Morphological selection and the evaluation of potential tradeoffs between escape from predators and the climbing of waterfalls in the Hawaiian stream goby Sicyopterus stimpsoni

Environmental pressures may vary over the geographic range of a species, exposing subpopulations to divergent functional demands. How does exposure to competing demands shape the morphology of species and influence the divergence of populations? We explored these questions by performing selection experiments on juveniles of the Hawaiian goby Sicyopterus stimpsoni, an amphidromous fish that exhibits morphological differences across portions of its geographic range where different environmental pressures predominate. Juvenile S. stimpsoni face two primary and potentially opposing selective pressures on body shape as they return from the ocean to freshwater streams on islands: (1) avoiding predators in the lower reaches of a stream; and (2) climbing waterfalls to reach the habitats occupied by adults. These pressures differ in importance across the Hawaiian Islands. On the youngest island, Hawai'i, waterfalls are close to shore, thereby minimizing exposure to predators and placing a premium on climbing performance. In contrast, on the oldest major island, Kaua'i, waterfalls have eroded further inland, lengthening the exposure of juveniles to predators before migrating juveniles begin climbing. Both juvenile and adult fish show differences in body shape between these islands that would be predicted to improve evasion of predators by fish from Kaua'i (e.g., taller bodies that improve thrust) and climbing performance for fish from Hawai'i (e.g., narrower bodies that reduce drag), matching the prevailing environmental demand on each island. To evaluate how competing selection pressures and functional tradeoffs contribute to the divergence in body shape observed in S. stimpsoni, we compared selection imposed on juvenile body shape by (1) predation by the native fish Eleotris sandwicensis versus (2) climbing an artificial waterfall (～100 body lengths). Some variables showed opposing patterns of selection that matched predictions: for example, survivors of predation had lower fineness ratios than did control fish (i.e., greater body depth for a given length), whereas successful climbers had higher fineness ratios (reducing drag) than did fish that failed. However, most morphological variables showed significant selection in only one treatment rather than opposing selection across both. Thus, functional tradeoffs between evasion of predators and minimizing drag during climbing might influence divergence in body shape across subpopulations, but even when selection is an important contributing mechanism, directly opposite patterns of selection across environmental demands are not required to generate morphological divergence.     

Food habits of fishes in azostera marina bed at aburatsubo, central japan

To clarify the feeding habits of seagrass fishes, the gut contents of 31 fish species collected in aZostera marina bed at Aburatsubo central Japan, were examined. Ontogenetic changes in food preference were recognized in 12 species. In general, juveniles of the latter preyed mainly on small crustaceans (e.g., gammaridean amphipods) or planktonic animals (e.g., calanoid and cyclopoid copepods), subsequently changing to other prey items (e.g., hard-shelled animals) with growth. Cluster analysis based on dietary overlaps showed that the seagrass fish assemblage comprised seven feeding guilds (small-crustacean, planktonic-animal, large-crustacean, polychaete, fish, hard-shelled mollusc and detritus feeders). Of these, small-crustacean feeders and planktonic-animal feeders were the most abundantly represented, including juveniles of several species, which, when adult, transferred to other feeding guilds. On the other hand detritivores were represented by a single species.     

