温度升高对昆虫发生发展的影响

全世界地表平均温度在上个世纪增加了0.74℃,并且在未来还会持续增加。在过去的20年,气候变暖对生物系统的影响吸引了大量的研究。本文综述了由温度升高为主要驱动因子的气候变化对昆虫适合度的影响,主要从昆虫越冬存活率、化性(世代数)、扩散迁移、发生分布、物候关系5个方面阐述气候变暖对昆虫发生发展的作用,认为未来应长期进行昆虫种群动态监测预警,更关注气候变暖下植物-害虫-天敌互作关系的研究。     

Female common lizards (Lacerta vivipara) do not adjust their sex-biased investment in relation to the adult sex ratio

Sex allocation theory predicts that facultative maternal investment in the rare sex should be favoured by natural selection when breeders experience predictable variation in adult sex ratios (ASRs). We found significant spatial and predictable interannual changes in local ASRs within a natural population of the common lizard where the mean ASR is female-biased, thus validating the key assumptions of adaptive sex ratio models. We tested for facultative maternal investment in the rare sex during and after an experimental perturbation of the ASR by creating populations with female-biased or male-biased ASR. Mothers did not adjust their clutch sex ratio during or after the ASR perturbation, but produced sons with a higher body condition in male-biased populations. However, this differential sex allocation did not result in growth or survival differences in offspring. Our results thus contradict the predictions of adaptive models and challenge the idea that facultative investment in the rare sex might be a mechanism regulating the population sex ratio.     

Linking environmental warming to the fitness of the invasive clam Corbicula fluminea

Climate warming is discussed as a factor that can favour the success of invasive species. In the present study, we analysed potential fitness gains of moderate warming (3 °C above field temperature) on the invasive clam Corbicula fluminea during summer and winter. The experiments were conducted under seminatural conditions in a bypass-system of a large river (Rhine, Germany). We showed that warming in late summer results in a significant decrease in the clams' growth rates (body mass and shell length increase) and an increase in mortality rate. The addition of planktonic food dampens the negative effect of warming on the growth rates. This suggests that the reason for the negative growth effect of temperature increase in late summer is a negative energetic balance caused by an enhanced metabolic rate at limited food levels. Warming during early summer revealed contrasting effects with respect of body mass (no warming effect) and shell length (increased shell growth with warming). This differential control of both parameters further enhances the loss of the relative (size-specific) body mass with warming. In contrast, warming in winter had a consistently positive effect on the clams' growth rate as demonstrated in two independent experiments. Furthermore, the reproduction success (as measured by the average number of larvae per clam) during the main breeding period (April) was strongly enhanced by experimental warming during winter, i.e. by eight times during the relatively cold winter 2005/2006 and by 2.6 times during the relatively warm winter 2007/2008. This strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere. However, warm summer events might counteract the positive winter warming effect, which could balance out the fitness gains.     

Environmental warming increases invasion potential of alpine lake communities by imported species

Global warming increasingly pressures species to show adaptive migratory responses. We hypothesized that warming increases invasion of alpine lakes by low-elevation montane zooplankton by suppressing native competitors and predators. This hypothesis was tested by conducting a two-factor experiment, consisting of a warming treatment (13 vs. 20°C) crossed with three invasion levels (alpine only, alpine+montane, montane only), in growth chambers over a 28-day period. Warming significantly reduced total consumer biomass owing to the decline of large alpine species, resulting in greater autotrophic abundance. Significant temperature-invasion interactions occurred as warming suppressed alpine zooplankton, while stimulating certain imported species. Herbivorous invaders suppressed functionally similar alpine species while larger native omnivores reduced invasion by smaller taxa. Warming did not affect total invader biomass because imported species thrived under ambient and warmed alpine conditions. Our findings suggest that the adaptability of remote alpine lake communities to global warming is limited by species dispersal from lower valleys, or possibly nearby warmer alpine ponds.     

Stress and body condition as prenatal and postnatal determinants of dispersal in the common lizard (Lacerta vivipara)

Dispersal is a complex phenomenon affected by multiple factors. Among the factors that influence dispersal in the common lizard (Lacerta vivipara), poor maternal body condition and stress are known to decrease dispersal propensity of juveniles. But the effect of individual factors on dispersal could change when several of them act concurrently or at different developmental stages. Prenatal factors can affect clutch and/or juvenile characteristics that later affect dispersal. Postnatal influences are mainly exerted on juvenile dispersal behavior. We investigated the role of body condition and stress on dispersal at a prenatal and a postnatal stage. Stress was mimicked by experimentally increasing corticosterone levels in pregnant females and recently born juveniles. We considered (1). the influence of maternal body condition and prenatal corticosterone treatment on clutch, juvenile characteristics and on dispersal behavior and (2). the influence of juvenile body condition and postnatal corticosterone treatment on juvenile dispersal behavior. There was an interaction between maternal condition and prenatal corticosterone treatment on juvenile dispersal. Dispersal decreased with maternal corticosterone increase only in juveniles from the more corpulent females, while it increased with juvenile body condition. Good maternal body condition affected clutch and juvenile characteristics favoring dispersal, while elevation of corticosterone level (stress) exerted the opposite effect. Juvenile body condition favored dispersal, while there was no effect of postnatal corticosterone treatment on juvenile dispersal propensity.     

