A hybrid zone between Chorthippus parallelus parallelus and Chorthippus parallelus erythropus (Orthoptera: Acrididae): morphological and electrophoretic characters

Two subspecies of the grasshopper Chorthippus parullelus have distributions that abut in the Pyrenees. We have studied morphological and electrophoretic variation in II populations near Mont Louis, Pyrénées-Orientales, France. The two subspecies differ in several morphological characters and at one enzyme locus, esterase-2, and in this area they hybridize forming a cline in morphology less than 5 km wide. Examination of museum specimens suggests that this hybrid zone extends for most of the length of the Pyrenees, possibly breaking down in the extreme west. As the two subspecies are known to differ in mating behaviour this hybrid zone is well suited to the study of reinforcement.     

Spatial variation of biochemical and ecological phenotypes in Drosophila: Electrophoretic and quantitative variation

Electrophoretic variation at three enzyme loci-alcohol dehydrogenase (Adh), glycerophosphate dehydrogenase (Gpdh), triosephosphate isomerase (Tpi)- is compared in Australian Drosophila melanogaster populations at three levels of spatial heterogeneity; among breeding sites, within populations, and between populations at the geographic level. Heterogeneity at the breeding site level greatly exceeds that among adults within populations, indicating greater intermixing at the mobile adult stage than at the developmentally immature and less migratory larval stage. Heterogeneity at the microspatial level is large relative to the geographic level at two of these loci. Spatial patterns of variation in ecological phenotypes are also considered. It is argued that electrophoretic variants may contribute little to an understanding of this quantitative variation, and that a more useful approach in ecological genetics is to consider ecological phenotypes as primary data.     

黑线姬鼠(Apodemus agrarius)的种群繁殖参数及其地理分异特征

黑线姬鼠（Apodemus agrarius）是我国广大地区的主要害鼠之一,是余庆县农田害鼠优势种,占总鼠数的94.81%。探讨其种群繁殖参数的变动规律及其地理分异特征,对其种群数量预测预报具有重要意义。通过对1987-2005年贵州省余庆县黑线姬鼠种群繁殖参数分析结果表明：研究期间共解剖标本5497只,其中,雌鼠2698只,雄鼠2799只,黑线姬鼠在当地1-11月份均可繁殖,主要繁殖期在3-10月份,每年4-5月份和8-9月份出现2次妊娠高峰。种群总性比（♀/♂）为0.96,多年平均怀孕率为36.91%±6.79%,平均胎仔数为5.33±1.07只,平均繁殖指数为0.81±0.17,平均睾丸下降率为59.13%±7.89%。不同年龄组种群繁殖力存在显著差异,随着种群年龄的增长繁殖力不断增加,成年Ⅰ组、成年Ⅱ组、老年组是种群繁殖的主体。种群繁殖参数不同年度之间比较稳定,不同月份、不同季节之间变化差异较大,具有明显的季节变化特征。年均种群密度与年均繁殖指数呈极显著正相关,与胎仔数显著正相关,与年均怀孕率、睾丸下降率、性比相关性不显著,繁殖指数是影响黑线姬鼠种群密度的重要因子。比较全国各地黑线姬鼠种群繁殖参数的地理分异特征认为,黑线姬鼠种群繁殖参数具有明显的地理分异现象,胎仔数、生殖强度由南向北逐渐增加,具有随纬度的升高趋向增加的特征;在高纬度地区繁殖时间较短;性比与纬度、经度的变化关系密切;各繁殖参数与海拔的变化相关性不明显,可排除海拔因素的影响。     

Inter‐ and intraspecific variation in mycotoxin tolerance: A study of four Drosophila species

