Diversification of ectoparasite assemblages and climate: an example with fleas parasitic on small mammals

Aim We studied the relationships between the numbers of species and numbers of higher taxa (genera, tribes, subfamilies and families) in flea assemblages of small mammalian hosts with the aims of: (a) comparing these relationships across different regions, and (b) testing the hypothesis that flea assemblages in warmer regions diversify mainly via intrahost speciation, whereas those in colder regions diversify mainly via host switching. Location The study used previously published data on flea assemblages on small mammalian hosts from 25 different regions of the Holarctic. Methods The number of flea genera, tribes, subfamilies or families in an assemblage (host species) was plotted against the number of flea species in this assemblage for each region separately, and a power function was fitted to the resulting relationships. Then, the values of the exponent of the power function for a region were regressed against the mean annual temperature in this region, across all regions. Results The relationships between the number of flea species and the numbers of flea genera, tribes, subfamilies or families on a host species in each region were found to be well described by simple power functions. The exponent of the power function of the relationship between the number of flea species and the number of flea genera per host tended to decrease with increasing local mean annual temperature. When two apparent outliers from the trend (corresponding to regions where sampling was not performed as in other regions) were omitted from the analysis, the negative relationship between temperature and the exponent of the power function between the number of flea species and number of flea genera per host became highly significant. No relationship was found between the values of the exponents of the power functions between the number of flea species and the number of flea tribes, subfamilies or families per host, and the mean local annual temperature. Main conclusions The results suggest that the diversification of flea assemblages is associated with climatic variables. In warm regions, the greater number of congeneric species per flea assemblage, reflected by the lower exponent of the power function, may well be the outcome of intrahost speciation. This indicates that, as regional temperature increases, intrahost speciation becomes a relatively more important mode of diversification than acquisition of fleas via host switching.     

Characterization and immunological comparison of isoenzymes of phospholipases A2 from snake venoms of different genera and families.

Phospholipases A2 (PLA2) were isolated and purified from the Taiwan cobra (Naja naja atra) and several snake species of the same or different genera by semipreparative cation-exchange and reversed-phase HPLC. They were shown to possess different enzymatic activity toward the synthetic substrate L-alpha-lecithin by the fatty-acid titration method. The immunological cross-reactivity of these structurally similar isotoxins was investigated using immunodiffusion, precipitin reaction and enzyme-linked immunosorbent assay (ELISA). PLA2 from the venoms of the same species such as the Taiwan cobra (Naja naja atra) and the Indian cobra (Naja naja naja) showed a high degree of antigenic resemblance whereas no immunoreactivity was observed among those PLA2 from different genera. Quantitative immunoreactivity assays by ELISA revealed the partial cross-reactivity between the antibody against PLA2 of Taiwan cobra and those isoenzymes from snakes of remotely-related species. The immunological relatedness between PLA2 of the representative snake species of different genera and families is shown to be correlated with the extent of sequence homology among these enzymes.     

Chironomidae of the Holarctic region: a comparison of ecological and functional traits between North America and Europe

Chironomidae (Diptera) are widespread, abundant, diverse and ubiquitous, and include genera and species that are distributed across the Holarctic region. However, the geographical barriers between continents should have resulted in intraspecific population differentiation with reflection on individual biological and ecological traits. Our aim was to test for potential differences in Chironomidae species/genus and traits between the Nearctic and Palearctic regions. We compared the Chironomidae trait information gathered in two databases; one database was developed in Europe and the other in North America. Common genera and species of both databases were selected, and the common traits were adjusted into the same trait categories. Data were transformed into presence/absence and divided into Eltonian (biological/functional) and Grinnellian (ecological) traits. Common genera and common species were analyzed using Fuzzy correspondence analysis (FCA). Differences between databases occur for all trait domains. Yet, Eltonian traits showed lower level of concordance than Grinnellian traits at the species level. Different biological characteristics in the Nearctic and Palearctic regions may indicate that Chironomidae have different adaptions to similar ecological environments due to intraspecific variability or even trait plasticity.     