Heterozygosity and components of fitness in a strain of rainbow trout

We examined the relationship between multilocus heterozygosity and several components of fitness in the Arlee strain of rainbow trout (Salmo gairdneri) . There is a significant negative association between multilocus heterozygosity and standardized rate of oxygen consumption (VO₂) in 168 fish produced from a pooled mating between 55 females and 60 males. Fish which are more heterozygous also tend to be longer, heavier and have a significantly greater condition factor than fish which are less heterozygous. However, no relationship is evident between VO₂, weight, length, condition factor and multilocus heterozygosity within two full-sib families. These results indicate that the larger size of more heterozygous fish may partially be attributed to the increased metabolic efficiency in heterozygotes compared to homozygotes and that these differences may only be detectable at the population level. More heterozygous females of the same age also have larger eggs. Energy conversion may be more efficient in more heterozygous females resulting in the production of larger eggs. The prediction that fish with faster developmental rates are metabolically more efficient and, therefore, have lower VO₂ was also tested. Earlier hatching fish from five families do not have significantly lower VO₂ than their later hatching full-sibs.     

Low genetic variation reduces cross-compatibility and offspring fitness in populations of a narrow endemic plant with a self-incompatibility system

Genetic variation was shown earlier to bereduced in smaller populations of the narrowendemic putatively self-incompatible Cochlearia bavarica. To test whether thisnegatively affects plant fitness by reducedavailability of compatible mates and byinbreeding depression, we studied effects ofpopulation size and pollination treatments oncross-compatibility and offspring fitness in 16isolated populations of this plant. After openpollination, compatibility of crosses (i.e.,whether at least one fruit developed per markedflower), fruit set of compatible crosses, andcumulative fitness (number of plants permaternal ovule) after 14 months in a commongarden were lower for plants from smallerpopulations. Throughout the study, cumulativefitness was lower after hand pollination withpollen of one donor than after open pollination(finally 73.4% lower), suggesting that severalpollen donors or single pollen donors of higherquality are involved in open pollination.Moreover, cumulative fitness was lower afterhand selfing than after hand outcrossing(finally 69.4% lower), indicating bothinbreeding depression and reduced compatibilityafter selfing. High self-compatibility(40.6%), dry stigmas, and differences in thecompatibility of 11 of 33 experimentalreciprocal crosses between plant pairsconfirmed that C. bavarica has asporophytic self-incompatibility system, as iscommon in the Brassicaceae. Our studydemonstrates, that plants in smallerpopulations of species with a sporophyticself-incompatibility system can experiencetwofold fitness reductions associated withreduced genetic variability, i.e., twofoldgenetic Allee effects: via reducedcross-compatibility and via reduced offspringfitness.     

The importance of phylogenetic scale in tests of Bergmann's and Rapoport's rules: lessons from a clade of South American lizards

We tested for the occurrence of Bergmann's rule, the pattern of increasing body size with latitude, and Rapoport's rule, the positive relationship between geographical range size and latitude, in 34 lineages of Liolaemus lizards that occupy arid regions of the Andean foothills. We tested the climatic-variability hypothesis (CVH) by examining the relationship between thermal tolerance breadth and distribution. Each of these analyses was performed varying the level of phylogenetic inclusiveness. Bergmann's rule and the CVH were supported, but Rapoport's rule was not. More variance in the data for Bergmann's rule and the CVH was explained using species belonging to the L. boulengeri series rather than all species, and inclusion of multiple outgroups tended to obscure these macroecological patterns. Evidence for Bergmann's rule and the predicted patterns from the CVH remained after application of phylogenetic comparative methods, indicating a greater role of ecological processes rather than phylogeny in shaping the current species distributions of these lizards.     

