Chemical information from the fungus Amylostereum areolatum and host-foraging behaviour in the parasitoid Ibalia leucospoides

Abstract.  Parasitoids locate hosts using reliable and predictable cues such as smells derived from host plants or from the hosts themselves. For host species that live with mutualistic organisms, such as several wood boring insects, cues derived from the symbionts are likely to be exploited by specific parasitoids. Through a set of bioassays, the behaviour of the parasitoid Ibalia leucospoides Hochenwarth (Hymenoptera: Ibaliidae) is studied in response to the fungus Amylostereum areolatum Boidin (Basidiomycotina: Corticiaceae), a symbiont of its host, the wood wasp Sirex noctilio Fabricius (Hymenoptera: Siricidae). The results show that parasitoids are attracted to the fungus when growing naturally within pine logs, and also when growing on an artificial medium. Fungal volatiles also elicit increased parasitoid activity and may provide information on relative densities of hosts available for parasitization. It is speculated that the the chemical information derived from the host fungal symbiont comprises reliable and detectable host-locating cues used by parasitoids to search for concealed hosts.     

A preliminary examination of genetic variation in a peripheral population of Blanding's turtle, Emydoidea blandingii

Random amplified polymorphic DNA (RAPD) was used to compare the Nova Scotia population of Blanding's turtle (Emydoidea blandingii) with several populations from the species' main range. The Nova Scotia population is believed to have been isolated from the main range for 4000-8000 years. Cluster analysis using a neighbour-joining algorithm produced a dendrogram showing the Nova Scotia population clustering separately from those populations in the main range. Analysis of molecular variance shows 34.28% of total variance to be accounted for between the Nova Scotia population and populations in the main range. While this study is preliminary, the results suggest that the Nova Scotia population of Blanding's turtle may be important to the maintenance of genetic diversity in the species.     

海草克隆性及其种群遗传效应

海草是适应在海洋环境中生存和繁殖的单子叶植物,由于所处环境常存在潮汐、风暴等的干扰,海草形成了一系列适应特征,克隆性是其中突出的一个.所有的海草都具有水平根状茎,许多海草也具有垂直根状茎,在一些海草中,也观察到无性生殖(无融合生殖).与克隆生长有关的参数(如节间长度、间隔子长度、分枝角度以及延伸速率和分枝率等)对于海草的克隆生长有着决定性影响,但繁育系统对克隆斑块大小也有较大影响.强烈的克隆性影响着海草的遗传变异.总体来看,海草种群内遗传多样性比陆生植物低,也低于另一类海洋高等植物-红树植物,利用DNA标记观察到的多样性高于等位酶标记.在一些海草植物种群中观察到较高的克隆多样性,但也有一些种群由单一基因型或少量基因型组成,其原因主要是由于奠基者效应和克隆生长.通常克隆植物中基因流有限,但是海草的克隆片段可能远距离扩散,从而提高种群间的基因流.就克隆生长对种群空间结构和交配系统的影响进行了综述.     

Genetic variation and population structure of cod, Gadus morhua L., in some fjords in northern Norway

Biochemical genetic polymorphism in cod from several fjords in Troms, northern Norway was analysed. Gene frequencies at several polymorphic loci ( Hb, Pgi, Ldh, Pgm, Gpd and Idh ) are given. Significant variation was found both within and between fjords, and even between samples from the same locality sampled in different years, indicating a mosaic structure of the cod population in the area studied. The results of the haemoglobin variation are compared to similar results obtained more than 20 years ago in the same and adjacent areas. The biochemical genetic variation is discussed in relation to stability of gene frequencies, isolation mechanisms and migration patterns.     

Allozyme and microsatellite genetic variation in natural samples of zebrafish,Danio rerio

In this paper, we report the results from allozyme and microsatellite markers in natural populations of the zebrafish, a species of great significance in biological studies. Four zebrafish wild samples from West Bengal, India, were analysed in a preliminary survey of levels and patterns of genetic variation. Results indicate high levels of genetic variability and weak genetic structure, although the latter is consistent with the geographical features of the area under study, sampling sites being located in the Ganges and Brahmaputra delta region, which is characterized by high waterways connectivity.     