Reserve mass and dispersal investment in relation to geographic range of plant species: phylogenetically independent contrasts

Recent studies have reported conflicting evidence about correlations between seed size and plant species geographic range sizes. Using phylogenetically independent contrasts (PICs) within genera, we found no consistent differences in reserve mass between species with similar dispersal morphology and «wide>> versus «narrow>> geographic ranges. There was also no tendency within genera for broad ranged species to be those that allocate a larger percentage of the resources invested in each diaspora to dispersal structures. PICs were also constructed between species having a tenfold difference in seed size. In these PICs, the larger seeded species often occupied a greater number of regions than species with smaller seed sizes. This result was generated primarily through the comparison of species from different genera, families or higher level taxa which differed not only in seed mass but also in dispersal modes and growth forms. Finally, comparing species within Acacia and Eucalyptus having similar seed size but different dispersal modes, we found that bird dispersal (in Acacia ) and possession of a wing for wind dispersal (in Eucalyptus ) was associated with wider geographic range compared to lower-investment dispersal modes. Taken together, these comparisons indicate that seed size is not itself important as a factor influencing breadth of geographic range. Dispersal mode and growth form may have an influence, however, and seed size differences may be associated with contrasts in dispersal mode or growth form.     

Convergent incidences of Wolbachia infection in fig wasp communities from two continents

Wide surveys suggest that Wolbachia bacteria infect ca. 20% of all insect species, but particular taxonomic or ecological groups may display significantly higher or lower incidences. We studied 61 fig wasp species in Australia and found the highest known incidence (67%) of infection in a targeted study of this nature. A comparable study in Panama reported a similar figure (59%), confirming the exceptionally high incidence of Wolbachia in fig wasps. Importantly, these are two independent estimates of Wolbachia incidence in fig wasp communities, because no host species, or even genera, are shared between localities. The high level of infection may reflect enhanced opportunities for horizontal transmission inside fig fruits. Although incidence was similar in Panama and Australia, the actual strains involved were different and region-specific. Local strains were shared by several host species, although there was often no obvious (direct) ecological link between two hosts with the same infection.     

Patterns of species diversity on an oceanic versus a continental island mountain: a hypothesis on species diversification1

Abstract. The vegetation on a wet mountain slope on Haleakala (an oceanic island) is compared with that on Kinabalu (a continental island) to examine relationships between regional floristic richness and α- and β-diversities. The two mountains are similar in their constant tropical climate, generic and family-level floristic elements and geological age of the summit regions, but different in regional floristic richness (rich on Kinabalu vs. poor on Haleakala). α-diversity of canopy and subcanopy tree species was much higher on Kinabalu than in comparable zones on Haleakala. Average turnover rate of species (as logarithmic community similarity) on the slope was one order of magnitude greater on Kinabalu than on Haleakala (0.127 vs. 0.017 per 100 m alt.). While there were genera with wide altitudinal ranges on both mountains, a large proportion of the genera was differentiated into parapatric altitudinal congeners on Kinabalu. By contrast, most genera are altitudinally monotypic on Haleakala. The number of sympatric congeners per genus, and the frequency of multi-specific genera per plot were high on lower slopes but decreased with increasing altitude on Kinabalu, whereas the values were low across all altitudes on Haleakala. These patterns suggest that sympatric and parapatric species radiation was less on Haleakala than on Kinabalu. This may be related to Haleakala's initially poor and disharmonic flora.     