Many mycophagous Drosophila species have adapted to tolerate high concentrations of mycotoxins, an ability not reported in any other eukaryotes. Although an association between mycophagy and mycotoxin tolerance has been established in many Drosophila species, the genetic mechanisms of the tolerance are unknown. This study presents the inter‐ and intraspecific variation in the mycotoxin tolerance trait. We studied the mycotoxin tolerance in four Drosophila species from four separate clades within the immigrans‐tripunctata radiation from two distinct locations. The effect of mycotoxin treatment on 20 isofemale lines per species was studied using seven gross phenotypes: survival to pupation, survival to eclosion, development time to pupation and eclosion, thorax length, fecundity, and longevity. We observed interspecific variation among four species, with D. falleni being the most tolerant, followed by D. recens, D. neotestacea, and D. tripunctata, in that order. The results also revealed geographical variation and intraspecific genetic variation in mycotoxin tolerance. This report provides the foundation for further delineating the genetic mechanisms of the mycotoxin tolerance trait.     

Intraspecific Morphological Variation Among Populations of Pratylenchus brachyurus and P. coffeae

Three populations of Pratylenchus coffeae and two of P. brachyurus, each originating from a single female, were maintained on Citrus spp. or Solanum nigrum L. for several years under greenhouse conditions. Nematodes were extracted from roots, and adult female specimens were killed, fixed, and mounted in glycerine for microscopic study. Variables measured were distance between vulva and anus and lengths of the stylet, posterior uterine sac, and tail. The mean data and coefficients of variability suggest that styler length had the least variability, and length of posterior uterine sac the most. When males and distinct spermathecae are not evident in P. coffeae populations, the species can he distinguished from P. brachyurus by a shorter mean stylet length, longer mean posterior uterine sac length, and much longer distance between the vulva and anus.     

Population structure and skeletal variation in the Late Woodland of west-central Illinois

This paper analyzes nonmetric trait variation in 11 late Late Woodland (ca. AD 700-1000) and one Mississippian (AD 1000-1300) skeletal samples from west-central Illinois from a population-structure perspective. Most of the sites are of the Bluff phase of Late Woodland in the lower Illinois River valley; others are from a nearby, contemporary archaeological phase. Late Woodland as a whole era (ca. AD 250-1000) was a period of marked population growth and expansion into new regional environments, trends that accompanied horticultural intensification in the area. Overall variation between sites was low, but males, females, and the total sample exhibited a significant geographic component to variation due to interregional morphological differences. The Bluff sites tended to group together relative to the non-Bluff sites. However, there was no significant geographic component to variation among the Bluff sites. The results are only partially consistent with archaeological data suggesting population growth and expansion through fissioning. Previous studies have demonstrated significant heterogeneity for nonmetric trait frequencies among Middle Woodland (ca. 100 BC to AD 250) sites, suggesting a Middle to Late Woodland change in population structure that lowered levels of morphological variation. This supports a model of increased intra- and interregional interaction from Middle to Late Woodland times developed from ceramic data by Braun and by Braun and Plog.     

Functional characterization of powdery mildew resistance gene MlIW172, a new Pm60 allele and its allelic variation in wild emmer wheat

Wild emmer wheat (Triticum dicoccoides, WEW) is an immediate progenitor of both the cultivated tetraploid and hexaploid wheats and it harbors rich genetic diversity against powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt). A powdery mildew resistance gene MlIW172 originated from WEW accession IW172 (G-797-M) is fine mapped in a 0.048 centimorgan (cM) genetic interval on 7AL, corresponding to a genomic region spanning 233 kb, 1 Mb and 800 kb in Chinese Spring, WEW Zavitan, and T. urartu G1812, respectively. MlIW172 encodes a typical NLR protein NLR^IW172 and physically locates in an NBS-LRR gene cluster. NLR^IW172 is subsequently identified as a new allele of Pm60, and its function is validated by EMS mutagenesis and transgenic complementation. Haplotype analysis of the Pm60 alleles reveals diversifications in sequence variation in the locus and presence and absence variations (PAV) in WEW populations. Four common single nucleotide variations (SNV) are detected between the Pm60 alleles from WEW and T. urartu, indicative of speciation divergence between the two different wheat progenitors. The newly identified Pm60 alleles and haplotypes in WEW are anticipated to be valuable for breeding powdery mildew resistance wheat cultivars via marker-assisted selection.     

