Local Environmental Variables Research Articles

Terrestrial habitat and individual fitness increase survival of a freshwater turtle in an urban landscape

Urbanisation is causing rapid land-use change worldwide. Populations of freshwater turtles are vulnerable to impacts of urbanisation such as habitat loss, fragmentation and degradation, because many species require interconnected aquatic and terrestrial habitats. Understanding the processes that underpin survival in urban areas is critical in managing species that may vary in their responses to urbanisation. Here, we conducted a mark-recapture study of a common freshwater turtle (Chelodina longicollis) at 20 wetlands over five years across a broad geographical gradient in a large and expanding Australian city. Our aim was to examine relationships between survival and a broad suite of local and landscape environmental variables, and body condition. Using capture-recapture models, we found a positive relationship between the probability of survival of C. longicollis and the proportion of green open space in a 1-km radius around a wetland. There was a positive relationship between survival of female C. longicollis and body condition. Survival probabilities generally did not differ substantially among males, females or juveniles, or seasons. We found evidence of adult turtle mortality resulting from recreational fishing. Our results demonstrate the importance of terrestrial habitat surrounding wetlands for freshwater turtle survival in an urban environment. Our results suggest that management actions for C. longicollis in urban areas need to protect green spaces surrounding wetlands (e.g. parks and remnant vegetation) and discourage human actions that threaten turtle survival. Our study adds to mounting evidence that conserving freshwater turtle populations in urban areas requires managers to consider life cycle requirements over broad spatiotemporal scales.

Macroecology of seed banks: The role of biogeography, environmental stochasticity and sampling

AbstractAimThe study of seed banks has been mainly conducted at local scales, thereby hampering our general understanding of the assembly processes of these biodiversity reservoirs. Here, we aim to document worldwide macroecological patterns of seed bank diversity and of their similarity with aboveground vegetation. Our second aim is to investigate the likely drivers of these macroecological patterns and to lay the foundation of a metacommunity theory of seed banks.LocationWorldwide.Time period1989–2005.Major taxa studiedPlants.MethodsWe compiled a worldwide dataset of 130 seed banks located in grasslands. We assessed the likely drivers of seed bank diversity and similarity with aboveground vegetation, using structural equation modelling. We then developed a time‐averaged neutral model of coupled seed bank–vegetation (S‐V) dynamics that includes the effect of environmental stochasticity, and we compared its predictions with empirical findings.ResultsWe found evidence for two weak latitudinal gradients in seed bank diversity and S‐V similarity, with larger species richness and smaller similarity closer to the tropics. We then showed that seed bank richness and S‐V similarity are correlated with the following four distinct drivers: local environmental variability, plant regional diversity, seed bank density and sampling area. Finally, we showed that the predictions of the time‐averaged neutral model are remarkably in accord with empirical observations.Main conclusionsOur results lay the foundations of a metacommunity theory for seed banks. They challenge the standard view that seed banks are principally structured by environmental variability, by highlighting the additional key roles of dispersal and stochastic sampling on seed bank diversity patterns.

Transcriptome mining of immune-related genes in the muricid snail Concholepas concholepas

The population of the Chilean endemic marine gastropod Concholepas concholepas locally called “loco” has dramatically decreased in the past 50 years as a result of intense activity of local fisheries and high environmental variability observed along the Chilean coast, including episodes of hypoxia, changes in sea surface temperature, ocean acidification and diseases. In this study, we set out to explore the molecular basis of C. concholepas to cope with biotic stressors such as exposure to the pathogenic bacterium Vibrio anguillarum. Here, 454pyrosequencing was conducted and 61 transcripts related to the immune response in this muricid species were identified. Among these, the expression of six genes (CcNFκβ, CcIκβ, CcLITAF, CcTLR, CcCas8 and CcCath) involved in the regulation of inflammatory, apoptotic and immune processes upon stimuli, were evaluated during the first 33 h post challenge (hpc). The results showed that CcTLR, CcCas8 and CcCath have an initial response at 4 hpc, evidencing an up-regulation from 4 to 24 hpc. Notably, the response of CcNFKB occurred 2 h later with a statistically significant up-regulation at 6 hpc and 10 hpc. Furthermore, the challenge with V. anguillarum induced a statistically significant down-regulation of CcIKB between 2 and 10 hpc as well as a down-regulation of CcLITAF between 2 and 4 hpc followed in both cases by an up-regulation between 24 and 33 hpc. This work describes the first transcriptomic effort to characterize the immune response of C. concholepas and constitutes a valuable transcriptomic resource for future efforts to develop sustainable aquaculture and conservations tools for this endemic marine snail species.

