Density effects on life-history traits of an island lizard population

Long-term monitoring of life-history traits and the effects of density upon them were studied in an island population of the lizardEumeces okadae. Although life-history traits such as clutch size, egg size and the proportion of mature reproductive females varied little over 7 years in the intact population, manipulation of density to simulate decreased population density enhanced juvenile growth rate, age at first reproduction, frequency of female reproduction and size-specific clutch mass. In particular, the proportion of mature females reproducing annually increased almost 10 times from 5.6% to 53.8% after the removal of some lizards. However, body size at first reproduction and egg size were almost identical under both high and low density conditions. This study suggests that there were strong density-dependent effects on several life-history traits and thatE. okadae attained a density close to the carrying capacity of the environment.     

中国鸟类的生活史和生态学特征数据集

中国现有1,445种鸟类, 是世界上鸟类物种数最多的国家之一。物种特征反映了生物有机体的功能和适合度, 在生态学、进化生物学和保护生物学研究中具有重要作用。但是, 目前还没有关于我国鸟类生活史、生态学和地理分布等物种特征的完整数据库。通过系统查阅文献和各种数据资料, 本文共收集整理出了中国1,445种鸟类17个功能特征数据: 体重、体长、嘴峰长、翅长、尾长、跗蹠长、食性、窝卵数、卵大小、卵体积、巢址、巢的类型、集群状况、迁徙状况、是否特有种、地理分布范围和分布省份等。在这些特征中, 除迁徙状况、是否特有种、地理分布范围和分布省份外, 其余特征数据均存在不同程度的缺失, 数据的完整度为60.83%‒100%。本数据库是目前关于中国鸟类最新和最全的物种特征数据库, 期望能为我国鸟类生态学、进化生物学、生物地理学、保护生物学等研究提供支持。     

中国两栖类生活史和生态学特征数据集

截至2021年底, 中国共记载591种两栖类(不包括外来入侵种), 是世界上两栖类物种数最多的国家之一。物种特征影响和决定了物种在环境中的生存能力, 在进化生物学、生态学和保护生物学研究中具有重要作用。目前, 中国两栖类在线数据库(https://www.amphibiachina.org)已经整理了我国两栖类的形态特征、生物学信息和地理分布等部分物种特征, 但仍缺乏一个完整的、可自由检索的数据集。通过系统查阅文献和数据检索, 本文收集整理了中国全部591种本土两栖类的22个特征数据, 包括物种发现时间(最早发现和描述新物种文章的发表时间)、模式产地、中国受威胁等级、全球受威胁等级、致危因子、是否中国特有种、是否岛屿特有种、雄性体长、雌性体长、窝卵数、卵径、产卵地点、幼体主要生境、成体微生境、活动模式、生殖周期、繁殖时间、是否有亲本照顾、受精方式、海拔范围、分布地区、分布省份数。除了物种发现时间、是否岛屿特有种、分布地区、分布省份数外, 其余特征数据都有不同程度的缺失, 数据完整度为27.92%-100%, 平均完整度为71.72%, 标准差为24%。本数据集是目前我国两栖类最新和最全的物种特征数据库, 希望可以为我国两栖类生态学、保护生物学、生物地理学等研究提供数据支持。     

中国蜥蜴类生活史和生态学特征数据集

截至2020年底, 中国共有226种蜥蜴类(不包括外来入侵种), 是世界上蜥蜴类多样性最丰富的国家之一。系统整理中国现有蜥蜴类的特征数据在物种起源与进化、形成与灭绝、保护生物学等研究中具有重要意义。但是, 目前还没有关于我国蜥蜴类生活史、生态学和地理分布等物种特征的完整数据库。本文通过系统查阅文献和数据资料, 共收集整理了中国现有226种本土蜥蜴类19个特征数据: 描述年份、中国受威胁等级、全球受威胁等级、是否中国特有种、是否岛屿特有种、平均体长、平均体重、食性、窝卵数、繁殖模式、四肢发育、活动时间、栖息生境、栖息地类型、栖息地宽度、海拔分布范围、地理分布范围、动物地理界和分布省份。在上述特征中, 除了四肢发育、描述年份、是否中国特有种、是否岛屿特有种和分布省份外, 其余特征数据均存在不同程度的缺失, 数据完整度为47.14%-100%。本数据集是目前关于中国蜥蜴类最新和最全的物种特征数据库, 可为我国蜥蜴类生态学、进化生物学、生物地理学和保护生物学等研究领域提供数据支持。     

