Pattern of differentiation in the annual killifish genus Austrolebias (Cyprinodontiformes: Rivulidae) from a biosphere reserve site in South America: a multidisciplinary approach

The annual killifish genus Austrolebias includes approximately 38 species distributed throughout the Paraná-Plata basin and Patos-Merín system. Within the Austrolebias adloffi species complex, the Uruguayan populations of Austrolebias charrua were considered as an intergradation between A. adloffi and Austrolebias viarius populations. Austrolebias charrua presents an intermediate phenotype between both taxa and high levels of morphological and chromatic variability. In the present study, we incorporate different methodological approaches (molecular, morphology, and gamete ultrastructure) to elucidate the pattern of differentiation among the parapatric taxa ( A. charrua , Austrolebias reicherti , A. viarius ) distributed in a Biosphere Reserve Site. Analyses of cytochrome b sequences show high values of DNA polymorphism, in particular for A. charrua. This is in accordance with both morphological and gametic variation. Using a statistical parsimony network based on these sequences and analysis of morphological data, past fragmentation and range expansion involving perhaps secondary contact between A. charrua and A. reicherti could be proposed. Coloration pattern and morphometric analyses showed an unexpected higher similarity between the most distantly-related taxa, A. viarius and A. charrua . This could be the result of retention of ancestral polymorphisms, especially in A. charrua populations from ponds of higher elevation, or to directional selection acting in similar ecological environments. Because these annual killifish species are considered endangered, our work reinforces the high priority need to include them in a conservation programme.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 620–635.     

Multiple simultaneous speciation in killifishes of the Cynolebias adloffi species complex (Cyprinodontiformes, Rivulidae) from phylogeography and chromosome data

The annual killifishes of the genus Cynolebias Steindachner, 1876, include one of the well-supported clades composed of the Cynolebias adloffi species complex of the Bañados del Este Biosphere Reserve Site, from the Atlantic coastal wetlands in Uruguay. One member of this clade, Cynolebias charrua , has been considered as an intergradation complex of populations between C. adloffi and C. viarius by showing high levels of morphological variability. Systematic affinities between both taxa have been historically discussed. In the present study, a phylogeographic approach based on mitochondrial cytochrome b haplotype analysis and chromosome data are presented. According to the present data a scenario of a multiple simultaneous speciation process and perhaps reticulation events is possible in the C. adloffi species complex, followed by divergence associated with Quaternary marine transgressions in this region. This hypothetic scenario could explain the remarkable genetic diversity and the lack of phylogenetic resolution among clades in C. charrua , as well as the disconcordance in the phylogenetic relationships among Cynolebias from different data sets. Several parameters of DNA polymorphism and chromosome data have also suggested that populations of C. charrua from southern Laguna Merin, in eastern Uruguay and southern Brazil, could represent a relictual group from a widespread ancestral population. Chromosome rearrangements like pericentric inversions in isolated populations could have triggered cladogenetic events from this highly polymorphic population. Present analysis suggests that the metapopulation could represent the management units in these endangered killifishes and that the populations of C. charrua from the Laguna Merin basin could be included in a high-priority conservation programme.     

Control of the flexible annual/biennial life cycle of the heather psyllid Strophingia ericae

Abstract. Strophingia ericae (Curtis) (Homoptera: Psylloidea) takes one or two years to complete its life cycle. In both cases eggs hatch over a prolonged period from midsummer, possibly extending into the following spring at high altitude, and instars overlap in time. Instar III is the predominant overwintering stage in the lowland, annual cycle, whereas in the upland, biennial cycle most first-year nymphs overwinter in instars I and II and most second-year nymphs in instar V. When moved to the laboratory, instars IV and V from a predominantly annual population showed accelerated development in response to elevated temperatures and to long days in both mid-winter and early spring. In the biennial life cycle, short autumn days retard instar V development but the response to photoperiod disappears by the end of winter. Exposure to LD 18 : 6 h retarded development of early instars in the annual population, resulting in an accumulation in instar III. The proportion of overwintering instars I and II rises with increase in altitude and moult to instar III becomes progressively delayed. Nymphs that reach instar III under long daylengths in the year following hatching are channelled towards the biennial cycle. Exposure of a predominantly biennial population to 15 °C and LD 18 : 6 h after midsummer, thus avoiding autumn conditions, promoted the rapid development of overwintered nymphs, switching the cycle from biennial to annual.     

