DIFFERENCES IN RESTING-SITE PREFERENCE IN TWO COEXISTING LAND SNAILS, ARIANTA ARBUSTORUM AND ARIANTA CHAMAELEON (HELICIDAE), ON ALPINE SLOPES

Resting-site preference and patterns of spatial distributionwere examined in the sympatric land snails Arianta arbustorumand A. chamaeleon on two opposite slopes in the south-easternAlps, Austria. The two slopes did not differ in proportion ofA. arbustorum and A. chamaeleon (74.4% vs. 25.6% on the NNE-exposedslope and 68.3% vs. 31.7% on the SSW-exposed slope). Individualsof both species showed aggregated dispersion patterns. The nearest-neighbourmethod indicated that in both species snail aggregations predominantlyconsisted either of A. arbustorum or A. chamaeleon on the NNE-exposedslope with a mosaic of rocks and distinct patches of differentplants. On the SSW-exposed slope, which was less variable invegetation cover, snail aggregations consisted of conspecificand hetero-specific individuals. Juvenile and adult A. arbustorumpreferred to rest attached to leaves of Adenostyles alliariae,but avoided rock surfaces and patches of grass on the NNE-exposedslope. In contrast, juvenile and adult A. chamaeleon preferentiallyrested on rock surfaces, and also avoided grass patches. Juvenileand adult A. chamaeleon did not differ in resting-site preference,whereas small differences in resting sites were observed betweenjuvenile and adult A. arbustorum. Differences in resting-sitepreference is one way of niche differentiation which may allowindividuals of the two Arianta species to coexist. (Received 14 March 1996; accepted 8 July 1996)     

VARIATION IN SNAIL SPECIES WIDESPREAD ON PORTO SANTO, MADEIRAN ARCHIPELAGO

Shell variation has been studied in two widespread land snailsfrom Porto Santo, Madeiran archipelago: the helicid speciesor species complex Heterostoma paupercula (Lowe) and the clausiliidspecies Boett-geria lowei Albers. Samples were collected fromthe mainland and the offshore islets from sea level to the highestaltitude. Shell size, colour and presence or absence of penstometeeth were scored in H. paupercula and some individuals weredissected to examine genitalia. Shell size and rib number werescored in B. lowei. In B. lowei size declines and rib number increases with altitude.In H. paupercula samples from sandy locations have a largershell size and a higher frequency of pale colour than thosefrom non-sandy locations. On average, sandy sites have a loweraltitude than non-sandy ones, however, so that these two variablesare confounded. The survey shows that shell characters of akind used in taxonomy are subject to variation associated withecology, this must be borne in mind when assessing present-daytaxa and morphological change through the fossil sequence. Thedata for H. paupercula support the conclusion that it is a singlespecies variable in shell characters and polymorphic for hemiphally. ⁴Present address for Gao Gaixt Biology Department, Shanxi EducationalCollege, Taiyuan, Shanxi, P.R.China (Received 27 February 1995; accepted 27 August 1995)     

ADAPTATION AND MALADAPTATION IN SELFING AND OUTCROSSING SPECIES: NEW MUTATIONS VERSUS STANDING VARIATION

Evolution of selfing from outcrossing recurrently occurred in many lineages, especially in flowering plants. Evolution of selfing induces dramatic changes in the population genetics functioning but its consequences on the dynamics of adaptation have been overlooked. We studied a simple one‐locus model of adaptation where a population experiences an environmental change at a given time. We first determined the effect of the mating system on the genetic bases and the speed of adaptation, focusing on the dominance of beneficial mutations and the respective part of standing variation and new mutations. Then, we assumed that the environmental change is associated with population decline to determine the effect of the mating system on the probability of population extinction. Extending previous results, we found that adaptation is more efficient and extinction less likely in outcrossers when beneficial mutations are dominant and codominant and when standing variation plays a significant role in adaptation. However, given adaptation does occur, it is usually more rapid in selfers than in outcrossers. Our results bear implications for the evolution of the selfing syndrome, the dynamics of the domestication process, and the dead‐end hypothesis that posits that selfing lineages are doomed to extinction on the long run.     

