Variation in reproductive life-history traits of Chinese Bulbuls(Pycnonotus sinensis)along the urbanization gradient in Hangzhou,China

Urbanization brings new selection pressures to wildlife living in cities,and changes in the life-history traits of urban species can reflect their responses to such pressures.To date,most of the studies investigating the impacts of urbanization on avian life-history traits are conducted in Europe and North America,while such studies are often lacking in quickly developing countries in Asia(e.g.,China).In this study,we examined the variations in reproductive life-history traits of Chinese Bulbuls(Pycnonotus sinensis)along the urbanization gradient in Hangzhou,China.We detected 234 natural nests of Chinese Bulbuls and continuously monitored them in two continuous breeding seasons from 2012 to 2013.We collected data on seven life-history traits(laying date,incubation period,nestling period,clutch size,egg volume,hatching success rate,and fledging success rate).We used infrared cameras to record the number of feedings per hour as the measure of food resources for the nestlings.We measured nest predation pressure by monitoring 148 natural breeding nests during breeding seasons and 54 artificial nests immediately after breeding seasons.We then calculated the urbanization synthetic index(USI)as a measure of the level of urbanization and examined its relationship with the seven life-history traits.We found that Chinese Bulbuls laid eggs significantly earlier with increasing USI.However,the other six life-history traits did not vary significantly with the USI.Moreover,the feeding frequency of chicks increased significantly with the USI,but the nest predation pressure of Chinese Bulbuls decreased significantly with the USI.Increased food resources and reduced nest predation pressure in cities may lead to earlier laying date of Chinese Bulbuls.Further study should test whether the earlier laying date of Chinese Bulbuls is the result of phenotypic plasticity or genetic change.

Effects of life-history components on population dynamics of the rare endangered plant <i>Davidia involucrata</i>

In order to estimate the most effect stage and process on population growth and effective conserve the rare endangered plant Davidia involucrata, we analyzed the dynamics and the contributions of life-history components on population dynamics based on Lefkovitch matrix model and sensitivity analysis. The life cycle of Davidia involucrata was divided into six stages (seed, seedling, juvenile, immature, early adult and late adult) based on the species characteristics and published literature data, the survival rates in each life-history stage were simulated using a static life table, and the fecundity of each stage was determined according to sample information. The results showed that the structure of the observed population was not ideal, and the numbers of seedlings and coppice shoots was similar. The population growth rate was influenced largely by individual growth process, and asexual reproduction made a larger contribution to population growth than sexual reproduction. However, sexual reproduction was more important than asexual reproduction, because most asexual reproducing individuals (the coppice shoots) were derived mainly from human destruction (e.g. felling trees). The most important stage was stage V (late adult), associated with seed production and germination. Therefore, conservation of Davidia involucrata populations should focus on stage V and sexual reproduction, in order to improve the seed production and germination rate, and to promote population stability and development.

Covariation in Insular Life-history Traits of the Rice Frog(Fejervarya limnocharis)in Eastern China

Although shifts in life-history traits of insular vertebrates, as compared with mainland populations, have been observed in many taxa, few studies have examined the relationships among individual life-history traits on islands. Lifehistory theory also predicts that there is a trade-off between body size and reproductive effort, and between egg size and clutch size. We surveyed the rice frog, Fejervarya limnocharis, on 20 islands within the Zhoushan Archipelago and two nearby sites on the mainland of China to compare differences in life-history traits and to explore relationships among those traits. Rice frog females reached a greater body size on half of the smaller islands among the total 20 surveyed islands, and larger egg size, decreased clutch size and reduced reproductive effort on most of the islands when compared to the two mainland sites. Insular body size was negatively correlated with reproductive effort. There was a negative correlation between egg size and clutch size. Results suggest that life-history theory provides a good explanation for co-variation between body size and reproductive effort, and between egg size and clutch size in rice frogs on the islands.

