Finding Hybrid Incompatibilities Using Genome Sequences from Hybrid Populations

Natural hybrid zones offer a powerful framework for understanding the genetic basis of speciation in progress because ongoing hybridization continually creates unfavorable gene combinations. Evidence indicates that postzygotic reproductive isolation is often caused by epistatic interactions between mutations in different genes that evolved independently of one another (hybrid incompatibilities). We examined the potential to detect epistatic selection against incompatibilities from genome sequence data using the site frequency spectrum (SFS) of polymorphisms by conducting individual-based simulations in SLiM. We found that the genome-wide SFS in hybrid populations assumes a diagnostic shape, with the continual input of fixed differences between source populations via migration inducing a mass at intermediate allele frequency. Epistatic selection locally distorts the SFS as non-incompatibility alleles rise in frequency in a manner analogous to a selective sweep. Building on these results, we present a statistical method to identify genomic regions containing incompatibility loci that locates departures in the local SFS compared with the genome-wide SFS. Cross-validation studies demonstrate that our method detects recessive and codominant incompatibilities across a range of scenarios varying in the strength of epistatic selection, migration rate, and hybrid zone age. Our approach takes advantage of whole genome sequence data, does not require knowledge of demographic history, and can be applied to any pair of nascent species that forms a hybrid zone.     

Reproductive Isolation with Little Genetic Divergence in Sympatric Populations of Brown Trout (SALMO TRUTTA)

Two reproductively isolated demes of brown trout coexist in a small Swedish mountain lake, Lake Bunnersj?rna. We electrophoretically examined 102 specimens from that lake for 27 enzymes encoded by 54 loci. The two demes are fixed for different alleles at a lactate dehydrogenase locus (LDH-1); statistically significant allele frequency differences at five other loci further support the complete lack of gene flow between these demes. There are significant differences in growth rates between fish in the two demes, but no further morphological differentiation h-s been detected.--In light of these findings, the genetic distance between these populations is surprisingly small (Nei's I = 0.975). These demes represent one of the least genetically divergent, reproductively isolated sympatric pair of vertebrate populations that have been identified. The results are discussed from both an evolutionary and ecological perspective.     

Behavioural Reproductive Isolation in a Rotifer Hybrid Zone

A hybrid zone between two Brachionus plicatilis rotifer mitochondrial DNA (mtDNA) lineages was recently described in the Iberian Peninsula between a pond (Santed 2) and a lake (Gallocanta). The patterns of mitochondrial and nuclear genetic variation observed suggested that gene flow is mainly male-mediated from the lake to the pond. Here we test two hypotheses: (a) that male-mediated gene flow occurs through assortative mating between individuals from these ponds, (b) that behavioural isolation occurs between the two mtDNA lineages. We isolated, reared and genotyped rotifer clones from resting eggs collected in the sediments of these and two other distant ponds. We devised a quick, inexpensive RFLP method to discriminate between B. plicatilis and its sibling species B. ‘Manjavaeas’ and between both mtDNA B. plicatilis lineages. Behavioural no-choice tests using new-born, virgin males and females were performed between five clones. B. ‘Manjavacas’ and B. plicatilis were reproductively isolated. B. plicatilis clones did not show evidence of reproductive isolation, regardless of their mtDNA lineage, except Santed 2 males, which discriminated strongly against Gallocanta females. These results could help to explain the discrepancies between mitochondrial and nuclear genetic variation reported in the two populations.     

Mate Choice by Non-Virgin Females Contributes to Reproductive Isolation between Populations of the Harlequin Beetle-Riding Pseudoscorpion

