Spatial Variability in Species Composition in Birds and Insects

If spatial patterns of change within a habitat were similar for both vertebrates and insects, then vertebrates would provide useful surrogates for designing reserves for the conservation of invertebrates. Data from two eucalypt habitats were analysed to determine levels of habitat richness, site richness and species turnover in birds and insects. For birds the relatively low species richness and turnover indicated that sites within the habitat were similar in composition. In wet eucalypt forests Diptera were very speciose with over 1,000 morphospecies sorted. Species turnover was slightly higher than for birds, indicating a large number of species change from site to site. In dry eucalypt woodland, insects trapped through the winter months were not speciose but turnover between sites was very large. This suggests reserves designed to conserve insects may need to be larger than for birds in order to include the high site variability and richness of insect communities.Spatial patterns of birds and insects were investigated further, to determine if sites that were closer together were more similar for both birds and insects. No patterns were found for birds in either habitat suggesting birds are not responding to changes in the environment at this scale. Diptera in wet eucalypt forest showed higher similarity between close sites than distant sites, while for winter insects in dry eucalypt woodland the relationship was significant when two outlier points were removed. Overall, birds are not good surrogates for insects in either habitat as no relationship between birds and insects in site-to-site similarity was found.     

Temporal and Spatial Order in the Central Plains

Abstract

The major archeological complexes of the Central Plains can be arranged according to the Willey and Phillips system, thus recognizing not only content but time and space diemnsions.     

Seasonal and Acute Changes in Adrenocortical Responsiveness in an Arctic-Breeding Bird

The Lapland longspur,Calcarius lapponicus,times its breeding season so that chicks hatch coincident with the brief period of food abundance in the high arctic. This synchronization requires that all reproductive activities occur in over a much shorter period than at lower latitudes. Because of the known influence of stress hormones on delaying breeding in temperate-zone birds and the detrimental effects of such delays in the arctic, we expected the performance of the hypothalamic–pituitary–adrenal (HPA) axis of arctic-breeding birds to show less sensitivity to environmental stress than their mid-latitude counterparts. We found that adrenocortical responsiveness to the standardized stress of capture and handling, measured by taking five serial blood samples for corticosterone during the course of a 1-hr period, was similar to many temperate passerines and was also similar both between male and female longspurs and between the migratory and reproductive phases. However, the profile of plasma corticosterone during capture stress was significantly damped in longspurs sampled as they began their postnuptial molt. In addition, we had the opportunity to examine endocrine responses to a natural environmental stress in 1989 during a 3-day snowstorm which concealed available food resources. During this storm longspurs formed progressively larger flocks each day, with females abandoning incubation duties by the third day. Birds captured during the storm showed highly significant increases in both the rate of plasma corticosterone increase during capture and the peak postcapture level compared with birds sampled before the storm. This increased adrenal potential suggests increased activity of the HPA axis in response to severe conditions and is reminiscent of the response to fasting. Although the storm occurred during incubation, and reproductive hormone levels had begun to decline, we measured significant reductions in luteinizing hormone in both males and a subset of females captured during the storm.     

Spatial and Temporal Patterns in Assemblages of Temperate Reef Fish

SYNOPSIS. For reef fish in temperate marine regions, such componentsof local assemblage diversity (i.e., within a reef) as speciesrichness, total fish density, and rank order of abundance canremain relatively constantthrough time. Long-term data (17 years)for assemblages on 2 reefs in Southern California revealed that,despite high turnover in rare species, overall species richnesswas affected only moderately by major oceanographicdisturbances.This resilience of the assemblage is in marked contrast to hightemporal variation in densities exhibited by many local populationsof individual species, and it suggests that measurements ofdiversity to indicate status of an assemblage should be usedwith caution. Here we consider various processes and factors,together with the spatial and temporal scales over which theyoperate, that can influence local diversity (and its estimation)of reef fishes. Mechanisms that can "buffer" local diversityof reef fishes include dispersal of young that inter-connectssubpopulations, high "inertia" in relative abundance and populationstructures (especially for long-lived species), and broad ecologicalrequirements of many species. These considerations suggest thatthe effect of disturbances on local diversity of reef fisheswill depend in part on the magnitude, duration, frequency andspatial scale of the perturbation. While long-term data arefew, available information suggests that, due to life historycharacteristics of the fish and the spatial and temporal scalesat which disturbances are likely to occur, assemblages of temperatemarine reef fish might be relatively resilient to environmentalperturbations     

Spatial and Temporal Variation of Phenanthrene-Degrading Bacteria in Intertidal Sediments

