The distribution of Gobius cobitis in the British Isles

Records of occuerence of Gobius cobitis on the British coast are listed from the literature and from extensive collecting in interfidal areas. In Britain the number of suitable habitats is reduced and the density of population is lower than in the Channel Islands and Brittany.     

The importance of xylem constraints in the distribution of conifer species

Vulnerability of stem xylem to cavitation was measured in 10 species of conifers using high pressure air to induce xylem embolism. Mean values of air pressure required to induce a 50% loss in hydraulic conductivity (φ₅₀) varied enormously between species, ranging from a maximum of 14.2±0.6 MPa (corresponding to a xylem water potential of −14.2 MPa) in the semi-arid species Actinostrobus acuminatus to a minimum of 2.3±0.2 MPa in the rainforest species Dacrycarpus dacrydioides . Mean φ₅₀ was significantly correlated with the mean rainfall of the driest quarter within the distribution of each species. The value of φ₅₀ was also compared with leaf drought tolerance data for these species in order to determine whether xylem dysfunction during drought dictated drought response at the leaf level. Previous data describing the maximum depletion of internal CO₂ concentration (c_i) in the leaves of these species during artificial drought was strongly correlated with φ₅₀ suggesting a primary role of xylem in effecting leaf drought response. The possibility of a trade-off between xylem conductivity and xylem vulnerability was tested in a sub-sample of four species, but no evidence of an inverse relationship between φ₅₀ and either stem-area specific (K_a) or leaf-area specific conductivity (K₁) was found.     

Parasitoid hymenopterans of Costa Rica: Geographical distribution of the species associated with fruit flies [Diptera: Tephritidae]

The geographical distribution of the parasitoid species associated with fruit flies in Costa Rica is presented. In a study of 319 fruit samples infested with larvae of fruit flies, collected from 135 localities, 8 parasitoid species were recovered from 11.0% of the fruit samples. Two species are considered to be indigenous, two were introduced for the biological control ofCeratitis capitata (Wiedemann) in this country, at least 3 unidentified species of eucoiline cynipoids and one species of uncertain origin was found for the first time. The identified parasitoids were:Doryctobracon crawfordi (Viereck) (indigenous),D. areolatus (Szépligeti) (indigenous),Biosteres longicaudatus Ashmead (introduced),Aceratoneuromyia indica (Silvestri) (introduced) andTrichopria sp. (indigenous?). The introduced species were more frequently associated withAnastrepha spp. than withC. capitata. The need for systematic monitoring of populations of released parasitoid species is suggested.     

Predicting and mapping the spatial distribution of Chamaecyparis formosensis in central Taiwan in a GIS with species distribution models

Analyzing the relationship between species and environment is always a focal question of ecological research. In recent years species distribution models (SDMs) has been widely used to predict the spatial distribution of species. SDMs are numerical tools that combine observations and species occurrence or abundance with environmental variables to predict the spatial distribution of species across landscapes, sometimes requiring extrapolation in space and time. Chamaecyparis formosensis (Taiwan red cypress, TRCs) is a coniferous species endemic to Taiwan, where it natural grows in the central mountains at moderate to high altitudes of 800–2800 m, and most stands in the range of 1500–2150 m. It is threatened by habitat loss and over-cutting for its valuable timber. To preserve TRCs species and achieve sustainable use of biological resources, we choose TRCs as a target for the study to predict its distribution in central Taiwan.The pure forests of TRCs in the study area were mainly located in Pachsienshan (P), Shouchentashan (S) and Baigou Mountain (B) in central Taiwan, and the distribution data were originally obtained by The Third Survey of Forest Resources and Land Use in Taiwan. Elevation, slope, aspect, and three vegetation indices were derived from both SPOT-5 satellite images and DEM. GIS technique was used to overlay those factors. Discriminant analysis (DA), decision tree (DT) and maximum entropy (MAXENT), three commonly used SDMs, were applied based on above-mentioned six variables to predict the suitable habitat of TRCs, and to evaluate which the best model is in terms of accuracy and efficiency. Three experiment designs (ED1, ED2 and ED3) with different combinations of samples were used for model building and validation. The 200 target samples were collected from the site P–B, B–S and P–S for model building under ED1, ED2 and ED3 respectively, while the 100 samples were collected from the site S, P and B for model validation. All experiment designs had same 1350 background samples. The results showed that the overall accuracy and kappa coefficient of DT (96%, 0.88) was higher than that of MAXENT (91%, 0.70), and their accuracies were better than that of DA (84%, 0.58). All the three models were highly efficient in implementation of model construction and evaluation, while the DT model was difficult for generating the entire predicted map of potential habitat due to its complex conditional sentence. Vegetation indices derived from SPOT-5 satellite images could not improve model accuracy because of its insufficiency of spectral resolution and spatial resolution. High spatial resolution and spectral resolution remotely sensed imagery should be used in our future research to improve model performance and reliability.     

