Effects Of Environmental Variables Research Articles

Body size shapes song in honeyeaters.

Birdsongs are among the most distinctive animal signals. Their evolution is thought to be shaped simultaneously by habitat structure and by the constraints of morphology. Habitat structure affects song transmission and detectability, thus influencing song (the acoustic adaptation hypothesis), while body size and beak size and shape necessarily constrain song characteristics (the morphological constraint hypothesis). Yet, support for the acoustic adaptation and morphological constraint hypotheses remains equivocal, and their simultaneous examination is infrequent. Using a phenotypically diverse Australasian bird clade, the honeyeaters (Aves: Meliphagidae), we compile a dataset consisting of song, environmental, and morphological variables for 163 species and jointly examine predictions of these two hypotheses. Overall, we find that body size constrains song frequency and pace in honeyeaters. Although habitat type and environmental temperature influence aspects of song, that influence is indirect, likely via effects of environmental variation on body size, with some evidence that elevation constrains the evolution of song peak frequency. Our results demonstrate that morphology has an overwhelming influence on birdsong, in support of the morphological constraint hypothesis, with the environment playing a secondary role generally via body size rather than habitat structure. These results suggest that changing body size (a consequence of both global effects such as climate change and local effects such as habitat transformation) will substantially influence the nature of birdsong.

On-deck vs. laboratory analyses of the sound velocity of sediments from the Huanghai and Bohai seas

One popular method of obtaining the acoustic parameters of seabed sediments is by measuring the sound velocity of sediment samples in a laboratory. However, the effects of environmental variation and physical perturbation on acoustic properties are typically neglected in the application of such measured acoustic parameters. In this study, sediment samples were collected from the Huanghai and Bohai seas to measure sound velocity both on the deck and in the laboratory using a digital sonic measuring system. Additionally, sediment compositions, physical and mechanical properties and microstructures were determined. Sound velocity comparisons between on-deck and laboratory measurements indicate that laboratory-measured velocities are generally higher than those measured on the deck, with differences ranging from 1.45 m/s to 130.05 m/s, due to the water loss and densification of sedimentary particles in laboratory settings. The discrepancy of sound velocities measured in the laboratory and on the deck also differ based on the types of sediments sampled. Overall, the discrepancy increases with measurement frequency, increasing average grain diameter and sand content, as well as with decreasing clay content.

The effect of environmental variations on the production of the principal agricultural products in Colombia.

The agricultural sector of Colombia supports the national economy and food security due to the rich lands for cultivation. Although Colombia has a vast hydrological basin, climate change can impact agricultural productivity, generating economic and social adverse effects. For this, we evaluated the impact of some environmental variables on the production of the most sold crops using production, climatic, and hydrological data of the 1121 municipalities from 2007 to 2020. We modeled the production of coffee, rice, palm oil, sugarcane, and corn, adopting a Bayesian spatio-temporal model that involved a set of environmental variables: average temperature, minimum temperature, maximum temperature, evapotranspiration, precipitation, runoff, soil moisture, vapor pressure, radiation, and wind speed. We found that increases in the average temperatures can affect coffee (-0.2% per °C), rice (-3.76% per °C), and sugarcane (-0.19% per °C) production, meanwhile, these increases can boost palm oil (+2.55% per °C) and corn (+1.28% per °C) production in Colombia. This statement implies that the agricultural sector needs to substitute land use, promoting the production of palm oil and corn. Although our results did not find a significant effect of hydrological variables in any crop, suggesting that the abundance of water in Colombia might balance the impact of these variables. The increases in vapor pressure impact all the crops negatively (between -11.2% to -0.43% per kPa), except rice, evidencing that dry air conditions affect agricultural production. Colombia must manage the production location of the traditional products and implement agro-industrial technologies to avoid the climate change impact on crops.

Should landscape variation in population status be assessed with individual‐ or population‐level indicators?

AbstractMonitoring trends in wildlife populations is essential to effective management. Evaluating only a single metric can be cost‐effective; however, how a given metric responds to environmental variation may differ from other population‐ or individual‐level metrics. Consequently, conclusions about the effect of environmental variation on a species should consider the relationship between different metrics. We investigated how population‐level metrics (occupancy and relative abundance) and an individual‐level metric (body condition) responded to landscape variation in 3 semi‐aquatic salamander species. In the summer of 2015 and 2016, we conducted repeated count surveys at 71 streams on the Cumberland Plateau, Tennessee, USA, actively counting and measuring salamanders. We estimated occupancy and abundance of larval and post‐metamorphic animals using community‐occupancy and community‐N mixture models, respectively. We estimated body condition of the most observed life stage for each species using a standardized mass index. All models included the same set of covariates for comparison. Occupancy and abundance responses for each life stage‐by‐species combination were positively correlated for 4 of 6 combinations, with salamander abundance responding to a larger suite of covariates. Body condition was not linked to covariates in the same fashion as population‐level metrics, although consistency across species was detected for 1 covariate, watershed size. Our results indicate that inter‐specific and inter‐life stage variation in evaluated metrics is present within salamanders of this study system. Management for populations of salamanders in the region should consider monitoring multiple response metrics, to capture both population‐ and individual‐level responses, as these may not always be correlated.