Sex-specific life-history trait expression in hybrids of a cave- and surface-dwelling fish (Poecilia mexicana, Poecilidae)

Evaluating the fitness of hybrids can provide important insights into genetic differences between species or diverging populations.We focused on surface-and cave-ecotypes of the widespread Atlantic molly Poecilia mexicana and raised F1 hybrids of reciprocal crosses to sexual maturity in a common-garden experiment.Hybrids were reared in a fully factorial 2 x 2 design consisting of lighting(light vs.darkness)and resource availability(high vs.low food).We quantified survival,ability to realize their full reproductive potential(i.e.,completed maturation for males and 3 consecutive births for females)and essential life-history traits.Compared to the performance of pure cave and surface fish from a previous experiment,F1s had the highest death rate and the lowest proportion of fish that reached their full reproductive potential.We also uncovered an intriguing pattern of sex-specific phenotype expression,because male hybrids expressed cave molly life histories,while female hybrids expressed surface molly life histories.Our results provide evidence for strong selection against hybrids in the cave molly system,but also sug-gest a complex pattern of sex-specific(opposing)dominance,with certain surface molly genes being dominant in female hybrids and certain cavemollygenes beingdominant in malehybrids.

Impacts of oxygen deficiency on embryo life-history traits of migratory locust Locusta migratoria from low and high altitudes

Hypoxia challenges aerobic organisms in numerous environments,and hypoxic conditions may become more severe under future climate-change scenarios.The impact of hypoxia on the development of terrestrial insect embryos is not well understood.Here,to address this gap,embryonic life-history traits of migratory locust Locusta migratoria from low-altitude and high-altitude regions were compared under 2 oxygen levels:normoxia(i.e.,21 kPa oxygen partial pressure and mild hypoxia(i.e.,10 kPa oxygen partial pressure).Our results demonstrated that,whether reared under normoxia or mild hypoxia,L.migratoria from high-altitude populations had longer developmental times,reduced weight,and lower mean relative growth rate as compared with those from low-altitude populations.When transferred from normoxia to mild hypoxia,nearly all the tested lifehistory traits presented significant negative changes in the low-altitude populations,but not in the high-altitude populations.The factor'strain'alone explained 18.26%-54.59%of the total variation for traits,suggesting that the phenotypic differences between L.migratoria populations from the 2 altitudes could be driven by genetic variation.Significant genetic correlations were found between life-history traits,and most of these showed differentiation between the 2 altitudinal gradients.G-matrix comparisons showed significant structural differences between L.migratoria from the 2 regions,as well as several negative covariances(i.e.,trade-offs)between traits in the low-altitude populations.Overall,our study provides clear evidence that evolutionary divergence of embryonic traits between L.migratoria populations from different altitudes has occurred.

Altitudinal variation in life-history features of a Qinghai-Tibetan Plateau lizard

Environmental changes along an altitudinal gradient can facilitate the differentiation of life-history features in ectothermic species,but little attention has been devoted to the reciprocal influence of altitude and alpine slope directionality on life-history variation.According to life-history theory,increased environmental stress causes a change in reproductive allocation from number to quality of offspring,as well as a stronger trade-off between size and number of offspring.To clarify the influence of environmental pressures on the life-history features of the Qinghai toad-headed lizard Phrynocephalus vlangalii along an altitudinal cline,we surveyed late pregnant females from 3 populations of low(2,600 m),middle(3,400 m),and high(3,600 m)elevations in the Dangjin Mountain of Gansu,China from July to October 2019,and compared their inter-population differences in maternal body size,reproductive characteristics,offspring growth,and locomotor performance.Because of lower temperatures,higher humidity,and lower light intensity caused by slope aspect and altitude,the middle-altitude region experienced stronger environmental stress than the high-and low-altitude regions.Our results showed that females were larger at middle-and high-altitude sites and smaller at the low-altitude site,following Bergmann’s rule.We also found that females from low-altitude population gave birth earlier than those from the middle and high altitudes.Our results showed a shift in the offspring size-number trade-off of P.vlangalii in response to colder and harsher environments,with lizards from the alpine steppe(i.e.the middle-and high-altitude habitats)producing fewer but larger offspring than those from the warm steppe(i.e.the low-altitude habitat).Low-altitude juveniles grew faster than high-altitude ones,but at the same rates as middle-altitude juveniles.This result demonstrates that the growth of P.vlangalii was associated with temperature and light intensity.Our findings contribute to enhancing our understanding of the altitudinal variation in life-history features of plateau ectotherms and their phenotypic plasticity or local adaptation.

