A CONVENIENT METHOD FOR RECORDING AND PROCESSING FIELD DATA

Brooke, R. K. 1984. A history of the Redeyed Dove in the southwestern Cape Province, South Africa. Ostrich 55:12-16.

At present the Redeyed Dove occurs throughout the southwestern Cape although more sparsely in the arid northwest. The literature is confused on whether the Redeyed Dove Streptopelia semitorquata has always existed in the southwestern Cape, has immigrated from the southern or eastern Cape or was introduced to the area in 1933 at Elgin from stock bred up from an importation from Beira, Moçambique. Evidence is presented that it has always been present in the southwestern Cape. The birds introduced near Elgin came from a short-winged, richly coloured population of nominate semitorquata whereas the indigenous birds belong to the long-winged, pallid australis. Specimens shot in the 1940s and 1950s show the characteristics of a hybrid swarm between the two races and more recent data suggest that this condition persists.     

鱼探仪数据记录和处理软件系统的开发

目前国际上应用声纳技术进行鱼类资源评估的应用研究已经比较普遍,并且研制了各种形式的数据记录和处理系统1、2。但是,对于我国的研究者来说,国外成型产品的价格昂贵,影响了这项技术的实际应用。1997-1999年间,配合对中华鲟繁殖群体数量的调查,我们购买一些关键部件组装了一套针对中华鲟繁殖亲鱼的声纳鱼探仪系统,并自行设计、开发了数据记录、处理软件。经过两年的测试修改和实际应用,目前已经比较完善。本文对其结构和设计原理进行简单介绍。       

MAINTENANCE OF ECOLOGICALLY SIGNIFICANT GENETIC VARIATION IN THE TIGER SWALLOWTAIL BUTTERFLY THROUGH DIFFERENTIAL SELECTION AND GENE FLOW

Differential selection in a heterogeneous environment is thought to promote the maintenance of ecologically significant genetic variation. Variation is maintained when selection is counterbalanced by the homogenizing effects of gene flow and random mating. In this study, we examine the relative importance of differential selection and gene flow in maintaining genetic variation in Papilio glaucus. Differential selection on traits contributing to successful use of host plants (oviposition preference and larval performance) was assessed by comparing the responses of southern Ohio, north central Georgia, and southern Florida populations of P. glaucus to three hosts: Liriodendron tulipifera, Magnolia virginiana, and Prunus serotina. Gene flow among populations was estimated using allozyme frequencies from nine polymorphic loci. Significant genetic differentiation was observed among populations for both oviposition preference and larval performance. This differentiation was interpreted to be the result of selection acting on Florida P. glaucus for enhanced use of Magnolia, the prevalent host in Florida. In contrast, no evidence of population differentiation was revealed by allozyme frequencies. F_ST-values were very small and Nm, an estimate of the relative strengths of gene flow and genetic drift, was large, indicating that genetic exchange among P. glaucus populations is relatively unrestricted. The contrasting patterns of spatial differentiation for host-use traits and lack of differentiation for electrophoretically detectable variation implies that differential selection among populations will be counterbalanced by gene flow, thereby maintaining genetic variation for host-use traits.     

QUANTITATIVE GENETIC MODELING AND INFERENCE IN THE PRESENCE OF NONIGNORABLE MISSING DATA

Natural selection is typically exerted at some specific life stages. If natural selection takes place before a trait can be measured, using conventional models can cause wrong inference about population parameters. When the missing data process relates to the trait of interest, a valid inference requires explicit modeling of the missing process. We propose a joint modeling approach, a shared parameter model, to account for nonrandom missing data. It consists of an animal model for the phenotypic data and a logistic model for the missing process, linked by the additive genetic effects. A Bayesian approach is taken and inference is made using integrated nested Laplace approximations. From a simulation study we find that wrongly assuming that missing data are missing at random can result in severely biased estimates of additive genetic variance. Using real data from a wild population of Swiss barn owls Tyto alba, our model indicates that the missing individuals would display large black spots; and we conclude that genes affecting this trait are already under selection before it is expressed. Our model is a tool to correctly estimate the magnitude of both natural selection and additive genetic variance.     