Damage Detection of Structures Considering Environmental Variations Based on the Deviation Patterns of Natural Frequencies

The fundamental objective of structural damage detection is to ascertain the presence of damage in the structure under monitoring. Environmental variations (especially temperature) may also cause the aberration of dynamic properties. This could result in false alarms and pose a threat to the reliability of vibration-based damage detection. In this paper, a new approach toward damage detection under varying environmental conditions is investigated based on the deviation patterns of natural frequencies. The idea is derived from the fact that most damage occurs in a local area of a structure while environmental variations affect the whole structure. Natural frequencies deviate from their previous state in different patterns based on the causation of the deviation. The method uses simple mathematics to distinguish the two patterns using the first 10 natural frequencies of a structure. The proposed method was applied in two case studies including a numerical model with severe temperature variations simulated in ABAQUS and 1-year health monitoring data of a cable-stayed bridge in China as a real case study. By implementing the proposed method, the effects of environmental variations were eliminated in both case studies and damage was accurately detected before it was evident to the visual inspections of the bridge.

Phenotypic evolution as an Ornstein-Uhlenbeck process: The effect of environmental variation and phenotypic plasticity.

Here we investigate phenotypic evolution from the perspective of the Ornstein-Uhlenbeck (OU) process. Evolutionarily speaking, the model assumes the existence of stabilizing selection toward a phenotypic optimum. The standard (OU) model is modified to include environmental variation by taking a moving phenotypic optimum and endowing organisms with phenotypic plasticity. These two processes lead to an effective fitness landscape, which deforms the original. We observe that the simultaneous occurrence of environmental variation and phenotypic plasticity leads to skewed phenotypic distributions. The skewness of the resulting phenotypic distributions strongly depends on the rate of environmental variation and strength of selection. When generalized to more than one trait, the phenotypic distributions are not only affected by the magnitude of the rate of environmental variation but also by its direction. A remarkable feature of our predictions is the existence of an upper bound for the critical rate of environmental variation to allow population persistence, even if there is no cost associated with phenotypic plasticity.

Rhinoceros accounting in Kruger National Park, South Africa

Trends in rhinoceroses (rhinos) in Kruger National Park (Kruger) is of key concern. Poaching drives trends in the Park. Reconciling annual population estimates with yearly reports of poached carcasses fuels public critique. We account for trends in rhinos by extracting time series of estimates. Progressively modelling influences of management introductions and removals, effects of environmental variation and rhino density, direct impacts of poaching, consequences of imperfect carcass detection, and indirect impacts of deaths of dependent calves form the basis of accounting for rhinos. Models that considered all these influences explained 93% of white and 83% of black rhino population trends. In addition, the models predicted 2,515 white and 225 black rhinos, similar to estimates of 2,607 (95% CI: 2,475–2,752) and 202 (95% CI: 172–237) during 2020 respectively. The best model, however, predicts slow recovery with a white rhino population equivalent to pre-poaching achieved between 2030 and 2040. For black rhinos, recovery to pre-poaching population size would be between 2040 and 2050. The poaching onslaught in Kruger disrupted eruptive white rhino dynamics and prevented black rhinos from transitioning into eruptive dynamics. Authorities require innovative approaches within and beyond Kruger to help re-ignite rhino conservation.

Feeding mediated web-building plasticity in a cobweb spider.

