Neural network modeling of dissolved oxygen in the Gru?a reservoir, Serbia

The objective of this study is to develop a feedforward neural network (FNN) model to predict the dissolved oxygen in the Gru?a Reservoir, Serbia. The neural network model was developed using experimental data which are collected during a three years. The input variables of the neural network are: water pH, water temperature, chloride, total phosphate, nitrites, nitrates, ammonia, iron, manganese and electrical conductivity. Sensitivity analysis is used to determine the influence of input variables on the dependent variable. The most effective inputs are determined as pH and temperature, while nitrates, chloride and total phosphate are found to be least effective parameters. The Levenberg-Marquardt algorithm is used to train the FNN. The optimal FNN architecture was determined. The FNN architecture having 15 hidden neurons gives the best choice. Results of FNN models have been compared with the measured data on the basis of correlation coefficient (r), mean absolute error (MAE) and mean square error (MSE). Comparing the modelled values by FNN with the experimental data indicates that neural network model provides accurate results.     

Can a marine pest reduce the nutritional value of Mediterranean fish flesh?

Biological invasions are deemed as one of the most severe threats to biodiversity and can result in huge economic impacts on natural resources. Many studies have assessed structural changes caused by the introduction of nonindigenous species, but urgent questions remain to be answered about the complex indirect effects of invasive pests on marine biodiversity at the species and ecosystem level. Previous investigations focusing on the biological invasion by Caulerpa racemosa in the Mediterranean indicated that the lipophilic algal metabolite caulerpin accumulates in the tissues of the native edible white sea bream Diplodus sargus feeding on the exotic alga. The level of caulerpin in D. sargus has been thus used as an indicator of the trophic exposure of the fish to the seaweed and related with adverse effects on the fish health. In the present study, we show that the C. racemosa-based diet can also alter muscle fatty acids composition in the white sea bream by reducing the percentage of polyunsaturated fatty acids of the n-3 and n-6 series, such as eicosapentaenoic (C20:5), docosahexaenoic (C22:6) and arachidonic acids (C20:4). This represents both a real threat to the health of fish unable to biosynthesize these essential fatty acids and an impoverishment of an important source of essential fatty acids for human nutrition, which helps to prevent cardiovascular diseases, diabetes, hepatic steatosis, cancer and neurological disorders. On the whole, this work sheds light on an unexplored and critical aspect of biological invasions with implication on the health of both humans and the environment.     

Long-term roosting data reveal a unimodular social network in large fission-fusion society of the colony-living Natterer’s bat (Myotis nattereri)

Behavioral Ecology and Sociobiology - In many tropical birds, both sexes use conspicuous vocal signals during territorial interactions. Although a growing number of studies examine male and female...     

Vulnerability of newly settled red drum (Sciaenops ocellatus) to predatory fish: is early-life survival enhanced by seagrass meadows?

We conducted predation experiments to evaluate the vulnerability of red drum Sciaenops ocellatus (Linnaeus) larvae and early juveniles to pinfish Lagodon rhomboides (Linnaeus) predators. Experiments were designed to analyze the effects of habitat complexity, prey size, and rearing condition on prey vulnerability. Three structurally different habitats [unvegetated (substrate only), shoal grass Halodule wrightii (Aschers) and turtle grass Thalassia testudinum (Bank ex König)] were simulated in experimental mesocosms. Instantaneous hourly mortality rates (Z?h^?1 predator^?1) for hatchery-reared red drum were significantly higher in the unvegetated habitat (0.189) than in either shoal grass (0.069) or turtle grass (0.046). A similar trend in predation mortality was observed for wild-caught red drum; instantaneous hourly mortality rates were 0.166, 0.047, and 0.021 in unvegetated, shoal grass, and turtle grass habitats, respectively. Mortality rates (adjusted means) for hatchery red drum were higher than for wild individuals in all three habitats; however, the differences were not significant. Predation mortality decreased with increasing prey size (3 to 9% decrease in Z per mm increase in length), suggesting that small red drum (i.e. new settlers) were most vulnerable to predators. We conclude that habitat complexity is critical to the survival of newly settled red drum, and changes in the complexity or areal coverage of natural seagrass meadows may affect early-life survival and possibly recruitment levels.     