墨蚜蝇(双翅目,食蚜蝇科,食蚜蝇亚科)八种雄性外生殖器比较

作者对墨蚜蝇族中3属8种昆虫:东方墨蚜蝇Melanostoma orientale,方斑墨蚜蝇M.mellinum,梯斑墨蚜蝇M.scalare,天台墨蚜蝇M.tiantaiensis,黑腹宽跗蚜蝇Platycheirus albimanus,叉尾宽跗蚜蝇P.bidentatus,斜斑宽跗蚜蝇P.scutatus,圆斑宽扁蚜蝇Xanthandrus comtus进行了雄性外生殖器的比较研究,并分别予以绘图和描述。结果表明,雄性外生殖器在属内种间形态结构很相似,仅在尾器颜色、阳茎基部形状等方面有微小的区别;而在属间主要是背针突和上叶的形态和结构存在较大的不同。     

美国纽约州阔叶林物种多度格局的研究(英文)

物种多度格局是群落结构的重要反映 ,近年来又受到生态学家的重视。用 5种生态位模型研究美国纽约州“城 -郊 -乡”生态样带温性落叶阔叶林的物种多度格局。其中 3个模型 ,即几何级数模型、生态位重迭模型和分割线段模型拟合效果很好 ,它们既适合于简单群落 ,又适合于复杂群落结构的研究。另外两个模型 ,即随机分配模型和优势优先模型拟合效果不如前三个模型 ,可能仅适合于简单的群落研究。森林群落不同功能层的物种多度格局相似 ;沿“城 -郊 -乡”生态样带 ,森林群落的结构一致 ;物种多度格局与物种多样性指数结合使用可以更好地研究群落的结构特征。     

Mycelium of Arbuscular Mycorrhizal fungi (AMF) from different genera: form, function and detection

It is often assumed that all species of arbuscular mycorrhizal fungi (AMF) have the same function because of the ubiquity of the arbuscular mycorrhizal symbiosis and the fact that all AMF occupy the same plant/soil niche. Despite apparent differences in the timing of evolutionary divergence and the morphological characteristics of AMF from the different genera, the majority of studies on these fungi use only species of Glomus. There is increasing evidence, however, that the mechanisms involved in the establishment of a mycorrhiza may differ for species and genera of AMF and influence their subsequent function. The aim of this paper is to highlight the diversity in the form and function of AMF from different genera, knowledge of which is vital in understanding their ecological roles. Potential use of biochemical and molecular approaches to detect AMF in planta and ex planta is also discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Geographical location determines the population structure in phyllosphere microbial communities of a salt-excreting desert tree

The leaf surfaces of Tamarix, a salt-secreting desert tree, harbor a diverse community of microbial epiphytes. This ecosystem presents a unique combination of ecological characteristics and imposes a set of extreme stress conditions. The composition of the microbial community along ecological gradients was studied from analyses of microbial richness and diversity in the phyllosphere of three Tamarix species in the Mediterranean and Dead Sea regions in Israel and in two locations in the United States. Over 200,000 sequences of the 16S V6 and 18S V9 hypervariable regions revealed a diverse community, with 788 bacterial and 64 eukaryotic genera but only one archaeal genus. Both geographic location and tree species were determinants of microbial community structures, with the former being more dominant. Tree leaves of all three species in the Mediterranean region were dominated by Halomonas and Halobacteria, whereas trees from the Dead Sea area were dominated by Actinomycetales and Bacillales. Our findings demonstrate that microbial phyllosphere communities on different Tamarix species are highly similar in the same locale, whereas trees of the same species that grow in different climatic regions host distinct microbial communities.     