Seasonal aspects of the life cycles of Carabus granulatus and C. glabratus (coleoptera, carabidae) in the northern taiga

The seasonal dynamics of the activity and the demographic structure of Carabus granulatus and C. glabratus populations was studied in the northern taiga of European Russia. The period of adult activity lasts for 90 days from early June to late August with the maximal activity observed in June. At the northern boundary of the range, the spring species Carabus granulatus retains its annual life cycle typical of this species in the other part of the range. At the same time, the reproductive period decreases, resulting in the synchronization of the development of specimens within the population. In the autumn species C. glabratus, a biennial life cycle with early summer reproduction is formed in the zone of broad-leaved forests of the northern taiga instead of the annual cycle. This species is characterized by the presence of two groups of individuals developing for two years each, but their development is shifted by a year. Such strategy results in the annual breeding of the species.     

Chronobiological Characteristics of the Development and Course of Gestosis during the First Pregnancy

The regularities of the development and the course of gestosis were studied as dependent on the seasonal and individual annual rhythms of the woman. It was revealed that the maximum prevalence of this complication took place in the fourth quarter of the woman’s individual annual cycle and in winter. The results can be used for early prevention of gestosis in obstetric practice.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 92–95.Original Russian Text Copyright © 2005 by Kalent’eva, Barbarash.     

北京主要气传致敏花粉年浓度峰值日期预测

花粉是我国北方引发过敏性鼻炎最主要过敏原,花粉症发病期与花粉浓度高峰期吻合。基于北京地区2012至2020年花粉季多站、逐日分类花粉浓度观测数据分析,得出北京地区花粉浓度在3月上旬至5月中旬(可进一步划分为3月中旬至4月上旬和4月下旬至5月上旬两个高峰期)和8月中旬至9月中旬分别存在两个高峰期,第一个高峰期内优势致敏花粉种类为柏科、杨柳科和松科,第二个高峰期内优势致敏花粉种类为桑科、菊科蒿属和藜科。根据优势致敏花粉年浓度峰值日期观测数据,使用与花粉采样站点位置相匹配的逐日气象观测数据累积值,基于作物模型概念和模糊逻辑原理建立了北京地区主要气传致敏花粉年浓度峰值日期预测模型。经检验,柏科、杨柳科、松科、桑科、菊科蒿属和藜科花粉模型预测准确率分别为87.8%、80.0%、64.4%、86.7%、78.8%和81.8%。基于北京地区主要气传致敏花粉年浓度峰值日期预测模型可为本地花粉症防治提供理论参考。     

绵枣儿花芽分化的形态解剖学研究

为探明绵枣儿(Barnardia japonica)在哈尔滨地区的年生长节律以及花芽分化进程,该文以从长白山引种至东北林业大学花卉研究所苗圃内的绵枣儿为材料,采用田间观察法研究绵枣儿的年生长节律,并采用石蜡切片法观察其花芽分化各阶段的形态解剖学特征。结果表明:(1)绵枣儿在哈尔滨地区的生长节律大致可以分为四个时期,即花芽分化与发育期、开花期、结实期、休眠期。(2)绵枣儿花芽分化进程可以分为七个阶段,即4月中上旬,由于土壤温度较低,鳞茎仍处于未分化期; 4月下旬进入花序原基分化期; 5月上旬苞片原基分化; 5月下旬为小花原基分化期; 5月末至6月初花被片原基分化; 6月上旬进入雄蕊原基分化期; 6月下旬为雌蕊原基分化期。该研究明确了绵枣儿在哈尔滨地区的年生长节律和花芽分化各阶段的解剖学特性,为园林应用和新品种的选育提供了一定的科学依据。     

黄鳝卵巢发育的研究

作者对252尾黄鳝卵巢标本进行观察记录,运用常规染色法、组织化学法和扫描电镜研究了黄鳝的卵子发生、卵巢发育和卵巢周年变化规律。讨论了黄鳝的卵黄发生、卵巢发育分期和产卵类型等问题。本研究为黄鳝人工繁殖提供有关科学依据。     