Phenanthrene-degrading bacteria were isolated from a 1-m² intertidal sediment site in Boston Harbor. Samples were taken six times over 2 years. A total of 432 bacteria were isolated and characterized by biochemical testing. When clustered on the basis of phenotypic characteristics, the isolates could be separated into 68 groups at a similarity level of approximately 70%. Several groups (a total of 200 isolates) corresponded to well-characterized species belonging the genera Vibrio and Pseudomonas. Only 51 of the 437 isolates (<11.7% of the total) hybridized to a DNA probe that encodes the upper pathway of naphthalene and phenanthrene degradation in Pseudomonas putida NCIB 9816. A cluster analysis indicated that the species composition of the phenanthrene-degrading community changed significantly from sampling date to sampling date. At one sampling time, 12 6-mm-diameter core subsamples were taken within the 1-m² site to determine the spatial variability of the degrading communities. An analysis of molecular variance, performed with the phenotypic characteristics, indicated that only 6% of the variation occurred among the 12 subsamples, suggesting that the subsamples were almost identical in composition. We concluded that the communities of phenanthrene-degrading bacteria in the sediments are very diverse, that the community structure undergoes significant change with time but does not vary significantly on a spatial scale of centimeters, and that the predominant genes that encode phenanthrene degradation in the communities are not well-characterized.     

Spatial and Temporal Clustering of Chikungunya Virus Transmission in Dominica

Using geo-referenced case data, we present spatial and spatio-temporal cluster analyses of the early spread of the 2013–2015 chikungunya virus (CHIKV) in Dominica, an island in the Caribbean. Spatial coordinates of the locations of the first 417 reported cases observed between December 15^th, 2013 and March 11^th, 2014, were captured using the Global Positioning System (GPS). We observed a preponderance of female cases, which has been reported for CHIKV outbreaks in other regions. We also noted statistically significant spatial and spatio-temporal clusters in highly populated areas and observed major clusters prior to implementation of intensive vector control programs suggesting early vector control measures, and education had an impact on the spread of the CHIKV epidemic in Dominica. A dynamical identification of clusters can lead to local assessment of risk and provide opportunities for targeted control efforts for nations experiencing CHIKV outbreaks.     

Temporal Analogues to Spatial K Functions

In this article, the spatial statistic known as the K function is adapted for temporal processes and patterns. The (optimal) K-function estimator is used in a testing procedure to determine whether behavior patterns of exposed rats versus control rats are different. Specifically, the temporal analogue to the K function is given and an approximately optimal estimator is developed. Next, a testing procedure, to determine whether a group of point patterns is generated from complete temporal randomness, is given. Finally, a testing procedure, to compare pairwise two groups of point patterns to each other, is given. The testing procedures are illustrated with rat-behavior data from both a control-control experiment as well as an exposed-control experiment, where in the latter case a difference in behavior is known to exist.     

Managing Spatial and Temporal Switchgrass Biomass Yield Variability

Biorefineries that plan to use switchgrass exclusively will encounter year-to-year variability in feedstock production. The economic success of the biorefinery will depend in part on the ability of the management team to strategically identify land for conversion from current use to the production of switchgrass enabling a flow of feedstock for the life of the biorefinery. The objective of this research is to determine the optimal quality, quantity, and location of land to lease while considering the spatial and temporal variability of switchgrass biomass yield. A calibrated biophysical simulation model was used to simulate switchgrass biomass yields for 50 years based on historical weather data from 1962 to 2011, for three land capability classes for each of 30 counties. Mathematical programming models were constructed and solved to determine the optimal leasing scheme for each of three strategies for a biorefinery that requires 2,000 Mg/day. As expected, a model based on the assumption that the average yield would be obtained in each year finds that production from land identified for leasing would be insufficient to fulfill the biorefinery’s needs in half of the years. In the absence of other sources of biomass, the feedstock shortage would require forced idling of the biorefinery for an average of 29.5 days during these years. Results of a strategy of leasing sufficient land to cover feedstock needs in the worst year from among 50 years for which data are available are compared to that of a strategy enabling year-to-year storage.     