The distribution of species of the genusThermocyclops (Copepoda,Cyclopoida) in the western hemisphere,with description ofT. parvus,new species

The distribution and ecology of species of cyclopoid copepods of the genusThermocyclops in the western hemisphere are reviewed. These are:Thermocyclops brehmi (Kiefer),T. crassus (Fischer),T. decipiens (Kiefer),T. hastatus antillensis Herbst,T. inversus (Kiefer),T. minutus (Lowndes),T. tenuis (Marsh),T. tenuis longifurcatus Pesce, andT. parvus, new species.T. brehmi is known from microlimnotopes in a restricted region in northern Argentina and Uruguay, whileT. crassus has been reliably recorded only from small ponds in Costa Rica.T. decipiens, with many records from northern Argentina to Costa Rica, Guatemala and the Antilles, is often numerous in mesotrophic and eutrophic lakes and reservoirs. The range ofT. minutus extends over tropical and subtropical lowlands of South America from northern Argentina to Venezuela; this species prefers oligotrophic and mesotrophic conditions in larger lakes.T. inversus may prefer mildly carbonate waters and inhabits large and small reservoirs, natural lakes, ponds, wells and caves from northeastern Brazil to Mexico and the Antilles.T. tenuis ranges from northern Argentina to the Antilles and the southern United States, inhabiting large and small, natural and artificial bodies of water.T. tenuis longifurcatus is known only from two wells on Bonaire,T. hastatus antillensis from a well on the island of Guadeloupe, andT. parvus only from plankton samples from the Florida Everglades. Knowledge of population dynamics, feeding and reproductive biology of several planktonic species is reviewed.     

The influence of climatic factors on the distribution of C4 species in Europe

A checklist of the currently-known C4 species which occur in Europe was compiled, and the number of these found in European territories was ascertained. Their contribution to the local floras range from 4.35% in the Azores to 0% in Svalbard. Subsequently, a stepwise multiple regression analysis was used to correlate the relative abundances of four subdivisions of C4 species with climatic variables derived for each territory from meteorological tables. The four subdivisions were: (a) total number of C4 species; (b) number of native C4 species; (c) C4 monocots and (d) C4 dicots. These values were expressed as percentages of either the total flora, (a), or the native flora ((b), (c) and (d)) for the regressions. The abundance of each C4 subdivision was found to be strongly correlated with temperature, and to a lesser extent, negatively with precipitation. Habitat information about the European C4 species was also analysed and it was concluded that their apparent preference for maritime and ruderal habitats indicates some form of competitive advantage of the pathway under saline or disturbed conditions. A small number of European C4 species was identified whose distribution appears to be anomalous with respect to temperature and/or soil moisture content.Nomenclature follows Tutin et al. Flora Europaea.     

Sub-fossil beetle assemblages associated with the "mammoth fauna" in the Late Pleistocene localities of the Ural Mountains and West Siberia

The distribution of beetles at the end of the Middle Pleninglacial (=terminal Quaternary) was examined based on sub-fossil material from the Ural Mountains and Western Siberia, Russia. All relevant localities of fossil insects have similar radiocarbon dates, ranging between 33,000 and 22,000 C14 years ago. Being situated across the vast territory from the southern Ural Mountains in the South to the middle Yamal Peninsula in the North, they allow latitudinal changes in beetle assemblages of that time to be traced. These beetles lived simultaneously with mammals of the so-called "mammoth fauna" with mammoth, bison, and wooly rhinoceros, the often co-occurring mega-mammalian bones at some of the sites being evidence of this. The beetle assemblages found between 59° and 57°N appear to be the most interesting. Their bulk is referred to as a "mixed" type, one which includes a characteristic combination of arcto-boreal, boreal, steppe and polyzonal species showing no analogues among recent insect complexes. These peculiar faunas seem to have represented a particular zonal type, which disappeared since the end of the Last Glaciation to arrive here with the extinction of the mammoth biota. In contrast, on the sites lying north of 60°N, the beetle communities were similar to modern sub-arctic and arctic faunas, yet with the participation of some sub-boreal steppe components, such as Poecilus ravus Lutshnik and Carabus sibiricus Fischer-Waldheim. This information, when compared with our knowledge of synchronous insect faunas from other regions of northern Eurasia, suggests that the former distribution of beetles in this region could be accounted for both by palaeo-environmental conditions and the impact of grazing by large ruminant mammals across the so-called "mammoth savannas".     