石羊河下游白刺灌丛演替过程中群落结构及数量特征

白刺灌丛(Nitraria tangutorum Bobr.)是在石羊河下游存活面积最大的天然植被类型,研究不同演替阶段白刺灌丛群落的结构和数量特征可为该区白刺群落保护与恢复提供科学依据.根据白刺灌丛生长及其生境状况,在石羊河下游选择了初期发育、稳定、衰退、严重衰退的群落,研究了各演替过程中各阶段的群落物种组成、生活型谱,群落盖度、群落物种多样性及各演替阶段群落的相似性特征.结果表明,从初期发育阶段到稳定阶段的群落物种数量明显减少,而从稳定阶段至严重衰退阶段的演替过程中群落物种是逐渐增加的.在整个演替过程中,1年生植物所占比例逐渐增加,至严重衰退阶段时1年生植物所占的比重高达80％.不同演替阶段群落盖度最高、最低值出现的月份也不相同,5-10月群落盖度的平均值为稳定阶段＞初期发育阶段＞衰败阶段＞严重衰败阶段.各演替阶段多样性Simpson、Shannon-Wiener指数以及Pielou均匀度指数5-10月均呈现波动变化特征,Simpson、Shannon-Wiener指数大小顺序均表现为初期发育阶段＞严重衰退阶段＞衰退阶段＞稳定阶段,而均匀度Pielou指数为衰退阶段＞严重衰退阶段＞稳定阶段＞初期发育阶段.各演替阶段群落之间的相似性均较低,演替序列越相近,相似性系数越高.     

Gonadal development and spawning of female ocean whitefish, Caulolatilus princeps (Pisces: Branchiostegidae) in the Bay of La Paz, B.C.S., Mexico

The developmental stages of the gonads and the spawning season of the ocean whitefish, Caulolatilus princeps , were determined. Gonad maturation is annual, and the spawning season is prolonged, from late autumn to early spring. From November to March, around 80% of the females were in an advanced mode of gonadal development, and in April most gonads were spent. From May to October the gonads were at rest and preparing for the next spawning season.
The gonadosomatic index describes the reproductive activity of the species adequately.     

Looking for age-related growth decline in natural forests: unexpected biomass patterns from tree rings and simulated mortality

Forest biomass growth is almost universally assumed to peak early in stand development, near canopy closure, after which it will plateau or decline. The chronosequence and plot remeasurement approaches used to establish the decline pattern suffer from limitations and coarse temporal detail. We combined annual tree ring measurements and mortality models to address two questions: first, how do assumptions about tree growth and mortality influence reconstructions of biomass growth? Second, under what circumstances does biomass production follow the model that peaks early, then declines? We integrated three stochastic mortality models with a census tree-ring data set from eight temperate forest types to reconstruct stand-level biomass increments (in Minnesota, USA). We compared growth patterns among mortality models, forest types and stands. Timing of peak biomass growth varied significantly among mortality models, peaking 20–30 years earlier when mortality was random with respect to tree growth and size, than when mortality favored slow-growing individuals. Random or u-shaped mortality (highest in small or large trees) produced peak growth 25–30 % higher than the surviving tree sample alone. Growth trends for even-aged, monospecific Pinus banksiana or Acer saccharum forests were similar to the early peak and decline expectation. However, we observed continually increasing biomass growth in older, low-productivity forests of Quercus rubra, Fraxinus nigra, and Thuja occidentalis. Tree-ring reconstructions estimated annual changes in live biomass growth and identified more diverse development patterns than previous methods. These detailed, long-term patterns of biomass development are crucial for detecting recent growth responses to global change and modeling future forest dynamics.     

Oxygen consumption during embryonic development of the annual fish Nothobranchius korthausae with special reference to diapause

The oxygen consumption of Nothobranchius korthausae eggs in different developmental stages, including diapause II and III, was measured. Oxygen consumption increases exponentially during embryonic development. In diapause II and III there is a drop in oxygen consumption, which attains a minimal level in diapause II after 3 weeks and in diapause III after 2 weeks. During early development the embryos can escape from hypoxic stress by entering diapause I and II. During late embryogenesis embryos in diapause III can escape from hypoxic stress by hatching. We conclude that survival of annual fish embryos is enhanced during conditions of low oxygen concentration by reduced oxygen consumption rates during diapause.     