Phantom hitch-hikers mislead estimates of genetic variation in Antarctic mosses

Previous studies of Antarctic mosses employing RAPDs have reported extraordinarily high levels of genetic variation, even within a single clump of moss. This is unexpected given their extreme isolation in Antarctica and lack of sexual reproduction. We offer an alternative explanation: that unusually elevated levels of genetic variability are artefacts from contamination of a number of biota known to be naturally associated with Antarctic mosses. We utilized sequence variation of nrITS and RAPDs to further investigate the effect of naturally occurring contaminants on estimates of genetic variation of mosses. Our results indicate that these ``phantom hitch-hiker' contaminants hinder attempts to accurately and reliably estimate levels of genetic variation by non-specific PCR-based approaches. Furthermore, screening samples via amplification of nrITS failed to identify all contaminated samples, hence we caution against relying solely on ``quick' screening methods and suggest that suspect samples be carefully examined for contamination.     

Sequence variation and genetic diversity in the giant panda

About 336–444 bp mitochondrial D-loop region and tRNA gene were sequenced for 40 individuals of the giant panda which were collected from Mabian, Meigu, Yuexi, Baoxing, Pingwu, Qingchuan, Nanping and Baishuijiang, respectively. 9 haplotypes were found in 21 founders. The results showed that the giant panda has low genetic variations, and that there is no notable genetic isolation among geographical populations. The ancestor of the living giant panda population perhaps appeared in the late Pleistocene, and unfortunately, might have suffered bottleneck attacks. Afterwards, its genetic diversity seemed to recover to some extent. Project supported by the “8.5” Key Project of Chinese Academy of Sciences, the Chairman Foundation of Chinese Academy of Sciences, K. C. Wang Education Foundation, the Applied Basic Research Foundation of Yunnan, the National Natural Science Foundation of China, the Special Foundation for Returned Chinese Scientists, and Zoological Society of San Diego.     

杨树无性系木材基本密度和纤维素含量株内变异

对I-69[Populus deltoids Bartr. cv. Lux]、I-72杨[P. ×euramericana (Dode) Guinier cv. San Martino]、 NL-80351[I-69 × I-63(P. deltoids Bartr. cv. Harvard)]、南林-95 、南林-1388 、南林-895 、南林-447等7个杨树无性系的木材基本密度和纤维素含量进行了系统研究.其中,南林-95、南林-1388、南林-895 、南林-447是从I-69 × I-45 [P.×euramericana (Dode) Guinier cv. I-45/51]杂交F1代中选育出来的新无性系.研究结果表明,同为11 a生时,7个无性系胸径处木材基本密度差异达显著水平,从大至小依次为南林-895、I-72、I-69、南林-1388、南林-95、NL-80351、南林-447;不同杨树无性系间胸径处纤维素含量也存在显著差异,从高至低依次排序为南林-95、南林-447、南林-895、南林-1388、I-69、NL-80351、I-72.木材基本密度和纤维素含量在株内的径向变异规律均为从髓心向外以曲线形式缓慢增大,其中后者的变异模式为以多项式方程来描述的效果最好.木材基本密度纵向变异规律为从树干基部向上有随树木高度的增加而逐渐增大的趋势,木材基本密度最小值出现在基径处.本文的研究结果可为杨树人工林的定向培育提供理论依据.     

Mating frequency, genetic structure, and sex ratio in the intermorphic female producing ant species Myrmecina nipponica