The role of introduced species in shaping the distribution and abundance of island reptiles

Summary Species interactions, as revealed by historical introductions of predators and competitors, affect population densities and sometimes result in extinctions of island reptiles. Mongoose introductions to Pacific islands have diminished the abundance of diurnal lizards and in some cases have led to extinctions. Through these population level effects, biogeographic patterns are produced, such as the reciprocal co-occurrence pattern seen with the tuatara and its predator, the Polynesian rat, and with the tropical gecko competitorsHemidactylus frenatus andLepidodactylus lugubris in urban habitats in the Pacific. Although competition has led to changes in abundance and has caused habitat displacement and reduced colonization success, extinctions of established reptile populations usually occur only as a result of predation.These introductions, along with many manipulative experiments, demonstrate that present day competition and predation are potent forces shaping community structure and geographic distributions. The human introduction of species to islands can be viewed as an acceleration of the natural processes of range expansion and colonization. The immediate biotic consequences of these natural processes should be of the same intensity as those of the human introductions. Coevolution may subsequently act to ameliorate these interactions and reduce the dynamical response of one species to the other. The role played by coevolution in mediating interactions between competitors and predator and prey is highlighted by the susceptibility of predator-naive endemic species to introduced predators and the invalidity of species-poor communities.     

10种鸣禽控制鸣啭神经核团大小与鸣唱复杂性的相关性

为进一步揭示鸣禽鸣唱行为的神经生物学机制 ,本实验先对 8个科 10种鸣禽的鸣唱行为进行了观察和录音 ,并借助声谱软件分析了每种鸣禽的鸣唱复杂性。鸣唱语句复杂性的评价指标包括 :短语总数、每个短语中所含的平均音节数及音节种类数、所有短语的总音节数及音节种类数、最长短语的音节数及音节种类数。然后 ,测定了前脑三个鸣啭学习控制核团和一个与发声无关的视觉参考核团体积 ,分析了鸣唱语句复杂性和这些核团大小间的相关关系。结果表明 :1)HVC和HVC/Rt与 7种鸣唱语句复杂性指标无关 ;RA和RA/Rt与总音节种类数相关 ;AreaX与总音节数及音节种类数相关 ;2 )HVC/RA和HVC/X比值与多个鸣唱语句复杂性指标相关。结果提示 :鸣禽鸣唱复杂性不同特征可能受不同神经控制     

The cell cycle related apoptotic susceptibility to arsenic trioxide is associated with the level of reactive oxygen species

Double staining flow cytometry was performed using 7-amino actinomycin D and 6-carboxy-2‘,7‘-dichlorodihydrofluorescein diacetate, to detect the level fluctuation of reactive oxygen species (ROS) during the cell cycle of normal NB4 cells. Our results showed that NB4 cells possessed higher level of ROS in G2/M phase than in G1 and S phases. Double staining flow cytometry, with TdT mediated dUTP nick end labeling (Tunel) and propidium iodide(PI), indicated that As2O3 (2μM) could induce apoptosis in NB4 cells prevailingly from G2/M phase, and this efficacy was enhanced upon co-administration of 2, 3-dimethoxy-1, 4-naphthoquinone (DMNQ) (2.5μM) which could produce the endogenous ROS. These results suggested that different ROS level in different cell cycle phases of NB4 cells might determin the selective induction of G2/M apoptosis and the cells‘ susceptibility to apoptosis by As2O3.     

