Female Ginseng” Angelica sinensis (Apiaceae) and cross-species amplification

Angelica sinensis (Apiaceae) is an endangered alpine herb that is widely used as a medicinal plant in traditional Chinese medicine (TCM). Wild populations of A. sinensis have become quite rare in China. Thus, population genetics studies of this species are urgently needed for its effective conservation and sustainable use. However, to date, no microsatellite loci have been isolated in A. sinensis. To address this issue, we isolated 18 polymorphic loci and genotyped 120 individuals collected from 6 populations. The number of alleles per locus ranged from 1.2 to 5.5, and the average was 2.4. The observed and expected heterozygosity per locus for a population varied, respectively, from 0.000 to 0.983 (averaged at 0.198) and from 0.066 to 0.661 (averaged at 0.333). Deviation from the Hardy–Weinberg equilibrium (p < 0.01) was observed for 4 to 14 loci in various populations. These microsatellite markers were cross-amplified in 10 species affinis, and 7 loci were successfully amplified in all species. These microsatellite markers are useful for genetic studies, the conservation management of A. sinensis, and identification of A. sinensis.     

The genetic basis of evolutionary change in gene expression levels

The regulation of gene expression is an important determinant of organismal phenotype and evolution. However, the widespread recognition of this fact occurred long after the synthesis of evolution and genetics. Here, we give a brief sketch of thoughts regarding gene regulation in the history of evolution and genetics. We then review the development of genome-wide studies of gene regulatory variation in the context of the location and mode of action of the causative genetic changes. In particular, we review mapping of the genetic basis of expression variation through expression quantitative trait locus studies and measuring the cis/trans component of expression variation in allele-specific expression studies. We conclude by proposing a systematic integration of ideas that combines global mapping studies, cis/trans tests and modern population genetics methodologies, in order to directly estimate the forces acting on regulatory variation within and between species.     

Population genetic diversity and divergence of the halobiotic herb Limonium sinense estimated by AFLP and ISSR, and implications for conservation

Limonium sinense is a halobiotic herb endemic to China that has been traditionally used for hundreds of years for its good restorative function. Genetic variation and population structure of this species were investigated by using amplified fragment length polymorphisms (AFLPs) and inter simple sequence repeats (ISSRs). A high level of genetic diversity was detected [AFLP: H _E = 0.284, percentage of polymorphic loci (PPL) = 92.68 %; ISSR: H _E = 0.257, PPL = 85.71 %] at the species level with POPGENE. Based on analysis of molecular variation (AMOVA), the among-population component accounted for 29.03 % (AFLP) and 28.81 % (ISSR) of the genetic variation, indicating that most of the genetic variation was between individuals within populations. The Shannon diversity index (I) was higher for AFLP (0.432) than for ISSR (0.395). Five main clusters were shown in the unweighted pair-group method with arithmetic mean (UPGMA) dendrogram created using TFPGA, consistent with the result of principal coordinate analysis using NTSYS. In situ conservation is advocated first. Keeping a stable environment for this halobiotic herb is necessary. For ex situ conservation, it is important to establish a germplasm bank. AFLP and ISSR markers were proved to be efficient tools in assessing the genetic variation among populations of L. sinense. The patterns of variation appeared to be consistent for these two marker systems, and they can be used for management of genetic structure, protection of the halobiotic plant, and conservation of germplasm.     

Isolation and characterization of polymorphic microsatellite markers for the endangered Korean freshwater fish Hemibarbus mylodon

Korean barbel, Hemibarbus mylodon, is an endangered freshwater species endemic to Korea. In order to undertake a conservation program for this species in Korea, it is essential to evaluate its genetic diversity and population structure. For this purpose, we developed 10 polymorphic microsatellite markers and examined their allelic variation using a total of 60 wild individuals collected from three different localities. The number of alleles per locus ranged from three to 26. The expected and observed heterozygosities per locus ranged from 0.19 to 0.94 and from 0.20 to 0.98, respectively. Significant departures from Hardy–Weinberg equilibrium expectations occurred in four loci. These markers will be useful for the assessment of genetic diversity for this species.     

Conservation management of rare and predominantly selfing tropical trees: an example using Hopea bilitonensis (Dipterocarpaceae)

Hopea bilitonensis is an extremely rare and predominantly selfing dipterocarp in Peninsular Malaysia. A comprehensive research was initiated to assess the ecological genetics of H. bilitonensis to elucidate specific ecological and genetic requirements and subsequently to recommend conservation strategies. The objective for conservation of a rare plant such as H. bilitonensis differs from that of a common plant. For common plants, the conservation strategies are to prevent the species from becoming endangered. In contrast, for rare plants, the final race against extinction is being fought. Tropical forests are rich in plant species diversity and obtaining adequate knowledge to set conservation strategies for the majority of these species might be difficult. Thus, it is suggested that for the conservation of tree species, the species can be grouped according to their life history traits. The information generated for a species can then be adapted to species that have similar types of life history traits. We have recently generated the ecological genetics information for a rare and predominantly outcrossed dipterocarp (Shorea lumutensis). This study on H. bilitonensis will provide ecological genetics information for the conservation of rare and predominantly selfing dipterocarps.     