Studies of Temporal and Spatial Peculiarities of Somitogenesis in Fish Embryos

New data were obtained corroborating that somitogenesis is a rhythmic process, in which the time of somite formation is strictly constant. This constant ( _s ) can be considered as a natural unit of developmental biological clock characterizing rhythmic processes. The constant _s can be determined with an exceptional accuracy that has no analogs among the known biological processes. This fact alone suggests that the accuracy of developmental clock is very high. In addition to the constancy of _s , all forming somites have equal linear size along the notochord axis. In the process with strictly constant temporal and spatial factors, time plays the leading role in triggering the formation of new somite. This became clear in studies of twin embryos. Both embryos had the same number of somites but they were shorter than in the normal embryos. Also, we measured the length of head and both segmented and unsegmented caudal parts of the trunk. Combined with the published data on somitogenesis, our results suggest that the previously proposed scheme for the role of developmental clock in embryogenesis predicts: (1) a possible loss of some embryonic stages without serious consequences for subsequent development and (2) periodic switching on/off any embryonic processes (at the molecular, cellular, or supercellular level) with intervals multiple to _s .     

Tenascin-r基因在斑马鱼胚胎发育中时空表达规律

Tenascin-r(TNR)是一种脊椎动物细胞外基质糖蛋白,在不同的物种间具有高度保守性,主要表达于神经系统,通过调节基质粘附状态和基质间相互作用而促进细胞的迁移、增殖和分化.在小鼠等动物模型中,TNR在中枢神经系统的发育中起重要作用,能控制大脑活动、调节适应性行为.而在斑马鱼研究中,TNR仅在视神经的发育和修复中起作用,通过对TNR在斑马鱼胚胎发育时期时空表达规律的研究,可以为利用斑马鱼进一步研究TNR的功能建立一个平台.     

Spatial and Temporal Trade-Offs by Bluegills in Floodplain River Ecosystems

Ecological trade-offs by organisms to minimize mortality and maximize growth is a foundational theme in ecology. Yet, these trade-offs are rarely examined within spatially complex, temporally variable ecosystems, such as floodplain rivers. Here, we evaluate ecological trade-offs across space and time for the bluegill (Lepomis macrochirus) in two unregulated river ecosystems in southeastern USA. Life-history differences among spatially segregated main channel and floodplain lake populations were used to assess effects of habitat type on bluegill fitness. Growth, condition, and gonadal somatic index were all significantly enhanced in floodplain lakes relative to the main channel. Furthermore, stomach fullness was significantly higher, and predator densities significantly lower in floodplain lakes thereby providing an ecological explanation for the life-history plasticity observed across the riverscape. However, historical observations suggested that although floodplain lakes are highly productive for bluegills, they are also prone to complete desiccation by drought approximately every 5 years, revealing the ultimate value of channel habitat, which does not dry, as desiccation refugia. Bluegills are faced with a balancing act associated with variation in foraging opportunities, and risks to predation and desiccation, that change in both the temporal and the spatial dimensions of floodplain rivers. The differential responses to these opportunities and risks help to explain why both habitats remain actively populated by bluegills, as well as many other organisms, in these and many other natural rivers.     

Temporal and Spatial Distribution Patterns of Larval Trichoptera in Madeiran Streams

Temporal and spatial distribution patterns of lotic larval trichopteran assemblages in relation to environmental variables were investigated in Madeiran streams using multivariate analyses. TWINSPAN classification detected distinct faunal assemblages related to spatial factors between non-polluted high altitude sites and lower lying enriched sites where tolerant taxa were predominant but showed strong seasonal shifts in species composition and abundance. The 15 TWINSPAN end groups were grouped into five arbitrary clusters based upon the seasonal and spatial changes in the trichopteran assemblages detected by the analysis. Significant differences between environmental variables (distance from source, altitude, temperature, conductivity, alkalinity and nitrate) and the trichopteran assemblages (using trichopteran based metrics) of these clusters were confirmed by the Kruskal-Wallis test (H) and Dunn’s test. Chemical classification of samples within the clusters revealed a strong association between trichopteran assemblages and water quality. Canonical Correspondence Analysis and Monte Carlo global permutation tests also identified significant associations between the larval assemblages and physicochemical variables such as temperature and conductivity along a strong physical gradient (altitude, slope) and nitrate along a weaker seasonal gradient. Analysis of functional feeding group distribution patterns clearly showed that mid to high altitude indigenous woodland sites were trophically diverse whilst the lower reaches of the islands streams are trophically impoverished with strong seasonal shifts between two feeding groups of enrichment tolerant taxa. Trichopteran shredders are exclusive to indigenous woodland sites, indicating a limited distribution associated with land use, allochthonous input and habitat destruction. The results indicate that several ‘environmental filters’ operate at different levels upon the islands trichopteran fauna, producing temporally and spatially distinct ‘subsets’ of species best able to exploit conditions and resources at a given site or time, confounding the direct comparison of these insular systems with the findings of the River Continuum Concept, traditionally associated with unaffected continental lotic systems.     