Highly variable species distribution models in a subarctic stream metacommunity: Patterns, mechanisms and implications

Abstract Metacommunity theory focuses on assembly patterns in ecological communities, originally exemplified through four different, yet non‐exclusive, perspectives: patch dynamics, species sorting, source‐sink dynamics, and neutral theory. More recently, three exclusive components have been proposed to describe a different metacommunity framework: habitat heterogeneity, species equivalence, and dispersal. Here, we aim at evaluating the insect metacommunity of a subarctic stream network under these two different frameworks. We first modelled the presence/absence of 47 stream insects in northernmost Finland, using binomial generalised linear models (GLMs). The deviance explained by pure local environmental (E), spatial (S), and climatic variables (C) was then analysed across species using beta regression. In this comparative analysis, site occupancy, as well as taxonomic and biological trait vectors obtained from principal coordinate analysis, were used as predictor variables. Single‐species distributions were better explained by in‐stream environmental and spatial factors than by climatic forcing, but in a highly variable fashion. This variability was difficult to relate to the taxonomic relatedness among species or their biological trait similarity. Site occupancy, however, was related to model performance of the binomial GLMs based on spatial effects: as populations are likely to be better connected for common species due to their near ubiquity, spatial factors may also explain better their distributions. According to the classical four‐perspective framework, the observation of both environmental and spatial effects suggests a role for either mass effects or species sorting constrained by dispersal limitation, or both. Taxonomic and biological traits, including the different dispersal capability of species, were scarcely important, which undermines the patch dynamics perspective, based on differences in dispersal ability between species. The highly variable performance of models makes the reliance on an entirely neutral framework unrealistic as well. According to the three‐component framework, our results suggest that the stream insect metacommunity is shaped by the effect of habitat heterogeneity (supporting both species‐sorting and mass effects), rather than species equivalence or dispersal limitation. While the relative importance of the source‐sink dynamics perspective or the species‐sorting paradigm cannot be deciphered with the data at our disposal, we can conclude that habitat heterogeneity is an important driver shaping species distributions and insect assemblages in subarctic stream metacommunities. These results exemplify that the use of the three‐component metacommunity framework may be more useful than the classical four perspective paradigm in analysing metacommunities. Our findings also provide support for conservation strategies based on the preservation of heterogeneous habitats in a metacommunity context.

Seasonality and microhabitat selection in a forest-dwelling salamander.

Many small terrestrial vertebrates exhibit limited spatial movement and are considerably exposed to changes in local environmental variables. Among such vertebrates, amphibians at present experience a dramatic decline due to their limited resilience to environmental change. Since the local survival and abundance of amphibians is intrinsically related to the availability of shelters, conservation plans need to take microhabitat requirements into account. In order to gain insight into the terrestrial ecology of the spectacled salamander Salamandrina perspicillata and to identify appropriate forest management strategies, we investigated the salamander's seasonal variability in habitat use of trees as shelters in relation to tree features (size, buttresses, basal holes) and environmental variables in a beech forest in Italy. We used the occupancy approach to assess tree suitability on a non-conventional spatial scale. Our approach provides fine-grained parameters of microhabitat suitability and elucidates many aspects of the salamander's terrestrial ecology. Occupancy changed with the annual life cycle and was higher in autumn than in spring, when females were found closer to the stream in the study area. Salamanders showed a seasonal pattern regarding the trees they occupied and a clear preference for trees with a larger diameter and more burrows. With respect to forest management, we suggest maintaining a suitable number of trees with a trunk diameter exceeding 30cm. A practice of selective logging along the banks of streams could help maintain an adequate quantity of the appropriate microhabitat. Furthermore, in areas with a presence of salamanders, a good forest management plan requires leaving an adequate buffer zone around streams, which should be wider in autumn than in spring.