Behavioral plasticity has been proposed as a means by which animals alter their phenotypes in response to changing conditions. Animals may display behavioral plasticity as a consequence of environmental variation. The detritus-based, bell-shaped cobweb spider Campanicola campanulata is an ideal model to study behavioral plasticity, because its web architecture is easy to be quantified, and the functions of different parts of the web are clear. Though the plasticity of cobweb architecture has been reported in a few species, retreats as important defensive structures have rarely been considered before because retreats in most cobwebs are relatively small compared with the web size. We studied the web-building behaviors of C. campanulata under different feeding regimes. We set up 3 spider treatments with different feeding conditions: marginally well fed, moderately well fed, and extremely well fed, and observed the differences in the web architecture among them. In addition, we measured the mechanical properties of anchor silk, and also calculated the foraging and defense investment of the spiders. The results showed that marginally well-fed spiders build cobwebs with significantly longer length of anchor silk, lower retreat to the ground, more number and longer gumfooted lines, and larger capture area, while extremely well-fed spiders build cobwebs with significantly bigger retreat volume and higher height of retreat to the ground. In addition, marginally well-fed spiders invest significantly less during cobweb construction. However, there was no significant difference between the breaking force and elongation at break in anchor silk among different treatments. These results demonstrated that marginally well-fed spiders invest more in foraging, and extremely well-fed spiders invest more in defense, and the spider made a balance between foraging and predator avoidance in response to changes in physiological state. Our study strengthens the current understanding of web construction in cobweb spiders, especially those facing high costs during retreat construction.

Effect of Environmental Variations on Macro-benthos Occurrence and Abundance of the Red Sea Coast of Egypt

Effect of Environmental Variations on Macro-benthos Occurrence and Abundance of the Red Sea Coast of Egypt

Effects of population density on static allometry between horn length and body mass in mountain ungulates

Little is known about the effects of environmental variation on allometric relationships of condition‐dependent traits, especially in wild populations. We estimated sex‐specific static allometry between horn length and body mass in four populations of mountain ungulates that experienced periods of contrasting density over the course of the study. These species displayed contrasting sexual dimorphism in horn size; high dimorphism in Capra ibex and Ovis canadensis and low dimorphism in Rupicapra rupicapra and Oreamnos americanus. The effects of density on static allometric slopes were weak and inconsistent while allometric intercepts were generally lower at high density, especially in males from species with high sexual dimorphism in horn length. These results confirm that static allometric slopes are more canalized than allometric intercepts against environmental variation induced by changes in population density.

Double brooding of Tree Swallows (Tachycineta bicolor) in southeast Tennessee

Double brooding, a second breeding attempt following the successful fledging of a previous brood, has the potential to substantially increase annual reproductive success of a given bird species. Tree Swallows (Tachycineta bicolor) have a wide breeding distribution, which makes them suitable subjects for looking at effects of environmental variation on their breeding biology. One aspect of Tree Swallow breeding that is not well studied is double brooding. During this study, double brooding was frequent, ranging from 37% to 57% each year. Single broods and first broods did not differ from each other, however second broods had smaller clutches, fewer fledglings, and reduced hatching success. Double brooded females had a median date of first egg laying that was 5 d earlier than single brooded females. Based on other studies of double brooding in Tree Swallows, the observed differences may be attributable to factors such as reduced food supplies later in the season, female age, breeding experience, and/or nesting date. The results demonstrate the necessity for studying this species over a broader portion of its range to better understand its population dynamics and reproductive potential.

Some species flourish when many do not: a pattern in data on ecological communities

Patterns in species × sample tables of communities depend above all on the organisms of the data sets and the conditions involved. Patterns that surpass individual sets are of special interest. Our question, looking for a shared pattern in 12 sets, is if relative abundances among species are independent of the sample, or formulated alternatively, if species have abundances that are correlated with total abundances over samples. For exploration we study the overdispersion/aggregation of the data. A relatively high variation in the total abundances of samples is noticed, indicating an effect of environmental variation. Overdispersion imposes constraints on the accommodation of relatively high abundance values to samples with a relatively low total abundance. The null hypothesis of ‘no association’ is modelled by permutation/resampling of the data at the level of the individual. A correlation study of actual and permuted sets is performed. All actual sets contain a significant number of species that defy our question. These species flourish when many do not. The relation of our question with issues in theoretical ecology, such as the assumption of a neutral effect of environmental conditions and/or of neutral characteristics of species, is discussed.

Fine-scale effect of environmental variation and distance from watercourses on pteridophyte assemblage structure in the western Amazon

Fine-scale effect of environmental variation and distance from watercourses on pteridophyte assemblage structure in the western Amazon

Autofocus Measurement for Electronic Components Using Deep Regression

Image-based focus measurement in the manufacturing process is important for tasks such as automated inspection, automated assembly, and autosoldering. To inspect or manipulate an object, the visual system must sense the best image position to ensure that all the details of the product can be viewed. For this reason, an autofocus system is required. Traditional autofocus systems based on depth-from-focus (DFF) or depth-from-defocus (DFD) rely on a series of images by moving the lens with a control motor to find the sharpest location. The processing time defers it for in-line, real-time industrial applications. In this article, we propose a deep neural network regressor for fast and accurate autofocus. The convolutional neural network (CNN) model is proposed and evaluated for the autofocus task on a variety of electronic surfaces, including wafers, liquid crystal display (LCD), and ball grid array (BGA). The proposed deep regression model requires only one single sensed image of the object to estimate the depth. The effect of environmental variations in the illumination is evaluated for the robustness of the proposed method. Experimental results indicate the proposed CNN Regressor can achieve fast and accurate results for the tested objects with repetitive and arbitrary patterns.