Do social spiders cooperate in predator defense and foraging without a web?

Nearly all social spiders spin prey-capture webs, and many of the benefits proposed for sociality in spiders, such as cooperative prey capture and reduced silk costs, appear to depend on a mutually shared web. The social huntsman spider, Delena cancerides (Sparassidae), forms colonies under bark with no capture web, yet these spiders remain in tightly associated, long-lasting groups. To investigate how the absence of the web may or may not constrain social evolution in spiders, we observed D. cancerides colonies in the field and laboratory for possible cooperative defense and foraging benefits. We observed spiders’ responses to three types of potential predators and to prey that were introduced into retreats. We recorded all natural prey capture over 447 h both inside and outside the retreats of field colonies. The colony’s sole adult female was the primary defender of the colony and captured most prey introduced into the retreat. She shared prey with younger juveniles about half the time but never with older subadults. Spiders of all ages individually captured and consumed the vast majority of prey outside the retreat. Young spiders benefited directly from maternal defense and prey sharing in the retreat. However, active cooperation was rare, and older spiders gained no foraging benefit by remaining in their natal colony. D. cancerides does not share many of the benefits of group living described in other web-building social spiders. We discuss other reasons why this species has evolved group living.     

Who’s what? Prompt recognition of social status in crayfish

Crayfish are excellent model organisms to study the proximate mechanisms underlying the maintenance of dominance hierarchies in invertebrates. Our aim here was to investigate whether Procambarus clarkii males use social eavesdropping to discriminate dominant from subordinate crayfish. To this end, we conducted an experiment composed of a “passive” and an “active” phase. In the passive phase, “focal” individuals were allowed (treatment 1) or not (treatment 2) to see and smell two size-matched crayfish fighting while, in the subsequent active phase, they were allowed to freely interact with the fighting dyad. None of the recorded variables showed any significant difference between the two treatments, but, invariably, focal individuals were able to promptly discriminate dominant from subordinate crayfish. This study provides evidence that male crayfish recognize the social status of a conspecific without the need of direct or indirect experience with it and avoid dominants—and thus dangerous opponents—by means of a badge of status. A form of “winner and loser effects” could also contribute to the structuring of dominance/subordinate relationships. The implication of these results in understanding the maintenance of dominance hierarchies in invertebrates are discussed and compared with findings previously achieved in the context of mate choice by P. clarkii females, who do appear to use eavesdropping to identify dominants and subordinates.     

Is sexual monomorphism a predictor of polygynandry? Evidence from a social mammal, the collared peccary

Sexual dimorphism is common in polygynous species, and there is clear evidence that both intra-sexual competition and female preferences can drive the evolution of large body size in males. In contrast, sexual monomorphism is often argued to reflect a relaxation of male mate competition or an intensification of resource competition among females. Alternatively, it might imply opportunities for females to circumvent or counteract male mate competition in a polygynandrous mating system. We test the prediction that sexual monorphism is associated with polygynandry in the collared peccary (Pecari tajacu, Tayassuidae), a social ungulate closely related to the old-world suids. The genetic mating system in the Tayassuidae is unknown, but its sexual monomorphism presents a striking contrast to the strong size dimorphism found in most Suidae, so that a departure from the polygynous system common in Suidae would be noteworthy. We characterized genetic relationships among adults within herds in three geographically distinct populations, assigned parents to 75 offspring, and tested for skew in individual reproductive success. Parentage assignment data indicated that multiple males sire offspring within a herd, and in the population for which genetic data were most complete, 19% of parentage assignments were potentially sired by extra-herd males. Some litters have multiple sires, and neither males nor females monopolized reproduction, even in small herds. This result supports our prediction and suggests that sexual monomorphism may either select for or be an evolutionary consequence of a promiscuous mating system.     

Do biodiversity indices behave as expected from traits of constituent species in simulated scenarios?