Adaptive inter-population differences in blue tit life-history traits on Corsica

Few studies of natural populations have investigated how phenotypic variation across populations relates to key factors in the environment and landscape structure. In the blue tits of southern France, inter-population differences in reproductive life-history traits (e.g. laying date and clutch size) are small, whatever the timing of maximum caterpillar availability, a key factor for offspring survival in tits. These small differences are attributed to gene flow between local populations occupying different habitat types. In contrast, in blue tits on the island of Corsica, we noted large differences in reproductive life-history traits between two populations, where each population is synchronized with the peak-date of caterpillar abundance. These occur over a short geographical distance (25km). Considering our study within a framework of long-term population studies in tits, our results support the hypothesis that different blue tit populations on Corsica show adaptive differences in life-history traits, and suggest that landscape structure at a small spatial scale can have profound effects on adaptive between-population differentiation in life-history traits that are closely linked with fitness.     

中国哺乳动物形态、生活史和生态学特征数据集

物种特征是生物对生存环境适应和响应的表现, 反映了物种的生态位、适合度和生态功能。特征数据库的建立和共享是研究生物多样性维持与丧失、物种进化与适应、生态过程与生态系统功能、物种对气候变化和人类干扰响应、种内与种间关系等的基础。中国是世界哺乳动物物种数最多的国家之一, 然而目前中国还没有包含哺乳动物形态、生活史、生态学和地理分布等物种特征的数据库。我们系统查阅了文献和各种数据资料, 共收集整理出中国有分布记录的754种哺乳动物(包括近些年野外绝灭种、分布存疑种)的体重、脑容量、体长、尾长、前臂长(翼手目)、后足长、耳长、性成熟时间、妊娠期、窝崽数、年窝数、世代长度、食性、活动模式、是否特有种、濒危等级、海拔范围、栖息地类型、栖息地宽度、动物地理界、生物群系、分布型、动物地理区划和分布省份或水域等24个生态特征数据。在这些特征中, 除了分布省份或水域及是否特有种外, 其余特征数据均存在不同程度的缺失, 数据的完整度为30%‒100%。本数据库收录的哺乳动物种数为目前中国哺乳动物种数的上限, 为中国哺乳动物研究提供了基础数据, 推进中国哺乳动物多样性信息共享和深度挖掘。     

Impact of inter‐ and intra‐specific competition among larvae on larval,adult, and life‐table traits of Aedes aegypti and Aedes albopictus females

1. Few studies have taken a comprehensive approach of measuring the impact of inter‐ and intra‐specific larval competition on adult mosquito traits. In this study, the impact of competition among Aedes aegypti (L.) and A. albopictus (Skuse) was quantified over the entire life of a cohort. 2. Competitive treatments affected hatch‐to‐adult survivorship and the development time to adulthood of females for both species but affected the median wing length of females only for A. albopictus. Competitive treatments had no significant effect on the median adult female longevity nor were there any effects on other individual traits related to blood feeding and reproductive success. 3. Analysis of life table traits revealed no effect of competitive treatment on the net reproductive rate (R₀) but there were significant effects on the cohort generation time (T_c) and the cohort rate of increase (r) for both species. 4. Inter‐ and intra‐specific competition among Aedes larvae may produce individual and population‐level effects that are manifest in adults; however, benign conditions may enable resulting adults to compensate for some impacts of competition, particularly those affecting blood‐feeding success, fecundity, and the net reproductive rate, R₀. The effect of competition, therefore, affects primarily larva‐to‐adult survivorship and the larval development time, which in turn impacts the cohort generation time, T_c, and ultimately the cohort rate of increase, r. 5. The lack of effects of the larval rearing environment on adult longevity suggests that effects on vectorial capacity owing to longevity may be limited if adults have easy access to sugar and bloodmeals.     

