With climate change leading to poleward range expansion of species, populations are exposed to new daylength regimes along latitudinal gradients. Daylength is a major factor affecting insect life cycles and activity patterns, so a range shift leading to new daylength regimes is likely to affect population dynamics and species interactions; however, the impact of daylength in isolation on ecological communities has not been studied so far. Here, we tested for the direct and indirect effects of two different daylengths on the dynamics of experimental multitrophic insect communities. We compared the community dynamics under “southern” summer conditions of 14.5‐hr daylight to “northern” summer conditions of 22‐hr daylight. We show that food web dynamics indeed respond to daylength with one aphid species (Acyrthosiphon pisum) reaching much lower population sizes at the northern daylength regime compared to under southern conditions. In contrast, in the same communities, another aphid species (Megoura viciae) reached higher population densities under northern conditions. This effect at the aphid level was driven by an indirect effect of daylength causing a change in competitive interaction strengths, with the different aphid species being more competitive at different daylength regimes. Additionally, increasing daylength also increased growth rates in M. viciae making it more competitive under summer long days. As such, the shift in daylength affected aphid population sizes by both direct and indirect effects, propagating through species interactions. However, contrary to expectations, parasitoids were not affected by daylength. Our results demonstrate that range expansion of whole communities due to climate change can indeed change interaction strengths between species within ecological communities with consequences for community dynamics. This study provides the first evidence of daylength affecting community dynamics, which could not be predicted from studying single species separately. 相似文献
Obesity and related metabolic disorders constitute one of the most pressing heath concerns worldwide. Increased adiposity is linked to autophagy upregulation in adipose tissues. However, it is unknown how autophagy is upregulated and contributes to aberrant adiposity. Here we show a FoxO1-autophagy-FSP27 axis that regulates adipogenesis and lipid droplet (LD) growth in adipocytes. Adipocyte differentiation was associated with upregulation of autophagy and fat specific protein 27 (FSP27), a key regulator of adipocyte maturation and expansion by promoting LD formation and growth. However, FoxO1 specific inhibitor AS1842856 potently suppressed autophagy, FSP27 expression, and adipocyte differentiation. In terminally differentiated adipocytes, AS1842856 significantly reduced FSP27 level and LD size, which was recapitulated by autophagy inhibitors (bafilomycin-A1 and leupeptin, BL). Similarly, AS1842856 and BL dampened autophagy activity and FSP27 expression in explant cultures of white adipose tissue. To our knowledge, this is the first study addressing FoxO1 in the regulation of adipose autophagy, shedding light on the mechanism of increased autophagy and adiposity in obese individuals. Given that adipogenesis and adipocyte expansion contribute to aberrant adiposity, targeting the FoxO1-autophagy-FSP27 axis may lead to new anti-obesity options. 相似文献
Reproductive aging is associated with ovulatory defects. Age-related ovarian fibrosis partially contributes to this phenotype as short-term treatment with anti-fibrotic compounds improves ovulation in reproductively old mice. However, age-dependent changes that are intrinsic to the follicle may also be relevant. In this study, we used a mouse model to demonstrate that reproductive aging is associated with impaired cumulus expansion which is accompanied by altered morphokinetic behavior of cumulus cells as assessed by time-lapse microscopy. The extracellular matrix integrity of expanded cumulus–oocyte complexes is compromised with advanced age as evidenced by increased penetration of fluorescent nanoparticles in a particle exclusion assay and larger open spaces on scanning electron microscopy. Reduced hyaluronan (HA) levels, decreased expression of genes encoding HA-associated proteins (e.g., Ptx3 and Tnfaip6), and increased expression of inflammatory genes and matrix metalloproteinases underlie this loss of matrix integrity. Importantly, HA levels are decreased with age in follicular fluid of women, indicative of conserved reproductive aging mechanisms. These findings provide novel mechanistic insights into how defects in cumulus expansion contribute to age-related infertility and may serve as a target to extend reproductive longevity. 相似文献
The major processes generating pattern in plant community composition depend upon the spatial scale and resolution of observation, therefore understanding the role played by spatial scale on species patterns is of major concern. In this study, we investigate how well environmental (topography and soil variables) and spatial variables explain variation in species composition in a 25-ha temperate forest in northeastern China. We used new variation partitioning approaches to discover the spatial scale (using multi-scale spatial PCNM variables) at which environmental heterogeneity and other spatially structured processes influence tree community composition. We also test the effect of changing grain of the study (i.e. quadrat size) on the variation partitioning results. Our results indicate that (1) species composition in the Changbai mixed broadleaf-conifer forest was controlled mainly by spatially structured soil variation at broad scales, while at finer scales most of the explained variation was of a spatial nature, pointing to the importance of biotic processes. (2) These results held at all sampling grains. However, reducing quadrat size progressively reduced both spatially and environmentally explained variance. This probably partly reflects increasing stochasticity in species abundances, and the smaller proportion of quadrats occupied by each species, when quadrat size is reduced. The results suggest that environmental heterogeneity (i.e. niche processes) and other biotic processes such as dispersal work together, but at different spatial scales, to build up diversity patterns. 相似文献