It is believed that diversity of plant communities has a positive effect on their productivity. The benefits of diversity are described by “biodiversity indices”, comparing yield of mixtures with yields of monocultures of constituent species. These indices are supposed to capture also the main mechanisms leading to increased yield. We have constructed a spatially explicit individual based model, simulating even-aged stand development, and compared the behaviour of selected biodiversity indices (overyielding, selectivity and complementarity) with expectations based on life history traits of constituent species. The results are based on comparisons of two species mixtures with corresponding monocultures. We designed three scenarios of changes in the two species life history differentiation, and compared the behaviour of the indices with expectation based on it. In the first scenario, selectivity was driven by increasing size inequality of the two species, mostly in accordance with expectations. The second scenario presents increasing shade tolerance of the smaller species that increased complementarity, again mostly as expected. In the last scenario, shortening of length of stress tolerance of the weaker species surprisingly increased values of the biodiversity indices. For each setting, we varied sowing density and spatial pattern of the constituent species. The behaviour of the indices was influenced by both factors, but the effect of density was more pronounced. In particular, at high sowing densities, the most important interactions happened in the very early stages of mixture development, and the behaviour of the indices was often counter-intuitive.     

Sedentary or mobile? Variability in space and depth use of an exploited coral reef fish

Movement of fishes defines the distribution and abundance of populations and occurs on a range of spatial and temporal scales. To successfully parameterise assessments and design management strategies for exploited fish populations, knowledge and consideration of their movement patterns are essential. Since the efficacy of management approaches vary depending on the sedentary or mobile nature of the target species, presence, space use and depth utilisation were examined to understand the movement patterns of redthroat emperor Lethrinus miniatus. Sixty individuals were monitored for up to 12 months in an acoustic array comprising three coral reefs, and variation in space use and movement patterns was observed among 26 individuals. Half of the individuals were recorded only in proximity of one receiver along the reef edge, while the other half were detected at multiple receivers and used horizontal areas of approximately 4 km². Periods of non-detection and lower detection frequency at night (χ ₁ ²  = 342.157, P < 0.001) indicated individuals may move away from the monitored reef edge to the adjacent sandy habitat, but most movements outside the array remain unknown. Long-distance movement was recorded for one individual, recaptured ~160 km from the release location. Generally, no trends in depth use were apparent, L. miniatus inhabited a variety of depths, which were not related to individual size or time of day, yet some effect of month was evident. Variation in movement among adult L. miniatus indicates that while some individuals undergo broader-scale movement, spatial closures that cover individual reefs (>4 km²) could provide protection from fishing for the proportion of the population that displayed high site fidelity and moderate-sized activity spaces (over a period of up to 12 months).     

Opportunistic discrimination of alien eggs by social wasps (Polistes biglumis, Hymenoptera Vespidae): a defense against social parasitism?

Foundresses of the social wasp Polistes biglumis were tested to see whether they were able to recognize alien eggs experimentally introduced into their own nests. Foundresses removed alien conspecific reproductive-destined eggs while they accepted worker-destined eggs. The results indicate that social wasps discriminate among eggs and that they discriminate against alien eggs destined to produce unrelated reproductives. P. biglumis is a strictly solitary founding species, with no reproductive competition within colonies; thus, brood discrimination abilities could have evolved as a counteradaptation against intra- and inter-specific brood parasitism. Received: 12 May 2000 / Revised: 15 July 2000 / Accepted 20 July 2000     

Is frequent consumption of tuna fish safe? Evidence of liver damages in rats fed on red or white meat from tuna fish caught in the Gulf of Gab��s (Tunisian coast)

In recent years, a number of studies have clearly pointed out the nutritional benefits of fish consumption. However, some concerns about potential health risks derived from contaminants found in fish have also been raised. Therefore, balancing adequately the risks and benefits of fish consumption is currently a health key issue. As tuna fish represents a large part of the traditional food in some countries, the possible impact of tuna fish consumption on public health was investigated. Hepatic damages following consumption of tuna fish white (ordinary) or red (dark) muscle were evaluated in rat. Under our experimental conditions, feeding the animals for 60?days with white or, more markedly, red tuna meat resulted in 1) an elevated uric acid level in blood, 2) an accumulation of lead in liver, 3) an atrophy of liver, 4) an increase in plasma aspartate aminotransferase and alanine aminotransferase activities, and 5) an oxidative stress in liver including an increased level of lipids peroxidation and enhanced activities of superoxide dismutase, catalase and glutathione peroxidase. In addition, liver histology revealed several abnormalities. These alterations could be attributed to both lead accumulation and high purine levels in tuna meat. We conclude that attention should be paid to a possible health impact of frequent and important consumption of tuna fish meat, especially the dark one.     