DETECTING RANGE EXPANSIONS FROM GENETIC DATA

We propose a method that uses genetic data to test for the occurrence of a recent range expansion and to infer the location of the origin of the expansion. We introduce a statistic ψ (the directionality index) that detects asymmetries in the 2D allele frequency spectrum of pairs of population. These asymmetries are caused by the series of founder events that happen during an expansion and they arise because low frequency alleles tend to be lost during founder events, thus creating clines in the frequencies of surviving low‐frequency alleles. Using simulations, we show that ψ is more powerful for detecting range expansions than both and clines in heterozygosity. We also show how we can adapt our approach to more complicated scenarios such as expansions with multiple origins or barriers to migration and we illustrate the utility of ψ by applying it to a data set from modern humans.     

活体动物全细胞记录技术及其应用

活体动物全细胞记录技术不仅可以用于研究感觉系统对自然刺激（如视觉系统的光刺激、听觉系统的声音刺激等）反应的特性和规律,还可以较准确地记录细胞的突触电位（包括阈下反应）,实现EPSP和IPSP的相对分离,并实现活体细胞内灌流,从而进一步研究感觉信息的处理机制。本文较为详细地介绍了在活体动物上进行全细胞记录的方法,包括一些技术细节和关键仪器设备的选取原则,举例说明了该技术在视觉系统研究和体感系统研究中的应用,并讨论了这一方法在神经科学中的应用前景。     

GENETIC VARIATION,DIFFERENTIATION, AND EVOLUTION IN A SPECIES COMPLEX OF TROPICAL SHRUBS BASED ON ISOZYMIC DATA

An isozyme investigation of the Lisianthius skinneri (Gentianaceae) species complex in central Panama assayed levels of genetic variation within and among isolated populations and was used to reconstruct phylogenetic relationships within the complex. The widespread and low elevation L. skinneri and one derived cloud forest endemic species, L. habuensis, are depauperate in genetic variation. Three other endemic cloud forest species exhibiting larger population sizes and apparently more outcrossed breeding systems have higher levels of heterozygosity but retain low levels of allelic diversity. More than 90% of the genetic variation in the species complex is confined to among-population differentiation rather than witnin-population variation. Isozyme-based relationships within the species complex using both genetic divergence values (Fitch and Margoliash algorithm) and shared allelic states (Nelson and Van Horn algorithm) are identical. This network is not entirely congruent with a previous DNA-based network. Geographical isolation, small population size, low allelic diversity, and high levels of among-population differentiation suggest that repeated instances of founder events and genetic drift have been important in the evolution of this tropical shrub complex.     

猪CAST基因的遗传多态性及遗传效应分析

采用PCR—SSCP方法对猪cAST基因遗传多态性进行分析。并研究基因型与肉质性状和背膘厚的相关性。根据猪CAST基因的cDNA序列（M20160）设计7对引物。结果在F1／R1。F6／R6引物对扩增的片段上发现了多态性。并对纯合子进行测序。发现317位A—G突变。2042位G—C突变。基因型在不同猪种分布的多重比较结果表明。长白猪、大白猪和杜洛克猪与沂蒙黑猪和莱芜猪比较差异极显著（P〈0．01）。固定效应模型分析结果表明,嫩度及背膘厚基因型间差异显著（P〈0．05）,而pH值、温度及滴水损失基因型间差异不显著（P〉0．05）。最小二乘分析结果表明,不同猪种比较,屠宰12h和24h后肌肉温度、30min和1h后pH值及滴水损失差异显著（P〈0．05）;BBCC和BBDD单元型个体与其他单元型个体比较肌肉嫩度的差异显著（P〈0．01）。AACC和AADD单元型个体与其他单元型个体比较背膘厚的差异显著（P〈0．01）。因此,推测CAST基因对猪肉品质及背膘厚存在一定的影响。将CAST基因应用于猪育种过程中的标记辅助选择将可以改善猪肉品质。加快猪的育种进程。     

NUCLEAR AND MITOCHONDRIAL SEQUENCE DATA REVEAL AND CONCEAL DIFFERENT DEMOGRAPHIC HISTORIES AND POPULATION GENETIC PROCESSES IN CARIBBEAN REEF FISHES