Spatial and Temporal Distribution of Song in the Yellowhammer Emberiza citrinella

The temporal and spatial distribution of song was studied in a population of yellowhammers Emberiza citrinella. Song was most frequent during the breeding season, and within the breeding season during the fertile period of both first, second, and replacement clutches. Song activity peaked at sunrise and sunset. During the fertile period most singing took place in the central parts of the territory. Song post heights peaked during the fertile period, and more song posts lacked foliage at that time. Intrusions by male conspecifics peaked in the fertile period and in territories where males sang relatively little. Song activity and mate guarding were strongly positively correlated. Song volume was loud and song was thus apparently used in long-distance communication. These observations are in accordance with a male deterrence hypothesis, suggesting that males sing to deter neighbouring males from trespassing during the fertile period of their mate. A female attraction hypothesis, suggesting that males sing to attract neighbouring females and thereby obtain extra-pair copulations, and a female reproduction hypothesis, suggesting that males sing to start the female reproductive cycle, were partly supported by observations.     

Spatial Pattern and Temporal Dynamics of Bryophyte Assemblages in Saline Grassland

Dynamics of bryophyte assemblages of saline grassland were studied in Hungary. A survey was carried out in two permanent plots by annual sampling of 0.25-m² quadrats over a 9-year period. The study investigated: i) the extent of spatial and temporal dependence of the assemblages and individual species; ii) the turnover of individual species and its relationship to life-strategy types and iii) the effect of annual weather conditions on species performance. One of the plots showed succession; the frequency of some perennial species increased, while that of some short-lived species decreased; this process was independent of local weather conditions. The other plot showed a non-directional fluctuation, which was partly related to precipitation in winter and early spring. The spatial and temporal dependence of this assemblage was low; many short-lived species had a high turnover in the studied community. In stable periods, neutral dynamic processes characterize the bryophyte assemblages of the studied saline grassland and the occurrences of species were more or less independent in space and time. Short-lived species showed high fluctuations and were probably influenced by weather conditions or other factors. However, the frequency of perennial species, which were influenced by local conditions, could directionally change displacing the short-lived ones during succession. The relationships between turnover and life-strategy types were weak, both the group of colonist and shuttle species were dynamically heterogeneous. Longer observations are needed for a clearer exploration of the relationships between vegetation changes and weather conditions.     

Temporal and Spatial Stability of Ammonia-Oxidizing Archaea and Bacteria in Aquarium Biofilters

Nitrifying biofilters are used in aquaria and aquaculture systems to prevent accumulation of ammonia by promoting rapid conversion to nitrate via nitrite. Ammonia-oxidizing archaea (AOA), as opposed to ammonia-oxidizing bacteria (AOB), were recently identified as the dominant ammonia oxidizers in most freshwater aquaria. This study investigated biofilms from fixed-bed aquarium biofilters to assess the temporal and spatial dynamics of AOA and AOB abundance and diversity. Over a period of four months, ammonia-oxidizing microorganisms from six freshwater and one marine aquarium were investigated at 4–5 time points. Nitrogen balances for three freshwater aquaria showed that active nitrification by aquarium biofilters accounted for ≥81–86% of total nitrogen conversion in the aquaria. Quantitative PCR (qPCR) for bacterial and thaumarchaeal ammonia monooxygenase (amoA) genes demonstrated that AOA were numerically dominant over AOB in all six freshwater aquaria tested, and contributed all detectable amoA genes in three aquarium biofilters. In the marine aquarium, however, AOB outnumbered AOA by three to five orders of magnitude based on amoA gene abundances. A comparison of AOA abundance in three carrier materials (fine sponge, rough sponge and sintered glass or ceramic rings) of two three-media freshwater biofilters revealed preferential growth of AOA on fine sponge. Denaturing gel gradient electrophoresis (DGGE) of thaumarchaeal 16S rRNA genes indicated that community composition within a given biofilter was stable across media types. In addition, DGGE of all aquarium biofilters revealed low AOA diversity, with few bands, which were stable over time. Nonmetric multidimensional scaling (NMDS) based on denaturing gradient gel electrophoresis (DGGE) fingerprints of thaumarchaeal 16S rRNA genes placed freshwater and marine aquaria communities in separate clusters. These results indicate that AOA are the dominant ammonia-oxidizing microorganisms in freshwater aquarium biofilters, and that AOA community composition within a given aquarium is stable over time and across biofilter support material types.