What enables coexistence in plant communities? Weak versus strong species traits and the role of local processes

Explaining the coexistence of species that basically depend on the same resources has been a brainteaser for generations of ecologists. Different mechanisms have been proposed to facilitate coexistence in plant communities, where space is an important resource. Using a stochastic cellular automaton simulation model we analyze - separately and in combination - the influence of different species traits and processes which alter local competition on the coexistence of plant species over a fixed time horizon. We show that different species traits operate on different time scales in competition. We therefore suggest the concept of weak versus strong traits according to short- or long-term exclusion of species differing in these traits. As a consequence, highly non-linear trade-offs between weak and strong traits can result in communities. Furthermore, we found that trade-offs based on physiological species traits such as plant lifetime, dispersal range and plant growth, did not support broad and long-term coexistence—further processes such as density-dependent mortality and light-dependent colonization were necessary. This suggests that coexistence in plant communities requires (stabilizing) local processes to support the (equalizing) trade-offs in species traits.     

Latitude or biogeographic breaks? Determinants of phenotypic (co)variation in fitness-related traits in Betaeus truncatus along the Chilean coast

Ectothermal organisms distributed along environmental gradients in a wide geographical distribution display extensive phenotypic variation. This is particularly pervasive along latitudinal clines, which are linked to gradual changes in environmental factors. Widespread species may also be distributed among biogeographic breaks, which in contrast to smooth clines, often show abrupt changes in phenotypic traits. In species with widespread latitudinal distribution that also encompass important biogeographical breaks, it is not clear which of those factors prevails on shaping the phenotypic variation or if some traits are particularly more sensitive to one or the other. To evaluate this, we measured 4 fitness-related traits in 6 populations of the intertidal snapping shrimp Betaeus truncatus, as its distribution along Chile expands over 40° in latitude and three major biogeographical provinces. Here, we statistically evaluated the role of both, latitude and biogeographic breaks, on mean population values of fitness-related traits but also on the variances and covariances (i.e., P-matrix) between them. Overall, our results (1) indicate that latitude is more important than breaks in shaping the phenotypic variation of most of these fitness-related traits, (2) show that the differences in the variance–covariance relationship among traits between the extremes of the gradient arises from gradual increases in variance and rather sharp changes in covariance at mid-latitudes and (3) show that at present, it is difficult to unambiguously determine whether natural selection or plasticity is responsible for the observed pattern in means, variances and covariances and only further work might disentangle these possibilities.     

How stable are personalities? A multivariate view of behavioural variation over long and short timescales in the sheepshead swordtail,Xiphophorus birchmanni

Many studies have revealed repeatable (among-individual) variance in behavioural traits consistent with variation in animal personality; however, these studies are often conducted using data collected over single sampling periods, most commonly with short time intervals between observations. Consequently, it is not clear whether population-level patterns of behavioural variation are stable across longer timescales and/or multiple sampling periods or whether individuals maintain consistent ranking of behaviours (and/or personality) over their lifetimes. Here, we address these questions in a captive-bred population of a tropical freshwater poeciliid fish, Xiphophorus birchmanni. Using a multivariate approach, we estimate the among-individual variance-covariance matrix (I), for a set of behavioural traits repeatedly assayed in two different experimental contexts (open-field trials, emergence and exploration trials) over long-term (56 days between observations) and short-term (4-day observation interval) time periods. In both long- and short-term data sets, we find that traits are repeatable and the correlation structure of I is consistent with a latent axis of variation in boldness. While there are some qualitative differences in the way individual traits contribute to boldness and a tendency towards higher repeatabilities in the short-term study, overall, we find that population-level patterns of among-individual behavioural (co)variance to be broadly similar over both time frames. At the individual level, we find evidence that short-term studies can be informative for an individual’s behavioural phenotype over longer (e.g. lifetime) periods. However, statistical support is somewhat mixed and, at least for some observed behaviours, relative rankings of individual performance change significantly between data sets.     