The effect of temperature on the formation and decay of the multiline EPR signal species associated with photosynthetic oxygen evolution

We have investigated the effects of temperature on the formation and decay of the light-induced multiline EPR signal species associated with photosynthetic oxygen evolution (Dismukes, G.C. and Siderer, Y. (1980) FEBS Lett. 121, 78–80). (1) The decay rate following illumination is temperature dependent: at 295 K the half-time of decay is about 40 s, at 253 K the half-time is approx. 40 min. (2) A single intense flash of light becomes progressively less effective in generating the multiline signal below about 240 K. (3) Continuous illumination is capable of generating the signal down to almost 160 K. (4) Continuous illumination after a preilluminating flash generates less signal above 200 K than at lower temperatures. Our results support the conclusion of Dismukes and Siderer that the S₂ state gives rise to this multiline signal; we find that the S₁ state can be fully advanced to the S₂ state at temperatures as low as 160 K. The S₂ state is capable of further advancement at temperatures above about 210 K, but not below that temperature.     

Diverse genomic species and evidences of symbiotic gene lateral transfer detected among the rhizobia associated with Astragalus species grown in the temperate regions of China

Based on the analyses of ribosomal DNA and housekeeping genes, a total of 118 bacterial isolates obtained from 13 Astragalus species grown in the temperate region of China were identified as 19 genomic species of Mesorhizobium, Rhizobium, Sinorhizobium and Bradyrhizobium, two of them being putatively new species. Phylogenetic comparison of symbiotic genes (nodC and nifH) and housekeeping genes showed that the symbiotic genes of the Astragalus rhizobia were maintained by both vertical and horizontal transfer. The results demonstrated that the Astragalus species were very promiscuous hosts for rhizobia and that their rhizobia had very diverse genomic and symbiotic gene backgrounds.     

Repair process and enzymatic activity associated with induction of shell regeneration in the invasive species Pomacea canaliculata

ABSTRACT

This study investigated the repair process and enzymatic activity responses after induction of shell regeneration in Pomacea canaliculata. The survival rates, height of regenerated shell, and activities of alkaline phosphatase (ALP) and carbonic anhydrase (CA) were investigated and recorded for 15 days. A triangular piece of shell about 8?mm wide was excised from the ventral region of the shell. On the basis of photographs and enzyme assay, it was concluded both yellow-shell apple snails and black-shell apple snails had high survival rates (100%). The regenerated new shell was initially thin, with the wound sealed 5 days after induction of shell regeneration; after that the regenerated shell thickened. Three snails were sampled at 0, 0.5, 1, 2, 3, 5, 10 and 15 days after shell excision for analysis of enzymatic activity of ALP and CA. Trends of the activity of ALP and CA in the mantle were similar. Initially they both showed a decline on the first day, then rose on following days. Activity of ALP declined to a minimum on the first day, and an activity peak in both colour forms appeared on the fifth day (P?<?0.05) and was maintained for the rest of the experiment. The minimum value of CA occurred after 0.5 days, and a significant increase was also observed on the fifth day (P?<?0.05). This study has revealed that apple snails have good shell regeneration abilities, and that ALP and CA probably play a crucial role in shell growth and regeneration.     

The number of species occurring in a sample of a biotic community and its connections with species-abundance relationship and spatial distribution

Connections among species-abundance (i-m _i ), species-frequency (i-F _i ), and species-sample size (S _n -n) relationships were examined on the basis of the mapping data of a natural forest in Thailand. The spatial distribution of individual trees without any discrimination of species was nearly random. Provided that the spatial distribution of each species was random, thei-m _i and thei-F _i relationship was reconstructed from each other in terms of the total number of species (S) and the total number of individuals (N) in the data. The number of species (S _n ) in a subsample consisting ofn individuals was then obtained from thei-F _i relationship. Logarithm ofS _n increased with logn and showed a convex curve through the origin. The values of diversity indices based onN andS(orn andS _n ) were affected by sample size. These trends were further examined on the basis of 944 data sets of biotic communities and three mathematical models of anS-N relationship. The properties of species-area relation were discussed in the light of these results.     