Determining whether reproductive isolation evolves through mate choice and/or gametic factors that prevent fertilization or through the post‐zygotic mechanisms of hybrid sterility or inviability is fundamental to understanding speciation. Investigation of the pre‐ and post‐zygotic components of reproductive isolation is facilitated in the pseudoscorpion, Cordylochernes scorpioides, by its indirect method of sperm transfer and viviparous embryonic development. Previous research on this species, in which mate discrimination was assessed in virgin females, suggested that female choice played only a minor role in reproductive isolation between populations from French Guiana and Panamá. Here, in a study of three allopatric populations of C. scorpioides from Panamá, we assessed mating‐stage isolation in both virgin and once‐mated females, and found that female discrimination depends critically on mating status. Virgin females were almost invariably receptive, showing no tendency to discriminate against males from allopatric populations. By contrast, non‐virgin females were significantly more likely to reject foreign males than males from their own population. Male sexual motivation could not account for differences in either female sexual receptivity or male success in sperm transfer. Allopatric and sympatric males did not differ in number of spermatophores deposited as either a female’s first or second mate. Nonetheless, allopatric males achieved significantly lower sperm transfer success not only with choosy, non‐virgin females but also with virgin females. Given the lack of behavioral discrimination by virgin females, female receptivity was not the only factor influencing differences in sperm transfer success. Multivariate analysis of spermatophore morphology suggests that the higher failure rate of matings between allopatric males and virgin females resulted from population differences in sperm packet architecture. Overall, our findings indicate that assessment of discrimination against allopatric males that is limited to virgin females may seriously underestimate the contribution of female mate choice to reproductive isolation between populations.     

The Evolutionary Dynamics of Genetic Incompatibilities Introduced by Duplicated Genes in Arabidopsis thaliana

Although gene duplications provide genetic backup and allow genomic changes under relaxed selection, they may potentially limit gene flow. When different copies of a duplicated gene are pseudofunctionalized in different genotypes, genetic incompatibilities can arise in their hybrid offspring. Although such cases have been reported after manual crosses, it remains unclear whether they occur in nature and how they affect natural populations. Here, we identified four duplicated-gene based incompatibilities including one previously not reported within an artificial Arabidopsis intercross population. Unexpectedly, however, for each of the genetic incompatibilities we also identified the incompatible alleles in natural populations based on the genomes of 1,135 Arabidopsis accessions published by the 1001 Genomes Project. Using the presence of incompatible allele combinations as phenotypes for GWAS, we mapped genomic regions that included additional gene copies which likely rescue the genetic incompatibility. Reconstructing the geographic origins and evolutionary trajectories of the individual alleles suggested that incompatible alleles frequently coexist, even in geographically closed regions, and that their effects can be overcome by additional gene copies collectively shaping the evolutionary dynamics of duplicated genes during population history.     

The Population Genetics of Speciation: The Evolution of Hybrid Incompatibilities

Speciation often results from the accumulation of ``complementary genes,' i.e., from genes that, while having no deleterious effect within species, cause inviability or sterility when brought together with genes from another species. Here I model speciation as the accumulation of genic incompatibilities between diverging populations. Several results are obtained. First, and most important, the number of genic incompatibilities between taxa increases much faster than linearly with time. In particular, the probability of speciation increases at least as fast as the square of the time since separation between two taxa. Second, as Muller realized, all hybrid incompatibilities must initially be asymmetric. Third, at loci that have diverged between taxa, evolutionarily derived alleles cause hybrid problems far more often than ancestral alleles. Last, it is ``easier' to evolve complex hybrid incompatibilities requiring the simultaneous action of three or more loci than to evolve simple incompatibilities between pairs of genes. These results have several important implications for genetic analyses of speciation.     

Dobzhansky-Muller and Wolbachia-Induced Incompatibilities in a Diploid Genetic System

Genetic incompatibilities are supposed to play an important role in speciation. A general (theoretical) problem is to explain the persistence of genetic diversity after secondary contact. Previous theoretical work has pointed out that Dobzhansky-Muller incompatibilities (DMI) are not stable in the face of migration unless local selection acts on the alleles involved in incompatibility. With local selection, genetic variability exists up to a critical migration rate but is lost when migration exceeds this threshold value. Here, we investigate the effect of intracellular bacteria Wolbachia on the stability of hybrid zones formed after the Dobzhansky Muller model. Wolbachia are known to cause a cytoplasmic incompatibility (CI) within and between species. Incorporating intracellular bacteria Wolbachia can lead to a significant increase of critical migration rates and maintenance of divergence, primarily because Wolbachia-induced incompatibility acts to reduce frequencies of F1 hybrids. Wolbachia infect up to two-thirds of all insect species and it is therefore likely that CI co-occurs with DMI in nature. The results indicate that both isolating mechanisms strengthen each other and under some circumstances act synergistically. Thus they can drive speciation processes more forcefully than either when acting alone.     

