Genetic Diversity and Relationship of Yunnan Native Cattle Breeds and Introduced Beef Cattle Breeds

In this study, random amplified polymorphic DNA (RAPD) analysis was used to estimate genetic diversity and relationship in 134 samples belonging to two native cattle breeds from the Yunnan province of China (DeHong cattle and DiQing cattle) and four introduced beef cattle breeds (Brahman, Simmental, MurryGrey, and ShortHorn). Ten primers were used, and a total of 84 bands were scored, of which 63 bands (75.0%) were polymorphic. The genetic distance matrix was obtained by proportions of shared fragment. The results indicate that the Yunnnan DeHong cattle breed is closely related to the Brahman (Bos indicus), and the Yunnan DiQing cattle breed is closely related to the Simmental, ShortHorn, and MurryGrey (Bos taurus) breeds. Our results imply that Bos indicus and Bos taurus were the two main origins of Yunnan native cattle. The results also provide the basic genetic materials for conservation of cattle resources and crossbreeding of beef cattle breeds in South China.     

Genetic Diversity in Introduced Populations with an Allee Effect

A phenomenon that strongly influences the demography of small introduced populations and thereby potentially their genetic diversity is the demographic Allee effect, a reduction in population growth rates at small population sizes. We take a stochastic modeling approach to investigate levels of genetic diversity in populations that successfully overcame either a strong Allee effect, in which populations smaller than a certain critical size are expected to decline, or a weak Allee effect, in which the population growth rate is reduced at small sizes but not negative. Our results indicate that compared to successful populations without an Allee effect, successful populations with a strong Allee effect tend to (1) derive from larger founder population sizes and thus have a higher initial amount of genetic variation, (2) spend fewer generations at small population sizes where genetic drift is particularly strong, and (3) spend more time around the critical population size and thus experience more genetic drift there. In the case of multiple introduction events, there is an additional increase in diversity because Allee-effect populations tend to derive from a larger number of introduction events than other populations. Altogether, a strong Allee effect can either increase or decrease genetic diversity, depending on the average founder population size. By contrast, a weak Allee effect tends to decrease genetic diversity across the entire range of founder population sizes. Finally, we show that it is possible in principle to infer critical population sizes from genetic data, although this would require information from many independently introduced populations.     

Differential Resource Use between Native and Introduced Gray Squirrels

Differences in habitat requirements and the spatial distribution of habitat for native and introduced species can determine outcomes of biological invasions. Introduced eastern gray squirrels (Sciurus carolinensis) have displaced native red squirrels (S. vulgaris) in Europe and have been implicated as a contributing factor to the decline of western gray squirrels (S. griseus) in North America. Eastern and western gray squirrels are associated with oak (Quercus spp.), but little is known about how these species interact. From April 2007 to April 2012, we radio-tracked sympatric eastern and western gray squirrels in western Washington to compare habitat use and evaluate competitive interactions. We developed resource utilization functions for each species and evaluated distribution of habitat on Joint Base Lewis-McChord, Washington, USA. Both species shared affinity for closed canopy forests and oaks; however, important differences in relationships with riparian areas and shrub cover resulted in low overlap in habitat distribution, which likely limited potential competitive interactions. Eastern gray squirrels appeared restricted to areas around wetlands likely because they supported the deciduous tree species that comprise habitat for this species in its native range. Use by western gray squirrels, but not eastern gray squirrels, significantly decreased with increasing shrub cover. Forestry practices that promote mixed oak-conifer with little shrub cover in uplands can benefit western gray squirrels and minimize interactions with eastern gray squirrels. © 2020 The Wildlife Society.     

Genetic Diversity and Population Structure of Native and Introduced Date Palm (Phoenix dactylifera) Germplasm in the United Arab Emirates

Date palm (Phoenix dactylifera) has been cultivated since ancient times, but little is known about its genetic diversity and population structure. Examination of 80 date palm accessions grown in the United Arab Emirates, including a collection of varieties from around the world, using 21 microsatellite markers, indicated extensive genetic diversity, with many accessions heterozygous for most markers. The average number of alleles per locus (19), expected heterozygosity (0.7), observed heterozygosity (0.25) and fixation indices (Fst?=?0.6, Rst?=?0.72) demonstrated significant population structure. Analysis with a model-based Baysian method, STRUCTURE 2.4.1, indicated that the 80 accessions could be broadly divided into nine groups. Independent samples of genotypes with the same name, collected from different experimental stations, usually clustered together. The study was enriched for germplasm from the United Arab Emirates (UAE), and one STRUCTURE-derived grouping consisted mainly of UAE accessions. In a few other clusters, several genotypes from the UAE, Iraq and Oman grouped together. Two clusters included accessions from both North Africa and the Middle East. Many accessions in the STRUCTURE-derived populations appeared to be genetic admixtures. The results indicated a broad dissemination of related germplasms across date-palm growing regions of the world, with very few alleles that still correlate with particular regional germplasms.     