Zuttiyeh面骨

在以色列Zuttiyeh发现的额面骨破片距今至少已120,000年,认识到它如此古老就提示它有可能是任何地中海地区较晚居民的祖先。有些人认为它是早期尼安德特人,而另一些人则认为它是解剖学上已具现代特征的智人中的早期者。我们认为这个标本最适于与周口店直立人相对比。经过系统比较我们发现两者有着细节上的相似性。尽管两个地点在时间和空间距离上有差别。在本文中我们以人类进化地区连续性的解释讨论了这个相似性的含义。这对于理解晚更新世地中海地区居民的祖先及其关系是重要的。由于它表明亚洲至少是某些现生人类群体的重要发源地,所以对于现代人起源的“伊甸园”理论有着重要的含义。     

SIMILARITIES AND DIFFERENCES IN ALTITUDINAL VERSUS LATITUDINAL VARIATION FOR MORPHOLOGICAL TRAITS IN DROSOPHILA MELANOGASTER

Understanding how natural environments shape phenotypic variation is a major aim in evolutionary biology. Here, we have examined clinal, likely genetically based variation in morphology among 19 populations of the fruit fly (Drosophila melanogaster) from Africa and Europe, spanning a range from sea level to 3000 m altitude and including locations approximating the southern and northern range limit. We were interested in testing whether latitude and altitude have similar phenotypic effects, as has often been postulated. Both latitude and altitude were positively correlated with wing area, ovariole number, and cell number. In contrast, latitude and altitude had opposite effects on the ratio between ovariole number and body size, which was negatively correlated with egg production rate per ovariole. We also used transgenic manipulation to examine how increased cell number affects morphology and found that larger transgenic flies, due to a higher number of cells, had more ovarioles, larger wings, and, unlike flies from natural populations, increased wing loading. Clinal patterns in morphology are thus not a simple function of changes in body size; instead, each trait might be subject to different selection pressures. Together, our results provide compelling evidence for profound similarities as well as differences between phenotypic effects of latitude and altitude.     

HYBRIDIZATION AND GEOGRAPHIC VARIATION IN TWO MEADOW KATYDID CONTACT ZONES

In this study, previously unrecognized hybridization was documented between two meadow katydids in each of two disjunct contact zones, in the southeastern United States and along the Potomac River near Washington, DC. These two zones have very different histories and dynamics of interaction between the two taxa. Orchelimum nigripes and O. pulchellum (Tettigoniidae: Conocephalinae) are distributed west and east, respectively, of the Appalachian Mountains, from the Great Lakes to the Gulf Coast and along the Atlantic Coastal Plain from New York to the Florida Keys, but are not found in the Appalachians themselves. In addition, during this century O. nigripes has become established in a small area east of the Appalachians, in the Potomac River basin, where it has completely replaced O. pulchellum along the river corridor above Washington, DC. I sampled katydids from 40 sites across both hybrid zones and mapped geographic patterns of genetic variation (allele frequencies at two diagnostic loci) and variation in a morphometric index for males. Although the two taxa are quite distinct over most of their extensive distributions, there is clear evidence of introgression in both contact zones. In the Deep South, samples from a transect along the Gulf Coast define a broad hybrid zone of about 50–100 km, while samples from a transect 200 km to the north define a zone of about 150–250 km in width. Only one Deep South population shows a deviation from Hardy-Weinberg equilibrium at either locus, and there is no evidence of linkage disequilibrium in any Deep South population. In the Potomac region, there is a narrow upstream-downstream hybrid zone along the river. Within the Potomac River floodplains downriver from Washington, DC, as well as outside the floodplains throughout the region, O. pulchellum is present in abundance, but O. nigripes markers are virtually absent. Within the floodplains upriver from Washington, DC, O. nigripes is abundant, but O. pulch***ellum markers are virtually absent. All four mixed ancestry Potomac populations sampled show strong and highly significant linkage disequilibrium, although only one clearly deviates from single-locus Hardy-Weinberg equilibrium. The position of the Deep South hybrid zone is generally consistent with interspecific and intraspecific phylogeographic patterns previously reported for numerous taxa from the southeastern United States. The observed genetic and morphometric clines appear to be the result of neutral introgression over thousands of years. In the much younger Potomac hybrid zone, O. nigripes appears to be spreading downriver, interbreeding with O. pulchellum, and replacing it. The mechanism for this replacement remains uncertain, but may be clarified by ongoing behavioral, genetic, and breeding studies.     