RT-qPCR normalization of reference genes in different lifehistory stages of Gracilaria vermiculophylla(Rhodophyta)

The quantitative realtime polymerase chain reaction(RT-qPCR)is a powerful and sensitive method to measure expression of targeted gene but it highly relies on the use of suitable reference genes for data normalization.We evaluated the expressions of 8 housekeeping genes:18S ribosomal rDNA(18S rDNA),28S ribosomal r DNA(28S rDNA),rubisco large subunit(rbc-L),β-actin(ACT),glyceraldehyde-3-phosphate dehydrogenase(GAPDH),elongation factor 1(EF1),β-tubulin(Tub B),and P-phycoerythrin B(PEB),to select the suitable reference genes for different life-history stages(tetrasporophyte,carposporophyte,and male/female gametophyte)of Gracilaria vermiculophylla by absolute quantitative method.Softwares geNorm and BestKeeper were used to verify the results acquired from copy number analysis.Results show that the expression of identified reference genes varied in comparing groups composed of different type of life stages.It is suggested that 18S rDNA and TubB could be used for highly complex samples composed of mixed ploidy and phases.18S rDNA and 28S rDNA were also preferred for using among the matured isomorphic samples.But for samples with different maturities,TubB and ACT were recommended for tetrasporophytes and gametophytes respectively.

The Combined Effect of Plastic Particles Size and Concentration on Rotifers’ (Brachionus plicatilis) Performance

The presence of microplastics in aquatic ecosystems is of increasing global concern.Nano-sized plastics,in particular,can penetrate the cell membrane and cause biological death.Our study evaluated the combined impacts of several polystyrene mi-crospheres’sizes and nominal concentrations on the overall performance changes of Brachionus plicatilis.Experimental animals were exposed to three microplastic sizes(0.08,0.5 and 6μm)and five nominal concentrations(0,0.5,2,8,32μg mL−1)for 20 d.Our results showed that the toxicological effect of particle size on rotifers did not significantly depend on the nominal concentration.The interaction between the nominal concentration and size occurred only for body length and lorica width.Specifically,high nominal concentrations of microplastics that were close to nanometer size significantly impaired the overall vitality of rotifers,embodied in shortage of body type,delay in the arrival of maturity,reduction in the cumulative number of neonates,and the advance of the death process.In comparison,fair-sized size(0.5 and 6μm)displayed non-significant damage except for individual groups.Most notably,the net reproductive yield was only a third of what it was in the original environment,implying that there was not much fertility left.Besides,with the development of rotifers,the adverse effects of polystyrene microsphere drive had become more and more serious.

Drivers of tree demographic trade-offs in a temperate forest

Background: The demographic trade-offs(i.e. growth and survival) play important roles in forest dynamics and they are driven by multiple factors, including species’ inherent life-history strategies(such as shade-tolerance and mycorrhizal type), neighborhood interactions(such as conspecific negative density dependence, CNDD), and abiotic environment pressures. Although studies found that CNDD occurred in tropical and temperate forest,attempts to identify how the variations in CNDD control their impacts on growth and survival remain debate. In the present study, we conducted an extensive field survey, and analyzed demographic rates from 24 co-occurring temperate tree species, in order to test the importance of CNDD in shaping the growth-survival trade-offs.Results: Our study found that density dependence and environmental filtering were strong predictors for individual growth-survival trade-offs, while they showed variations across shade-intolerant and ectomycorrhizal species, as well as saplings and juveniles with more negative CNDD. Species growth showed positive relationship with mortality. And our results also support the fact that CNDD drives species growth-survival trade-offs at the community level with environmental stress.Conclusions: Our study indicates that biotic interactions such as density dependence and environment filtering played an important role in growth-survival trade-offs, and confirmed that the Janzen-Connell hypothesis in temperate forest was associated with species life-history strategies. In addition, shade-tolerance, mycorrhizal type and life-stage of forest species responded differently to CNDD, thus providing insights regarding different community assembly mechanisms and their interactions. Therefore, it is important to take species survival with growth and species life-history strategies into account when focusing on forest dynamics.