Skull osteology and osteological phylogeny of the Western whip snake Hierophis viridiflavus (Squamata,Colubridae)

The skull osteology of Hierophis viridiflavus is here described and figured in detail on the basis of 18 specimens. The sample includes specimens from the ranges of both H. viridiflavus viridiflavus and H. viridiflavus carbonarius as well as specimens not identified at sub-specific level. The main characters that define H. viridiflavus in comparison to the parapatric congeneric species Hierophis gemonensis are wide maxillary diastema, basioccipital crest well distinct in three lobes and basioccipital process well marked. The foramina of the otoccipital and prootic, and the basioccipital process of the basioccipital are among the most ontogenetically variable characters, as indicated by two juvenile specimens included in the sample. A specimen-level phylogenetic analysis including H. gemonensis and other outgroups (overall 6 species, 26 specimens, 64 skull characters) recovered all H. viridiflavus specimens in one clade, indicating the presence of a clear phylogenetic signal in the applied characters. However, the resolution within the H. viridiflavus clade is poor the monophyly of H. viridiflavus carbonarius was retrieved, but not that of Hierophis v. viridiflavus. Probably due to the relatively high variability, the skull morphology does not support the recently proposed specific status of the two subspecies.     

浙江古田山自然保护区常绿阔叶林种子雨的时空变异

木本植物种子产量的时间和空间变化格局对植物更新以及群落组成和结构有着重要影响, 是种子雨研究的一个重要方面。2006年6月在古田山亚热带常绿阔叶林24 hm²样地布置了130个面积为0.5 m²的种子雨收集器, 每周收集一次。利用4年的种子雨数据, 研究了种子雨的时间和空间变异。主要结果如下: (1)共收集到124227粒成熟种子, 属于29科51属63种, 每月降水量与平均每月种子数、物种数均呈显著负相关; (2)种子产量在每年干季(秋季)有明显的高峰, 有10个物种在湿季扩散种子, 不同物种结实物候起始和终止时间有差异; (3)基于4年的种子雨数据, 几乎所有物种的种子雨均存在很大的年际变异, 收集到的所有物种的种子产量年际变异系数的中位数为1.72; (4)种子雨在不同收集器之间有很大的变异, 变异系数的中位数为8.06; 几乎所有物种的空间变异都远远大于时间变异, 这可能是由于母树的稀有性、种子传播距离的差异, 以及地形等因素造成。通过与巴拿马Barro Colorado Island 50 hm ²样地108个物种种子产量的年际变异系数相比较, 古田山种子雨数据支持了高纬度地区种子产量变异高于低纬度地区的假说。     

Phenotypic variation in colour pattern and seasonal plasticity in Eristalis hoverflies (Diptera: Syrphidae)

Abstract.

• 1 An examination of phenotypic variation in colour pattern was carried out on four Eristalis hoverfly species using museum material.
• 2 The amount of phenotypic variation varied substantially among the species with E.arbustorum being the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivus and E.nemorum), or a narrow range of colour variation (E.horticola).
• 3 Sexual colour dimorphism was apparent in all four species, but most pronounced in E.abusivus and E.nemorum.
• 4 There were good phenotype-season relationships shown by both sexes in all species, except for female E.abusivus and E.nemorum, with paler insects being more abundant during the warmer summer months.
• 5 Female, but not male, E.arbustorum collected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.
• 6 The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activity.