SPATIAL RELATIONSHIP AND GENE FLOW PATHS BETWEEN POPULATIONS OF THE ALPINE SNAIL ARIANTA ARBUSTORUM (PULMONATA: HELICIDAE)

The alpine snail Arianta arbustorum (Pulmonata, Helicidae) was sampled along an 8-km contour line in the Swiss Alps orthogonal to well-known altitudinal clines in life history and shell traits. The allele frequencies and the morphs of 16 populations were compared with habitats. Two hypotheses about the recolonization of the mountain slopes after the last glaciation were tested against the present population structure. The allele frequencies are best explained by the spatial structure whereas the morphs are better explained by the habitats. The genotypic distances point to a historical explanation by recolonization processes, the phenotypical dissimilarities to a selectionistic interpretation of the present distribution of the populations. The following conclusions are from the study of the spatial relationship and the gene flow paths for A. arbustorum at Mount Martegnas: (1) Streams are the main gene flow paths; gene flow is low, allowing differentiation of local populations. (2) Morphs and habitats are correlated, but the interpretation has to be made carefully. The spatial dependence of habitats has to be included into the analysis of selection. (3) The random assumption for gene flow of A. arbustorum is not a spatial isolation-by-distance model, but a functional isolation-by-distance model, assuming gene flow over the drainage system.     

柱隔孢属一新种和二新记录种

报道柱隔孢属新种：繁缕柱隔孢（RamulariamalachiiY.X.WangetX.Y.Wang）和二新记录种：颠茄柱隔孢（RatropaeAllesch）,夏枯草柱隔孢（RbaeumlerianaMoesz）。新种作了汉文和拉丁文描述,并附有形态图,同时讨论了与相近种之间的区别;对新记录种进行了汉文描述。标本保存于云南农业大学植物病理研究所,真菌标本室（MHYAU）。     

腐霉属的一个新种和二个新记录

本文报告作者1982—1983年在北京和广东一些地区土壤中用已知方法(余永年,1975)分离到的几种腐霉,其中1个新种(Pythium borealis sp.nov.)、2个国内未报道的种(P.oligandrum和P.myriotylum)和1个已知种的变异株(P.ultimum variant)。文中对以上各菌进行了形态学描述。     

四裂红景天与长鳞红景天叶片中抗氧化系统随海拔梯度的变化

以分布于乌鲁木齐河源区天山中段不同海拔高度的四裂红景天 (Rhodiolaquadrifida) (35 0 0~ 380 5m) 及长鳞红景天 (R.gelida) (380 5~ 4 0 10m) 为试材, 通过对比分析两种红景天在一连续的海拔梯度上种内及种间叶片膜脂过氧化及抗氧化保护系统的变化, 初步探讨植物对于高山极端环境的适应机制。结果显示, 分布于海拔较高的长鳞红景天其叶片中膜脂过氧化产物丙二醛 (MDA) 的含量明显高于分布海拔较低的四裂红景天, 而两种红景天种内膜脂过氧化水平则没有随海拔升高呈现出明显差异。此外, 抗氧化保护酶CAT, POD, SOD, GR和ASA_POD 的活性与非酶促抗氧化剂ASA、GSH的含量不仅在种间存在有明显差异, 长鳞红景天中明显高于四裂红景天, 而且在两种红景天种内亦随海拔升高有不同程度地提高。表明当海拔升高时, 虽然环境条件渐趋恶劣, 对植物造成的氧化胁迫增强, 但红景天脂膜保护系统的功能亦相应加强, 从而增强了其抵抗逆境胁迫的能力。其中以过氧化物酶POD的活性变化最为显著 :在 380 5m以下海拔区, 于四裂红景天叶片中均未检测到该酶活性, 而分布海拔较高的长鳞红景天叶片中该酶活性则随海拔升高明显增强, 推测POD可能在红景天适应特殊生境中起着重要的作用, 亦可能与高海拔区长鳞红景天取代四裂红景天有关。     

