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In a temperate climate, understory trees leaf out earlier than canopy trees, but the cause of this discrepancy remains unclear. This study aims to investigate whether this discrepancy results from ontogenic changes or from microclimatic differences. Seedlings of five deciduous tree species were grown in spring 2012 in the understory and at canopy height using a 45-m-high construction crane built into a mature mixed forest in the foothills of the Swiss Jura Mountains. The leaf development of these seedlings, as well as conspecific adults, was compared, taking into account the corresponding microclimate. The date of leaf unfolding occurred 10–40 d earlier in seedlings grown at canopy level than in conspecific adults. Seedlings grown in the understory flushed c. 6 d later than those grown at canopy height, which can be attributed to the warmer temperatures recorded at canopy height (c. 1°C warmer). This study demonstrates that later leaf emergence of canopy trees compared with understory trees results from ontogenic changes and not from the vertical thermal profile that exists within forests. This study warns against the assumption that phenological data obtained in warming and photoperiod experiments on juvenile trees can be used for the prediction of forest response to climate warming.

Cephalopods play a key role in the marine environment but knowledge of their feeding habits is limited by lack of data. Here, we have developed a new tool to investigate their feeding ecology by combining the use of their predators as biological samplers together with measurements of the stable isotopic signature of their beaks. Cephalopod beaks are chitinous hard structures that resist digestion and the stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) are indicators of the foraging areas and trophic levels of consumers, respectively. First, a comparison of δ13C and δ15N values of different tissues from the same individuals showed that beaks were slightly enriched in 13C but highly impoverished in 15N compared with lipid-free muscle tissues. Second, beaks from the same species showed a progressive increase in their δ15N values with increasing size, which is in agreement with a dietary shift from lower to higher trophic levels during cephalopod growth. In the same way, there was an increase in the δ15N signature of various parts of the same lower beaks in the order rostrum, lateral walls and wings, which reflects the progressive growth and chitinization of the beaks in parallel with dietary changes. Third, we investigated the trophic structure of a cephalopod community for the first time. Values of δ15N indicate that cephalopods living in slope waters of the subantarctic Kerguelen Islands (n=18 species) encompass almost three distinct trophic levels, with a continuum of two levels between crustacean- and fish-eaters and a distinct higher trophic level occupied by the colossal squid Mesonychoteuthis hamiltoni. δ13C values demonstrated that cephalopods grow in three different marine ecosystems, with 16 species living and developing in Kerguelen waters and two species migrating from either Antarctica (Slosarczykovia circumantarctica) or the subtropics (the giant squid Architeuthis dux). The stable isotopic signature of beaks accumulated in predators' stomachs therefore revealed new trophic relationships and migration patterns and is a powerful tool to investigate the role of the poorly known cephalopods in the marine environment.

Ozark hellbenders (Cryptobranchus alleganiensis bishopi) have undergone marked population declines across their entire distribution. A variety of ecological life history research has been conducted to determine the cause(s) of the declines. Historically, hellbender diet studies used stomach content examination methods; however, alternative approaches such as less intrusive stable isotope analyses are now options for researchers. The goals of our study were to conduct stable isotope analysis on live and formalin-preserved museum specimen Ozark hellbender tissues to identify diet composition in the Eleven Point and Spring rivers, Arkansas. Also, we used stable isotope analysis to investigate if Spring River hellbender diets have changed over time. We sampled fish, live hellbenders (non-destructively), and formalin-preserved hellbender tissues from museum collections for stable isotope analysis. We sampled crayfish for assemblage composition and stable isotope analysis. The results of our stable isotope study revealed three main findings: (1) there were no statistically significant differences between hellbender δ13C and δ15N values among sites and hellbender stable C and N isotopes were correlated with body length; (2) traditional δ13C versus δ15N bi-plots and trophic discrimination values did not provide complete discernment in hellbender diets; however, Bayesian MixSIAR models revealed hellbenders to be generalists, and (3) the use of δ13C and δ15N values adjusted historic formalin-fixed and ethanol preserved hellbenders matched well with current crayfish and fish stable isotope values based on Bayesian MixSIAR models. These findings provide important diet information and a possible tool to examine dietary patterns from preserved specimens that may be used for hellbender conservation and management.