The effect of land-use on the local distribution of palm species in an Andean rain forest fragment in northwestern Ecuador

The northern Andes is extremely rich in plant species, but this diversity is threatened by extensive deforestation. This study reports on how five palm species respond to human disturbance in an area of montane forest in Ecuador. The abundance of each species was determined in 250 40 × 30m plots, established in disturbed and undisturbed forest within an area of 3 × 3km and altitudes spanning 1248–1938m. Aiphanes erinacea (H. Karst.) H. Wendl. and to a lesser degree Geonoma undata Klotzsch were negatively affected by even moderate human disturbance, while Chamaedorea linearis (Ruiz & Pav.) Mart. and C. pinnatifrons (Jacq.) Oerst. benefitted from such disturbance and Prestoea acuminata (Willd.) H.E. Moore was unaffected given time enough to replenish its population after disturbance. At the scale of the plots, species richness was maximized in undisturbed forest. Aiphanes erinacea is endemic to northern Ecuador and southern Colombia and must be considered threatened by the extensive deforestation here. If the behaviour of these palms is representative of Andean rain forest plans in general, the negative effect of moderate anthropogenic disturbance on plant biodiversity at scales of 1km2 might be negligible. Thus, biologically sustainable logging could be possible.     

The ecology of six Rhododendron species (Ericaceae) with contrasting local abundance and distribution patterns in Hong Kong,China

Six native Rhododendron species grow in thedegraded, fire-prone landscape of Hong Kong: R. simsii andR. farrerae are common and widespread, R.moulmainense is relatively restricted, and R.championiae, R. hongkongense, and R.simiarum are rare. For all species except the rare R.simiarum, there was direct or indirect evidence of regrowth afterfire, but only the two smallest and commonest species grow in sites which arefrequently burned. Both flowered within 18 months of a fire. Most populationsofall species, except R. simiarum, had a deficiency ofindividuals in the smaller basal circumference classes. Seedlings were foundonly in three out of four plots of R. simiarum, and one ofR. farrerae. A few seedlings of the other rare specieswereseen in open, litter-free microsites outside the study plots, but no seedlingsof the most common species, R. simsii, were seen anywhere.In logistic regression models, one or more measures of plant size weresignificant positive predictors of flowering at least once in the three yearstudy period for all species, while percentage cover by surrounding vegetationhad a significant negative impact on all except R. simsiiand R. farrerae, for which no populations arestrongly-shaded. Although the absence of current recruitment is not necessarilya cause for concern in long-lived species that can resprout after fire, werecommend that active vegetation management should be tried to enhance thesurvival and reproduction of R. moulmainense, R.championiae and R. hongkongense, and that newpopulations of these species and R. simiarum should becreated.     

The influence of ionic composition on the distribution of nematode species in springs of the province of Granada (Spain)

The ionic composition of 38 mineral springs in the province of Granada (Spain), and the distribution of 45 species of nematodes belonging to orders Monhysterida, Araeolaimida, Chromadorida and Enoplida were examined. Water chemistry is used to make two diagrams representing anionic and cationic composition. Diagrams for anionic composition (given the greater variance seen in the springs considered) are used to illustrate the distribution of individual species. The results obtained from species distribution and the correlation between species made it possible to group species which could be associated with springs where each of the anions considered predominated. A greater number of species groups was found to inhabit springs in which chloride concentrations was less than 50% of the total concentration of anions.     

Comparative fecundity and associated factors for two sibling species of the Anopheles gambiaecomplex occurring sympatrically in The Gambia

Abstract. For two sibling species of mosquitoes belonging to the Anopheles gambiae complex of malaria vectors, the effects of body size (wing length) and bloodmeal size (haematin excretion) on fecundity of wild females were investigated in The Gambia, West Africa. Freshly blood-fed individuals from sympatric populations of An.arabiensis and An.gambiae sensu stricto were sampled by collection at 07.00–09.00 hours from within bednets during July/August 1993, at the beginning of the rainy season. The possible confounding effect of infection with Plasmodium parasites was removed by eliminating infected mosquitoes from the study samples. An.arabiensis females comprised 75% of the An.gambiae sensu law population and were significantly larger (greater mean wing length) than those of An.gambiae s.s. mosquitoes. Mean egg production per female (for the subsequent gonotrophic cycle, excluding pre-gravids) for the two species was not significantly different, though the relationship between wing length and egg production showed An.gambiae s.s. to be more fecund than the An.arabiensis of the same size. Pre-gravid An.gambiae s.s. had consumed significandy smaller bloodmeals than gravid females but the mean wing length of these two gonotrophic categories was not significantly different. In contrast, An.arabiensis pre-gravids were smaller and had consumed smaller bloodmeals than the gravids.