Poplar genomics is getting popular: the impact of the poplar genome project on tree research

Trees, due to their long life-span, have characteristics that distinguish them from annual, herbaceous plants. It is likely that many of these properties are based on a tree-specific genetic foundation. The U.S. Department of Energy initiated a genome-sequencing project for Populus, a model perennial plant. Through international collaboration and input to the sequencing effort, the annotated whole genome sequence of Populus trichocarpa will be released to the public in early 2004. This genomic resource will, for the first time, allow comparison between a perennial and an annual plant on a whole genome basis and therefore provide clues for molecular research on tree-specific questions like dormancy, development of a secondary cambium, juvenile-mature phase change, or long-term host-pest interactions. The approximately 520 Mbp of annotated genomic sequence will complement and expand the knowledge provided so far by the 125,000 ESTs from poplar that are available in public databases. This article introduces the international poplar research programmes and points out the significance of the poplar genome project for plant research.     

Sustainable production of crops and pastures under drought in a Mediterranean environment

Mediterranean environments are characterised by cool wet winters and hot dry summers. While native vegetation in Mediterranean-climatic zones usually comprises a mixture of perennial and annual plants, agricultural development in the Mediterranean-climatic region of Australia has led to the clearing of the perennial vegetation and its replacement with annual crops and pastures. In the Mediterranean environments of southern Australia this has led to secondary (dryland) salinisation. In order to slow land degradation, perennial trees and pasture species are being reintroduced to increase the productivity of the saline areas. The annual crops and pastures that form the backbone of dryland farming systems in the Mediterranean-climatic zone of Australia are grown during the cool wet winter months on incoming rainfall and mature during spring and early summer as temperatures and rates of evaporation rise and rainfall decreases. Thus, crop and pasture growth is usually curtailed by terminal drought. Where available, supplementary irrigation in spring can lead to significant increases in yield and water use efficiency. In order to sustain production of annual crops in Mediterranean environments, both agronomic and genetic options have been employed. An analysis of the yield increases of wheat in Mediterranean-climatic regions shows that there has generally been an increase in the yields over the past decades, albeit at a lower rate than in more temperate regions. Approximately half of this increase can be attributed to agronomic improvements and half to genetic improvements. The agronomic improvements that have been utilised to sustain the increased yields include earlier planting to more closely match crop growth to rainfall distribution, use of fertilisers to increase early growth, minimum tillage to enable earlier planting and increase plant transpiration at the expense of soil evaporation, rotations to reduce weed control and disease incidence, and use of herbicides, insecticides and fungicides to reduce losses from weeds, insects and disease. Genetic improvements include changing the phenological development to better match the rainfall, increased early vigour, deeper rooting, osmotic adjustment, increased transpiration efficiency and improved assimilate storage and remobilisation. Mediterranean environments that are subjected annually to terminal drought can be both environmentally and economically sustainable, but to maximise plant water use efficiency while maintaining crop productivity requires an understanding of the interaction between genotypes, environment and management.     

Preboreal oscillations inferred from Arctica islandica sclerochronology

An increasingly important source of annually resolved palaeoenvironmental proxy data originates from cross-dated incremental chronologies summarizing the shell growth of several individuals. Here, we have analysed annual increment variations in a collection of radiocarbon-dated shells of ocean quahog (Arctica islandica) from early Holocene prodelta deposits in north Norway. Radiocarbon dating of the shell material showed that the increments were formed contemporaneously during Preboreal times. The biologically youngest shell contains 35 annual increments, whereas the oldest shell shows 169 increments. Time-series of annual increments demonstrated clear age trends with the widest increments during the very early years of bivalve life, followed by a notable decline in increment widths as the bivalves aged. Subsequent to removing these biological trends from the series, a sclerochronological cross-dating was carried out and resolved the temporal alignments of the shell growth increment records relative to each other. The resulting shell growth increment chronology evidences vigorous growth variations. Spectral analysis of the chronology revealed 3.7- and 4.3-year periodicities, indicative of Preboreal environmental oscillations. Periodicities of longer period were not detected. Our results prove the value of radiocarbon-dated shell assemblages to build “floating” geochronologies for periods and regions where dead shells from museum collections or seabed are not obtainable. Increasing constructions of such chronologies enhance the potential of sclerochronological cross-dating of annual shell growth increment chronologies to depict and detail annually-resolved climate variability not only for late Holocene, as previously illustrated, but also for early Holocene times, when large-scale oscillations punctuated the global climate dynamics. Development of longer chronologies with higher sample replication remains an attainable interdisciplinary target.     