Biodiversity change under adaptive community dynamics

Compositional change is a ubiquitous response of ecological communities to environmental drivers of global change, but is often regarded as evidence of declining “biotic integrity” relative to historical baselines. Adaptive compositional change, however, is a foundational idea in evolutionary biology, whereby changes in gene frequencies within species boost population-level fitness, allowing populations to persist as the environment changes. Here, we present an analogous idea for ecological communities based on core concepts of fitness and selection. Changes in community composition (i.e., frequencies of genetic differences among species) in response to environmental change should normally increase the average fitnessof community members. We refer to compositional changes that improve the functional match, or “fit,” between organisms' traits and their environment as adaptive community dynamics. Environmental change (e.g., land-use change) commonly reduces the fit between antecedent communities and new environments. Subsequent change in community composition in response to environmental changes, however, should normally increase community-level fit, as the success of at least some constituent species increases. We argue that adaptive community dynamics are likely to improve or maintain ecosystem function (e.g., by maintaining productivity). Adaptive community responses may simultaneously produce some changes that are considered societally desirable (e.g., increased carbon storage) and others that are undesirable (e.g., declines of certain species), just as evolutionary responses within species may be deemed desirable (e.g., evolutionary rescue of an endangered species) or undesirable (e.g., enhanced virulence of an agricultural pest). When assessing possible management interventions, it is important to distinguish between drivers of environmental change (e.g., undesired climate warming) and adaptive community responses, which may generate some desirable outcomes. Efforts to facilitate, accept, or resist ecological change require separate consideration of drivers and responses, and may highlight the need to reconsider preferences for historical baseline communities over communities that are better adapted to the new conditions.     

淡水鱼类功能生态学研究进展

在全球变化和人类活动的影响下,生物多样性正以前所未有的速度丧失,全球生物正经受第六次生物多样性危机。淡水生态系统是最脆弱的生态系统之一。淡水鱼类作为淡水生态系统的重要组成部分,承受着日趋严重的气候变化、栖息地退化、生物入侵和过度捕捞等压力,面临巨大的威胁。在此背景下,如何准确评估鱼类种群和群落对环境变化的响应,以及鱼类群落结构和功能的变化对生态系统功能的影响是淡水鱼类多样性和淡水生态系统保护的关键问题。近年来,淡水鱼类功能生态学的快速发展为解答这一问题提供了一个框架。系统地介绍了淡水鱼类功能生态学主要研究内容、方法、进展及其应用,并着重介绍了淡水鱼类功能特征及其与环境的关系、环境变化下的功能生态学响应研究。据此提出了淡水鱼类功能生态学未来的重点研究方向,指出了其在鱼类多样性保护和资源利用等领域的应用前景。     

Gut responses to enteral nutrition in preterm infants and animals

Preterm birth is associated with immature digestive function that may require the use of total parenteral nutrition and special oral feeding regimens. Little is known about the responses to oral food in the preterm neonate and how enteral nutrients affect the immature gastrointestinal tract (GIT). In vivo studies are difficult to perform in laboratory rodents because of their small body size and that of immature organs at birth, and this makes the large farm animals (e.g., pigs, cattle, sheep) more attractive models in this field. In these species, preterm delivery at 88%-95% gestation is associated clinical complications and degrees of GIT immaturity similar to those in infants born at 70%-90% gestation. Studies in both animals and infants indicate that the immature GIT responds to the first enteral food with rapid increases in gut mass and surface area, blood flow, motility, digestive capacity, and nutrient absorption. To a large extent, the enteral food responses are birth independent, and can be elicited also in utero, at least during late gestation. Nevertheless, preterm neonates show compromised GIT structure, function, and immunology, particularly when delivered by caesarean section and fed diets other than mother's milk. Formula-fed preterm infants are thus at increased risk of developing diseases such as necrotizing enterocolitis, unless special care is taken to avoid excessive nutrient fermentation and bacterial overgrowth. The extent to which results obtained in preterm animals (most notably the pig) can be used to reflect similar conditions in preterm infants is discussed.     

Food habits of small fishes in a common reed <Emphasis Type="Italic">Phragmites australis</Emphasis> belt in Lake Shinji,Shimane, Japan

To clarify the feeding habits of reed fishes, the gut contents of 13 fish species collected in a Phragmites australis belt in Lake Shinji were examined. Six species showed ontogenetic and/or seasonal changes in food use patterns. Smaller individuals generally preyed on small planktonic items (e.g., calanoid and cyclopoid copepods) or small crustaceans (gammaridean amphipods), subsequently changing to other prey items (e.g., mysids and filamentous algae) with growth. The most important dietary items for the reed fish assemblage comprised planktonic copepods, gammaridean amphipods and mysids. However, the relative importance of these changed seasonally, gammaridean amphipods being the most important in autumn and winter, and planktonic copepods and mysids the most important in spring and in summer. Cluster analysis based on dietary overlaps showed that the reed fish assemblage comprised five feeding guilds (planktonic-copepod, mysid, gammaridean-amphipod, filamentous-algae, and detritus feeders). Of these, the three former guilds were the most abundantly represented, whereas detritivores were represented by a single species.     