帽儿山国家森林公园30年前后植物区系比较研究

该研究采用样方结合样线调查的方法,并综合文献资料,于1983年和2013年2次对帽儿山国家森林公园植物种类进行实地调查,并进行了区系特征的对比分析,为评估帽儿山国家森林公园植物保护状况提供依据。结果表明:(1)2013年研究区的植物科数量和组成与1983年相同,但2013年比1983年少20属60种,不同等级科组成差异较小,而不同等级属差异较大。(2)优势科组成差异较小,但2013年兰科(Orchidacea)由优势科变成了非优势科,而藜科(Chenopodiaceae)和松科(Pinaceae)由非优势科变成优势科;优势属组成差异较大,2013年比1983年少了8个优势属。(3)2次调查表征科组成变化较大,但表征属组成差异较小,2013年比1983年少了2个表征属。(4)1983年和2013年科、属、种的分布型均以温带性分布为主;科的分布型完全相同,属的分布型2013年比1983年少了地中海区-西亚至中亚分布型;种的分布型,2013年比1983年多了亚洲-北美-北极分布。研究认为,30年间帽儿山国家森林公园的植物区系构成基本稳定,说明对这一区域的植物保护总体有效,但属和种的数量明显减少,30年间物种多样性显著降低,尤其是某些重要的科,如兰科植物的减少,也说明植物保护现状依然不容乐观。     

Is abundance a species attribute? An example with haematophagous ectoparasites

Population density is a fundamental property of a species and yet it varies among populations of the same species. The variation comes from the interplay between intrinsic features of a species that tend to produce repeatable density values across all populations of the same species and extrinsic environmental factors that differ among localities and thus tend to produce spatial variation in density. Is inter-population variation in density too large for density to be considered a true species character? We addressed this question using data on abundance (number of parasites per individual host, i.e. equivalent to density) of fleas ectoparasitic on small mammals. The data included samples of 548 flea populations, representing 145 flea species and obtained from 48 different geographical regions. Abundances of the same flea species on the same host species, but in different regions, were more similar to each other than expected by chance, and varied significantly among flea species, with 46% of the variation among samples accounted by differences between flea species. Thus, estimates of abundance are repeatable within the same flea species. The same repeatability was also observed, but to a lesser extent, across flea genera, tribes and subfamilies. Independently of the identity of the flea species, abundance values recorded on the same host species, or in the same geographical region, also showed significant statistical repeatability, though not nearly as strong as that associated with abundance values from the same flea species. There were also no strong indications that regional differences in abiotic variables were an important determinant of variation in abundance of a given flea species on a given host species. Abundance thus appears to be a true species trait in fleas, although it varies somewhat within bounds set by species-specific life history traits.     

Molecular biogeography of cave life: a study using mitochondrial DNA from bathysciine beetles

This study focuses on phylogenetic relationships in two distinct species assemblages of cave-dwelling beetles with similar disjunct distributions in the Pyrenees and Sardinia. One assemblage contains six species in the genera Ovobathysciola (four species) and Patriziella (two species) on Sardinia and one species of Anillochlamys in the Pyrenees. Species within the two Sardinian genera co-occur in the same karst area. Although, they are believed to be each others closest relative, they have very different body types (globular body with short appendages in Ovobathysciola; elongated body with long appendages in Patriziella), which are believed to reflect different degrees of adaptation to cave life. The other assemblage of Bathysciine beetles includes three species in the genus Speonomus in the Pyrenees and one on Sardinia. All the species are rare and many are endangered. One issue of particular interest was whether Ovobathysciola and Patriziella are reciprocally monophyletic or whether each of the Patriziella species evolved independently from the co-occurring Ovobathysciola species, as the similar morphology of the Patriziella species might be due to convergence rather than common descent. Based on DNA sequences of the cytochrome oxidase I (COI) region of the mtDNA, neither scenario was supported. Rather, the two Patriziella species are sister taxa embedded within the Ovobathysciola radiation. In addition, the well-dated geological history of this region allowed us to calibrate absolute rates of COI evolution, the first such estimates for any insect. Finally this study suggests that the evolutionary acquisition of typical cave adaptations (e.g., elongated body and appendages) may occur at about the same rate as loss of traits (e.g., eyes and pigmentation) associated with cave life.     