1. Myrmecina nipponica has two types of colonies: a queen colony type, in which the reproductive females are queens and new colonies are made by independent founding, and an intermorphic female colony type, in which reproductive females belong to a wingless intermediate morphology between queen and worker, and where colonies multiply through colonial budding. 2. The mating frequencies of reproductive females in both types indicate monoandry. The relatedness among nestmates in both types was almost 0.75, however relatedness between mother and daughter in intermorphic female colonies was slightly higher than that of queen colonies. 3. The sex ratio (corrected investment female ratio) was 0.70 at the population level, suggesting that the sex ratio is controlled by workers in this species, however the ratio differed greatly between the two types of colonies. Queen colonies (n = 37) had a female‐biased sex ratio of 0.77 while intermorphic female colonies (n = 33) had a ratio of 0.56. 4. Each reproductive intermorphic female was accompanied by an average of 2.9 workers (including virgin intermorphic females) in the colonial budding, and when the investment to those workers was added to the female investment, the sex ratio reached 0.81. 5. The frequency distribution of sex ratio was bimodal, with many colonies producing exclusively males or females, however mean estimated relatedness within colonies was almost 0.75. These data are inconsistent with the genetic variation hypothesis, which is one of the predominant hypotheses accounting for the between‐colony variation in sex ratio.     

Quantitative genetic approach for assessing invasiveness: geographic and genetic variation in life-history traits

Predicting the spread of invasive species is a challenge for modern ecology. Although many invasive species undergo genetic bottlenecks during introduction to new areas resulting in a loss of genetic diversity, successful invaders manage to flourish in novel environments either because of pre-adaptations or because important traits contain adaptive variation enabling rapid adaptation to changing conditions. To predict and understand invasion success, it is crucial to analyse these features. We assessed the potential of a well-known invader, the Colorado potato beetle (Leptinotarsa decemlineata), to expand north of its current range in Europe. A short growing season and harsh overwintering conditions are apparent limiting factors for this species’ range. By rearing full-sib families from four geographically distinct populations (Russia, Estonia, Poland, Italy) at two fluctuating temperature regimes, we investigated (a) possible differences in survival, development time, and body size among populations and (b) the amount of adaptive variation within populations in these traits. All populations were able to complete their development in cooler conditions than in their current range. A significant genotype–environment interaction for development time and body size suggests the presence of adaptive genetic variation, indicating potential to adapt to cooler conditions. The northernmost population had the highest survival rates and fastest development times on both temperature regimes, suggesting pre-adaptation to cooler temperatures. Other populations had minor differences in development times. Interestingly, this species lacks the classical trade-off between body size and development time which could have contributed to its invasion potential. This study demonstrates the importance of considering both ecological and evolutionary aspects when assessing invasion risk.     

Living in a jar: genetic variation and differentiation among laboratory strains of the red flour beetle

The red flour beetle, Tribolium castaneum, is a common pest, which has become an important model study organism, especially in genetic, ecological and evolutionary research. Although almost all studies on this species have been conducted using established laboratory strains, very little is known about the loss of genetic diversity within the strains and genetic divergence between different laboratory stocks. In this study, five long‐term laboratory strains and one wild strain were examined for genetic variation at 12 microsatellite loci, which were designed using publicly available sequences. One of the laboratory strains is resistant to phosphine and one to organophosphorous insecticides. All strains had significant amounts of molecular variation, but genetic diversity in the laboratory strains was lower than in the wild‐derived strain used as control. We observed significant molecular divergence among the strains, however, the relationship between them reflected resistance status rather than geographic origins. We found no evidence for recent bottlenecks, but the wild‐derived population showed signs of demographic expansion. A novel multivariate method, multiple co‐inertia analysis, revealed that the two loci contributing most to the divergence between the resistant strains were located on the eighth chromosome, near genes associated with insecticide resistance.     

Multilocus genetic relationships between clinical and environmental Aeromonas strains

Allelic variations in the chromosomal genome of 120 isolates of motile Aeromonas (A. hydrophila, A. sobria and A. caviae) and eight reference strains with one Plesiomonas shigelloides were assessed by analysis of electrophoretically demonstrable polymorphism in 16 genes encoding metabolic enzymes. The strains were collected from humans (n = 59) and from the aquatic environment (n = 61) in canton Tessin, Switzerland. Clustering of the electrophoretic types (ET) from a matrix of pairwise genetic distances, based on the 16 enzyme loci, confirmed the genetic distinctness of the three species. Furthermore, A. hydrophila and A. sobria were divided in three and two groups respectively. For each species clinical strains were well differentiated from those collected in the environment.     