Mitochondrial and nuclear sequence data should recover historical demographic events at different temporal scales due to differences in their effective population sizes and substitution rates. This expectation was tested for two closely related coral reef fish, the tube blennies Acanthemblemaria aspera and A. spinosa. These two have similar life histories and dispersal potentials, and co‐occur throughout the Caribbean. Sequence data for one mitochondrial and two nuclear markers were collected for 168 individuals across the species’ Caribbean ranges. Although both species shared a similar pattern of genetic subdivision, A. spinosa had 20–25 times greater nucleotide sequence divergence among populations than A. aspera at all three markers. Substitution rates estimated using a relaxed clock approach revealed that mitochondrial COI is evolving at 11.2% pairwise sequence divergence per million years. This rapid mitochondrial rate had obscured the signal of old population expansions for both species, which were only recovered using the more slowly evolving nuclear markers. However, the rapid COI rate allowed the recovery of a recent expansion in A. aspera corresponding to a period of increased habitat availability. Only by combining both nuclear and mitochondrial data were we able to recover the complex demographic history of these fish.     

HOW SIMILAR ARE GENETIC CORRELATION STRUCTURES? DATA FROM MICE AND RATS

An integral assumption of many models of morphometric evolution is the equality of the genetic variance-covariance structure across evolutionary time. To examine this assumption, the quantitative-genetic aspects of morphometric form are examined for eight pelvic traits in laboratory rats (Rattus norvegicus) and random-bred ICR mice (Mus musculus). In both species, all traits are significantly heritable, and there are significant phenotypic and genetic correlations among traits, although environmental correlations among the eight traits are low. The size relations among the pelvic variables are isometric. Three matrix-permutation tests are used to examine similarity of phenotypic, genetic, and environmental covariance and correlation matrices within and between species. Independent patterns of morphometric covariation and correlation arise from genetic and environmental effects within each species and from environmental effects between species. The patterns of phenotypic and genetic covariation and correlation are similar within each species, and the phenotypic and genetic correlations are also similar between these species. However, genetic covariance matrices show no significant statistical association between species. It is suggested that the assumption of equality of genetic variance-covariance structures across divergent taxa should be approached with caution.     

GENETIC DRIFT AND COLLECTIVE DISPERSAL CAN RESULT IN CHAOTIC GENETIC PATCHINESS

Chaotic genetic patchiness denotes unexpected patterns of genetic differentiation that are observed at a fine scale and are not stable in time. These patterns have been described in marine species with free‐living larvae, but are unexpected because they occur at a scale below the dispersal range of pelagic larvae. At the scale where most larvae are immigrants, theory predicts spatially homogeneous, temporally stable genetic variation. Empirical studies have suggested that genetic drift interacts with complex dispersal patterns to create chaotic genetic patchiness. Here we use a coancestry model and individual‐based simulations to test this idea. We found that chaotic genetic patterns (qualified by global F_ST and spatio‐temporal variation in F_ST's between pairs of samples) arise from the combined effects of (1) genetic drift created by the small local effective population sizes of the sessile phase and variance in contribution among breeding groups and (2) collective dispersal of related individuals in the larval phase. Simulations show that patchiness levels qualitatively comparable to empirical results can be produced by a combination of strong variance in reproductive success and mild collective dispersal. These results call for empirical studies of the effective number of breeders producing larval cohorts, and population genetics at the larval stage.     

杨属遗传多样性研究进展

 生物多样性的研究和保护是目前全世界普遍关注的问题,其中研究较多的是遗传多样性、物种多样性及生态系统多样性,遗传多样性作为生物多样性的重要组成部分,是生态系统多样性和物种多样性的基础方面。杨树是世界各国普遍种植的木本植物,研究其遗传多样性具有重要的理论和实践意义,国内外都开展了广泛研究。本文综述了杨属(Populus)植物的派、种及无性系等在表型、染色体、蛋白质及DNA水平的遗传多样性的研究进展。其表型多样性主要体现在不同水平上的种群大小、形态特征、物候期、材性以及对生物或非生物逆境的抗性等方面;在杨属植物中已发现有天然的三倍体及三倍体/非整倍体的杂交种存在;蛋白质的多态性主要集中于同工酶的研究,用于不同杨属植物的遗传差异,无性系或品种的特征、分化和遗传研究;DNA多态性是研究最多的,RFLP、RAPD、AFLP和SSR等分子标记已广泛用于杨属的遗传多样性研究中,根据不同的研究目的所选择的DNA（nDNA, cpDNA或mtDNA）也不同。并根据国内的研究现状,提出了几点建议。