Morphological traits mediate fish occurrences in oil palm-impacted tropical streams

1. Land-use change is a leading driver of biodiversity loss, especially in tropical fresh waters where the conversion of natural forest to monoculture plantations impacts freshwater fish assemblages. The environmental pathways underpinning shifts in fish assemblages, however, are poorly understood, but could potentially be inferred from trait–environment relationships.
2. We addressed this knowledge gap using eco-morphological traits to explain fish occurrences in oil palm-impacted streams of the Endau drainage in Peninsular Malaysia. We also investigated how traits relate to differences in environmental conditions associated with land-use change. We then integrate findings from the above to test how potential pathways of land-use driven environmental changes can impact species occurrences through effects on life history, feeding habits, and mobility.
3. Mixed-effects models show that fishes with superior (upward-facing) mouths and low body mass were more likely to occur in oil palm streams than forest streams, and these traits were associated with grass-dominated riparian zones and reduced woody debris in oil palm streams, respectively. Structural equation models show that mouth positions statistically mediated the effect of riparian vegetation on fish species occurrences in oil palm streams. Specifically, fishes with superior mouths were more likely to feed on terrestrial invertebrates.
4. Our analysis of easily measurable traits revealed pathways of land-use impact that are potentially more widely applicable than conventional taxa-based approaches. Fishes with superior mouths tended to occur in oil palm streams as they were able to more effectively exploit inputs of terrestrial invertebrates that are potentially associated with grass-dominated riparian vegetation.
5. Moreover, shifts in traits may suggest land-use driven changes in stream ecosystem functioning (e.g. in terms of the role of terrestrial subsidies), thereby informing targeted management actions in land-use impacted habitats (e.g. retention/restoration of riparian trees).

     

Tissue-specific accumulation and speciation of selenium in rainbow trout (Oncorhynchus mykiss) exposed to elevated dietary selenomethionine

The toxicity of selenium in fish is influenced by its chemical speciation and the exposure route. In the natural environment, selenium exposure to fish occurs primarily in the form of selenomethionine in diet. Thus, the main objective of this study was to examine the tissue-specific selenium burden and speciation in fish exposed to elevated dietary selenomethionine. Rainbow trout (Oncorhynchus mykiss) were treated with dietary selenomethionine (40 μg g(-1) dry mass) for 2 weeks, and at the end of the exposure different tissue samples were collected to assess the tissue-specific distribution and speciation of selenium. We used synchrotron-based X-ray absorption near edge spectroscopy (XANES) to determine the selenium speciation profile. Selenomethionine, selenocysteine and selenocystine were found to be the predominant form of selenium in all of the tissues; however their relative proportion varied across different tissues. In general, the organs primarily involved in selenium handling in fish (e.g., liver, kidney) accumulated a higher percentage of selenocystine. We also found that dietary selenomethionine exposure resulted into a marked increase in selenium burden of all major tissues in fish including the brain. Collectively, our findings provide new insights into the tissue-specific distribution and speciation of selenium in fish exposed to selenomethionine via diet.     