The Potential Impact of An Introduced Shrub on Native Plant Diversity and Forest Regeneration

Over a period of 20 years, Chinese privet, Ligustrum sinense, invaded a mixed hardwood forest in western North Carolina, USA. The invasion penetrated about 30m under the canopy trees, providing 100% cover of the forest floor. Under the privets and in a nearby privet-poor reference area we marked off twenty, one square meter plots with string. All plants in each square meter of both areas were tallied in the spring of 1999 and young trees less than 1m high were again counted in September. We removed privets of the invaded area in November and again tallied all plants in both areas the following spring of 2000. In the spring of 1999, the mean number of herb species per square meter under the privet was 41%, and stem counts 75% less than in the reference area. 42% of herb species found in the reference area were missing under the privet. After removing the privets in the fall of 1999, the number of both native species and stems increased in the privet area the following spring. Plots of density of two native plants against privet density showed both native plants decreasing under increasing privet cover. In the spring of 1999, there were 4 species and 274 stems of tree seedlings in the privet area. In September of that year, we found only one small American holly tree, a highly shade-tolerant species, remaining under the privet. Our data support the thesis that Chinese privet can severely reduce herbaceous species and almost completely suppress tree regeneration in a mixed hardwood forest.     

Behavioral and Genetic Differentiation Between Native and Introduced Populations of the Argentine Ant

In this paper, we examine the hypothesis that reduced intraspecific aggression underlies the competitive prowess of Argentine ants in their introduced range. Specifically, we test three predictions of this hypothesis by comparing the genetic diversity, behavior, and ecology of Argentine ants in their native range to introduced populations. Differences between native and introduced populations of Argentine ants were consistent with our predictions. Introduced populations of the Argentine ant appear to have experienced a population bottleneck at the time of introduction, as evidenced by much reduced variation in polymorphic microsatellite DNA markers. Intraspecific aggression was rare in introduced populations but was common in native populations. Finally, in contrast to the Argentine ant's ecological dominance throughout its introduced range, it did not appear dominant in the native ant assemblages studied in Argentina. Together these results identify a possible mechanism for the widespread success of the Argentine ant in its introduced range.     

Genetic Diversity in Introduced Golden Mussel Populations Corresponds to Vector Activity

We explored possible links between vector activity and genetic diversity in introduced populations of Limnoperna fortunei by characterizing the genetic structure in native and introduced ranges in Asia and South America. We surveyed 24 populations: ten in Asia and 14 in South America using the mitochondrial cytochrome c oxidase subunit I (COI) gene, as well as eight polymorphic microsatellite markers. We performed population genetics and phylogenetic analyses to investigate population genetic structure across native and introduced regions. Introduced populations in Asia exhibit higher genetic diversity (H _E = 0.667–0.746) than those in South America (H _E = 0.519–0.575), suggesting higher introduction effort for the former populations. We observed pronounced geographical structuring in introduced regions, as indicated by both mitochondrial and nuclear markers based on multiple genetic analyses including pairwise Ф_ST, F _ST, Bayesian clustering method, and three-dimensional factorial correspondence analyses. Pairwise F _ST values within both Asia (F _ST = 0.017–0.126, P = 0.000–0.009) and South America (F _ST = 0.004–0.107, P = 0.000–0.721) were lower than those between continents (F _ST = 0.180–0.319, P = 0.000). Fine-scale genetic structuring was also apparent among introduced populations in both Asia and South America, suggesting either multiple introductions of distinct propagules or strong post-introduction selection and demographic stochasticity. Higher genetic diversity in Asia as compared to South America is likely due to more frequent propagule transfers associated with higher shipping activities between source and donor regions within Asia. This study suggests that the intensity of human-mediated introduction vectors influences patterns of genetic diversity in non-indigenous species.     