Morphologic variation in northern marginal Juniperus oxycedrus L. subsp. oxycedrus populations in Istria

Marginal tree populations are believed to be more differentiated and host less variation than central tree populations. The aim of this study was to perform a detailed morphometric study of J. oxycedrus L. subsp. oxycedrus in northern marginal populations in order to establish its phenotypic variation and geographical differentiation and to examine the eventual presence of putative species J. deltoides in Istria. Morphologic variation was studied in 16 northern marginal populations in Istria. Nine morphological traits from a minimum of 50 leaves from each of 206 individuals and two morphological traits from 30 to 50 seed cones in each of 103 females were measured. Phenotypic variation in Istrian populations was high and of a similar magnitude to that found in the centre of the distribution area. Gender dimorphism in leaf morphology was detected, but the study failed to confirm its uniform distribution pattern. Significant and surprisingly high among-population differentiation (8–30%) was revealed. Average leaf shape in the study area is clearly “delta-shaped” characterised by a relatively wide leaf base. However, no significant differences in any of the studied traits were found between the marginal Istrian populations and the more central populations analysed in our earlier studies.     

Biochemical genetic variation in populations of Larus argentatus and Larus fuscus in northwestern Europe

The techniques of biochemical population genetics were used to examine the relationships between two apparently closely related species and their component subspecies which form the Larus argentatus/fuscus species complex in northwest Europe. The systematics and taxonomy of these populations in this part of the circum-polar ring are complex and it was thought that this type of analysis might clarify the taxonomic relationships. Samples were obtained from breeding colonies along a transect from northern France (47°N), through Britain to arctic Norway (70°N), with additional samples from the Camargue on the Mediterranean coast (42°N). Twenty-one enzyme systems were examined using starch gel electrophoresis. No interspecific differences were found and only one locus (glutamate oxaloacetate transaminase) was polymorphic. There were no allelic differences within geographical groups of populations, although there were some differences between some of the subspecies. The low levels of heterozygosity ( H = 0.0081 and H = 0.0031) are considered to arise from a combination of two factors: the low levels of heterozygosity which appear to be characteristic of birds and population effects. Furthermore, no interspecific differences were detected ( I = 0.999) indicating the morphological changes rather than changes at structural gene loci may have been more important in speciation.     

RAPD分析花椰花不同品种的遗传变异

利用随机扩增多态性DNA（RAPD）方法,对13个花椰花品种的基因组DNA进行多态性分析。选用20个10bp随机引物,共扩增出175条DNA片段,其中多态性片段118例,占67．4％,结果表明,花椰花品种间具有丰富的遗传多样性。依据扩增结果进行遗传相似系数分析,构建聚类分析树状图。初步探讨了各品种间的遗传变异关系及RAPD技术在花椰花种质资源分类鉴定和育种工作中的应用前景。     

A preliminary investigation of allozyme genetic variation and population geographical structure in Aphanius fasciatus from Italian brackish-water habitats

A total of 150 individuals from Aphanius fasciatus from coastal brackish-water habitats was analysed by allozyme electrophoresis to collect data on its genetic variation. From 22 enzymes, 43 putative enzyme-coding loci were resolved, 12 of which were polymorphic at P_0·99 level. Only one of the 31 probability tests showed a significant departure from the Hardy-Weinberg equilibrium. Aphanius fasciatus showed low levels of genetic polymorphism, with expected heterozygosity values ranging from 0·027 (S.E.=0·013) to 0·064 ( s.e. =0·023). Nei's genetic distances between populations ranged from 0·002 to 0·042. Weir & Cockerham F -statistics showed high levels of genetic heterogeneity among populations (jackknifed θ=0·302, s.e. =0·045) and estimates of N _m were < 1, indicating restricted gene flow. Significant positive correlation between genetic distance and geographical distance matrices, detected by Mantel's test ( g =1·941; P 0·001), is consistent with the prediction that the species is genetically structured by isolation-by-distance.     