Genetic variation within and among range-wide populations of three ecotypes of the Japanese grenadier anchovy Coilia nasus with implications to its conservation and management

Studies of range-wide populations can contribute to the comprehension of the relative roles of historical events and contemporary factors that influence genetic variation within and among populations.Japanese grenadier anchovy,Coilia nasus,is a commercially important fish,which widely distributes in the Changjiang River,the coasts of China and Korea,and the Ariake Sea of Japan.This species exhibits three life-history strategies(anadromous,landlocked and freshwater resident forms).Using two fragments of nuclear DNA,genetic variation within and among 18 populations across the rivers and coast of China and Ariake Sea of Japan was examined.Patterns of genetic diversity and divergence among populations varied widely across C.nasus'range,and indicated the different effects of historical events and anthropogenic factors.Strong genetic divergence between freshwater resident populations and other populations suggested that historical geographical factors greatly influenced the genetic structure of C.nasus.Significant genetic differentiation observed among lakes in lower Changjiang River and Huaihe River might be probably influenced by hydraulic facilities.The population genetic structure among the three ecotypes revealed in the present study indicated an important role for environment variation,and the factors responsible for shaping C.nasus different life history strategies might also impact population structure.

Environmental management and sustainable development in forested mountain areas of northeast China

This paper studied the sustainable development through a reasonable management of the social, economic and natural environment in a forested mountain area of northeast China. In order to show the local people how to manage their most important forest resource, we analyzed the life-history process of the key species and the influencing factors that were associated with the forest regeneration and sustainability. Pollination and fertilization were mainly affected by weather conditions. Light intensity under the forest canopy was the key factor that controlled seedlings growth and saplings survival. Periodic seeds setting caused the fluctuations of rodents and other related animals in the food chain. Squirrels played a very important role in the forest regeneration, theses animals were the absolutely indispensable components of the forest ecosystem. How to understand the co-evolutionary relationships among species in the forest ecosystems was very important for the conservation of biodiversity and maintenance of ecosystem itegrity. In conservation of the natural resources, we studied the social and economic environment of the forested mountain area. It is very hard to effectively protect the forest resources and maintain the normal life of the local people under the regime of the “unified administration and enterprise system”. Reforms are needed both in administrative institutions and in enterprise management. In the end, this paper proposed that we should not only protect the trees, the related animals, the ecological habitats, and the whole forest ecosystems, but also consider the human activities and their basic requirements so as to realize a sustainable development in the forested mountain areas.

Habitat structure directly affects aggression in convict cichlids Archocentrus nigrofasciatus

Aggressive behavior can be an important factor in determining how animals use and divide space and resources. Previous studies have shown that aggression in fishes can be influenced by a variety of factors, including water temperature and resource levels. In this study, we tested if the amount of habitat structure in the environment affected aggression levels in female convict cichlids Archocentrus nigrofasciatus. We performed a laboratory experiment in which we placed female convict cichlids into an aquarium with low or high amounts of habitat structure and monitored the dominant female＇s behavior toward the subordinate female. Aggressive behavior in convict cichlids primarily consists of chases and bites. We found that the total time the dominant female spent chasing the subordinate female was greater when there was a low amount of habitat structure as compared to when there was a high amount of habitat structure. We also found that both the average duration of a chasing bout and the number of bites directed at the subordinate fish increased when there was a low amount of structure, but the number of chases did not. These results indicate that increased habitat structural complexity decreases aggressive behavior in convict cichlids [Current Zoology 56 （1）： 52-56, 2010].

Redox physiology in animal function:The struggle of living in an oxidant environment

A strong focus of ecological research for several decades has been to understand the factors underlying the variation in animal life-histories. In recent times, ecological studies have begun to show that oxidative stress may represent another important modulator of competitive trade-offs among fitness traits or of positively integrated patterns of traits. Therefore, incorporating mechanisms underlying oxidative physiology into evolutionary ecology has the potential to help understand variation in life-history strategies. In this review, I provide a general overview of oxidative stress physiology, and subsequently focus on topics that have been neglected in previous ecological reviews on oxidative stress. Specifically, I introduce and discuss the adaptations that animals have evolved to cope with oxidative stress; the environmental stressors that can generate changes in oxidative balance; the role of reactive species in transduction of environmental stimuli and cell signaling; and the range of hormetic responses to oxidative stress [Current Zoology 56 （6）： 687-702, 2010].