Defensive coloration that reduces the risk of predation is considered to be widespread in animals. Many closely related species adopt differing coloration strategies during the life cycle, including crypsis, conspicuousness, and ontogenic change between the two coloration types. Here, we use a dynamic state‐dependent approach to use ecological and intrinsic factors to predict the proportion of the developmental period of immature animals that should be spent as cryptic or conspicuous, and when conspicuous coloration should be reliably associated with investment in defenses. The model predicts that animals should change color more than once during development only in specific circumstances. In contrast, change from crypsis to conspicuous can occur over a range of conditions related to the frequency of detection by predators, but may also depend on the opportunity costs of crypsis and the effect of size on the deterrent effect of conspicuous coloration. We also report the results of a survey of coloration strategies in lepidopteron larvae, and note a qualitative agreement with the predictions of our model in the relationship between body size and coloration strategy. Our results provide explanations for several widespread antipredator coloration phenomena in prey animals, and provide a comprehensive predictive framework for the types of coloration strategies that are employed in nature.

Clearance rate of the planktonic cyclopoid copepod Mesocyclops dissimilis on the planktonic calanoid copepod Eodiaptomus japonicus was measured in laboratory experiments. Ontogenetic changes were investigated using several combinations of different developmental stages of the two species. To minimize the side effects of laboratory experiments, predation was examined for a short duration using field-captured animals at natural prey densities and temperatures. Individual predators showed a large variation in the clearance rate even within replicates of the same experiment. The clearance rates of adult female predators on late naupliar prey were similar (about 0.15 L/ind/d) within a range of prey density 12-31/ind./L. Ontogenetic tendencies in clearance rate, though seldom significant, translated to an increase with development of the predators and a decrease with that of the prey. Present clearance rates and the natural densities of predators and prey suggest that M. dissimilis was sometimes an influential predator of E. japonicus in the field.

The offshore marine ecosystem of the Canadian Beaufort Sea faces the double pressure of climate change and industrialization. Polar cod ( Boreogadus saida ) is a pivotal forage species in this ecosystem, accounting for 95 % of the pelagic fish assemblage. Its vertical distribution over the annual cycle remains poorly documented. Hydroacoustic records from 2006 to 2012 were analysed to test the hypothesis that age-0 polar cod segregate vertically from larger congeners. Trawls and ichthyoplankton nets validated the acoustic signal. Fish length, weight, and biomass were estimated from new regressions of target strength and weight on standard length. Polar cod were vertically segregated by size in all months, with small age-0 juveniles in the epipelagic (<100 m) layer and larger age-1+ deeper in the water column. From December to March, the biomass of age-1+ peaked in a mesopelagic layer between 200 and 400 m. With increasing irradiance from April to July, the mesopelagic layer deepened and extended to 600 m. Starting in July, age-0 polar cod formed an epipelagic scattering layer that persisted until November. From September onward, age-0 left the epipelagic layer to join small age-1+ in the upper mesopelagic layer. Low biomass in the mesopelagic layer from February to September likely resulted from large polar cod settling on the seafloor to avoid diving marine mammals. Longer ice-free seasons, warmer sea-surface temperatures, or an oil spill at the surface would likely impact epipelagic age-0, while mesopelagic age-1+ would be vulnerable to an eventual oil plume spreading over and above the seafloor.

In two Costa Rican and three Honduran sites that vary in rainfall and soil properties, we used natural isotopes, a soil water balance model, and broad-scale climate-based drought indices to study shifts in water use with ontogeny from seedlings to mature tropical live oak (Quercus oleoides) trees. Water use patterns help to explain persistence of this broadly distributed species in Mesoamerica and to evaluate likely threats of ongoing climate changes. At the end of the dry season, soil δ18O profiles can be described by one-phase exponential decay curves. Minimum values reflect geographic origins of the last significant rain event, and curvature is inversely related to canopy closure, demonstrating its role in controlling topsoil evaporation. Partitioning of soil water sources for transpiration was analyzed with a mixing model. In the Costa Rican sites, in a relatively dry year, saplings and mature trees took up water from the upper soil. In a relatively wet year in the Honduran sites, we observed deeper water extraction. In all sites, soil storage dampens extreme variation in water availability. The size dependence of water uptake with larger stems exploiting deeper layers is translated into variation in bulk leaf δ13C-based water use efficiency (WUE) with the exception of mature trees. From 1932 to 2015, drought severity was evaluated with the Standardized Precipitation Evapotranspiration Index (SPEI) concurrently with simulations of the soil water balance model. Drought occurrence increased, regardless of the time period, averaged across 6, 12, or 24 months. All ontogenetic stages in all populations experienced frequent water limitation. We found evidence for linear trends toward aridification with increases of return periods of drought for October SPEI-24 declining from 42 to 6 yr in Costa Rica and from 21 to 7 yr in Honduras and recent occurrence of multiyear droughts from 2013 to 2016. October SPEI-12 and SPEI-24 were significantly related to the Oceanic Ni~no Indices demonstrating that local inter-annual variations in drought severity in Mesoamerica are modulated by large-scale climate forces. Drought severity in the near-term future depends on the extent to which the Pacific will adopt a more La Niña-like vs. a more El Niño-like state under ongoing climatic changes.