Mathematical Modelling of the Transmission Dynamics of Contagious Bovine Pleuropneumonia Reveals Minimal Target Profiles for Improved Vaccines and Diagnostic Assays

Contagious bovine pleuropneumonia (CBPP) is a cattle disease that has hampered the development of the livestock sector in sub-Saharan Africa. Currently, vaccination with a live vaccine strain is its recommended control measure although unofficial antimicrobial use is widely practiced. Here, modelling techniques are used to assess the potential impact of early elimination of infected cattle via accurate diagnosis on CBPP dynamics. A herd-level stochastic epidemiological model explicitly incorporating test sensitivity and specificity is developed. Interventions by annual vaccination, annual testing and elimination and a combination of both are implemented in a stepwise manner and their effectiveness compared by running 1000 simulations per intervention over ten years. The model predicts that among the simulated interventions, the ones likely to eliminate the disease from an isolated herd all involved annual vaccination of more than 75% of the animals with a vaccine that protects for at least 18 months combined with annual testing (and elimination of positive reactors) of 75% of the animals every six months after vaccination. The highest probability of disease elimination was 97.5% and this could occur within a median of 2.3 years. Generally, our model predicts that regular testing and elimination of positive reactors using improved tests will play a significant role in minimizing CBPP burden especially in the current situation where improved vaccines are yet to be developed.     

Chick Nutrition and Mortality in Captive Willow Ptarmigan (Lagopus L. Lagopus)

Willow ptarmigan chicks were reared during 8 years on concentrates supplemented with blueberry plants. Mortality during the first 3 weeks after hatching ranged between 33 and 65 %, and was mainly caused by enteritis and digestive tract obstructions. The annual variations in chick survival seemed to be caused by the variations in plant phenology. The survival was highest when spring and blueberry plant development was late, and lowest when spring was early and warm, leading to early lignification of blueberry plant leaves.     

Growth rate and age at migration of Anguilla anguilla

The length, age and growth rate were investigated for downstream migrating male and female eels in the unexploited Burrishoole system, western Ireland. Significant differences were found in the age and length at migration with the larger, older female eels also showing faster annual growth as early as the first year in fresh water. Female eels normally migrated at lengths from 40.5 cm, exceptionally to 92.9 cm, and male eels at lengths between 28.9 and 46'0 cm. Back-calculation showed an irregular pattern of fast and slow annual growth. Mean annual growth increments were almost always greater for females than for males.     

A Variable- and Person-Oriented Investigation of Preschool Competencies and Head Start Children's Transition to Kindergarten and First Grade

There is a widespread belief that youth drop out of youth development programs during the middle school years. Alternative explanations for the smaller number of adolescent program participants have yet to be explored. We examine age trends in program enrollment using data from over 221,000 youth enrolled in the California 4-H Youth Development Program from 1992 to 2002. We include sex, race/ethnicity, rural/urban residence, and project participation as predictors of dropout. Our results indicate that the peak in enrollment in early adolescence that is observable from annual enrollment data can be accounted for by stable and high enrollment turnover before age 11, followed by increased program dropout and fewer new enrollments. These findings have implications for explanations of youth program participation and for youth development program enrollment strategies, both for the 4-H Youth Development program and for youth programs in general.     

The natural history of lung cancer in a periodically screened population

A mathematical model of the progression kinetics of lung cancer in a periodically screened population is proposed and data collected by the Memorial Sloan-Kettering Cancer Center in New York are used for parameter estimation. It is assumed that the development of adenocarcinoma of lung is a stochastic process with two stages, early and advanced, characterized by mean times, detection probabilities, and cure probabilities. Confidence regions of these parameters are estimated using a number of novel techniques. It is found, surprisingly, that the mean duration of the early stage is at least 4 years, the detectability less than .2, and the curability less than .5. These estimates imply that annual radiographic screening from age 45 to 80 might decrease mortality from adenocarcinoma of lung by something less than 20%.