Influence of a bimodal emergence strategy of a Dipteran host on life-history traits of its main parasitoids

Abstract. 1. Among a great diversity of other strategies, insects have evolved polymodal emergence patterns that can increase survival in the face of annual variations in environmental conditions. Delia radicum L. (Diptera: Anthomyiidae) is a polyvoltine pest that attacks several cultivated cruciferous species. At the time of emergence, most populations show a polymodal emergence of type A (i.e. all individuals that enter diapause in the same year terminate diapause the following growing season, and exhibit a bimodal emergence curve). This results in the occurrence of two sympatric phenotypes, early and late, which differ by the timing of adult emergence in both diapausing and non‐diapausing generations. 2. In Brittany, D. radicum pupae can be heavily parasitised by three parasitoids, Aleochara bilineata Gyll. (Coleoptera: Staphylinidae), Aleochara bipustulata L., and Trybliographa rapae (Hymenoptera: Eucoilidae). As in all parasitoids species, the successful development of both Aleochara species and T. rapae larvae depends mainly on the amount and quality of the food provided by the host. 3. The relationship between early and late host phenotype and (i) the parasitism efficiency, (ii) emergence patterns, and (iii) host selection behaviour were investigated for the three parasitoid species. 4. Depending on parasitoid species and their different parasitism and development mode, the results reveal that host phenotype can influence (i) survival and development time in T. rapae, and (ii) survival in Aleochara species. Aleochara larvae did not appear to discriminate between early and late host pupae on the basis of phenotype, but rather selected them according to their developmental stage. Furthermore, it was discovered that the same phenological strategy occurred in T. rapae and in D. radicum. However, for D. radicum the results indicate that such a strategy has a cost as the longer development time of late host pupae results in a longer period of time favourable for parasitism.     

Effects of intraspecific larval competition on adult longevity in the mosquitoes Aedes aegypti and Aedes albopictus

Abstract Larval competition is common in container‐breeding mosquitoes. The impact of competition on larval growth has been thoroughly examined and findings that larval competition can lead to density‐dependent effects on adult body size have been documented. The effects of larval competition on adult longevity have been less well explored. The effects of intraspecific larval densities on the longevity of adults maintained under relatively harsh environmental conditions were tested in the laboratory by measuring the longevity of adult Aedes aegypti (L.) and Aedes albopictus (Skuse) (Diptera: Culicidae) that had been reared under a range of larval densities and subsequently maintained in high‐ or low‐humidity regimes (85% or 35% relative humidity [RH], respectively) as adults. We found significant negative effects of competition on adult longevity in Ae. aegypti, but not in Ae. albopictus. Multivariate analysis of variance suggested that the negative effect of the larval environment on the longevity of Ae. aegypti adults was most strongly associated with increased development time and decreased wing length as adults. Understanding how larval competition affects adult longevity under a range of environmental conditions is important in establishing the relationship between models of mosquito population regulation and epidemiological models of vector‐borne disease transmission.     

The challenge of invasive mosquito vectors in the U.K. during 2016–2018: a summary of the surveillance and control of Aedes albopictus

Mosquito‐borne diseases resulting from the expansion of two key vectors, Aedes aegypti and Aedes albopictus (Diptera: Culicidae), continue to challenge whole regions and continents around the globe. In recent years there have been human cases of disease associated with Chikungunya, dengue and Zika viruses. In Europe, the expansion of Ae. albopictus has resulted in local transmission of Chikungunya and dengue viruses. This paper considers the risk that Ae. aegypti and Ae. albopictus represent for the U.K. and details the results of mosquito surveillance activities. Surveillance was conducted at 34 points of entry, 12 sites serving vehicular traffic and two sites of used tyre importers. The most common native mosquito recorded was Culex pipiens s.l. (Diptera: Culicidae). The invasive mosquito Ae. albopictus was detected on three occasions in southern England (September 2016, July 2017 and July 2018) and subsequent control strategies were conducted. These latest surveillance results demonstrate ongoing incursions of Ae. albopictus into the U.K. via ground vehicular traffic, which can be expected to continue and increase as populations in nearby countries expand, particularly in France, which is the main source of ex‐continental traffic.     

Pollution by conspecifics as a component of intraspecific competition among Aedes aegypti larvae

Abstract.  1. The role of pollution by conspecifics in the costs associated with larval intraspecific competition was investigated for Aedes aegypti (Diptera: Culicidae).
2. The growth of larval A. aegypti mosquitoes reared in clean water and water in which another larva had previously grown was compared; this procedure eliminates interactions through food consumption between competitors and allows the effects of other processes to be expressed.
3. A cost of growing in polluted water was found: this cost was expressed as an increase in developmental time and a reduction of adult longevity when starved, starved adult dry weight, and wing length.
4. Contrary to previously reported results of an experiment allowing for competition for food, these costs were not expressed in a sex-specific manner and were independent of the sex of the polluter.
5. It was thus demonstrated that competition arises from both resource depletion and other effects that result in deterioration of the environment, with chemical pollution of the environment being the most likely cause.     

