Browse results

You are looking at 1 - 10 of 1,633 items for :

  • Primary Language: English x
Clear All

G. Brabata, C. Battisti, R. Carmona and C.A. Sánchez-Caballero

The Chametla wetland is used by shorebirds as a stopover site during their autumn migration and it is also an important breeding area for several species of waterbirds. The objective of this work was to compare the bird assemblages in Chametla wetland during three sampling periods: 1) 1991–1992; 2) 1997–1998 which was subjected to El Nino Southern Oscillation (ENSO) climate conditions and 3) 2005–2006. Bird communities were characterized in terms of species composition and diversity, using similarity analysis. Bird assemblage composition differed across years and seasons. Seasonal variations in composition and diversity were related to the presence/absence of phenological-characterized species (migratory vs. wintering species). The highest species richness was recorded under the ENSO period (1997–1998). We observed a sharp decrease in shorebird numbers, with evident stress at the assemblage level throughout the entire study period. There seems to be a transition of the bird assemblages from shorebird dominance to a dominance by long-legged wading birds and waterfowl species, which could be related to water level variation and changes in the quality/availability of food in the intertidal zone. The joint pressures of regional climate variation combined with local anthropogenic perturbations may lead to changes in bird assemblage in the Chametla wetland.

Facundo Xavier Palacio, Mariano Ordano and Santiago Benitez-Vieyra

The use of multiple regression analysis to quantify the regime and strength of natural selection in nature has been an influential approach in evolutionary biology over the last 36 years. However, many studies fail to report the protocol of estimation of selection coefficients (selection gradients) and the specific model assumptions, thus failing to verify and reproduce the estimation of selection coefficients. We present a brief overview of the Lande and Arnold’s approach and a step-by-step R routine to aid researchers to perform a verifiable and reproducible regression analysis of natural selection. The steps involved in the analysis include: (1) assessing collinearity between phenotypic traits, (2) testing normality of model residuals, and (3) testing multivariate normality of phenotypic traits. We also performed a series of simulations to test the effect of non-symmetrical (skewed) phenotypic traits on the estimation of linear selection gradients. These showed that the bias in the linear gradient increased with increased skewness in phenotypic traits for the quadratic model, whereas the linear gradient of a model with only linear terms was nearly independent of trait skewness. If none of the above assumptions are met, selection gradients need to be estimated from two separate equations, whereas standard errors must be computed using other methods (e.g. bootstrapping). We expect that the procedure outlined here and the availability of analytical codes motivate the verifiability and reproducibility of the Lande and Arnold’s approach in the study of microevolution.

Edith Katsnelson Ilan, Orli Bobek, Adiv Gal, David Saltz and Uzi Motro

We studied Lesser Kestrels’ (Falco naumanni) conditional nest-site fidelity, i.e., fidelity that depends on the outcome of the previous nesting attempt in that site. In particular, we were interested in examining whether individual kestrels practice a Win–Stay/Lose–Shift (WSLS) strategy towards their nest-sites; that is, does the tendency to use the same nest-site increase following a successful nesting season, but decrease following a failure. For that purpose, we documented the use of nest-sites by Lesser Kestrels and the breeding success in these sites during 1998–2003 in the city of Jerusalem (Israel). We found that while Lesser Kestrels do not practice WSLS strategy towards their nest-site, the males (but not the females) do so towards their sub-colony – they tend to stay in the same sub-colony if their nesting was successful, whereas they tend to migrate to a different sub-colony after failure. A possible explanation to this sexual difference in WSLS behavior can arise from the fact that changing a sub-colony entails a change of hunting area. The male, being the main food provider in the Lesser Kestrel, may be more sensitive to this opportunity.