Small‐clawed otters (Aonyx cinereus) in Indonesian rice fields: latrine site characteristics and visitation frequency

AbstractLatrine sites, or areas where otters scent‐mark and deposit feces, are a habitat feature that serve an important role in communication for many otter species. The small‐clawed otter (Aonyx cinereus) inhabits both natural and rice field landscapes in Southeast Asia. However, latrine site use by small‐clawed otters in rice field landscapes is largely unknown. Based on a 53‐week field survey and landscape analyses, we investigated latrine site use by small‐clawed otters in rice field landscapes in West Sumatra, Indonesia. Using land use and/or local environmental variables as predictors, we performed generalized linear model analyses to explain the spatial patterns of latrine site occurrence and otter visitation frequency to latrine sites. We determined that small‐clawed otters use some latrine sites repeatedly over time; 10 latrine sites were still in use more than 7 years after their initial discovery. Generalized linear model analyses revealed that an intermediate number of rice field huts was the single most important predictor of latrine site occurrence, whereas distance to the nearest settlement, distance to the river, and mean water depth of the rice field adjacent to the latrine site were important predictors of otter visitation frequency to latrine sites. These results indicate that the latrine site preferences of small‐clawed otters in rice field landscapes are strongly associated with intermediate levels of rice farming activities. Indonesian rice fields are being degraded or disappearing at an accelerated rate because of land conversion and modernization of agriculture. We emphasize an urgent need for design and implementation of otter‐friendly rice farming to conserve small‐clawed otters.

Do metacommunities vary through time? Intermittent rivers as model systems

AbstractAimMetacommunity assembly mechanisms have been traditionally considered stable through time. However, in highly dynamic systems with varying local environmental conditions and patch connectivity, communities are likely to experience temporal shifts in their assembly mechanisms. Here, we used a set of perennial (PR) and intermittent (IR) rivers to assess if assembly mechanisms vary seasonally in response to flow intermittence.LocationMediterranean climate region (100,000 km2), Spain.MethodsWe used a modelling approach to assess the relative effect of environmental sorting and dispersal‐based processes on aquatic invertebrate metacommunities within and across river types at four distinct hydrological periods. We used local environmental variables to assess environmental sorting, and considered geographical, network and topographical distances as different dispersal surrogates. Linear mixed effect models accounting for the non‐independence of pairwise distances were used to assess the relationships between community dissimilarity and distance matrices.ResultsAssembly mechanisms were more temporally stable in PR than in IR. In PR, community dissimilarities were equally related to environmental and geographical distances suggesting codominance of species sorting and dispersal‐based assembly mechanisms. In IR, environmental distance best explained community dissimilarities during the dry period when flow cessation imposes strong environmental sorting, whereas metacommunity organization was much more stochastic during the rewetting period when high flows may randomly reorganize communities. Dispersal processes dominated assembly mechanisms between PR and IR during the rewetting period suggesting an increase in recolonization processes linking both river types following the dry period. Geographical and topographical distances best explained community variability, suggesting that overland dispersal dominates in river networks fragmented by drying events.Main conclusionsAquatic invertebrate metacommunity assembly mechanisms vary seasonally in response to changes in hydrological conditions. The temporal dimension should be better incorporated into metacommunity studies in highly dynamic systems such as intermittent rivers.