Food factors and gastrointestinal function: a critical interface

The gastrointestinal tract (GIT) is an interface between the external environment and the body and functions to extract nutrients from foods as well as handle the various non-nutrient compounds found in foods. Thus factors in foods that affect health and disease may mediate their effects either through a direct effect on the GIT or indirectly by the pattern of absorption and subsequent metabolism through the GIT. To explore this relationship one must consider both the physiological responses of the GIT induced by factors in foods as well as the implications of GIT adaptation for metabolism. Metabolic adaptations to dietary factors such as cholesterol levels, glucose and insulin response, and immune function appear to be modulated by the manner in which food factors are metabolized in the GIT. New research is needed to understand the inter-relationship between food factors that stimulate GIT response and the subsequent influence on metabolism that influences risk factors for disease and health promotion.     

Functional diversity and trait–environment relationships of stream fish assemblages in a large tropical catchment

1. The species composition of stream fish assemblages changes across the longitudinal fluvial gradient of large river basins. These changes may reflect both zonation in species distributions and environmental filtering of fish traits as stream environments change from the uplands to the lowlands of large catchments. Previous research has shown that taxonomic diversity generally increases in larger, lowland streams, and the River Continuum Concept, the River Habitat Template and other frameworks have provided expectations for what functional groups of fishes should predominate in certain stream types. However, studies addressing the functional trait composition of fish assemblages across large regions are lacking, particularly in tropical river basins. 2. We examined functional trait–environment relationships and functional diversity of stream fish assemblages in the Río Grijalva Basin in southern Mexico. Traits linked to feeding, locomotion and life history strategy were measured in fishes from streams throughout the catchment, from highland headwaters to broad, lowland streams. Relationships between functional traits and environmental variables at local and landscape scales were examined using multivariate ordination, and the convex hull volume of trait space occupied by fish assemblages was calculated as a measure of functional diversity. 3. Although there were a few exceptions, functional diversity of assemblages increased with species richness along the gradient from uplands to lowlands within the Grijalva Basin. Traits related to swimming, habitat preference and food resource use were associated with both local (e.g. substratum type, pool availability) and landscape‐scale (e.g. forest cover) environmental variables. 4. Along with taxonomic structure and diversity, the functional composition of fish assemblages changed across the longitudinal fluvial gradient of the basin. Trait–environment relationships documented in this study partially confirmed theoretical expectations and revealed patterns that may help in developing a better understanding of general functional responses of fish assemblages to environmental change.     

Review: The development of the gastrointestinal tract microbiota and intervention in neonatal ruminants

The complex microbiome colonizing the gastrointestinal tract (GIT) of ruminants plays an important role in the development of the immune system, nutrient absorption and metabolism. Hence, understanding GIT microbiota colonization in neonatal ruminants has positive impacts on host health and productivity. Microbes rapidly colonize the GIT after birth and gradually develop into a complex microbial community, which allows the possibility of GIT microbiome manipulation to enhance newborn health and growth and perhaps induce lasting effects in adult ruminants. This paper reviews recent advances in understanding how host-microbiome interactions affect the GIT development and health of neonatal ruminants. Following initial GIT microbiome colonization, continuous exposure to host-specific microorganisms is necessary for GIT development and immune system maturation. Furthermore, the early GIT microbial community structure is significantly affected by early life events, such as maternal microbiota exposure, dietary changes, age and the addition of prebiotics, probiotics and synbiotics, supporting the idea of microbial programming in early life. However, the time window in which interventions can optimally improve production and reduce gastrointestinal disease as well as the role of key host-specific microbiota constituents and host immune regulation requires further study.     

植物功能性状与环境和生态系统功能

植物性状反映了植物对生长环境的响应和适应,将环境、植物个体和生态系统结构、过程与功能联系起来(所谓的“植物功能性状”)。该文介绍了植物功能性状的分类体系,综述了国内外植物功能性状与气候(包括气温、降水、光照)、地理空间变异(包括地形地貌、生态梯度、海拔)、营养、干扰(包括火灾、放牧、生物入侵、土地利用)等环境因素,以及与生态系统功能之间关系的研究进展,探讨了全球变化(气候变化和CO₂浓度升高)对个体和群落植物功能性状的影响。植物功能性状的研究已经取得很多成果,并应用于全球变化、古植被恢复和古气候定量重建、环境监测与评价、生态保护和恢复等研究中,但大尺度、多生境因子下的植物功能性状研究仍有待于加强,同时需要改进性状的测量手段;我国的植物功能性状研究还需要更加明朗化和系统化。     