Konul G. Hasanova

The purpose of this research was to study the dynamics of melatonin, insulin, adrenaline and glucose in the blood of rabbit kits (prior and subsequent to prenatal hypoxia) at various stages of fetal growth and development; to study the ability of kits to withstand physical exertion of various intensity and duration in light and dark. The study of hypoxia exposure factors, photoperiodic factors and methods for correcting its effects is one of the pressing issues currently facing experimental and clinical physiology. In this context, it is important to study the effect of prenatal hypoxia on hormones synthesizing and expressing principles in the early periods of postnatal ontogenesis. This research shows that melatonin level decreases with increasing insulin and increases with decreasing insulin in animals of different ages kept under conditions of constant light and constant darkness, while the level of adrenaline decreases at physical exertion, but increases with a decrease in melatonin. This research confirms the inverse relationship between the levels of melatonin and insulin and between the levels of melatonin and adrenaline. Kits being in constant darkness have increasing melatonin, which by contrast decreases under conditions of constant light.

Xinguang Yang, Xilai Li, Mingming Shi, Liqun Jin and Huafang Sun

Replacement of topsoil to an appropriate depth is one of the key methods for ecological restoration. The objective of this study was to investigate the effects of topsoil replacement depth on vegetation and soil properties, and to identify the optimum soil depth for reclamation of coal mine spoils in a cold alpine mining area. We sowed 3 herbaceous species after coal mine spoil heaps were treated with topsoil to 3 depths (0, 20‒25, 40‒45 cm). The variations in vegetation community structure, plant growth, soil properties were measured at different replaced topsoil depths. The correlations between plant and soil properties were analyzed statistically. The results showed species richness, diversity and evenness were not significantly different among different depths of topsoil (P > 0.05). Vegetation coverage, density, height and aboveground biomass increased significantly (P < 0.05) with increasing topsoil depth. Soil properties did not change significantly with increasing topsoil depth (P > 0.05), but soil organic matter was significantly higher at 40‒45 cm topsoil depth than at other two depths (P < 0.05). All soil properties, with the exception of total potassium, were positively correlated with the plant growth parameters. The 40‒45 cm topsoil depth of replacement should be considered as effective method in reclaiming coal mine spoils. The use of both topsoil replacement to a depth of 40‒45 cm and sowing of suitable herbaceous seeds is found to be an effective restoration strategy. Additionally, fertilization might be used as a substitute for artificial topsoil replacement to improve soil quality and speed up revegetation process by the positive plant-soil interactions.

Zhen Zhang, Lichao Wang, Jing Liu, Zhaorong Dong, Wei Xu and Shiping Wang

Understanding the reproductive response of host plants to herbivores is important in grazing ecology and grassland management. Simulated grazing experiments were conducted to determine the influence of different grazing intensities on reproductive performance of a shrub, Caragana microphylla Lam. The total leaf mass, total flower mass, total flower mass allocation, and single flower mass allocation decreased with increased grazing intensity. The total spine mass, single flower mass and total spine mass allocation increased with increased grazing intensity. The stem mass, stem mass allocation and total leaf mass allocation had not significant change with the increasing grazing intensity. Under heavy grazing treatments, the host plants significantly decreased their investment in reproduction and increased investment in physical defense organs. Although there were no significant differences in the number of ovules among different grazing intensities, herbivory negatively affected reproductive performance, including the number of flowers, the number of pollen grains per flower, the number of ripe seeds and the rate of pod-set in host plants. These results indicate that there are trade-offs among vegetative and reproductive and defensive organs. Compared with male reproduction, female reproductive performance was less sensitive to herbivory and grazing intensity. Moreover, pollen grains from heavily browsed plants seemed to be less likely to sire pods and ripe seeds than those from unbrowsed plants, indicating that herbivory not only decreased pollen production, but also adversely affected pollen performance.

Adiv Gal, David Saltz and Uzi Motro

The effect of food supplement to Lesser Kestrel (Falco naumanni) nests during the nestling period (from hatching to fledging) was studied in two nesting colonies in Israel – Alona and Jerusalem. Our hypothesis, based on diminishing returns considerations, was that food supplement will have a greater effect on fledgling success in the food-limited, urban colony of Jerusalem, than in the rural colony of Alona. Indeed, food supplement had a significantly positive effect on breeding success in both colonies. However, and contrary to our prediction, the decrease in chick mortality between supplemented and control nests in Jerusalem was not larger than in Alona (actually it was numerically smaller, albeit not significantly so). This implies either that additional factors, possibly urbanization associated, other than food limitation, might be responsible for the difference in nesting success of Lesser Kestrels between Alona and Jerusalem, and/or that the amount or the nutritional quality of the additional food provided to supplemented nests (three mice per chick per week), was not enough.