Inverse Power Law for Complete Basis Limit of CCSD(T) Theory for OH Vibrational Potential Energies of Water Molecules

Quantum chemical electronic energy of a molecular system depends on the level of the employed basis functions. The inverse power laws describing the convergences of the calculated Hartree–Fock (HF) and electronic correlation energies of water molecules have been determined by fitting the energies predicted by the CCSD(T) theory with various levels of correlation consistent basis functions. The law was applied to calculate the energies of a few simple water clusters by varying the OH bond distance of a molecule in order to understand how the two parts of the potential energy subject to the stretching motion of water molecules depend on the variation of local environments. It is found that the HF energy strongly depends on the environments of a local OH bond while the correlation energy is almost insensitive to the neighboring molecules. This suggests that the HF theory may have a great advantage in saving computation time for efficient calculations of vibrational frequencies widely distributed due to the inhomogeneity in the local environments of water molecules in the condensed phases.

Thermal barriers constrain microbial elevational range size via climate variability.

Range size is invariably limited and understanding range size variation is an important objective in ecology. However, microbial range size across geographical gradients remains understudied, especially on mountainsides. Here, the patterns of range size of stream microbes (i.e., bacteria and diatoms) and macroorganisms (i.e., macroinvertebrates) along elevational gradients in Asia and Europe were examined. In bacteria, elevational range size showed non-significant phylogenetic signals. In all taxa, there was a positive relationship between niche breadth and species elevational range size, driven by local environmental and climatic variables. No taxa followed the elevational Rapoport's rule. Climate variability explained the most variation in microbial mean elevational range size, whereas local environmental variables were more important for macroinvertebrates. Seasonal and annual climate variation showed negative effects, while daily climate variation had positive effects on community mean elevational range size for all taxa. The negative correlation between range size and species richness suggests that understanding the drivers of range is key for revealing the processes underlying diversity. The results advance the understanding of microbial species thermal barriers by revealing the importance of seasonal and diurnal climate variation, and highlight that aquatic and terrestrial biota may differ in their response to short- and long-term climate variability.

Bird Diversity and Its Relationship with Habitat Characteristics in High Andean Peatbogs

High Andean peatbogs are key functional wetlands in the dry Puna region and essential in conserving local biodiversity, including bird communities. We surveyed the bird communities of 18 peatbogs in the Argentinean Puna (Salta and Catamarca Provinces) to describe their species composition, their patterns of species richness and diversity; and their relationship to landscape features and local environmental variables. In total, we registered 60 species belonging to 21 families during summer 2014–2015. Species richness ranged from six to 20 species per peatbog. The Bright-rumped Yellow-finch Sicalis uropygialis, Ash-breasted Sierra Finch Phrygilus plebejus, Golden-spotted Ground Dove Metriopelia aymara and Puna Miner Geositta punensis were the most abundant representative species. The change in bird species composition among peatbogs showed a nested structure. The present study is the first one made for the avifauna of peatbogs of the Argentinean Puna and shows that the peatbogs with more irregular forms and more interconnected with other wetlands support more abundance and diversity of birds.

The role of local and regional environmental factors for Calanus finmarchicus and C. hyperboreus abundances in the Nordic Seas

In the advective realm of the seas, it is challenging to disentangle the role of regional and local processes on zooplankton populations. However, comparative studies of spatially separated zooplankton populations can provide valuable insights into this issue. We studied interannual abundance variation of the key zooplankton species Calanus finmarchicus and C. hyperboreus in three near-shore locations of the Nordic Seas: off northern Norway, Svalbard, and northern Iceland. Average abundances of both species were similar among locations, while in each location the abundance of C. finmarchicus was about an order of magnitude higher than the abundance of C. hyperboreus. The abundance of both species decreased in northern Norway, while C. finmarchicus abundance increased in northern Iceland. C. finmarchicus abundance in northern Norway covaried with regional climate, while the Svalbard Calanus populations were related to local environment (hydrography, phytoplankton). In northern Iceland, C. finmarchicus abundance covaried with local environmental factors, while C. hyperboreus abundance covaried with climate variability. Top-down forcing could not be investigated. The results indicate that the mechanisms relating regional climate variability (North Atlantic and Arctic oscillations) to Calanus abundance are mediated through advection of water masses, while more local environmental variability involved bottom-up processes or advection.