Incipient Reproductive Isolation between Geographic Populations of Ophryotrocha labronica (Polychaeta, Dorvilleidae)

Åkesson, B. (Department of Zoology, University of Gothenburg, Göteborg, Sweden.) Incipient reproductive isolation between geographic populations of Ophryotrocha labronica (Polychaeta, Dorvilleidae). Zocl. Scripta 1 (5): 207–210, 1972.–The mechanism of sex determination and the incipient reproductive isolation between geographic populations of Ophryotrocha labronica are studied in intra- and interpopulation crosses. Two populations from the Naples area and one from Leghorn are employed in the crosses. The considerable genetic difference between the Leghorn population and any of the Naples populations is reflected in some crossing combinations by changes in sex ratios, by occurrence of individuals with a reduced viability in the progeny, by a decreased mating propensity, and by discrimination of mates from alien populations. It is stated that the changes in sex ratios, the decreased mating propensity, the dwarfed individuals in the progeny, and the preferential mating all reflect the incompatibility of gene complexes. The differences between reciprocal crosses are not fully explained. The occurrence of extranuclear DNA, as well as the existence of a maternal heredity in intrapopulation crosses, indicate that cytoplasmic inheritance may be one of the factors behind these reciprocal differences.     

Sexual Activity and Reproductive Isolation Between Age‐specific Selected Populations of Seed Beetle

We evaluated the degree of reproductive isolation between laboratory populations of the seed beetle (Acanthoscelides obtectus) selected to reproduce early (E) or late (L) in life, where different levels of sexual activity and sexual discrimination have been detected. We found a significant level of behavioral isolation among populations within the E selection regime in which beetles showed enhanced early‐life fitness traits and low sexual activity. In contrast, substantially higher levels of sexual activity and an indiscriminate mating system inhibited rather than promoted pre‐zygotic isolation between the L populations. Our results indicate that the study of sexual activity levels may be crucial for understanding the first steps in the pre‐zygotic isolation among allopatric populations subjected to uniform selection.     

植物种群的繁殖对策

植物种群的繁殖对策钟章成（西南师范大学,重庆６３０７１５）ＲｅｐｒｏｄｕｃｔｉｖｅＳｔｒａｔｅｇｉｅｓｏｆＰｌａｎｔＰｏｐｕｌａｔｉｏｎｓ．￥ＺｈｏｎｇＺｈａｎｇｃｈｅｎｇ（ＳｏｕｔｈｗｅｓｔＣｈｉｎａＴｅａｃｈｅｒｓＵ－ｎｉｖｅｒｓｉｔｙ,Ｃｈｏｎ...     

Patterns of Genetic and Reproductive Traits Differentiation in Mainland vs. Corsican Populations of Bumblebees

Populations on islands often exhibit lower levels of genetic variation and ecomorphological divergence compared to their mainland relatives. While phenotypic differentiation in characters, such as size or shape among insular organisms, has been well studied, insular differentiation in quantitative reproductive traits involved in chemical communication has received very little attention to date. Here, we investigated the impact of insularity on two syntopic bumblebee species pairs: one including species that are phylogenetically related (Bombus terrestris and B. lucorum), and the other including species that interact ecologically (B. terrestris and its specific nest inquiline B. vestalis). For each bumblebee species, we characterized the patterns of variation and differentiation of insular (Corsican) vs. mainland (European) populations (i) with four genes (nuclear and mitochondrial, 3781 bp) and (ii) in the chemical composition of male marking secretions (MMS), a key trait for mate attraction in bumblebees, by gas chromatography-mass spectrometry (GC-MS). Our results provide evidence for genetic differentiation in Corsican bumblebees and show that, contrary to theoretical expectations, island populations of bumblebees exhibit levels of genetic variation similar to the mainland populations. Likewise, our comparative chemical analyses of MMS indicate that Corsican populations of bumblebees are significantly differentiated from the mainland yet they hold comparative levels of within-population MMS variability compared to the mainland. Therefore, insularity has led Corsican populations to diverge both genetically and chemically from their mainland relatives, presumably through genetic drift, but without a decrease of genetic diversity in island populations. We hypothesize that MMS divergence in Corsican bumblebees was driven by a persistent lack of gene flow with mainland populations and reinforced by the preference of Corsican females for sympatric (Corsican) MMS. The impoverished Corsican bumblebee fauna has not led to relaxation of stabilizing selection on MMS but to consistent differentiation chemical reproductive traits on the island.     