CAUSES OF VARIATION IN BIOTIC INTERACTION STRENGTH AND PHENOTYPIC SELECTION ALONG AN ALTITUDINAL GRADIENT

Understanding the causes of variation in biotic interaction strength and phenotypic selection remains one of the outstanding goals of evolutionary ecology. Here we examine the variation in strength of interactions between two seed predators, common crossbills (Loxia curvirostra) and European red squirrels (Sciurus vulgaris), and mountain pine (Pinus uncinata) at and below tree limit in the Pyrenees, and how this translates into phenotypic selection. Seed predation by crossbills increased whereas seed predation by squirrels decreased with increasing elevation and as the canopy became more open. Overall, seed predation by crossbills averaged about twice that by squirrels, and the intensity of selection exerted by crossbills averaged between 2.6 and 7.5 times greater than by squirrels. The higher levels of seed predation by crossbills than squirrels were related to the relatively open nature of most of the forests, and the higher intensity of selection exerted by crossbills resulted from their higher levels of seed predation. However, most of the differences in selection intensity between crossbills and squirrels were the result of habitat features having a greater effect on the foraging behavior of squirrels than of crossbills, causing selection to be much lower for squirrels than for crossbills.     

QUANTITATIVE VARIATION IN PHLOX: COMPARISON OF SELFING AND OUTCROSSING SPECIES

Variation of 20 quantitative characters was examined within and among 10 populations of the predominantly outcrossing Phlox drummondii and 4 populations of the predominantly selfing P. cuspidata grown in a greenhouse. Multivariate analysis of variance, considering all characters simultaneously, indicated that there were significant differences among populations in both species while analysis of individual characters demonstrated that there were significant population differences for 19 characters in P. drummondii and 13 characters in P. cuspidata. On average, 16% of the total phenotypic variation in P. drummondii occurred among populations compared to less than 4% of the total variation in P. cuspidata. In addition, P. drummondii exhibited significant differences among families within populations more frequently than P. cuspidata. Most observed variation in both species occurred within families where environmental and genetic sources of variation could not be partitioned. There was a trend for P. drummondii to have higher heritabilities than P. cuspidata for most characters even when assumptions about breeding systems were relaxed. Thus, the outbreeding species exhibited larger genetic differences among populations and among families within populations than the selfing species in the greenhouse environment. These data suggest that P. drummondii has the greater evolutionary potential of the two species and are consistent with the hypothesis that differences in population structure result from differences in the breeding systems of the two species.     

虫霉目新种和新记录

本文报道了虫霉目的一个新种和3个新记录种。新种叶蝉虫疫霉(Erynia cicadellisLi et Fan sp.nov.)是我国南方稻叶蝉虫霉流行病的病原之一,与近缘种飞虱虫疫霉[E．Deiphaeis (Heri) Humber et Ben-Ze’ev] 的主要区别在于后者孢子较大,且不具有假根。蚜虫疫霉[E. aphidis (Hoffm.) Humber et Ben-Ze'ev]系世界不常见种,国内首次在陕西岚皋及福州的桃蚜上记录;飞虱虫疫霉和佩氏虫疫霉[E．Petchii Ben-Ze'ev et Kenneth)皆系南方褐稻虱虫霉流行病的病原。     