     

A model of geographical, environmental and regional variation in vegetation composition of pyrogenic grasslands of Florida

Aim To develop a landscape‐level model that partitions variance in plant community composition among local environmental, regional environmental, and purely spatial predictive variables for pyrogenic grasslands (prairies, savannas and woodlands) throughout northern and central Florida. Location North and central Florida, USA. Methods We measured plant species composition and cover in 271 plots throughout the study region. A variation‐partitioning model was used to quantify components of variation in species composition associated with the main and interaction effects of soil and topographic variables, climate variables and spatial coordinates. Partial correlations of environmental variables with community variation were identified using direct gradient analysis (redundancy analysis and partial redundancy analysis) and Monte Carlo tests of significance. Results Community composition was most strongly related to edaphic variables at local scales in association with topographic gradients, although geographically structured edaphic, climatic and pure spatial effects were also evident. Edaphic variables explained the largest portion of total variation explained (TVE) as a main effect (48%) compared with the main effects of climate (9%) and pure spatial factors (9%). The remaining TVE was explained by the interaction effect of climate and spatial factors (13%) and the three‐way interaction (22%). Correlation analyses revealed that the primary compositional gradient was related to soil fertility and topographic position corresponding to soil moisture. A second gradient represented distinct geographical separation between the Florida panhandle and peninsular regions, concurrent with differences in soil characteristics. Gradients in composition corresponded to species richness, which was lower in the Florida peninsula. Main conclusions Environmental variables have the strongest influence on the species composition of Florida pyrogenic grasslands at both local and regional scales. However, the limited distributions of many plant taxa suggest historical constraints on species distributions from one physiographical region to the other (Florida panhandle and peninsula), although this pattern is partially confounded by regionally spatially structured environmental variables. Our model provides insight into the relative importance of local‐ and regional‐scale environmental effects as well as possible historical constraints on floristic variation in pine‐dominated pyrogenic grasslands of the south‐eastern USA.     

Variation in cyanogenesis in plants with season and insect pressure

Cyanogenesis of 800 plant specimens (108 species) growing on a sandy tract of land between the sea and an inner lagoon 400 m distant was found to increase with insect density and, hence, with distance from the seashore and seasonal variation towards summer.     

Challenges in studying genomic structural variant formation mechanisms: the short-read dilemma and beyond

Next-generation sequencing (NGS) technologies have revolutionised the analysis of genomic structural variants (SVs), providing significant insights into SV de novo formation based on analyses of rearrangement breakpoint junctions. The short DNA reads generated by NGS, however, have also created novel obstacles by biasing the ascertainment of SVs, an aspect that we refer to as the 'short-read dilemma'. For example, recent studies have found that SVs are often complex, with SV formation generating large numbers of breakpoints in a single event (multi-breakpoint SVs) or structurally polymorphic loci having multiple allelic states (multi-allelic SVs). This complexity may be obscured in short reads, unless the data is analysed and interpreted within its wider genomic context. We discuss how novel approaches will help to overcome the short-read dilemma, and how integration of other sources of information, including the structure of chromatin, may help in the future to deepen the understanding of SV formation processes.     

Circadian and weekly variation and the influence of environmental variables in acute myocardial infarction

Objectives

The aim of our study was to investigate the circadian and weekly variation and assess the influence of environmental variables on the occurrence of acute myocardial infarction (AMI).

Methods

Our study population consisted of 2983 consecutive patients admitted with AMI between January 2006 and May 2008. Data were abstracted from hospital records and partially from an electronic database. In patients with a known time of onset of AMI, circadian variation was analysed. In all patients, weekly variation of onset of AMI was analysed. Information on daily mean temperature, sunny hours, rainy hours, maximal humidity and mean atmospheric pressure was obtained from the KNMI database and the influence of these environmental variables on the incidence of AMI was analysed.

Results and conclusion

Incidence of AMI shows a circadian pattern with an increase in occurrence during daylight. AMI occurs equally on each day of the week and no relation was found between environmental variables and the occurrence of AMI.     