Location Is Everything, but Climate Gets a Share: Analyzing Small-Scale Environmental Influences on Breeding Success in the White-Throated Dipper

Ecological and evolutionary effects of environmental variation on wild populations are of particular interest in a changing world. Large-scale environmental indices are classically used as environmental explanatory variables to study climate change effects on wild populations. However, these measures neglect the fact that individuals are affected by the local conditions in their home ranges. Freshwater ecosystems are particularly sensitive to climate change induced alterations in precipitation and discharge affecting lower trophic level prey and cascading up the food chain to impact keystone species. Here, we study how small-scale environmental variation at the level of each territory affects fitness-related traits and in particular reproductive success in the white-throated dipper Cinclus cinclus, a bird dependent on aquatic prey. We take advantage of a long-term study of breeding dippers in a natural river system in Norway (1978-2015). We relate daily river discharge and other important hydrological and territory location variables to clutch and brood size simultaneously, while accounting for female age, polygyny, and population density. We also address uncertainty in estimates of both clutch and brood size when modelling reproductive success. The most influential variable overall was the altitudinal gradient, where birds breeding at higher altitudes laid fewer eggs and fledged fewer young. Clutch size decreased with increased population density and high temperatures, while it was positively affected by female age. Brood size varied greatly among territories, where some territories had consistently larger broods than others. Increased minimum and maximum temperatures, river discharge above 10 l/s and increased variability in snow depth had a positive effect on brood size, whereas polygyny had a negative effect. In conclusion, territory-specific variables explained a large amount of the variation in the reproductive output in the dipper, emphasizing the importance of the local habitat, and not only climatic variation, in a keystone species in freshwater ecosystems.

Demographic, Environmental, and Phenotypic Change but Genetic Consistency in the Jellyfish Mastigias papua.

AbstractSpatiotemporal environmental change can produce phenotypic differences within and between populations. For scyphozoans, the effect of environmental variation on phenotype has been unclear because of multiple challenges, including difficulties delimiting populations. Marine lakes, bodies of seawater entirely surrounded by land, provide an opportunity to study discrete populations and capture responses to perturbations. We use this opportunity to compare Mastigias papua (Lesson, 1830) medusae before and after a demographic and environmental perturbation. We reconstructed mitochondrial DNA haplotype networks, measured morphological variation, and assessed swimming behavior of pre- and post-perturbation samples to evaluate two hypotheses about the source of variation: recolonization from an alternate location or endemic phenotypic variation. We found significant differences between samples in morphology (F > 9.5, P < 0.001) and in two of three behaviors (F > 8.45, P < 0.005) but no substantial genetic differentiation (ΦST = 0.03, P = 0.09). We reject the hypothesis of recolonization because pre- and post-perturbation lake medusae were genetically similar to each other and also significantly different from any potential source locations (ΦST > 0.48, P > 0.001). We could not distinguish the source of endemic variation; this will require genomic or experimental analyses. Increasing climatic variability emphasizes the need for understanding population-level responses to environmental change and how responses may be modified by sources of intraspecific variation.

The Elevation does not strongly influence interspecific variation in body size of small Tropical endotherms

Introduction: Body size is an essential trait for endotherms to face the physiological requirements of cold, so there is a tendency to large body size at high altitudes and latitudes, known as Bergmann's rule. However, the validity of this ecomorphological rule to small-bodied endotherms across altitudinal gradients is poorly known. Objective: To understand the effects of environmental variation on body size, we assessed whether interspecific variation in body size of small tropical endotherms follows Bergmann's rule along tropical altitudinal gradients. Methods: We compiled data on elevational ranges and body masses for 133 species of hummingbirds of Colombia. We then assessed the association between body mass and mid-point of the altitudinal distribution using phylogenetic generalized least squares (PGLS) analyses under different evolutionary models. Results: We found a decelerating rate of evolution for body size since the Early Burst model of evolution provided a better fit to body mass data. For elevational range, we found a slow and constant rate since Pagel's lambda model provided a better fit to the mid-point of the altitudinal distribution data. Besides, phylogenetic regression analysis indicated that body mass and the altitudinal range of hummingbirds are associated through the phylogeny, with a positive but slight association (R2= 0.036). Conclusions: We found that body mass and altitude of hummingbirds are positively related, which is in agreement with expectations under Bergmann's rule. However, this association was weaker than expected for small and non-passerine birds like hummingbirds. Thus, our results suggest that environmental changes across altitudinal gradients do not strongly influence body mass in small tropical endotherms as hummingbirds.