Recent research undertaken in Mediterranean pine forests suggests that the establishment of Pinus pinea L. and Pinus pinaster Ait. natural regeneration is determined by different spatial and temporal factors. In this context, we analyzed the establishment and success of natural regeneration in these two species and we examined the hypothesis that the spatial pattern of natural regeneration depends on adult tree presence, density or stand composition, while temporal patterns are typically driven by climatic conditions. For the purposes of the experiment we used 1936 plots of 0.02 ha established in mixed and pure forests of P. pinea and P. pinaster in the Northern Plateau of Spain. Plots were installed following regeneration fellings, and regeneration was monitored annually between 2001 and 2015. We used contingency tables and principal component analysis (PCA) to evaluate the main factors affecting the spatial distribution of the regeneration. PCA was also used to assess the temporal variation as a function of climatic variables. Finally, we checked for the existence of interspecific and intraspecific synchrony through Tau-Kendall synchrony analysis. We found that natural regeneration of P. pinea was more successful than that of P. pinaster over the whole of the studied period. Contingency tables showed that P. pinaster regeneration was associated with conspecific adult trees, while the relationship between P. pinea regeneration and adult trees varied depending on the regeneration development stage, i.e., seedling or saplings. Furthermore, we found that natural regeneration in both species could be enhanced through the presence of mixtures of adult trees. The spatial variability, analyzed through PCA, showed similar responses in both species, although temporal variability associated with climate variables differed between P. pinea and P. pinaster. Finally, we found different synchrony patterns affecting natural regeneration, depending on the species and the regeneration stages. In this context, temporal patterns seem to be species specific during the sapling stage of regeneration. These findings allow the observed regeneration patterns in Mediterranean pinewoods to be generalized at forest management scale.

In the recent years, an identification of regulatory mechanisms underlying the general adaptation syndrome as an organism’s response to drastic emotional stress-evoking environmental changes is gaining in its importance. The ability to control over visceral functions plays a crucial role in stress reactions due to a threat of neurodynamic imbalance in sympathetic-parasympathetic relationships with the heart as their most vulnerable element. Fast stress adaptation promotes restoration not only of the sympathetic-parasympathetic balance, but also of energy metabolism. Taurine is one of the major regulatory molecules that activate metabolic processes. The present work addresses the following issues: (1) the descending influence of the paraventricular nucleus (PVN) on neural reaction of the solitary tract nucleus (STN), which is the first link in the visceral sensitivity pathway, (2) the mechanisms of central control over visceral reactions as investigated by mathematical modelling and analysis of the heart rate variability (HRV), and (3) morphofunctional changes in brain structures, integrating and regulating the visceral sphere (hypothalamic PVN, amygdala), under psycho-emotional stress with and without intraperitoneal injection of taurine (50 mg/kg). Acute and semichronic experiments were conducted on white nonlinear rats under 5-h immobilization stress. An extremely strong centralization of the vegetative HRV parameters (HR, VBI, SSTI) was revealed, with these parameters normalized on days 7 and 14 post taurine injection. An interaction and interdependence of the central regulatory mechanisms of cardiovascular reactions as well as a considerable protective role of taurine, promoting fast restoration of adaptive properties of the central and peripheral visceral sensitivity components under the development of long-term psycho-emotional stress, were shown.

The effect of rapid changes in ambient temperature on the biochemical profile of the blue mussel, Mytilus edulis L., was studied under aquarian conditions. It was shown that modifications in the content of reserve and structural lipids and their fatty acids, activity of lysosomal enzymes (β-glycosidase, cathepsins B and D), cytosolic calcium-dependent proteases (calpains) and phase II enzymes of xenobiotic transformation (glutathione S-transferase) reflect a nonspecific compensatory response of bivalves to the stress-inducing effect of environmental factors and indicate a metabolic rearrangement which occurs in mussels within the first hours of temperature changes. High initial level of glutathione S-transferase activity in control mussels as well as elevation of glutathione concentration during experiment may promote favorable recovery of mussels from the hypometabolic state.