Effects of dispersal mode on the environmental and spatial correlates of nestedness and species turnover in pond communities

Advances in metacommunity theory have made a significant contribution to understanding the drivers of variation in biological communities. However, there has been limited empirical research exploring the expression of metacommunity theory for two fundamental components of beta diversity: nestedness and species turnover. In this paper, we examine the influence of local environmental and a range of spatial variables (hydrological connectivity, proximity and overall spatial structure) on total beta diversity and the nestedness and turnover components of beta diversity for the entire macroinvertebrate community and active and passively dispersing taxa within pond habitats. High beta diversity almost entirely reflects patterns of species turnover (replacement) rather than nestedness (differences in species richness) in our dataset. Local environmental variables were the main drivers of total beta diversity, nestedness and turnover when the entire community was considered and for both active and passively dispersing taxa. The influence of spatial processes on passively dispersing taxa, total beta diversity and nestedness was significantly greater than for actively dispersing taxa. Our results suggest that species sorting (local environmental variables) operating through niche processes was the primary mechanism driving total beta diversity, nestedness and turnover for the entire community and active and passively dispersing taxa. In contrast, spatial factors (hydrological connectivity, proximity and spatial eigenvectors) only exerted a secondary influence on the nestedness and turnover components of beta diversity.

Unravelling region-specific environmental drivers of phytoplankton across a complex marine domain (off SW Iberia)

Phytoplankton, the dominant marine primary producers, are considered to be highly sensitive indicators of ecosystem condition and change. The southwest area off the Iberian Peninsula (SWIP, NE Atlantic) is located in a biogeographical transition zone between temperate and subtropical waters, and classified as being very vulnerable to climate change. SWIP includes a variety of oceanic and coastal domains, under the influence of topographic irregularities, coastal upwelling and continental freshwater outflows, that collectively challenge the understanding of phytoplankton dynamics and controls. This study aimed to evaluate patterns in seasonal and interannual variability in phytoplankton and underlying environmental determinants within specific regions of SWIP, during a 15-year period (1997–2012), and to assess whether climate variability affects the regions in different ways. Empirical Orthogonal Function (EOF) analysis of satellite-retrieved sea surface chlorophyll-a concentration (Chl-a), acquired from the Ocean Colour Climate Change Initiative (OC-CCI), 4-km, 16-day resolution, was used to regionalize the study area. Region-specific Chl-a variability patterns and their linkages with environmental determinants were explored using Generalized Additive Mixed Models (GAMM). A set of local physical-chemical variables, derived from satellite and model data, and large-scale climate indices, were used as environmental variables. EOF analysis of Chl-a variability over the heterogeneous SWIP area identified nine coherent regions, with distinctive variability patterns (4 coastals, 2 slopes and 3 open-ocean regions). Region-specific GAMM models explained between 32% and 82% of Chl-a variance, with higher explanatory power (>61%) for open ocean regions and coastal regions under increased riverine influence. Chl-a model predictors, as well as their effects, varied markedly among SWIP regions. However, climate-sensitive local environmental variables (sea surface temperature – SST and photosynthetically available radiation) emerged as the most influential general predictors overall, and large-scale climate indices showed significant but minor effects. Over oceanic SWIP regions, Chl-a (0.08–1.50μgL−1) showed a uni-modal annual cycle, with increases during the mixed-layer deepening and late-winter maxima, reflecting seasonal changes in SST and ocean stratification, and probably related to increased nutrient availability and/or decreased mortality. Over coastal regions south of 37°N, Chl-a (0.23–10μgL−1) also benefited from riverine discharges, mostly during winter, and upwelling induced by zonal westerly winds, stronger during summer. Over the Portuguese west coast region, Chl-a (0.26–2.20μgL−1) showed a uni-modal annual cycle, with summer maxima, associated with the stimulatory effects of meridional northerly winds and coastal upwelling that partially extended into slope waters. Chl-a interannual variability showed zonal differences within SWIP, with significant interannual patterns only for regions south of 37°N. Nonetheless, contrasting trends were detected in coastal (decline) and oceanic (increase) regions, possibly a consequence of between-region differences in the relative roles of nutrient and light limitation, corresponding to significant interannual increases in wind speed and mixed layer depth. Our study used a biologically-relevant objective regionalization of a heterogeneous area, to elucidate phytoplankton dynamics and controls. The region-specific associations observed between phytoplankton and multiple climate-sensitive environmental drivers over the SWIP area reinforce the role of phytoplankton as a strategic element for evaluating ecosystem responses to climate variability and change.