甘蔗杂交后代蔗汁品质性状的遗传分析

以4×3不完全双列杂交(NCⅡ)选配的12个杂交组合后代为材料,对蔗汁锤度、旋光读数、转光度、蔗汁蔗糖分、视纯度和重力纯度等6个品质性状进行配合力和遗传力分析。结果表明,品质性状的遗传主要由基因加性效应引起,其中蔗汁锤度、旋光读数、转光度、蔗汁蔗糖分主要由父本基因加性效应引起。CP72-330、HoCP93-750、桂糖91-116和粤糖92-1287等4个亲本的品质性状一般配合力(gca)为正值且较大,是配合力较好的高糖亲本。CP72-330×桂糖91-116及HoCP93-750×粤糖92-1287的品质性状特殊配合力(sca)相对效应值均为正值且较大,杂交后代品质性状平均值也较高,为较好的高糖杂交组合。品质性状父本gca方差大于母本gca方差,亲本gca方差为组合sca方差的7-28倍,广义遗传力(hB2)为58%-68%,狭义遗传力(hN2)为56%-60%,属于遗传能力较强的品质性状。     

Evidence of Pre-mating Reproductive Isolation in Two Allopatric Populations of the Vlei Rat,Otomys irroratus

Laboratory experiments were undertaken to ascertain whether or not individuals of two allopatric Otomys irroratus populations (Kamberg and Karkloof) distinguish between mates from the same (homotype) and the other (heterotype) population. The study aimed to establish the existence of pre-mating reproductive isolation mechanisms between the two populations. In both ‘whole-animal choice’ trials and olfactory discrimination tests, all females significantly preferred homotype stimulus males or odour. Although males of both populations preferred homotype females, males were less discriminating at the start of experiments, possibly because of increased exploratory drive at this time. Furthermore, Kamberg males demonstrated equal preference for both stimulus females during the dark phase of the light cycle; no explanation is given for this phenomenon. Overall, the results indicate the existence of population-specific courtship behaviour, with olfactory cues apparently playing an important role in mate recognition. It is therefore possible that, should representatives of the two populations meet in nature, they may be reproductively isolated through behavioural means.     

Reproductive Isolation in Hybrid Mice Due to Spermatogenesis Defects at Three Meiotic Stages