Spatial and temporal variation of ecosystem properties at macroscales

Although spatial and temporal variation in ecological properties has been well‐studied, crucial knowledge gaps remain for studies conducted at macroscales and for ecosystem properties related to material and energy. We test four propositions of spatial and temporal variation in ecosystem properties within a macroscale (1000 km's) extent. We fit Bayesian hierarchical models to thousands of observations from over two decades to quantify four components of variation – spatial (local and regional) and temporal (local and coherent); and to model their drivers. We found strong support for three propositions: (1) spatial variation at local and regional scales are large and roughly equal, (2) annual temporal variation is mostly local rather than coherent, and, (3) spatial variation exceeds temporal variation. Our findings imply that predicting ecosystem responses to environmental changes at macroscales requires consideration of the dominant spatial signals at both local and regional scales that may overwhelm temporal signals.     

Seed size variation: magnitude,distribution, and ecological correlates

Summary We examined seed-mass variation in 39 species (46 populations) of plants in eastern-central Illinois, USA. The coefficient of variation of seed mass commonly exceeded 20%. Significant variation in mean seed mass occurred among conspecific plants in most species sampled (by hierarchical ANOVA), averaging 38% of total variance. For most species, within-plant variation was the larger component of total variance, averaging 62% of total variance. Variation in seed mass among fruits within crops was significant in most species tested.We conclude that variation in seed mass among and within plants is widespread and common. There was little evidence of trade-offs between number of seeds and mean or variance of seed mass, and little correlational evidence of local competition for maternal resources. No consistent ecological (dispersal mode and growth form) correlates of variance of seed mass were evident.     

Allozyme differentiation of populations of the dogwhelk Nucella lapillus, (L.): the relative effects of geographic distance and variation in chromosome number

Geographic patterns of genie differentiation were compared with differentiation between karyotypes in the intertidal snail Nucella lapillus. Samples from 24 sites covering the species range in Europe and North America were analysed for allozyme variation at 16 soluble enzyme loci. Two homokaryotypes have been identified with diploid numbers 2n = 26 and 2n= 36 (variation is Robertsonian and hybrids have intermediate chromosome numbers) and samples were classified (on the basis of published data) according to karyotype. Group 1 consisted of samples from three English Channel populations of higher chromosome number (on average 2n > 32) and Group 2 consisted of the remaining 21 samples (presumed to be 2n= 26). Karyotype variation accounts for roughly the same amount of the absolute allozyme variance as geographic variation (46.3 °, and 53.7°, respectively). Yet the patterns of differentiation seen between karyotypes and with geographic separation are very different. In samples classified as 2n= 26 (Group 2), while there is a significant amount of heterogeneity (F_ST per locus averaged 0.128 for 10 polymorphic loci), allozyme variation occurs independently at different loci so mean genetic identity (Nei) is high: 0.972. There is only a slight decline in genetic identity with distance (genetic identity averaged 0.965 for amphi-atlantic comparisons) indicating that passive transport of juveniles or adults may contribute significantly to gene flow. Conversely, allozyme variation between karyotypes was concordant. High chromosome number populations possessed a suite of alleles at four allozyme loci (Esl-3, Lap-2, Mdh-1 and Pep-2) which were absent or rare in Group 2 samples resulting in high F_ST values for these loci (from 0.294 to 0.472) when karyotypic classes were combined. Consequently the mean genetic identity between these Robertsonian races is low, 0.856, and falls within the range more usually associated with congeneric comparisons than with con-specific comparisons. The mechanisms maintaining this genie difference are unclear. However the distribution of the karyotypes and physiological and morphological differences (in shell shape) between them strongly suggest that karyotypic variation in Nucella is adaptive.     

Hematocrits of free-ranging baboons: variation within and among populations

Hematocrits among free-ranging baboons (Papio hamadryas subsp.), from Awash in Ethiopia and Mikumi in Tanzania, varied by region, sex, age, and season of collection. Tanzanian animals had higher mean values than Ethiopian, and hematocrits were higher in the dry season. We discuss the comparability of field and laboratory data and possible reasons for the observed variation.