Genetic variability in the plasticity of leaf area expansion in response to water deficit has been reported in Arabidopsis thaliana. Here, the objective was to identify the underlying dynamic and cellular processes involved in this variability. Twenty-five accessions were subjected to identical soil water deficit treatments. In all accessions, the plasticity of leaf production was low compared with that of individual leaf expansion. A subset of accessions was selected for further dissection of individual leaf expansion into its underlying variables: the rate and duration of leaf expansion and epidermal cell number and area. In all accessions, water deficit had opposite effects on the rate and duration of leaf expansion. The accumulation of these effects was reflected in changes in final leaf area. At the cellular level, moderate water deficits had opposite effects on cell number and cell size, but more severe ones reduced both variables. The importance of these opposing effects is highlighted by the behaviour of the accession An-1, for which the compensation between the decrease in leaf expansion rate and the increase in the duration of expansion is total. This dynamic plasticity in response to water deficit is not detectable when only final measurements are done. 相似文献
We developed broad-scale habitat selection models for the distribution of red-legged partridge Alectoris rufa in a low-density area in northwestern Spain, the Baixa-Limia site of community importance (SCI). The fieldwork consisted
of ground surveys in 1 × 1 km squares. For habitat selection analysis, we used a 2 × 2 km grid integrating the information
obtained in the 1 × 1 km squares. As predictors we used environmental variables measured on digital 1:50,000 scale cartography
using a geographical information system (GIS). The red-legged partridge was scarce in the study area. The logistic regression
analysis carried out on data from the squares with probable and confirmed breeding included the area of scrubland and pastureland
with a positive sign. Using the breeding index category (BIC) three variables produced a slightly positive response: area
of scrubland and pastureland, length of border between scrublands and forests, and length of border between forests and dams.
The difficulty for modelling the habitat selection of this species could be due to human activities (hunting, habitat loss,
restocking of hunt species), and may have modified their habitat preferences. Furthermore, the occupation of suboptimal habitats
would distort the real habitat preferences. 相似文献
The connectivity among marine populations is determined by the dispersal capabilities of adults as well as their eggs and larvae. Dispersal distances and directions have a profound effect on gene flow and genetic differentiation within species. Genetic homogeneity over large areas is a common feature of coral reef fishes and can reflect high dispersal capability resulting in high levels of gene flow. If fish larvae return to their parental reef, gene flow would be restricted and genetic differentiation could occur. Larabicus quadrilineatus (Labridae) is considered as an endemic fish species of the Red Sea and Gulf of Aden. The juveniles of this species are cleaner fish that feed on ectoparasites of other fishes. Here, we investigated the genetic population structure and gene flow in L. quadrilineatus among five locations in the Red Sea to infer connectivity among them. To estimate genetic diversity, we analysed 369 bp of 237 mitochondrial DNA control region sequences. Haplotype and nucleotide diversities were higher in the southern than in the northern Red Sea. Analysis of molecular variance (amova) detected the highest significant genetic variation between northern and central/southern populations (Phi(CT) = 0.01; P < 0.001). Migration analysis revealed a several fold higher northward than southward migration, which could be explained by oceanographic conditions and spawning season. Even though the Phi(ST) value of 0.01 is rather low and implies a long larval dispersal distance, estimates based on the isolation-by-distance model show a very low mean larval dispersal distance (0.44-5.1 km) compared to other studies. In order to enable a sustainable ornamental fishery on the fourline wrasse, the results of this study suggest that populations in the northern and southern Red Sea should be managed separately as two different stocks. The rather low larval dispersal distance of about 5 km needs to be considered in the design of marine protected areas to enable connectivity and self-seeding. 相似文献
In intensively cultivated landscapes, the effects of land use – changing habitat quality and habitat availability - on wildlife populations are of major importance for wildlife management. Populations of some species reach high densities, grow rapidly, and can therefore cause damage to tree regeneration in forests; chamois (Rupicapra rupicapra) is an example. Other species, like capercaillie (Tetrao urogallus), suffer from substantial habitat loss resulting in a population decline. Consequently, the number of individuals and the quality of habitat are of crucial relevance for the development of wildlife management concepts. It is critical to know, which areas provide suitable habitat conditions for a species, and what quantity and quality of habitat is required to achieve a certain population size.
In order to evaluate habitat quality and to link wildlife research to practical habitat management, an integrated habitat management model has been designed. The model is based on a multi-dimensional habitat analysis which employs different methodological levels, which were defined according to different spatial scales. On a country scale (level 1), the wildlife ecological landscape type (WELT) is introduced. For this study the federal state of Baden-Wuerttemberg is divided into units which represent distinct regions with similar landscape ecological habitat conditions for wildlife species. On an eco-regional scale (level 2), the landscape ecological habitat potential (LEHP) was developed. It is based on the evaluation of species-related landscape parameters within an exemplary eco-region and provides information about the potential habitat available to a population. On two local scales (level 3: forest district, level 4: forest stand), a habitat structure analysis was conducted, which serves as a foundation for habitat improvement and the monitoring of habitat conditions. The three methodological elements WELT, LEHP and habitat structure analysis were integrated into a habitat management model. The model uses chamois and capercaillie as examples, but can be equally applied to other species and wildlife management regimes. 相似文献