COMPARATIVE METHODS AT THE SPECIES LEVEL: GEOGRAPHIC VARIATION IN MORPHOLOGY AND GROUP SIZE IN GREY-CROWNED BABBLERS (POMATOSTOMUS TEMPORALIS)

We show that a new comparative method that sheds light on evolutionary trends among species may also illuminate trends within species. This finding comes from a phylogenetic autocorrelation analysis of morphological traits among individuals sampled from ten populations of a cooperatively breeding songbird, the Grey-crowned Babbler (Pomatostomus temporalis). Highly variable mitochondrial DNA (mtDNA) sequences from both the eastern (Pomatostomus temporalis temporalis) and western (Pomatostomus temporalis rubeculus) lineages were used to define genetic distances among 120 individuals and to estimate correlations among individuals in wing length, tarsus length, and body weight via an intraspecific weighting matrix. The autoregressive model effectively removed intraspecific correlations for all three morphological variables, and the proportion of the total phenotypic variance due to genealogical relationships varied from 0.68 (weight) to 0.23 (tarsus). The analysis revealed correlations among the specific components of traits, in which none were previously detected (type-I error) and diminished correlations that appeared strong when phylogeny was ignored. Group size was the only trait for which the autoregressive model failed to remove intraspecific correlations, a result likely due to the plasticity, convergence, and clinal variation in this trait in both the eastern and western lineages. The autocorrelation analysis weakened significant negative correlations between group size and total values for wing length and body weight, but the interpretation of this result depends on the adaptive significance ascribed to the “phylogenetic component” of trait values removed by the analysis. Comparative methods employing distance matrices are one useful way of summarizing the pattern of nonhierarchical relationships among conspecific individuals (“tokogenetic” relationships, sensu Hennig).     

HYBRIDIZATION AND CHLOROPLAST DNA VARIATION IN A PINUS SPECIES COMPLEX FROM ASIA

Heterologous hybridization of chloroplast DNA (cpDNA) involving 30 endonucleaseprobe combinations was used to analyze cpDNA variation in multiple individuals and populations of Pinus tabulaeformis (Carr.), Pinus yunnanensis (Franchèt) and Pinus massoniana (Lamb.). Restriction fragment patterns detected by several combinations distinguished among the three species. The obtained cpDNA markers were subsequently used to examine cpDNA variation of Pinus densata (Masters), a putative tertiary hybrid between P. tabulaeformis and P. yunnanensis. The analysis demonstrated that P. densata populations harbor three different haplotypes. Two of these haplotypes are characteristic of P. tabulaeformis and P. yunnanensis. However, the third haplotype found in P. densata appears to be absent in other extant Asian Pinus species. It is suggested that the observed cpDNA composition of P. densata populations is a result of past hybridization involving P. tabulaeformis, P. yunnanensis, and a third unknown or extinct taxon. Chloroplast DNA polymorphism in P. densata was much greater than that for nuclear allozyme markers in this and the other Pinus species. Population differentiation was also substantial in P. densata and exceeded that for allozyme markers. In contrast, no cpDNA polymorphism was detected in populations of P. tabulaeformis, P. yunnanensis, and P. massoniana. The study suggests that interspecific gene exchange may lead to the creation of stable cpDNA polymorphism in conifer hybrids.     

姬花蚤属一新种及一新记录种（鞘翅目：花蚤科）

本文记述了近年在河北省张家口地区发现一种严重为害向日葵的姬花蚤属１新种──杨氏姬花蚤Ｍｏｒｄｅｌｌｉｓｔｅｎａ（ｓ．ｓｔｒ．）ｙａｎｇｉ,ｓｐ．ｎ．,还简述其生物学习性,同时记录了姬花蚤属１中国新记录种。模式标本保存在北京自然博物馆标本馆。