Integrating count and detection-nondetection data to model population dynamics.

There is increasing need for methods that integrate multiple data types into a single analytical framework as the spatial and temporal scale of ecological research expands. Current work on this topic primarily focuses on combining capture-recapture data from marked individuals with other data types into integrated population models. Yet, studies of species distributions and trends often rely on data from unmarked individuals across broad scales where local abundance and environmental variables may vary. We present a modeling framework for integrating detection-nondetection and count data into a single analysis to estimate population dynamics, abundance, and individual detection probabilities during sampling. Our dynamic population model assumes that site-specific abundance can change over time according to survival of individuals and gains through reproduction and immigration. The observation process for each data type is modeled by assuming that every individual present at a site has an equal probability of being detected during sampling processes. We examine our modeling approach through a series of simulations illustrating the relative value of count vs. detection-nondetection data under a variety of parameter values and survey configurations. We also provide an empirical example of the model by combining long-term detection-nondetection data (1995-2014) with newly collected count data (2015-2016) from a growing population of Barred Owl (Strix varia) in the Pacific Northwest to examine the factors influencing population abundance over time. Our model provides a foundation for incorporating unmarked data within a single framework, even in cases where sampling processes yield different detection probabilities. This approach will be useful for survey design and to researchers interested in incorporating historical or citizen science data into analyses focused on understanding how demographic rates drive population abundance.

Disentangling multi‐scale environmental effects on stream microbial communities

AbstractAimClimate change and anthropogenic environmental deterioration strongly affect aquatic microbial communities. Although microbes have irreplaceable roles in various ecosystems, the spatial variation in microbial communities has received less attention in comparison to macro‐organisms. Studies aiming to disentangle the effects of local environmental, catchment and climatic variables on microbial communities are also rare. Here, we disentangled the effects of local, catchment, spatial and climatic variables on boreal stream diatom and bacterial communities.LocationWestern FinlandMethodsWe sampled 21 boreal river basins comprising 105 study sites spanning 520 km in north‐south direction and 330 km in east‐west direction in western Finland. We used principal coordinates of neighbour matrix analysis (PCNM), redundancy analyses (RDA), variation partitioning, boosted regression trees (BRT) and regression analyses to examine variation in community composition and species richness.ResultsWater chemistry and physical variables had significant effects on the community composition of both microbial groups. Catchment level variables explained a slightly larger amount of variation in diatom community composition than local level variables. Agriculture was the most significant determinant of variation in diatom community composition among catchment level variables and was also related with variation in the richness of both groups. Of spatial and climatic variables, growing degree days (GDD) and spatial variables were the most significant drivers determining diatom community composition. GDD was also positively associated with the richness of diatoms and bacteria. Unique effects of spatial and climate variables accounted for the largest amount of variation in the community composition of both diatoms and bacteria.Main conclusionsOur results highlight that aquatic microbial communities can exhibit biogeographical variation at regional scales due to the joint influence of local, catchment and climatic variables, and possibly because of dispersal limitation. Catchment properties, especially agriculture, can be used as a proxy for the effects of landscape alteration on aquatic microbial communities.