Early in the process of speciation, reproductive failures occur in hybrid animals between genetically diverged populations. The sterile hybrid animals are often males in mammals and they exhibit spermatogenic disruptions, resulting in decreased number and/or malformation of mature sperms. Despite the generality of this phenomenon, comparative study of phenotypes in hybrid males from various crosses has not been done, and therefore the comprehensive genetic basis of the disruption is still elusive. In this study, we characterized the spermatogenic phenotype especially during meiosis in four different cases of reproductive isolation: B6-ChrX^MSM, PGN-ChrX^MSM, (B6 × Mus musculus musculus-NJL/Ms) F₁, and (B6 × Mus spretus) F₁. The first two are consomic strains, both bearing the X chromosome of M. m. molossinus; in B6-ChrX^MSM, the genetic background is the laboratory strain C57BL/6J (predominantly M. m. domesticus), while in PGN-ChrX^MSM the background is the PGN2/Ms strain purely derived from wild M. m. domesticus. The last two cases are F₁ hybrids between mouse subspecies or species. Each of the hybrid males exhibited cell-cycle arrest and/or apoptosis at either one or two of three distinct meiotic stages: premeiotic stage, zygotene-to-pachytene stage of prophase I, and metaphase I. This study shows that the sterility in hybrid males is caused by spermatogenic disruptions at multiple stages, suggesting that the responsible genes function in different cellular processes. Furthermore, the stages with disruptions are not correlated with the genetic distance between the respective parental strains.WHEN animals from genetically diverged populations hybridize, complete or partial sterility is often observed in the F₁ hybrids or in their descendants. This phenomenon belonging to postzygotic reproductive isolation accelerates irreversible genetic divergence by preventing free gene flow across the two diverging populations, and thereby plays a pivotal role in speciation. Sexual dimorphism is a general feature of reproductive isolation (Wu and Davis 1993; Laurie 1997; Orr 1997; Kulathinal and Singh 2008). In mammals, impairment is much more severe in males than in females, and in general the heterogametic sex is more sensitive to interspecific and intersubspecific genetic incompatibility. This phenomenon is well known as Haldane''s rule (Haldane 1922; Laurie 1997; Orr 1997).In many animals, the reproductive isolation is caused by spermatogenic disruptions characterized by reduced number of germ cells and small testis size. These animals include Drosophila (Joly et al. 1997), stickleback fish Pungitius (Takahashi et al. 2005), caviomorph rodent Thrichomys (Borodin et al. 2006), house musk shrew Suncus (Borodin et al. 1998), wallaby Petrogale (Close et al. 1996), and genus Mus (Forejt and Iványi 1974; Matsuda et al. 1992; Hale et al. 1993; Yoshiki et al. 1993; Kaku et al. 1995; Gregorová and Forejt 2000; Elliott et al. 2001, 2004; Good et al. 2008). Although reproductive isolation by spermatogenic impairment is a well-known phenomenon, its underlying genetic mechanism and molecular basis have remained elusive. The Dobzhansky–Muller model, which infers that hybrid sterility or inviability is caused by deleterious epistatic interactions between nuclear genes derived from their respective parent species or subspecies (Dobzhansky 1936; Muller 1942), is widely accepted in animals and plants and is also applicable to the sterility of hybrid animals in F₂ or backcross generations, so-called hybrid breakdown, in which the genes causing postzygotic reproductive isolation are partially recessive (Orr 2005).The genetic incompatibility between house mouse subspecies is an ideal animal model for studying the early stage of speciation. Two subspecies of mouse, Mus musculus domesticus and M. m. musculus, diverged from their common ancestor 0.3–1.0 MYA (Yonekawa et al. 1980; Moriwaki 1994; Bonhomme and Guénet 1996; Boursot et al. 1996; Din et al. 1996). M. m. domesticus ranges across western Europe and the Middle East, whereas M. m. musculus ranges throughout eastern Europe and northern Asia (Bonhomme and Guénet 1996). The two subspecies meet in a narrow hybrid zone, which is most likely maintained by a balance between dispersal and selection against hybrids (Hunt and Selander 1973; Bonhomme and Guénet 1996; Payseur et al. 2004). M. m. domesticus also displays reproductive isolation from the Japanese wild mouse, M. m. molossinus, which originated from hybridization of M. m. castaneus and M. m. musculus and its nuclear genome is predominantly derived from M. m. musculus (Yonekawa et al. 1980, 1988; Moriwaki 1994; Sakai et al. 2005). To investigate the reproductive isolation between M. m. domesticus and M. m. molossinus, we previously constructed a consomic strain B6-ChrX^MSM (Oka et al. 2004). This strain has the X chromosome from the MSM/Ms strain, which is derived from M. m. molossinus, in the genetic background of the laboratory strain C57BL/6J (B6), which is predominantly derived from M. m. domesticus (Moriwaki 1994). F₁ hybrid animals between B6 and MSM/Ms strains are fully fertile. On the contrary, B6-ChrX^MSM shows male-specific sterility characterized by a reduced sperm number and dysfunction of the sperm, including abnormal morphology and low motility, indicating that B6-ChrX^MSM is a model of hybrid breakdown in animals (Oka et al. 2004, 2007). Our previous study indicated that the abnormal morphology of the sperm head results from the genetic incompatibility between MSM/Ms-derived X-linked genes and B6 genes on autosomes including chromosomes 1 and 11 (Oka et al. 2007).In this study, to understand the genetic mechanism of reproductive isolation in mice, we first undertook in-depth characterization of phenotype for each B6-ChrX^MSM male especially during meiosis. Meiosis is a special cell division that produces four haploid cells after one round of chromosome replication and two rounds of chromosome segregation. During meiosis, homologous chromosomes pair, synapse, undergo crossing over, and achieve bipolar attachment to the spindle to segregate one set of chromosomes to each daughter cell. Homologous recombination is initiated during the leptotene stage of meiotic prophase I with the formation of DNA double-strand breaks (DSBs), which are repaired immediately during the zygotene stage or after crossing over of homologous chromosomes during the pachytene stage (Roeder 1997; Tarsounas and Moens 2001).During the first wave of spermatogenesis, most mitotic spermatogonia in the B6-ChrX^MSM testes fail to initiate meiotic DNA replication. Some proportion of those spermatogonia that enter into meiosis are again arrested and eliminated by apoptosis at the pachytene stage, resulting in the production of a small number of sperms. We extended the same analysis to three other cases of reproductive isolation. Another consomic strain PGN-ChrX^MSM has an MSM/Ms-derived X chromosome in the genetic background of the PGN2/Ms strain derived from wild mice (M. m. domesticus). PGN-ChrX^MSM males produce a small number of dysfunctional sperms as was the case with B6-ChrX^MSM males, but the former males show apoptosis mainly at metaphase of meiosis I. Furthermore, we examined F₁ hybrid males from intersubspecific cross of (B6 × M. m. musculus-NJL/Ms) and interspecific cross of (B6 × M. spretus). These F₁ hybrid males exhibited apoptosis at metaphase I and at the zygotene-to-pachytene stage of prophase I. As a whole, the postzygotic reproductive isolation in mice is caused by disruptions at a minimum of three different spermatogenic stages.     

