Coexistence and geographical distribution of Leguminosae in an area of Atlantic forest in the semi-arid region of Brazil

Understanding the factors that affect plant species distribution and coexistence in areas with high plant species diversity is a challenge for ecologists.According to some authors,species occupy specif...     

Activity and satiation state in Pterostichus melanarius: an experiment in different agricultural habitats

1. A capture–recapture experiment was conducted to examine the effects of satiation state on the activity and foraging efficiency of the carabid beetle Pterostichus melanarius Ill., in four different habitats (a hedge, a transition zone between the hedge and the adjacent wheat crop, the margin of the wheat crop, and the centre of the wheat crop) in an agricultural ecosystem in France. 2. Prey biomass and density decreased from the centre of the hedge to the crop margin and to the centre of the crop, where prey density was low but prey biomass was moderate. Starved and satiated beetles were released in circular enclosures and recaptured using pitfall traps for 6 days. 3. Immediately after release, starved P. melanarius were significantly more active than satiated beetles, but this difference disappeared after the first day. At each recapture date, starved individuals had gained weight whereas satiated individuals had lost weight. The analysis of activity and weight variation at the end of the first day indicated that the centre of the crop seemed to be the most favourable habitat for starved individuals to find food rapidly, whereas the behaviour of satiated individuals was identical in all habitats. 4. This experiment shows that habitat use of P. melanarius is flexible. The results are discussed in the context of the classical view of foraging behaviour in carabid beetles. The activity and foraging efficiency in P. melanarius in different habitats can be explained as the result of the interaction between individual satiation state, prey availability in the habitat, and particular preferences of the species.     

Role of carboxylate in the nitrogen metabolism of plants from different natural habitats

The carboxylate and organic nitrogen content was studied in plants from 5 different habitats in Austria in order to determine both the form of nitrogen utilized by the plants and the preferential site of nitrate reduction within the plant, if nitrate is the predominant nitrogen form and is reduced mainly in the shoots, the ratio between carboxylate and organic nitrogen should be about 1. Ratios less then 1 would indicate either participation of root reduction, transport of carboxylate from shoots to roots or ammonium/ammonia nutrition.
In the plants investigated, the lowest ratios were found in a bog, where ammonium is usually the predominant nitrogen form. Species from a xerophytic and a nutrient-rich habitat, as well as from a carr, showed higher organic nitrogen values. Highest contents of carboxylate and organic nitrogen were found in halophytes from the area around the take Neusiedlersee. As additional bicarbonate uptake is known to occur at these sites, accumulation of carboxylate here may not he related to nitrate reduction alone.
The relationship between the carboxylate/organic nitrogen ratio and N indicator values revealed the same pattern of differences in the plant species, indicating that the determination of these values could give information of ecophysiological characteristics of, and differences between, plant species from various habitats.     

Functional response of suspension feeding anuran larvae to different particle sizes at low concentrations (Amphibia)

The influence of particle size, initial particle concentration and larval stage on the ingestion rate, ‘retention efficiency’, and filtering rate of anuran larvae with varying filter apparatus anatomy and different life histories was investigated for four species. Larvae of premetamorphic Stages 28 and 32 and prometamorphic Stage 40 were selected for filtering experiments on the basis of their different growth rates. Three different sizes of silica gel particles were offered as mock food. Particle concentration was measured photometrically. The Michaelis-Menten model was used to describe the dependency of ingestion rate, filtering rate, and ‘retention efficiency’ upon initial particle concentration, and to calculate maximum ingestion rate, threshold concentration, and the half-saturation constant. (1) The highest ingestion rates, filtering rates and ‘retention efficiencies’ were achieved by Xenopus laevis larvae, followed by Bufo calamita larvae. Bufo bufo larvae lay at the opposite end of the scale. Rana temporaria larvae were placed between B. calamita and B. bufo larvae. This order is attributed to differences in life histories, especially the different breeding environments in which these larvae occur. (2) The larger the particle size and the older the stage, the greater the tendency toward saturation of the ingestion rate, filtering rate and ‘retention efficiency’. These filtration parameters are graded according to particle size. The ingestion rate (number of particles), filtration rate and ‘retention efficiency’ are greatest for PS3. Ingestion volume is greatest for PS 1. The difference between PS3 and PS2 on the one hand, and PS1 on the other, is often great; for Stage 28 X. laevis it is very great. This shows that larvae ingest large particles more effectively, and that the most effective ingestion takes place at Stages 28 and 32, owing to the growth function of these stages. The ability of larvae to ingest large particles effectively is possibly a very basic phylogenetic characteristic. (3) The threshold concentration is lowest when the particles are at their largest. In accordance with conclusions drawn by other authors, threshold feeding is attributed to regulation by buccal pumping and mucus production. Considerable importance is attributed to threshold feeding with respect to larval adaptation to oligotrophic environments.     