Evolutionary epidemiology of schistosomiasis: linking parasite genetics with disease phenotype in humans

Here we assess the role of parasite genetic variation in host disease phenotype in human schistosomiasis by implementing concepts and techniques from environmental association analysis in evolutionary epidemiology. Schistosomiasis is a tropical disease that affects more than 200 million people worldwide and is caused by parasitic flatworms belonging to the genus Schistosoma. While the role of host genetics has been extensively studied and demonstrated, nothing is yet known on the contribution of parasite genetic variation to host disease phenotype in human schistosomiasis. In this study microsatellite genotypes of 1561 Schistosoma mansoni larvae collected from 44 human hosts in Senegal were linked to host characteristics such as age, gender, infection intensity, liver and bladder morbidity by means of multivariate regression methods (on each parasite locus separately). This revealed a highly significant association between allelic variation at the parasite locus L46951 and host infection intensity and bladder morbidity. Locus L46951 is located in the 3′ untranslated region of the cGMP-dependent protein kinase gene that is expressed in reproductive organs of adult schistosome worms and appears to be linked to egg production. This putative link between parasite genetic variation and schistosomiasis disease phenotype sets the stage for further functional research.     

Fast and cost-effective mining of microsatellite markers using NGS technology: an example of a Korean water deer Hydropotes inermis argyropus

Background

Microsatellites, a special class of repetitive DNA sequence, have become one of the most popular genetic markers for population/conservation genetic studies. However, its application to endangered species has been impeded by high development costs, a lack of available sequences, and technical difficulties. The water deer Hydropotes inermis is the sole existing endangered species of the subfamily Capreolinae. Although population genetics studies are urgently required for conservation management, no species-specific microsatellite marker has been reported.

Methods

We adopted next-generation sequencing (NGS) to elucidate the microsatellite markers of Korean water deer and overcome these impediments on marker developments. We performed genotyping to determine the efficiency of this method as applied to population genetics.

Results

We obtained 98 Mbp of nucleotide information from 260,467 sequence reads. A total of 20,101 di-/tri-nucleotide repeat motifs were identified; di-repeats were 5.9-fold more common than tri-repeats. [CA]_n and [AAC]_n/[AAT]_n repeats were the most frequent di- and tri-repeats, respectively. Of the 17,206 di-repeats, 12,471 microsatellite primer pairs were derived. PCR amplification of 400 primer pairs yielded 106 amplicons and 79 polymorphic markers from 20 individual Korean water deer. Polymorphic rates of the 79 new microsatellites varied from 2 to 11 alleles per locus (H_e: 0.050–0.880; H_o: 0.000–1.000), while those of known microsatellite markers transferred from cattle to Chinese water deer ranged from 4 to 6 alleles per locus (H_e: 0.279–0.714; H_o: 0.300–0.400).

Conclusions

Polymorphic microsatellite markers from Korean water deer were successfully identified using NGS without any prior sequence information and deposited into the public database. Thus, the methods described herein represent a rapid and low-cost way to investigate the population genetics of endangered/non-model species.     

Variation at Innate Immunity Toll-Like Receptor Genes in a Bottlenecked Population of a New Zealand Robin

Toll-like receptors (TLRs) are an ancient family of genes encoding transmembrane proteins that bind pathogen-specific molecules and initiate both innate and adaptive aspects of the immune response. Our goal was to determine whether these genes show sufficient genetic diversity in a bottlenecked population to be a useful addition or alternative to the more commonly employed major histocompatibility complex (MHC) genotyping in a conservation genetics context. We amplified all known avian TLR genes in a severely bottlenecked population of New Zealand''s Stewart Island robin (Petroica australis rakiura), for which reduced microsatellite diversity was previously observed. We genotyped 17–24 birds from a reintroduced island population (including the 12 founders) for nine genes, seven of which were polymorphic. We observed a total of 24 single-nucleotide polymorphisms overall, 15 of which were non-synonymous, representing up to five amino-acid variants at a locus. One locus (TLR1LB) showed evidence of past directional selection. Results also confirmed a passerine duplication of TLR7. The levels of TLR diversity that we observe are sufficient to justify their further use in addressing conservation genetic questions, even in bottlenecked populations.     

Development of microsatellite markers for the endangered medicinal plant Launaea arborescens (Asteraceae)

• Premise of the study: Microsatellite loci were developed in Launaea arborescens, an endangered and medicinal Asteraceae species in North Africa, for further investigation of its conservation genetics. • Methods and Results: We isolated and characterized 10 polymorphic and nine monomorphic microsatellite loci from L. arborescens using the protocol of Fast Isolation by AFLP of Sequences COntaining repeats (FIASCO). For the 10 polymorphic loci, the number of alleles detected per locus varied from two to six, and the observed and expected heterozygosities ranged from 0.000 to 0.833 and 0.059 to 0.713, respectively. • Conclusions: The polymorphic markers provide a useful tool for conservation genetics studies of L. arborescens, including analysis of mating system, estimating gene flow, and identifying discrete genetic units within the species.     

varver: a database of microsatellite variation in vertebrates

Understanding how genetic variation is maintained within a species is important in ecology, evolution, conservation and population genetics. Tremendous efforts have been made to evaluate the patterns of genetic variation in natural populations of various species. For this purpose, microsatellites have played a major role since the 1990s. Here we describe a comprehensive database, varver (Variation in Vertebrates) that provides complete information regarding microsatellite variation in natural populations of vertebrates. For each species, varver includes basic information of the species, a list of publications reporting the microsatellite variation, and tables of genetic variation within and between populations (heterozygosity and F_ST). The geographic location and rough sampling range are also shown for each sampled population. The database should be useful for researchers interested in not only specific species but also comparing multiple species. We discuss the utility of microsatellite data, particularly for meta‐analyses that involve multiple microsatellite loci from various species. We show that in such analyses, it is extremely important to correct for biases caused by differences in mutation rate, mainly due to repeat unit and number.