Assessing Genetic Diversity of Brazilian Reef Fishes by Chromosomal and DNA Markers

Little is known on genetics of Brazilian coral reef fish and most of this information is limited to chromosome characterization of major representative species. The diploid chromosome number in marine fish varies from 2n= 22–26 to 2n = 240–260. Despite of this apparent diversity, most studied marine species have a diploid complement with 48 acrocentric chromosomes. This latter trend is mostly observed among Perciformes, an important major taxon of coral reef fishes. Studies in the families Pomacentridae, Pomacanthidae and Chaetodontidae, for example, have shown a common karyotype pattern entirely formed by 48 uniarmed chromosomes. However, rare numerical and structural chromosome polymorphisms and cryptic chromosome rearrangements involving heterochromatin segments and/or nucleolar organizing sites have been reported among such fishes. Although new chromosome forms can contribute to the establishment of genetically isolated populations, their role in reef fish speciation at marine realm still is an open question. More recently, genomic DNA analyses using RAPD and microsatellites, and sequencing and RFLP of mitochondrial DNA have increasingly been used in Atlantic reef fish species. Genetic homogeneity over wide geographical ranges has been reported for different fish groups, in contrast to several cases of population substructuring related to environmental constraints or evolutionary history. Amazonas outflow and upwelling on the Southeastern coast of Brazil are believed to be strong barriers to dispersal of some reef species. Moreover, it is suggested that the pattern of speciation and population structure at South Atlantic is quite distinctive from Pacific Ocean, even when comparing closely related taxa. Further genetic studies are strongly encouraged in Brazilian reef fishes in order to provide a reliable scenario of the genetic structure in this important and diverse fish group.     

中国引种桉树种质资源的遗传多样性分析

该研究从110对SSR引物中,选用47个扩增稳定、条带特异的SSR多态位点,对42种159份桉树种质材料进行PCR扩增,通过统计条带构建二维数据库的方法,进行遗传多样性分析和聚类分析。结果显示:(1)共检测到137个等位基因,平均每个位点等位基因数为2.915个,各位点等位基因变异范围为2~7个。(2)遗传多样性分析结果表明,平均Shannon’s信息指数为0.181,平均观察杂合度Ho为0.068,平均多态信息含量PIC为0.182。综合各指标分析发现,位点eSSR-GR018、eSSR-GR083和eSSR-GR109的多态性程度最高,反映的遗传信息量更大,能够在桉树种质资源的遗传多样性分析和种质鉴定等方面发挥更大的作用。(3)非加权类平均法(UPGMA法)和主坐标分析法(PCoA法)聚类分析均表明,159份桉树种质材料分为两大类群,且昆士兰桉和少花桉间具有较高的遗传相似度,很可能产生杂交种;聚类结果与基于形态学的HillJohnson分类系统基本一致。研究表明,中国引种的桉树种质资源具有较高水平的遗传多样性,该研究所选用的47对SSR引物可有效地应用于桉树种质资源的鉴定分析。     

Genetic Diversity in Alpine and Foothill Populations of Campanula rotundifolia (Campanulaceae)

Climatic constraints on insects in alpine environments have important consequences for the biology of their plant mutualists; in particular, reduced insect diversity and activity in alpine plant populations can result in pollinator-limited seed set and, potentially, in low genetic diversity. However, highly effective pollination by bumblebees in alpine populations can compensate for low visitation rates. In this study we hypothesized that, because of highly effective pollination by bumblebees, alpine populations of Campanula rotundifolia would not experience more frequent cycles of pollinator limitation than low-elevation populations and would therefore exhibit comparable levels of genetic variability and inbreeding to those found in foothill populations. Enzyme electrophoresis was used to assess genetic variability at nine putative loci in alpine and foothill populations of C. rotundifolia in Colorado. Genetic variability in C. rotundifolia was found to be comparable to that reported for other long-lived herbaceous perennials. Measures of genetic variability and fixation indices did not differ between high- and low-elevation populations and were consistent with Hardy-Weinberg expectations. Nonsignificant F(ST) values indicated no genetic differentiation among all populations.     

Genetic Diversity of Eukaryotic Microorganisms in Lake Taihu,a Large Shallow Subtropical Lake in China

We investigated the genetic diversity of eukaryotic microorganisms (0.8-20 mum) by sequencing cloned 18S rRNA genes in six genetic libraries constructed from six locations in Lake Taihu, a large shallow subtropical lake in China. Genetic libraries of eukaryotic ribosomal RNA were screened by restriction fragment length polymorphism (RFLP) analysis, and one clone representative of each RFLP pattern was partially sequenced. A total of 528 clones were clustered into 165 RFLP patterns and finally into 131 operational taxonomic unit (OTUs). Phylogenetic analysis revealed that each library included many unique OTUs, as well as members of distantly related phylogenetic groups. A majority of the clones were from alveolates, stramenopiles, cercozoa, cryptophytes, chlorophytes, and fungi, with members of choanoflagellida, euglenida, centroheliozoa, ancyromonadidae, ichthyosporea, and kathablepharid representing a minor fraction of the library. Six OTUs (15 clones) were not related to any known eukaryotic group. Canonical correspondence analysis suggested that the differences in eukaryotic microorganism community composition of in the six regions were partially related to trophic status, sediment resuspension, and top-down regulation by metazooplankton.     