Reproductive Isolation during Domestication

It has been hypothesized that reproductive isolation should facilitate evolution under domestication. However, a systematic comparison of reproductive barrier strength between crops and their progenitors has not been conducted to test this hypothesis. Here, we present a systematic survey of reproductive barriers between 32 economically important crop species and their progenitors to better understand the role of reproductive isolation during the domestication process. We took a conservative approach, avoiding those types of reproductive isolation that are poorly known for these taxa (e.g., differences in flowering time). We show that the majority of crops surveyed are isolated from their progenitors by one or more reproductive barriers, despite the fact that the most important reproductive barrier in natural systems, geographical isolation, was absent, at least in the initial stages of domestication for most species. Thus, barriers to reproduction between crops and wild relatives are closely associated with domestication and may facilitate it, thereby raising the question whether reproductive isolation could be viewed as a long-overlooked "domestication trait." Some of the reproductive barriers observed (e.g., polyploidy and uniparental reproduction), however, may have been favored for reasons other than, or in addition to, their effects on gene flow.     

Naturally Occurring Incompatibilities between Different Culex pipiens pallens Populations as the Basis of Potential Mosquito Control Measures

Background

Vector-borne diseases remain a threat to public health, especially in tropical countries. The incompatible insect technique has been explored as a potential control strategy for several important insect vectors. However, this strategy has not been tested in Culex pipiens pallens, the most prevalent mosquito species in China. Previous works used introgression to generate new strains that matched the genetic backgrounds of target populations while harboring a new Wolbachia endosymbiont, resulting in mating competitiveness and cytoplasmic incompatibility. The generation of these incompatible insects is often time-consuming, and the long-term stability of the newly created insect-Wolbachia symbiosis is uncertain. Considering the wide distribution of Cx. pipiens pallens and hence possible isolation of different populations, we sought to test for incompatibilities between natural populations and the possibility of exploiting these incompatibilities as a control strategy.

Methodology/Principal Findings

Three field populations were collected from three geographic locations in eastern China. Reciprocal cross results showed that bi-directional patterns of incompatibility existed between some populations. Mating competition experiments indicated that incompatible males could compete with cognate males in mating with females, leading to reduced overall fecundity. F1 offspring from incompatible crosses maintained their maternal crossing types. All three populations tested positive for Wolbachia. Removal of Wolbachia by tetracycline rendered matings between these populations fully compatible.

Conclusions/Significance

Our findings indicate that naturally occurring patterns of cytoplasmic incompatibility between Cx. pipiens pallens populations can be the basis of a control strategy for this important vector species. The observed incompatibilities are caused by Wolbachia. More tests including field trials are warranted to evaluate the feasibility of this strategy as a supplement to other control measures.     

吉富罗非鱼群体遗传多样性的AFLP分析

为了分析吉富罗非鱼的遗传多样性,为其育种提供理论依据,本实验利用5对引物组合(E-AGG/M-CTT, E-AGG/M-CTG, E-AAC/M-CAG, E-ACA/M-CTG, E-ACA/M-CAG)对广东省化州光辉养殖场有限公司新选育的吉富罗非鱼第16代群体(F16)进行遗传多样性的AFLP分析.27个个体共检出187个扩增位点,其中多态位点163个,平均每对引物扩增出32.6个位点,多态位点比例87.17%;平均Nei's基因多样性0.2886;平均Shannon's指数0.4339.结果说明实验群体存在较丰富的遗传多样性且保持有较高的遗传杂合度,具有进一步育种和开发的价值.