Rida Sultanova, Ildar I. Gabitov, Yulai A. Yanbaev, Fitrat G. Yumaguzhin, Maria V. Martynova, Ivan V. Chudov and Varys R. Tuktarov

The management of beekeeping on forest lands is a vivid manifestation of the multifunctional use of forests, which is based on its target cultivation. The work shows the development of beekeeping, identifies factors affecting the sustainable development of this industry, sets priorities for increasing the efficiency of utilization of forest honey resources of the Southern Urals, including the main melliferous - Tilia cordata Mill. The nature and characteristics of the influence of weather and climatic factors on the growth of bee colonies, their physiological state, composition, age representation of natural melliferous woody plants, the onset dates and the duration of their flowering were determined. It was found that, of the silvicultural and inventory indicators, the composition and age, density and type of forest most strongly influence the yield of honey. The activities of forest care are close to them in terms of importance. A system of organizational measures has been proposed, through which high efficiency of using forest feed resources and sustainable development of beekeeping can be achieved: keeping an optimal number of bee colonies in an apiary - up to 150 hives, based on providing one bee colony of 50-60 thousand individuals with at least 130 kg of nectar; the location of apiaries in the 3-kilometer zone of growth of forest melliferous plants, taking into account the productive emergence of bees in the 2.5-3.0 km; establishing clear nomadic routes based on a geobotanic inventory of forest and agricultural melliferous plants. Increasing the target indicator - the nectar productivity of forests without a gap in their use both in space and in time - can be achieved by growing multi-tiered forests of different age from Tilia cordata Mill.

Shai Meiri, Amos Belmaker, Daniel Berkowic, Kesem Kazes, Erez Maza, Guy Bar-Oz and Roi Dor

Faunal lists are important tools in ecology, biogeography, and conservation planning. Such lists can identify gaps in our knowledge of the distribution and taxonomy of regional faunas, and highlight issues needing further study. We present an up to date list of all land vertebrates occurring in Israel. We identify 786 species, of which 551 are birds, 130 are mammals, 97 are reptiles and eight are amphibians. Of these 369 species breed in Israel (including reintroductions), 199 (mostly birds) are regular visitors and 182 are accidental. Fourteen other species are invasive, and 22 species are extinct. We identify issues with the taxonomy and status of several species, and note recent developments in our understanding the Israeli land vertebrate fauna.

Xin Yin, Wei Qi and GuoZhen Du

A growing body of evidence from diversity-manipulation and natural studies suggests that the stability of community productivity increases with biodiversity; however, few studies have researched this relationship in a non-weeded grassland. To clarify this issue, we established an artificial grassland in 2003 using three common species, Elymus nutans, Festuca sinensis and Festuca ovina, which included seven different community structures (three monocultures, three two-species mixtures and one three-species mixture based on sown species) and two nutrient addition treatments (non-nutrient addition and nutrient addition). Data was collected over a three-year period (2011–2013). Our results showed that the sowing species modified realized species richness (i.e. the number of total species we observed in a community) and species evenness, but had negligible influences on community- and population-level stability. Furthermore, all of these variables were reduced by nutrient addition. These dynamics did not alter the positive influence of realized species richness on community stability, but restricted the stable effect of evenness because this effect was only significant under nutrient addition condition. The potential mechanisms underlying these processes were statistical averaging and species asynchrony, rather than overyielding effect. Conversely, population stability decreased with realized species richness in non-nutrient addition treatments. We conclude that biodiversity contributed to community- and population-level stability even in non-weeded experiment. This process resulted from different mechanisms that observed in weeded experiments. Further studies in other ecosystems (e.g. aquatic ecosystem) are needed to find a more general conclusion.