Geographical ecology of Tantilla melanocephala (Squamata: Serpentes: Colubridae) in a Neotropical region: a comparison of northeastern Atlantic Forest and Caatinga populations

ABSTRACT Studying species with wide geographical distributions allows the evaluation of the effects of environmental variation and phylogenetic constraints on the ecology of these organisms. The snake Tantilla melanocephala is widely distributed across South America in different environments (Amazonia, Atlantic Forest, Cerrado, Caatinga, and Chaco). We compared the morphology, diet, and reproduction of T. melanocephala inhabiting the northeastern Brazil in Atlantic Forest and Caatinga. In total, 161 individuals were collected from the Atlantic Forest and 88 were collected from Caatinga, and all had similar morphological and ecological traits. There was no sexual dimorphism within the biomes, and no morphological differences between individuals from both biomes. The species fed mainly on chilopods, and there were a few differences in the centipede species consumed in each biome. The volume of consumed prey did not differ between biomes, and clutch size was also similar (1–2 eggs), with differences during the egg-laying period reflecting environmental differences. The species has a continuous reproductive cycle in the Atlantic Forest and a seasonal reproductive cycle in Caatinga. Similarities in the morphology and ecology of T. melanocephala in the Atlantic Forest and Caatinga suggests that the species exhibits a high degree of phylogenetic conservatism.

Hummingbird torpor in context: duration, more than temperature, is the key to nighttime energy savings

Torpor is an important energy saving strategy in some small birds, but it has rarely been studied in natural field conditions. We compared torpor use across 43 wild‐caught individuals of eight hummingbird species across sites with different natural temperature regimes. Most laboratory studies focus on the relationship between metabolic rate and temperature, but our aim was to evaluate what environmental factors most influence hummingbird nighttime energy management under natural conditions. We found that the probability of an individual entering torpor was weakly correlated with mass but unrelated to nighttime temperature and that hummingbirds at both warm, tropical and cooler, temperate sites used torpor. Energy savings in torpor were maximized as ambient temperatures approached a species’ minimum body temperature, consistent with laboratory studies; energy savings ranged between 65 and 92% of energy per hour in torpor compared to normothermy. However, regardless of the degree of energy savings in torpor, variation in total nighttime energy expenditure was most significantly influenced by torpor bout duration. Lab studies largely assess the effect of temperature on torpor use, but our findings indicate that other environmental conditions are more important in determining hummingbirds’ total nighttime energy expenditure under natural temperature cycles. Our results show that a small endotherm's nighttime energy management in its natural habitat is more affected by torpor bout duration, which is linked to photoperiod, than by temperature. This result suggests that in their natural environments hummingbirds are able to save energy in torpor across a range of nighttime temperatures, indicating that they may have sufficient physiological flexibility to tolerate climatic variation.

Identifying the presence of structural damage: A statistical hypothesis testing approach combined with residual strain energy

A statistical hypothesis testing scheme is presented for damage detection considering environmental variations, in which the presence of damage is identified via Welch’s t-test by comparing the means of two groups of residual strain energy (RSE) samples from healthy and inspected structures. The RSE, as a damage indication feature, is determined from the mode shape residual (MSR), and the corresponding effects of environmental variations are eliminated via the PCA method. To further improve the damage sensitivity of RSE samples, an MSR selection strategy is proposed to examine the sensitivity of the available MSR matrices to damage and select the most effective MSR matrix. The sensitivity formula of the test statistic with respect to damage is derived and defined as the sensitivity index. Moreover, the mode shape expansion process is not required because an MSR that only includes x- or y-translational degrees of freedom (DoFs) at the measured points is sufficient for detecting damage. The effects of the location and extent of damage, incomplete measurements, and the critical value of the t-test on the performance of the proposed scheme are discussed by numerically analyzing an offshore platform. The results indicate that the scheme can simultaneously limit the probability of committing Type I and Type II errors under temperature variations and noise contamination. An analysis of field test data for a real-world wind turbine also indicates that this approach can avoid Type I error in a real marine environment.