Relationship between near-surface morphological traits of familiar plants and their ability for sediment retention in a dry-hot valley北大核心CSCD

To explore the sediment interception capacity of plants and its relationship with the surface morphological traits of plants, we used laboratory simulations and off-site flume experiments to study the ability for sediment retention of six familiar species: Leucaena leucocephala (LL), Melia azedarach (MA), Dodonaea viscosa (DV), Coriaria sinica (CS), Heteropogon contortus (HC), and Eulaliopsis binata (EB) aver two growth periods in the dry-hot river valley of the Jinsha River. We analyzed the relationship between near-surface morphological traits of individuals of six species and their ability for sediment retention. Our study resulted in three main observations. (1) In the flume experiment, three-month seedlings and one-year old seedlings of the six species showed different abilities for sediment retention. In the three-month seedlings, the ability for sediment retention of CS was the highest, followed by MA and LL, whereas it was the lowest in HC and EB. However, in one-year old seedlings, the ability for sediment retention of CS was the highest, but the ability for sediment retention of HC and EB was better than those of MA and LL. Hence, the ability for sediment retention of the six species fluctuated between different growth periods. (2) The three-month old and one-year old seedlings of all six species showed different near-surface morphological traits. (3) The sediment mass was significantly and positively correlated with near-surface leaf areas, crown lengths, crown widths, stem dry matter densities at the intersection volume, and above-ground biomass, but significantly and negatively correlated with the angle between stem and ground, indicating that these latter are the main near-surface morphological traits able to affect sediment retention. In addition, the sediment mass was also correlated (positively and negatively) with the stem epidermal crack number, stem dry matter content, leaf dry matter content at the intersection volume, and dry mass per unit volume of the intersection volume, which could also reflect the ability of sediment retention. We conclude that in the areas where plant measures are used to control soil erosion and intercept sediment, the key, above-mentioned plant morphological factors should be taken into account in order to select the optimal plant species. © 2018 Science Press. All rights reserved.     

Loud calls as a mechanism of social coordination in a fission–fusion taxon, the white-bellied spider monkey (Ateles belzebuth)

Spider monkeys (Ateles spp.) live in social groups that exhibit high levels of fission–fusion dynamics, in which group members form subgroups of varying sizes and compositions. Within these fluid societies, how individuals establish contact with dispersed group members with whom they might choose to associate remains unclear. Long-range vocalizations might facilitate interactions between group members and provide a means of social coordination in fission–fusion societies. We evaluated this possibility for one spider monkey vocalization, the loud call, by examining calling behavior, the relationship between loud calls and changes in subgroup size, and the response of individuals to distant calls and playback experiments in a single study group. We found that 82 % of loud calls were emitted within 30 min of a call from a different location, suggesting that individuals frequently emit loud calls in response to the calls of distant group members. Subgroups that emitted loud calls, especially those that responded to distant calls, were much more likely to experience an increase in subgroup size within an hour after calling than those that did not. Animals also approached distant loud calls more than they avoided or ignored these calls. Finally, playbacks of male calls demonstrated that females respond preferentially to the calls of some individuals over others. Taken together, these results provide support for the hypothesis that spider monkey loud calls function to facilitate and initiate interactions between dispersed group members and suggest that vocal signals can play an important role in influencing social interactions in fission–fusion societies.     

A paradox of the ciliates? High ciliate diversity in a resource-poor environment

Ecological theory predicts that low productivity systems should have low biodiversity. However, despite the oligotrophic status of the Gulf of Aqaba (Northern Red Sea) ciliate species richness was unexpectedly high. In addition, phytoplankton, as main ciliate prey, was made up by only few genera, indicating a significant niche overlap among the grazers. Up to 97% of the ciliates were from the same taxonomic group and of the same size range, implying very similar food niches. Ciliate diversity was highest at times of lowest chlorophyll concentrations, during the period of stable abiotic conditions, but relatively high genetic diversity within the ciliate prey, notably among the cyanobacteria Synechococcus and Prochlorococcus. In the absence of disturbance and with little predation pressure, the alternate explanations for the observed ciliate diversity are either very fine niche partitioning by the ciliates, or their competitive equivalence resulting in a random assortment of species immigrating from a larger metacommunity, in accordance with Hubbell’s, (The unified neutral theory of biodiversity and biogeography. Princeton University Press, Princeton, 2001) neutral model. While the use of species abundance distributions (SAD’s) is far from definitive, the theoretical SAD’s that best fit the Gulf of Aqaba ciliate data was most often not that expected by neutral theory.     