15科温带树木营养贮藏蛋白质的细胞学研究

利用光学显微镜技术和组织化学方法研究１５科２９种２变种 温带树木中的营养贮藏蛋白质（ＶＳＰｓ）的分布和形态。结果表明,ＶＳＰｓ在树木中的分布分为ＶＳＰｓ丰富、贫乏和缺乏３种类型。同时,ＶＳＰｓ有多种形态,大致可分为蛋白体状、颗粒状和絮状３种,这些形态的ＶＳＰｓ存在于不同的树木中或同一树种的不同细胞中。ＶＳＰｓ的有无、多少及其形态在不同科树木之间及同一科不同属树木之间存在在较大差异,但在同一属树种之     

Heterorhabditis spp. and Steinernema (= Neoaplectana) spp.: temperature, and aspects of behavior and infectivity

The infectivity of several species/strains of nematodes of the genera Heterorhabditis and Steinernema for postfeeding, 3rd instar larvae of the sheep blowfly, Lucilia cuprina, was tested in sand at various temperatures. Of the two genera, the steinernematids were more active at lower temperatures and parasitized L. cuprina over a greater temperature range. The temperature range of infectivity for L. cuprina differed between nematodes of the same genus and between strains of the same species. Parasitization of L. cuprina and Galleria mellonella occurred in a temperature range that was greater than that permitting nematode development and reproduction. Different strains of the same species were found to have different temperature limits for development and reproduction. Developmental rate was different for each nematode species tested with the heterorhabditids taking longer to complete their life cycle than did the steinernematids.     

The cellular slime mold guild and its bacterial prey: growth rate variation at the inter- and intraspecific levels

Summary A guild of cellular slime molds (CSM) consisting of two isolates from each of five species, representing two genera, and obtained from the same square meter of forest soil exhibited extensive growth rate variation when tested on a suite of 18 bacteria isolated from the same soil. Significant growth rate differences were found at each taxonomic level examined: among species of different genera, between genera, among species within genera, and between isolates (=clones) within species. The type of bacteria used as prey determined the relative rank of the growth rates in different CSM isolates, as well as the taxonomic level at which significant differences were found. We suggest a possible reconciliation between a previous hypothesis, based on competition, and contradictory experimental work on resource partitioning in this guild of bacterial predators. Our results raise a question about the efficacy of using single genotypes to represent a species when ecological ideas are developed through laboratory investigations.     

外来入侵植物和本地植物核DNA C-值的比较及其与入侵性的关系

用流式细胞仪测定了8科10属13种外来入侵植物、6种本地植物和1种外来非入侵植物的核DNAC-值。结果表明:作为整体,外来入侵植物的平均核DNAC-值显著低于本地种和外来非入侵种,但对同属不同类型植物进行比较,未发现一致的规律;在4个既包含外来入侵种又包含本地种的属中,泽兰属(Eupatorium)和鬼针草属(Bidens)外来入侵种的核DNAC-值显著低于同属本地种,莲子草属(Alternanthera)的2种外来入侵植物中仅有1个种的核DNAC-值显著低于同属本地种,而草胡椒属(Peperomia)外来入侵种的核DNAC-值显著高于同属本地种;表明核DNAC-值与外来植物入侵性无必然联系。     

A light and electron microscopic study of Scherffelia dubia, a new member of the scaly green flagellates (Prasinophyceae)

In clonal culture Scherffelia dubia (Perty) Pascher shows a considerable range of morphological variation, with different cell shapes being produced including those typical for three other species of Scherffelia Pascher ( S. opisthostigma Skuja, S. ovata Pascher, S. pelagica Skuja) and one species of Tetraselmis Stein ( T. bichlora Ettl & Ettl). It is concluded these taxa should be reduced to the synonymy of S. dubia , the type species of Scherffelia. The general cell morphology of S. dubia is described in detail, including a serial section and absolute configuration analysis of the flagellar apparatus. S. dubia is compared with species of Tetraselmis of which ultrastructural details are known and it is shown that both genera are very similar but the generic distinction is nevertheless justified. Main features of distinction include the pyrenoid (present in Tetraselmis but lacking in Scherffelia ) and the chloroplast (single and more or less cup-shaped in Tetraselmis , two separate lateral chloroplasts in Scherffelia ). Both genera are accommodated in the same family, the correct name being Chlorodendraceae and not Tetraselmidaceae or Platymonadaceae which have often been used.     