Emergent buffering balances evolvability and robustness in the evolution of phenotypic flexibility

Evolution of adaptive phenotypic flexibility requires a system that can dynamically restore and update a functional phenotype in response to environmental change. The architecture of such a system evolves under the conflicting demands of versatility and robustness, and resolution of these demands should be particularly evident in organisms that require external inputs for reiterative trait production within a generation, such as in metabolic networks that underlie yearly acquisition of diet‐dependent coloration in birds. Here, we show that a key structural feature of carotenoid networks–redundancy of biochemical pathways–enables these networks to translate variable environmental inputs into consistent phenotypic outcomes. We closely followed life‐long changes in structure and utilization of metabolic networks in a large cohort of free‐living birds and found that greater individual experience with dietary change between molts leads to wider occupancy of the metabolic network and progressive accumulation of redundant pathways in a functionally active network. This generated a regime of emergent buffering whereby greater dietary experience was mechanistically linked to greater robustness of resulting traits and an increasing ability to retain and implement previous adaptive solutions. Thus, experience‐related buffering links evolvability and robustness in carotenoid‐metabolizing networks and we argue that this mechanistic principle facilitates the evolution of phenotypic flexibility.     

Temporal variability in the spatial and environmental determinants of functional metacommunity organization – stream fish in a human‐modified landscape

1. Quantifying the relative importance of environmental filtering versus regional spatial structuring has become an intensively studied area in the context of metacommunity ecology. However, most studies have evaluated the role of environmental and spatial processes using taxonomic data sets of single snapshot surveys. 2. Here, we examined temporal changes in patterns and possible processes behind the functional metacommunity organization of stream fishes in a human‐modified landscape. Specifically, we (i) studied general changes in the functional composition of fish assemblages among 40 wadeable stream sites during a 3‐year study period in the catchment area of Lake Balaton, Hungary, (ii) quantified the relative importance of spatial and environmental factors as determinants of metacommunity structure and (iii) examined temporal variability in the relative role of spatial and environmental processes for this metacommunity. 3. Partial triadic analysis showed that assemblages could be effectively ordered along a functional gradient from invertebrate consuming species dominated by the opportunistic life‐history strategy, to assemblages with a diverse array of functional attributes. The analysis also revealed that functional fish assemblage structure was moderately stable among the sites between the sampling periods. 4. Despite moderate stability, variance partitioning using redundancy analyses (RDA) showed considerable temporal variability in the contribution of environmental and spatial factors to this pattern. The analyses also showed that environmental variables were, in general, more important than spatial ones in determining metacommunity structure. Of these, natural environmental variables (e.g. altitude, velocity) proved to be more influential than human‐related effects (e.g. pond area, % inhabited area above the site, nutrient enrichment), even in this landscape with relatively low variation in altitude and stream size. 5. Pond area was, however, the most important human stressor variable that was positively associated with the abundance of non‐native species with diverse functional attributes. The temporal variability in the relative importance of environmental and spatial factors was probably shaped by the release of non‐native fish from fish ponds to the stream system during flood events. 6. To conclude, both spatial processes and environmental control shape the functional metacommunity organization of stream fish assemblages in human‐modified landscapes, but their importance can vary in time. We argue, therefore, that metacommunity studies should better consider temporal variability in the ecological mechanisms (e.g. dispersal limitation, species sorting) that determine the dynamics of landscape‐level community organization.     