Acquisition of fission–fusion social organization in a chimpanzee (Pan troglodytes troglodytes) community released into the wild

The social aspects of primate reintroduction are of primary importance to the success of release programs and need to be assessed through the study of changes in social behavior over time. This study reports on the development of social structure and organization in a community of 37 chimpanzees (Pan troglodytes troglodytes) released into the wild in the Conkouati Douli National Park, Republic of Congo. Analyses of post-release monitoring data collected over 10 years on association patterns between individuals show that during the years following individual releases, chimpanzees exhibited changing social structure and organization until they stabilized in one community living in a fission–fusion system. Social organization development was directly affected by several factors including community size and experience in the wild, while social structure was affected by individual characteristics: gender, pre-release history, and release history. Similarities between social structure and organization observed in the released community and wild chimpanzee communities demonstrate that the release program is a success from a social point of view.     

Increased sedentariness in European Blackbirds following urbanization: a consequence of local adaptation?

Urbanization changes local environmental conditions and may lead to altered selection regimes for life history traits of organisms thriving in cities. Previous studies have reported changes in breeding phenology and even trends toward increased sedentariness in migratory bird species colonizing urban areas. However, does the change in migratory propensity simply represent a phenotypic adjustment to local urban environment, or is it genetically based and hence the result of local adaptation? To test this, we hand-raised European Blackbirds (Turdus merula) from urban and forest populations, quantified their nocturnal activity and fat deposition covering two complete migratory cycles and examined the consequences of a reduced migratory propensity for the timing of gonadal development (a physiological measure of the seasonal timing of reproduction). Although nocturnal activities differed strikingly between fall and spring seasons, with low activities during the fall and high activities during the spring seasons, our data confirm, even in birds kept from early life under common-garden conditions, a change toward reduced migratoriness in urban blackbirds. The first score of a principal component analysis including amount of nocturnal activity and fat deposition, defined as migratory disposition, was lower in urban than in forest males particularly during their first year, whereas females did not differ. The results suggest that the intrinsic but male-biased difference is genetically determined, although early developmental effects cannot be excluded. Moreover, individuals with low migratory disposition developed their gonads earlier, resulting in longer reproductive seasons. Since urban conditions facilitate earlier breeding, intrinsic shifts to sedentariness thus seem to be adaptive in urban habitats. These results corroborate the idea that urbanization has evolutionary consequences for life history traits such as migratory behavior.     

Smashing tests? Patterns and mechanisms of adult mortality in a declining echinoid population

Mass mortality of echinoids is well documented, and has potentially profound effects on benthic communities. However, no study to date has quantitatively investigated how regular, predictable events such as winter storms might lead to large mortality events in pivotal echinoid species. Hydrodynamic disturbances can be major drivers of crucial biological processes in benthic communities. For echinoid populations in particular, wave action in shallow waters generated by high winds (winter storms) can cause displacement, damage and even death to individuals. However, evidence for displacement-mediated mortality is scant in the literature, in part because it is so difficult to demonstrate in exposed environments where echinoids are frequently found. In this study, we examined mortality in a sheltered subtidal population of the European purple sea urchin Paracentrotus lividus over a 3-year period, and examined the role that dislodgement by wave action or predation might play in these mortality patterns. Because our study population has been in decline for the past three decades, we considered it important to evaluate its current status in addition to assessing the contribution that adult mortality makes to that decline. We sampled twice per month, using the density of freshly dead echinoid material to assess the extent of adult mortality. The Irish Meteorological Service provided our estimates of wind speed data. We compared historical and recent data on P. lividus size frequency data to investigate change the population structure (Poor recruitment would be caused by failure to spawn over a prolonged period). Our data suggest ongoing declines in this population, and support the theory that the decline of the P. lividus population of Lough Hyne is a result of persistent recruitment failure linked to repeated cool maximum sea surface temperatures. Although we found peaks of P. lividus mortality were coincident with spikes in wind speed, mortality was low, and seems unlikely to have contributed significantly to the dramatic decline in P. lividus in the past three decades.Communicated by J.P. Thorpe, Port Erin