Assessing the origin of Neotropical mountain dung beetle assemblages (Scarabaeidae: Scarabaeinae): the comparative influence of vertical and horizontal colonization

Aims The fauna of mountains and their surrounding regions are likely to be influenced principally by two biological processes: horizontal colonization along similar altitudinal levels by elements originating from lineages inhabiting higher latitudes; and vertical colonization by lineages from the same latitude, but at lower altitudes. We examine whether the expected patterns derived from the latter process can be observed in mountain dung beetle assemblages. Specifically, we study the variation in species composition and richness with altitude in five regions spanning elevation gradients, analysing whether the altitudinal rates of change in the number of species and genera differ, and whether beta‐diversity scores for adjacent sites in each altitudinal gradient are different for species and genera. Location Eastern Cordillera of the Colombian Andes. Methods Field work was carried out in 1997–99 at 27 sites in five regions with elevation gradients, with 10–32 pitfall traps placed in each site. For each altitudinal level the numbers of species and genera were analysed with respect to altitude, and the slope of the linear regression between these variables was calculated. The slope of the curve of the altitude against the cumulative number of species and genera was also calculated for each altitudinal gradient to describe the compositional change between adjacent sites (beta diversity). Species and generic slopes were compared using analysis of covariance. The turnover of species along each altitudinal gradient was measured using presence/absence data and Cody's beta‐diversity index between adjacent pairs of sites. A cluster analysis was used to detect faunistically homogeneous groups of localities. Results Species richness always decreased with altitude, although the slopes did not differ significantly from zero. The number of genera also decreased with increasing altitude, but generally at a significantly slower rate than for species. Variation in the species beta‐diversity scores between altitudinal levels did not follow a homogeneous pattern in the different regions. Two main altitudinal groups of sites with a boundary c. 1500–1750 m a.s.l. can be detected with respect to faunistic similarity. Low‐ and mid‐altitude sites are inhabited by all of the genera (19) and 80% of all species collected. Eight genera and 61 species (c. 60% of the total) are unable to inhabit high‐altitude sites, and only 20 species appear to be exclusive to these high‐altitude environments (> 2000 m a.s.l.). Main conclusions The dominant processes explaining dung beetle composition in the high north‐eastern Andean mountains are probably those of vertical colonization. The limited role of horizontal colonization processes, or colonization from northern or southern lineages, could be a consequence of the isolation and recent geological origin of these mountains.     

采用PCR-RFLP和RAPD对球壳孢目真菌系统学的研究

对球壳孢目真菌首次采用ＰＣＲ－ＲＦＬＰ和ＲＡＰＤ进行了系统发育研究。以ＩＴＳ１和ＩＴＳ４为引物对４属１２种２４个菌株的核糖体ＤＮＡ转录间区（ＩＴＳ）进行了ＰＣＲ扩增,４种内切酶（ＡｌｕＩ,Ｈｈａ,ＭｓｐＩ,ＴａｑＩ）酶切,结果表明：主要属的ＩＴＳ区长度不同,同属不同种相同。Ｃｏｎｉｏｔｈｙｒｉｕｍ,Ｐｈｙｌｏｓｔｉｃｔａ,Ａｓｃｏｃｈｙｔａ,ＳｅｐｔｏｒｉａＩＴＳ区长度分别为６３０,５６０,５５０,５４０ｂｐ;酶切图谱属间差别明显,属内种间基本一致,暗示传统的分种可能过细,某些种的成立还有商榷的余地,ＰＣＲ－ＲＦＬＰ对确定疑难种属的地位有重要的意义。３属８种１６个菌株的ＲＡＰＤ结果表明,种内图谱相同或图谱类型相同,而种间明显不同,揭示出过去所划分的种的确存在本质的差别,但是否达到种级的差别还有待于进一步研究