叶脉网络功能性状及其生态学意义

叶脉网络结构是叶脉系统在叶片里的分布和排列样式。早期叶脉网络结构研究主要集中在其分类学意义上; 近年来叶脉网络功能性状及其在植物水分利用上的意义已成为植物生态学研究的热点。该文介绍了叶脉网络功能性状的指标体系(包括叶脉密度、叶脉直径、叶脉之间的距离、叶脉闭合度等), 综述了叶脉网络功能性状与叶脉系统功能(包括水分、养分和光合产物等物质运输、机械支撑和虫害防御等)的关系, 叶脉网络功能性状与叶片其他功能性状(包括比叶重、叶寿命、光合速率、叶片大小、气孔密度等)的协同变异和权衡关系, 以及叶脉网络功能性状随环境因子(包括水分、温度、光照等)的变化规律等方面的最新研究进展。此外, 叶脉网络功能性状的研究成果也被应用于古环境重建、城市交通规划、流域规划及全球变化研究中。由于叶脉网络功能性状是环境因子与系统发育共同作用的结果, 未来开展分子—叶片—植物—生态系统等多尺度的叶脉网络功能性状研究, 理清叶脉网络功能性状与气孔失水—茎干导水—根系吸水等植物水分利用的关系, 将为预测植物及生态系统对全球变化的响应提供新的启示。     

The role of caveolae in endothelial cell dysfunction with a focus on nutrition and environmental toxicants

Complications of vascular diseases, including atherosclerosis, are the number one cause of death in Western societies. Dysfunction of endothelial cells is a critical underlying cause of the pathology of atherosclerosis. Lipid rafts, and especially caveolae, are enriched in endothelial cells, and down-regulation of the caveolin-1 gene may provide protection against the development of atherosclerosis. There is substantial evidence that exposure to environmental pollution is linked to cardiovascular mortality, and that persistent organic pollutants can markedly contribute to endothelial cell dysfunction and an increase in vascular inflammation. Nutrition can modulate the toxicity of environmental pollutants, and evidence suggests that these affect health and disease outcome associated with chemical insults. Because caveolae can provide a regulatory platform for pro-inflammatory signalling associated with vascular diseases such as atherosclerosis, we suggest a link between atherogenic risk and functional changes of caveolae by environmental factors such as dietary lipids and organic pollutants. For example, we have evidence that endothelial caveolae play a role in uptake of persistent organic pollutants, an event associated with subsequent production of inflammatory mediators. Functional properties of caveolae can be modulated by nutrition, such as dietary lipids (e.g. fatty acids) and plant-derived polyphenols (e.g. flavonoids), which change activation of caveolae-associated signalling proteins. The following review will focus on caveolae providing a platform for pro-inflammatory signalling, and the role of caveolae in endothelial cell functional changes associated with environmental mediators such as nutrients and toxicants, which are known to modulate the pathology of vascular diseases.     

Spatial isolation and fish communities in drainage lakes

Fifty-two drainage lakes, located in south-central Ontario, Canada, were examined to study the association of isolation- and environment-related factors with fish community composition. Eight quantitative measures of lake isolation were examined, each of which incorporated potential ecological "challenges" that a fish encounters when moving between lakes. A Procrustean approach was employed to assess the degree of concordance between fish assemblage structure, measures of lake isolation and environmental conditions (i.e., lake morphology and water chemistry). Our results revealed a high concordance between patterns in fish community composition and lake isolation and lake morphology at the watershed scale, suggesting that insular and habitat-related factors influence the structure of fish communities. At the scale of the individual lake, this relationship varied greatly, ranging from a strong match of community composition with both spatial and abiotic conditions to communities exhibiting weak association with these conditions. Furthermore, we showed that alternative measures of lake isolation provide additional insight into potential factors shaping patterns in fish community composition; information not provided using straight-line distances between lakes. Finally, the statistical methodology outlined in this paper provides a robust technique for assessing both the overall association between multivariate data matrices (i.e., landscape or regional scale), as well as facilitating the examination of smaller-scale relationships of individual observations (i.e., local scale).