Surviving winter hypoxia: behavioral adaptations of fishes in a northern Wisconsin winterkill lake

Synopsis Winterkill lakes often have a characteristic fish community, presumably composed of species able to survive winter hypoxia. Our research on a small winterkill lake in northern Wisconsin indicates that fishes common in winterkill lakes have behavioral adaptations for tolerating or avoiding winter hypoxia. We examined the distribution of fishes within the lake during one winter (December through May), and fish migrations into and out of the lake for two consecutive years. As DO within the lake declined in late fall, adult-sized fishes of four species, brook stickleback, finescale dace, redbelly dace, and fathead minnow, moved to the ice-water interface where DO levels were highest. Stickleback, and to a lesser extent, fathead minnows, also moved toward the more highly oxygenated water near the inlet. During the first year, young-of-the-year fishes of blacknose shiner, Iowa darter, redbelly dace, and fathead minnow, avoided hypoxic conditions by emigrating from the lake via the outlet stream in late fall and early winter while DO within the lake was still relatively high. Blacknose shiner, redbelly dace, and fathead minnow returned to the lake in spring. Almost no fishes were trapped leaving the lake in the second fall-winter season. Central mudminnows neither moved to the ice-water interface nor emigrated from the lake as DO dropped. Mudminnows survive winter hypoxia by breathing oxygen-containing bubbles trapped beneath the ice. These relatively simple behavioral adaptations allow fishes to survive or avoid hypoxic conditions lethal to other species and may help explain the consistency in fish communities of winterkill lakes.     

Multisequence comparisons in protein coding genes

A very powerful method for detecting functional constraints operative in biological macromolecules is presented. This method entails performing a base permanence analysis of protein coding genes at each codon position simultaneously in different species. It calculates the degree of permanence of subregions of the gene by dividing it into segments,c codons long, counting how many sites remain unchanged in each segment among all species compared. By comparing the base permanence among several sequences with the expectations based on a stochastic evolutionary process, gene regions showing different degrees of conservation can be selected. This means that wherever the permanence deviates significantly from the expected value generated by the simulation, the corresponding regions are considered “constrained” or “hypervariable”. The constrained regions are of two types: α and β. The α regions result from constraints at the amino acid level, whereas the β regions are those probably involved in “control” processing. The method has been applied to mitochondrial genes coding for subunit 6 of the ATPase and subunit 1 of the cytochrome oxidase in four mammalian species: human, rat, mouse, and cow. In the two mitochondrial genes a few regions that are highly conserved in all codon positions have been identified. Among these regions a sequence, common to both genes, that is complementary to a strongly conserved region of 12S rRNA has been found. This method can also be of great help in studying molecular evolution mechanisms.     

Spatial patterns in pupal mortality in urban palm caterpillars

Mortality factors were determined in over 20000 pupal skins of Brassolis sophorae and Opsiphanes invirae, collected from 55 sites in the urban area of Campinas, São Paulo, southeast Brazil. Almost 50% of B. sophorae pupae and 30% of O. invirae pupae were killed by various identifiable factors, which may have an appreciable influence in determining adult population size. Mortality was related to type of attachment site, distance from the center of the city, area occupied by buildings and houses, vegetation cover, and other urban variables. Exposed pupation sites such as outside walls had a lower frequency of successful eclosions than darker or more sheltered sites, such as offset skirting boards, garages, or mailboxes, which act as partial refuges against parasitoids. Mortality levels were higher in regions of the city with high vegetation cover. Vegetation cover and distance from the city center were the best predictors of parasitism level of B. sophorae by the chalcidid wasp Spilochalcis morleyi. The viability of S. morleyi (data from parasitized B. sophorae) did not differ significantly among different regions of the city. These data do not support an exclusive model of escape from parasites (or other natural enemies) for explaining the abundance of urban butterflies.This paper was presented at the VI INTECOL, Manchester, UK, in September 1994     

脉络宁合用蝮蛇抗栓酶治疗中风后遗症101例疗效评价

通过观察脉络宁合用蝮蛇抗栓酶分型治疗中风后遗症１０１的临床疗效,并与单用脉络宁对照组６９例比较。从而初步探讨２药联用对各型病例效应的机理,为优选本病的药疗方案提供参考资料。结果治疗组总有效率及中药病例有效率均显著高于对照组;各型病例治愈率及轻、重型病例有效率、重型患者显效率也都比对照组高;但各型病例好转率及轻、中型病例显效率２组结果无显著差异。     

不同类型棉田棉蚜种群动态研究

根据华北棉区8种不同时空类型棉蚜种群密度调查结果,分析和比较了不同播种时间、间套作及免耕措施对棉蚜种群密度的影响。     

云南巨蜥类物种多样性及其生境习性和现状的初步调查

巨蜥是世界上现存的一类最大的蜥蜴,隶爬行纲巨蜥科Varanidae,仅1科1属(Varanus)约36种,分布于澳洲、亚洲南部和非洲。中国历来记载仅有一种——V.salvator。然而,调查表明在云南边境地区实际分布着3种巨蜥,除V.salvator外,尚有V.irrawadicus和V.vietnamensis。本文讨论了这3种巨蜥的有效性,简要地报道了它们的生境、习性和生存现状,并就保护问题提出参考意见。