Large-scale intraspecific variation in life-history traits of European freshwater fish

Aims To test the magnitude and direction of the effects of large‐scale environmental factors (latitude and habitat type: lotic or lentic) on the intraspecific variations in multiple life‐history traits, across multiple European freshwater fish species. To test the relevance of defining species traits by quantifying the magnitude of interspecific vs. intraspecific variability in traits. Location Europe. Methods We obtained estimates of 11 fish traits from published sources for 1089 populations of 25 European freshwater fish species. Traits were: longevity, maximal length, growth rate, asymptotic length, mortality rate, age and length at maturation, fecundity, egg size, gonadosomatic index, and length of breeding season. We described population habitats by latitude and habitat type (lotic or lentic), when available. For each species we tested the combined effect of latitude and habitat type on the intraspecific variation of each trait using analysis of covariance (ancova ). We compared the intraspecific variation in traits with the variation between species using an analysis of variance (anova ) for each trait, all species pooled. Results We found a consistent effect in direction of latitude on six traits, but we showed that this effect is not always significant across species. Higher‐latitude populations often grew more slowly, matured later, had a longer life span and a higher maximal and asymptotic length, and allocated more energy to reproduction than populations at lower latitudes. By contrast, we noted only a slight effect of habitat type on the intraspecific variation in traits, except for Salmo trutta. All traits varied significantly between species. However, traits such as growth rate, mortality rate and length of breeding season varied more between populations than between species, whereas fecundity and traits associated with body length varied more between species. Main conclusions Latitude, in contrast to habitat type, is an important factor influencing several traits of geographically widely dispersed populations of multiple European freshwater fish species. Species traits that vary more between species than between populations are attractive variables for understanding and predicting the responses of stream fish communities to their environment.     

Seasonal life cycle and autogeny in the mosquitoAedes togoi in northern Kyushu,Japan, with experimental analysis of the effects of temperature,photoperiod and food on life-history traits

We studied seasonal changes in the larval population structure, adult size, and autogeny (egg production without a bloodmeal) of the mosquitoAedes togoi on the seacoast of northern Kyushu, Japan. The effects of temperature, photoperiod and food conditions on larval development, adult size and autogeny were studied in the laboratory.Aedes togoi overwintered in both the egg and larval stages and was multivoltine. Adult size was greater in spring and autumn and smaller in summer. Autogeny occurred in spring and autumn but not in summer. Autogenous females were larger than anautogenous females, and larger autogenous females produced more eggs. Laboratory experiments showed that autogeny was promoted under low temperature and short-day conditions which corresponded with spring/autumn conditions in the field. Experimental food limitation in the larval stage greatly reduced adult size and autogenous egg production. In the field, large inter-pool variations in adult size and autogeny rate probably resulted from variations in nutrient and crowding conditions. Seasonal autogeny ofAedes togoi was discussed in terms of life-history strategy under fluctuating environmental conditions where relative advantages of autogenous and anautogenous reproduction alternate seasonally.     

Lifetime selection on heritable life-history traits in a natural population of red squirrels

Abstract Despite their importance in evolutionary biology, heritability and the strength of natural selection have rarely been estimated in wild populations of iteroparous species or have usually been limited to one particular event during an organism's lifetime. Using an animal-model restricted maximum likelihood and phenotypic selection models, we estimated quantitative genetic parameters and the strength of lifetime selection on parturition date and litter size at birth in a natural population of North American red squirrels, Tamiasciurus hudsonicus. Litter size at birth and parturition date had low heritabilities ( h² = 0.15 and 0.16, respectively). We considered potential effects of temporal environmental covariances between phenotypes and fitness and of spatial environmental heterogeneity in estimates of selection. Selection favored early breeders and females that produced litter sizes close to the population average. Stabilizing selection on litter size at birth may occur because of a trade-off between number of offspring produced per litter and offspring survival or a trade-off between a female's fecundity and her future reproductive success and survival.     