56个中国地方猪种微卫星基因座的遗传多样性

采用FA0—ISAG联合推荐的27个微卫星DNA标记对56个中国地方猪品种和3个引进猪种(杜洛克猪、长白猪、大白猪)进行遗传多样性分析,通过计算等位基因频率、有效等位基因数、平均遗传杂合度、基因分化系数、多态信息含量和遗传距离并进行系统聚类分析,评估其种内遗传变异和种间遗传关系。以聚类结果为基础,将56个中国地方猪种分为12类：Ⅰ、Ⅱ和Ⅲ类都是《中国猪品种志》中的华北型猪种;Ⅳ类相当于其中的江海型猪种;Ⅴ、Ⅵ、Ⅶ、Ⅷ和Ⅸ类的品种大部分属于华中型;Ⅹ和Ⅺ类相当于华南型品种;Ⅻ类相当于西南型品种。提出保种场结合保护区是一种比较符合我国地方猪种实际状况的保种模式。研究结果可为我国地方猪种种质特性研究提供基础数据,为我国地方猪品种资源的合理保护和利用提供科学依据。     

Genetic Diversity in Five Iranian Native Chicken Populations Estimated by Microsatellite Markers

Iranian chicken genetic resources are characterized by a long history and a vast diversity. This study represents the first results from the selection and evaluation of five polymorphic microsatellite markers for the genetic assessment of five native chicken populations located in the northwestern (West Azerbaijan), northern (Mazandaran), central (Isfahan, Yazd), and southern (Fars) provinces of Iran. The number of alleles ranged from three to six per microsatellite locus. All populations were characterized by a high degree of genetic diversity, with the lowest heterozygosity found in the Isfahan population (62%) and the greatest in the populations from West Azerbaijan and Mazandaran (79%). The largest Nei’s unbiased genetic distance was found between the Isfahan and Fars populations (0.696) and the smallest between the Mazandaran and Yazd populations (0.097). The Isfahan population was found to be the most genetically distant among all populations studied. These results serve as an initial step in the plan for genetic characterization and conservation of Iranian native chickens.     

Introduced Plant Viruses and the Invasion of a Native Grass Flora

Weed and native grasses from the South Island of New Zealand were surveyed for virus infection. Cocksfoot mottle virus (CfMV) and Ryegrass mosaic virus (RgMV) were restricted to a few introduced species; however, Barley yellow dwarf viruses (BYDVs) have invaded native grasses in New Zealand. Virus incidence was significantly lower in the native species (2%) than in the introduced species (12%). Four different serotypes (RMV, RPV, PAV, MAV) were detected in the introduced grass flora but only two (RMV, PAV) were detected in native species. In experimental transmission tests the aphid vector Rhopalosiphum padi's survival was variable on the 20 native species tested but this was not due to the presence or absence of endophytic fungi as none were detected in the New Zealand species. Aphid numbers increased and plants were killed when R. padi fed on Agrostis muelleriana and Festuca multinodis. R. padi transmitted a PAV isolate to these and six other native species. BYDVs infected 4/5 of the subfamilies tested. Virus incidence in native Arundinoideae and Pooideae was significantly lower than in introduced Pooideae and Panicoideae. One species of Bambusoideae collected from the field was not infected but was found susceptible in glasshouse tests. Agrostis capillaris, Dactylis glomerata and Lolium perenne were identified as the most likely reservoirs of infection for the native flora. Anthoxanthum odoratum was not infected but if the SGV serotype and its vector Schizaphis graminum were ever introduced, A. odoratum could form an effective reservoir from near sea level into alpine areas. This revised version was published online in July 2006 with corrections to the Cover Date.     