Differentiation and levels of genetic variation in northern European lynx (Lynx lynx) populations revealed by microsatellites and mitochondrial DNA analysis

The European lynx (Lynx lynx) hasexperienced significant decline in populationnumbers over large parts of its formerdistribution area in central and northernEurope. In Scandinavia (Sweden and Norway), thespecies has been subject to intense hunting and inthe early 20th century the population size mayhave been as low as about 100 animals. Duringthe rest of the century there have beenalternating periods of restricted hunting andtotal protection. Future management of theScandinavian lynx population will requireinsight into what effects demographicbottlenecks may have had on genetic variabilityand structure. For this purpose, 276 lynxesfrom Sweden, Norway, Finland, Estonia andLatvia were analysed for polymorphism at 11feline microsatellite loci and at themitochondrial DNA (mtDNA) control region.Scandinavian lynxes were found to be fixed fora single mtDNA haplotype, while this and threeadditional haplotypes were seen in Finland andthe Baltic States (Estonia and Latvia); thehaplotypes were all very similar, onlydiffering at 1–4 sites within a 700 bp regionsequenced. Microsatellite variability wasmoderate (H_e = 0.51–0.62) with lowerheterozygosity and fewer alleles in Scandinaviathan in Finland and the Baltic States together,though significant so only for the latter.Heterozygosity data in Scandinavia wereconsistent with a recent population bottleneck.Various analyses (e.g. F_st, individual-basedtree, assignment test) revealed distinctgenetic differentiation between Scandinavianlynxes and animals from Finland and the BalticStates. Some structure was evident withinScandinavia as well, suggesting an isolation bydistance. The observed partition of geneticvariability between Scandinavia and the easterncountries thereof indicates that lynxpopulations from the two regions may need to beseparately managed. We discuss what factors canhave contributed to the population geneticstructure seen in northern European lynxpopulations of today.     

Spring phenology shows genetic variation among and within populations in seedlings of Scots pine (Pinus sylvestris L.) in the Scottish Highlands

Background: Genetic differentiation in phenotypic traits is often observed among forest tree populations, but less is known about patterns of adaptive variation within populations. Such variation is expected to enhance the survival likelihood of extant populations under climate change.

Aims: Scots pine (Pinus sylvestris) occurs over a spatially and temporally heterogeneous landscape in Scotland. Our goal was to examine whether populations had differentiated genetically in timing of bud flush in response to spatial heterogeneity and whether variation was also maintained within populations.

Methods: Two common-garden studies, involving maternal families of seedlings from 21 native pinewoods, were established and variation in the trait was measured at the beginning of the second growing season.

Results: Populations showed genetic differences in the trait correlated with the length of growing season at their site of origin, but the majority of variation was observed within populations. Populations also differed in their levels of variation in the trait; a pattern that may be influenced by spatial variation in the extent of temporal climate variability.

Conclusions: Our findings suggest that populations have adapted to their home environments and that they also have substantial ability to adapt in situ to changes in growing season length.     

Geographic variation and genetic aspects of reproductive diapause in Drosophila triauraria and D. quadraria

ABSTRACT. Geographic variation and genetic aspect of reproductive diapause were studied in Drosophila triauraria Bock & Wheeler and D. quadraria Bock & Wheeler, in relation to their quantitative response to photoperiods. D. quadraria from the subtropical region had no photoperiodic diapause. In D. triauraria strains, diapause was induced under LD 10:14 or 12:12, but not under LD 14:10 or longer photoperiods. Their diapause was induced more effectively and maintained longer by LD 10:14 than by LD 12:12. The duration of diapause was longer in a northern strain, but the diapause inducing process varied little among different geographical strains. Diapause incidence was 50% or lower in F₁ hybrids between D. triauraria and D. quadraria and backcross progenies between F₁ and D. quadraria , and about 70% in backcross progenies between F₁ and D. triauraria under LD 10:14, but very low under LD 12:12. The lower incidence of diapause in these F; and backcross progenies is assumed to be due to the less efficient induction of diapause, since once diapause was induced in them, it was maintained for a long time, especially in the backcross progenies between F₁ and D. triauraria. These experiments suggest that diapause induction and maintenance are different physiological processes controlled by different genetic systems.