Mosquitoes of Rarotonga,Cook Islands: A survey of breeding sites

Abstract

Two surveys of Rarotonga, Cook Islands (21°20^'S, 160°16^'W) were made to determine the mosquito fauna of the island, and to identify the habitats required for breeding by searching for larvae. The first survey was made during the “dry season” in May 2001, the second during the “wet season” in February 2002. The mosquito fauna comprised four species Culex (Culex) quinquefasciatus Say, Culex (Culex) annulirostris Skuse, Aedes (Stego‐myia) aegypti (Linnaeus) and Aedes (Stegomyia) polynesiensis Marks. Larvae of the Culex species were most often found in larger natural and artificial water bodies. The Aedes species bred in both natural and artificial containers of all sizes. Ae. polynesiensis was the most widespread species, using natural holes in all regions as well as artificial containers in the urban areas. Most larvae of Ae. aegypti were located in small artificial containers. The two Aedes species are the vectors of dengue fever on the island. Mosquito control during outbreaks should specifically target the artificial containers preferred by Aedes sp. for breeding habitats.     

A preliminary study on the effect of Cu,Pb and Zn contamination of soils on community structure and certain life-history traits of oribatids from urban areas

The effect of pollution of urban soils by traffic exhausts on oribatid mites was studied along a traffic gradient of the city of Thessaloniki. Although the population density of the main orbatid species appeared increased in polluted areas, the total orbatid numbers were reduced due to the reduction in species richness. The highest species diversity was recorded in moderately polluted areas. The morphometric characteristics as well as certain life-history traits did no correlate with the level of traffic influence. Nevertheless, these characteristics were considered important for the understanding of the pollution impact on life in soils. Moderate body size, sexual reproduction, increased reproductive effort and wide habitat preferences characterize species in urban sites. Scheloribates latipes and Tectocepheus sarekensis can be used as bioindicators for Pb and Zn pollution of soils, respectively.     

Responses to competition effects of two anuran tadpoles according to life-history traits

Experimental manipulations of the densities of two larval anurans, Pelodytes punctatus and Bufo bufo , showed that these species compete asymmetrically in semi-natural conditions. Growth, mass at metamorphosis, date of metamorphosis, and survival were used as measures of response to interspecific competition. A mechanistic approach was used to collect information on the behaviour of the two species in different conditions. The competitive superiority of Pelodytes at individual level was correlated with a larger body, faster growth rate, increased per capita competitive impact on conspecifics, and greater reduction in the availability of trophic and spatial resources. In the presence of Pelodytes, Bufo showed slower growth, smaller size at metamorphosis and reduced survival. In the interspecific treatments Bufo individuals modified their behaviour by increasing activity and use of the water column while Pelodytes did not change their foraging activity or space use in the aquaria. However, the presence of Bufo resulted in a reduced larval period and smaller size at metamorphosis. We hypothesise that the presence of Bufo act as a signal of environmental degradation and shorten the larval period of Pelodytes, a typical temporal pond breeder . The smaller Bufo tadpoles are potentially stronger competitors at population level because they use relatively large amounts of energy (greater densities and higher metabolic rates). Consequently, they use larger proportions of the shared resources than their larger competitor. A possible evolutionary response for larger tadpoles is the development of interference mechanisms or "escaping" from ephemeral ponds where mortality by drying represent a high risk.     

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 life-history 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.     

Physiological and biochemical response of Aedes aegypti tolerance to Bacillus thuringiensis

Bacillus thuringiensis subsp. israelensis (Bti) represents the only eco-friendly bio-degradable insecticide for mosquito-borne disease control. Our research aims to identify if mosquito detoxification enzymes play an important role in Bti tolerance mechanisms in the dengue vector, Aedes aegypti. Several enzymes, such as amylase, cytochromes P450, Na⁺/K⁺-ATPase, acetylcholinesterase, protease and glutathione S-transferase (GST) were analysed and level of activity determined in Ae. aegypti larvae after Bti treatment. Bti exposure significantly increased the level of amylase (183.2%) as well as the activity of cytochromes P450 (177.5%), and Na⁺/K⁺-ATPase (142.9%). On the other hand, there was a decrease of 8.6% and 11.4% in acetylcholinesterase and GST activity, and no significant effect in the total level of protease activity. We suggest that the variation in amylase, cytochromes P450, Na⁺/K⁺-ATPase, acetylcholinesterase, protease and GST activity may be associated with the Bti insecticidal mechanism. This study provides the basis of detoxifying enzymes in Bti tolerance.