The transcriptomic signature of responses to larval crowding in Drosophila melanogaster

Intraspecific competition at the larval stage is an important ecological factor affecting life-history,adaptation and evolutionary trajectory in holometabolous insects.However,the molecular pathways underpinning these ecological processes are poorly characterized.We reared Drosophila melanogaster at three egg densities(5,60,and 300 eggs/mL)and sequenced the transcriptomes of pooled third-instar larvae.We also examined emergence time,egg-to-adult viability,adult mass,and adult sex-ratio at each density.Medium crowding had minor detrimental effects on adult phenotypes compared to low density and yielded 24 differentially expressed genes(DEGs),including several chitinase enzymes.In contrast,high crowding had substantial detrimental effects on adult phenotypes and yielded 2107 DEGs.Among these,upregulated gene sets were enriched in sugar,steroid and amino acid metabolism as well as DNA replication pathways,whereas downregulated gene sets were enriched in ABC transporters,taurine,Toll/Imd signaling,and P450 xenobiotics metabolism pathways.Overall,our findings show that larval crowding has a large consistent effect on several molecular pathways(i.e.,core responses)with few pathways displaying density-specific regulation(i.e.,idiosyncratic responses).This provides important insights into how holometabolous insects respond to intraspecific competition during development.

Reproductive biology of Gazella arabica: Predictors of offspring weight and short- and long-term offspring survival

Reproductive traits are central to organismal fitness,and so the factors influencing patterns of reproduction and offspring survival are at the heart of biology.Making use of breeding data collected over 16 years at the King Khalid Wildlife Research Centre in Saudi Arabia,we investigated the reproductive biology of Arabian gazelles Gazella arabica.Offspring survival was mainly a function of birth weight,with heavier offspring having higher survival rates than lighter offspring.However,while sons were heavier than daughters,daughters had higher survival rates.We could not find evidence that giving birth to sons negatively impacts offspring weight in the following year.We uncovered large narrow-sense heritability(h2)in offspring weight at birth,while maternal effects(m2)on birth weight were of lesser importance.However,maternal effects on offspring survival were strong until weaning age,while paternal effects dominated survival to sexual maturity and first reproduction.We propose that variation in maternal postnatal care might overshadow the effects of maternal inheritance of birth weights,while the overall strong heritability of weight at birth and the paternal effects on survival llustrates strong variance in sire fitness based on genetic quality,suggesting a role for sexual selectionbyfemalemate choiceinwildpopulations.

Safety is increasingly important in cobweb spiders based on life history

Detritus-based,bell-shaped cobwebs are an ideal model to research the plasticity of web architecture due to clearly separate defense and foraging components.We performed a thoroughfield investigation on the web architectures of Campanicola campanulata to research its cobweb architecture variation during the growth process and analyzed the energy trade-offs between foraging and defense at different developmental stages.The results indicated that as female C.campanulata grew,they dedicated more energy to defense and less energy to foraging,while males dedicated less energy to both defense and foraging through the growth period.We hypothesize that cobweb spiders dedicate an increasing amount of energy to safety based on evidence obtained from their life-history.Meanwhile,we present a new model to investigate web architecture variation and provide a new framework to quantify the energy allocation between foraging and predator defense for web-building spiders.

Fish embryo and juvenile size under hypoxia in the mouth- brooding African cichlid Pseudocrenilabrus multicolor

We used a field survey and a laboratory rearing experiment to （a） examine response （size and survival） to life-long hypoxia in offspring of the African maternal mouth-brooding cichlid Pseudocrenilabrus multicolor victoriae （Seegers） and （b） explore the degree to which developmental response can be environmentaUy-induced. Embryo size metrics were quantified in 9 field populations across a range of dissolved oxygen （DO） concentrations. In the laboratory, first generation （F1） broods of low-DO origin were reared under high or low DO. Brooding period was quantified for the mothers; and egg size, egg metabolic rate and juvenile size-at-release were quantified in their （F2） offspring. The F2 offspring were split and grown for 3 months post-release under high or low DO, and juvenile size and survival were quantified. In the field survey, across stages, embryos from low-DO field populations were shorter and weighed less than embryos from high-DO populations. In the laboratory experi- ment, F2 eggs and juveniles-at-release from mother＇s mouth did not differ in mass, length, survival regardless of development DO environment. However, juveniles diverged in size after leaving mother＇s mouth, exhibiting smaller size when grown under low DO. Size differences in embryo size across field populations and divergence in embryo size after release from the mother＇s mouth support predictions for smaller body size under hypoxia. There was no evidence for negative effects on survival of juveniles after 3 months. Brooding period was 16% shorter in females reared under low DO suggesting that hypoxia may accelerate embryo de- velopment. This work provides insights into how bearer fishes respond to hypoxic stress relative to fishes with no post-spawning parental care; a shorter brooding interval and smaller body size may provide an optimal solution to parent and embryo survival under hypoxia in brooding fishes [Current Zoology 58 （3）： 401-412, 2012].