Diversity and Evolution of Body Size in Fishes

The diversity of body sizes observed among species of a clade is a combined result of microevolutionary processes (i.e. natural selection and genetic drift) that cause size changes within phylogenetic lineages, and macroevolutionary processes (i.e. speciation and extinction) that affect net rates of diversification among lineages. Here we assess trends of size diversity and evolution in fishes (non-tetrapod craniates), employing paleontological, macroecological, and phylogenetic information. Fishes are well suited to studies of size diversity and evolution, as they are highly diverse, representing more than 50% of all living vertebrate species, and many fish taxa are well represented in the fossil record from throughout the Phanerozoic. Further, the frequency distributions of sizes among fish lineages resemble those of most other animal taxa, in being right-skewed, even on a log scale. Using an approach that measures rates of size evolution (in darwins) within a formal phylogenetic framework, we interpret the shape of size distributions as a balance between the competing forces of diversification, pushing taxa away from ancestral values, and of conservation, drawing taxa closer to a central tendency. Within this context we show how non-directional mechanisms of evolution (i.e. passive diffusion processes) can produce an hitherto unperceived bias to larger size, when size is measured on the conventional log scale. These results demonstrate how the interpretation of macroecological datasets can be enriched from an historical perspective, and document the ways in which macroevolutionary and microevolutionary processes may be decoupled in the production of size diversity.     

Breakdown of Introduced and Native Leaves in Two Indian Streams

The decomposition of leaves of Ficus benghalensis. Anacardium occidentale. Acacia auriculiformis and Eucalyptus globulus was followed during 16 weeks in two streams in the Western Ghat forest region of Karnataka, India. The concentration of nitrogen increased during decay; the levels of phosphorus, soluble phenolics and calcium decreased. Fungal colonization of the leaves was followed by counting the numbers of conidia released during aeration. Highest conidium production was found on leaves of Ficus: benghalensis. Daily exponential decay coefficients κ where not significantly different between leaf species or streams and varied between −0.0063 and −0,0090. Correlation analyses between κ and initial leaf parameters (N, P, Ca, and phenolics) did not yield any significant values, but there was a significant linear correlation between κ values and log (maximum sporulation rate).     

从CIMMYT引进的人工合成六倍体小麦D染色体组微卫星分子标记的遗传差异

采用微卫星（SSR）分子标记技术,选用23个D染色体组特异性引的对来自CIMMYT的26份人工合成六倍体小麦D染色体组的遗传多样性进行了分析。研究发现,26份材料在D染色体组上存在丰富的等位基因变异（92个）,平均每个基因座为4个。遗传距离计算结果也显示,26份材料D染色体组之间具有较大的遗传差异,平均遗传距离高达0．4955。因此,人工合成六倍体小麦D染色体组中存在丰富的遗传多样性,可以作为拓宽普通小麦遗传基础的新的遗传变异来源。研究还发现,由同一个粗山羊草基因型与不同硬粒小麦杂交合成的人工合成六倍体小麦（如合成种17和18）在所用检测的23个基因座中有3个存在差异,说明小麦在多倍化后,供体基因组在重复序列区域会发生遗传分化。     

Molecular Characterization and Genetic Diversity of Insecticidal Crystal Protein Genes in Native Bacillus thuringiensis Isolates

The Western Ghats of Karnataka natural ecosystem are among the most diverse and is one of the eight hottest hotspots of biological diversity in the world, that runs along the western part of India through four states including Karnataka. Bacillus thuringiensis (Bt) strains were isolated from soils of Western Ghats of Karnataka and characterized by molecular and analytical methods as a result of which 28 new Bt-like isolates were identified. Bt strains were isolated from soil samples using sodium acetate selection method. The morphology of crystals was studied using light and phase contrast microscopy. Isolates were further characterized for insecticidal cry gene by PCR, composition of toxins in bacterial crystals by SDS-PAGE cloning, sequencing and evaluation of toxicity was done. As a result 28 new Bt-like isolates were identified. Majority of the isolates showed the presence of a 55 kDa protein bands on SDS-PAGE while the rest showed 130, 73, 34, and 25 kDa bands. PCR analysis revealed predominance of Coleopteran-active cry genes in these isolates. The variations in the nucleotide sequences, crystal morphology, and mass of crystal protein(s) purified from the Bt isolates revealed genetic and molecular diversity. Three strains containing Coleopteran-active cry genes showed higher activity against larvae Myllocerus undecimpustulatus undatus Marshall (Coleoptera: Curculionidae) than B. thuringiensis subsp. Morrisoni. Results indicated that Bt isolates could be utilized for bioinsecticide production, aiming to reduce the use of chemical insecticide which could be useful to use in integrated pest management to control agriculturally important pests for sustainable crop production.