Effects of B chromosomes and supernumerary segments on morphometric traits and adult fitness components in the grasshopper, Dichroplus elongatus (Acrididae)

The South American species, Dichroplus elongatus, is polymorphic for B chromosomes and supernumerary segments in chromosome pairs M6 (SS6), S9 (SS9) and S10 (SS10). Both forms of supernumerary heterochromatin shape chiasma frequency and distribution and B chromosomes also affect male fertility. Here, we analysed the effects of these polymorphisms on morphometric traits (total, 3rd femur, 3rd tibia, thorax and tegmen lengths) and several adult fitness components, including male and female mating success, and female reproductive potential. B chromosomes tend to decrease, and SS6 segments to increase the body size of carriers. The analysis of reproductive potential suggested that B chromosome carrying females have higher numbers of embryos per clutch and ovarioles per ovary. The uni- and multivariate analysis of mating success revealed that sexual selection favours larger individuals of both sexes and males with standard karyotype. B chromosomes may have accumulation mechanisms, which involve preferential transmission of B chromosomes to germ cells or functional gametes. The maintenance of Bs might be explained by interactions among accumulation mechanisms and trade-offs between detrimental and favourable effects on different fitness components.     

Warming alters the size spectrum and shifts the distribution of biomass in freshwater ecosystems

Organism size is one of the key determinants of community structure, and its relationship with abundance can describe how biomass is partitioned among the biota within an ecosystem. An outdoor freshwater mesocosm experiment was used to determine how warming of～4 °C would affect the size, biomass and taxonomic structure of planktonic communities. Warming increased the steepness of the community size spectrum by increasing the prevalence of small organisms, primarily within the phytoplankton assemblage and it also reduced the mean and maximum size of phytoplankton by approximately one order of magnitude. The observed shifts in phytoplankton size structure were reflected in changes in phytoplankton community composition, though zooplankton taxonomic composition was unaffected by warming. Furthermore, warming reduced community biomass and total phytoplankton biomass, although zooplankton biomass was unaffected. This resulted in an increase in the zooplankton to phytoplankton biomass ratio in the warmed mesocosms, which could be explained by faster turnover within the phytoplankton assemblages. Overall, warming shifted the distribution of phytoplankton size towards smaller individuals with rapid turnover and low standing biomass, resulting in a reorganization of the biomass structure of the food webs. These results indicate future environmental warming may have profound effects on the structure and functioning of aquatic communities and ecosystems.     

Reproduction and resource utilization of the ambrosia beetle,Xylosandrus mutilatus, in field and experimental populations

The reproduction process of the ambrosia beetle,Xylosandrus mutilatus (Blandford) (Coleoptera: Scolytidae), was examined by successive censuses of field populations and by artificial rearing experiments. The reproductive strategy is discussed in relation to utilization of fungal resources, the amount of which was evaluated by total gallery length (main gallery and side galleries) for the field populations or fungal area in the laboratory. Fecundity of mother adults increased with the expansion of gallery systems for cultivating their associated fungi. The number of offspring also depended on the amount of fungal resource, whereas the variation of female body size within a brood was not affected by the fungal amount. The body size apparently declined with delay in larval feeding period expressed as the order of pupation and eclosion in the field and with decreasing fungal area per larva in the laboratory. These results suggested that the combination of resource-dependent oviposition by a mother beetle and dominant resource utilization by earlier-hatched individuals in a brood can contribute to the efficient production of larger females when resources are limited.     

Natural selection on body size is mediated by multiple interacting factors: a comparison of beetle populations varying naturally and experimentally in body size

Body size varies considerably among species and among populations within species, exhibiting many repeatable patterns. However, which sources of selection generate geographic patterns, and which components of fitness mediate evolution of body size, are not well understood. For many animals, resource quality and intraspecific competition may mediate selection on body size producing large-scale geographic patterns. In two sequential experiments, we examine how variation in larval competition and resource quality (seed size) affects the fitness consequences of variation in body size in a scramble-competing seed-feeding beetle, Stator limbatus. Specifically, we compared fitness components among three natural populations of S. limbatus that vary in body size, and then among three lineages of beetles derived from a single base population artificially selected to vary in size, all reared on three sizes of seeds at variable larval density. The effects of larval competition and seed size on larval survival and development time were similar for larger versus smaller beetles. However, larger-bodied beetles suffered a greater reduction in adult body mass with decreasing seed size and increasing larval density; the relative advantage of being large decreased with decreasing seed size and increasing larval density. There were highly significant interactions between the effects of seed size and larval density on body size, and a significant three-way interaction (population-by-density-by-seed size), indicating that environmental effects on the fitness consequences of being large are nonadditive. Our study demonstrates how multiple ecological variables (resource availability and resource competition) interact to affect organismal fitness components, and that such interactions can mediate natural selection on body size. Studying individual factors influencing selection on body size may lead to misleading results given the potential for nonlinear interactions among selective agents.