Reproductive traits of the gray ratsnake Ptyas korros from three geographically distinct populations

Abstract We collected gravid gray rat snakes Ptyas korros from three geographically distinct populations in China, Chenzhou （CZ）, Jiangshan （JS） and Dinghai （DH）, to study geographical variation in female reproductive traits. Egg-laying dates differed among the three populations such that at the most northern latitude egg-laying was latest, and earliest at the most southern latitutde. Clutch size, clutch mass, egg mass, egg shape, within clutch variability in egg sizes and relative clutch mass differed among the three populations, whereas post-oviposition body mass did not. Except for egg-laying date, none of the traits examined varied in a geographically continuous trend. CZ and DH females, although separated by a distance of approximately 1100 km as the crow flies, were similar in nearly all traits examined. JS females were distinguished from CZ and DH females by their higher fecundity （clutch size）, greater reproductive output （clutch mass） and more rounded eggs. Our data do not validate the prediction that larger offspring should be produced in colder localities. The absence of an egg size-number trade-off in each of the three populations presumably suggests that P. korros is among species where eggs are well optimized for size within a population.

Species traits and shoot-root biomass allocation in 20 dry-grassland species

Aims A plant has a limited amount of resources at any time and it allo-cates them to different structures.in spite of the large number of previous studies on allocation patterns within single species,knowledge of general patterns in species allocation is still very limited.This is because each study was done in different condi-tions using different methodology,making generalization dif-ficult.We investigate intraspecific above-versus below-ground biomass allocation among individuals across a spectrum of dry-grassland plant species at two different developmental stages and ask whether allocation is age-and species specific,and whether differences among species can be explained by their life-history traits and phylogeny.Methods We collected data on above-and below-ground biomass of seedlings and adult plants of 20 species from a common garden experiment.We analysed data on shoot-root biomass allocation allometrically and studied the relationship between the allometric exponents(slopes on log-log scale),species life-history traits and phylogenetic distances.Important Findings We found isometric as well as allometric patterns of biomass alloca-tion in the studied species.Seedlings and adult individuals of more than half of the species differed in their above-versus below-ground biomass allometric exponents.Seedlings and adult individuals of the remaining species differed in their allometric coefficients(inter-cepts).Annual species generally allocated proportionally more to above-than below-ground biomass as seedlings than as adults,whereas perennial species showed the opposite pattern.Plant life-history traits,such as plant life span,age of first flowering,month in which the species begin flowering and specific leaf area were much more important in explaining differences in shoot-root allometry among species than were phylogenetic relationships.This suggests that allocation patterns vary greatly among closely related species but can be predicted based on species life-history traits.

How does male-male competition generate negative frequency-dependent selection and disruptive selection during speciation？

Natural selection has been shown to drive population differentiation and speciation. The role of sexual selection in this process is controversial; however, most of the work has centered on mate choice while the role of male-male competition in speciation is relatively understudied. Here, we outline how male-male competition can be a source of diversifying selection on male competitive phenotypes, and how this can contribute to the evolution of reproductive isolation. We highlight how negative frequency-dependent selection （advantage of rare phenotype arising from stronger male-male competition between similar male phenotypes compared with dissimilar male pheno- types） and disruptive selection （advantage of extreme phenotypes） drives the evolution of diversity in competitive traits such as weapon size, nuptial coloration, or aggressiveness. We underscore that male-male competition interacts with other life-history functions and that variable male com- petitive phenotypes may represent alternative adaptive options. In addition to competition for mates, aggressive interference competition for ecological resources can exert selection on compet- itor signals. We call for a better integration of male-male competition with ecological interference competition since both can influence the process of speciation via comparable but distinct mecha- nisms. Altogether, we present a more comprehensive framework for studying the role of male-male competition in speciation, and emphasize the need for better integration of insights gained from other fields studying the evolutionary, behavioral, and physiological consequences of agonistic interactions.