Environmental Control in Flow Bioreactors

The realization of physiologically-relevant advanced in vitro models is not just related to the reproduction of a three-dimensional multicellular architecture, but also to the maintenance of a cell culture environment in which parameters, such as temperature, pH, and hydrostatic pressure are finely controlled. Tunable and reproducible culture conditions are crucial for the study of environment-sensitive cells, and can also be used for mimicking pathophysiological conditions related with alterations of temperature, pressure and pH. Here, we present the SUITE (Supervising Unit for In Vitro Testing) system, a platform able to monitor and adjust local environmental variables in dynamic cell culture experiments. The physical core of the control system is a mixing chamber, which can be connected to different bioreactors and acts as a media reservoir equipped with a pH meter and pressure sensors. The chamber is heated by external resistive elements and the temperature is controlled using a thermistor. A purpose-built electronic control unit gathers all data from the sensors and controls the pH and hydrostatic pressure by regulating air and CO2 overpressure and flux. The system’s modularity and the possibility of imposing different pressure conditions were used to implement a model of portal hypertension with both endothelial and hepatic cells. The results show that the SUITE platform is able to control and maintain cell culture parameters at fixed values that represent either physiological or pathological conditions. Thus, it represents a fundamental tool for the design of biomimetic in vitro models, with applications in disease modelling or toxicity testing.

4D in situ visualization of electrode morphology changes during accelerated degradation in fuel cells by X-ray computed tomography

Abstract A four-dimensional visualization approach, featuring three dimensions in space and one dimension in time, is proposed to study local electrode degradation effects during voltage cycling in fuel cells. Non-invasive in situ micro X-ray computed tomography (XCT) with a custom fuel cell fixture is utilized to track the same cathode catalyst layer domain throughout various degradation times from beginning-of-life (BOL) to end-of-life (EOL). With this unique approach, new information regarding damage features and trends are revealed, including crack propagation and catalyst layer thinning being quantified by means of image processing and analysis methods. Degradation heterogeneities as a result of local environmental variations under land and channel are also explored, with a higher structural degradation rate under channels being observed. Density and compositional changes resulting from carbon corrosion and catalyst layer collapse and thinning are observed by changes in relative X-ray attenuation from BOL to EOL, which also indicate possible vulnerable regions where crack initiation and propagation may occur. Electrochemical diagnostics and morphological features observed by micro-XCT are correlated by additionally collecting effective catalyst surface area, double layer capacitance, and polarization curves prior to imaging at various stages of degradation.

Distribution of invasive Cylindrospermopsis raciborskii in the East-Central Europe is driven by climatic and local environmental variables.

Mechanisms behind expansion of an invasive cyanobacterium Cylindrospermopsis raciborskii have not been fully resolved, and different hypotheses, such as global warming, are suggested. In the East-Central Europe, it is widely occurring in western part of Poland but only in single locations in the East due to some limiting factors. Therefore, broad-scale phytoplankton survey including 117 randomly selected lakes in Poland and Lithuania was conducted. The results showed that C. raciborskii occurred widely in western part of Poland but was absent from other regions and Lithuania except one lake. The regions in which C. raciborskii was present had higher annual mean air temperature, higher maximum air temperature of the warmest month and higher minimum temperature of the coldest month, demonstrating that average air temperature, and indirectly, the duration of growing season might be more important factor driving C. raciborskii distribution than measured in situ water temperature. In turn, the presence of C. raciborskii in single localities may be more related to physiological adaptations of separated ecotype. Collectively, these results provide novel evidence on the influence of temperature on C. raciborskii distribution in East-European regions but also indicate high ecological plasticity of this species.

Microbial diversity in Chinese temperate steppe: unveiling the most influential environmental drivers.

Temperate steppe is extremely sensitive to the current global changes. However, what are the main environmental variables driving microbial diversity in temperate steppe are still unclear, something that impairs doing predictions about the expected effects of global changes on microbe-mediated ecological functions. This is why, in this study, the relationship between soil microbial diversity and environmental variables in Chinese temperate steppe is investigated. In this study, significant correlations between soil bacterial α-diversity and mean annual precipitation and the aridity index were observed at the whole region scale. No clear correlations between microbial α-diversities and other measured environmental variables were found at the whole temperate steppe region and sub-regions. On the other hand, β-diversity was strongly related to spatial variables and climate variables for bacteria, while spatial variables and soil organic matters were more related with fungal β-diversity. In addition, the mean annual temperature was highly correlated with microbial β-diversity at different spatial scales, suggesting that it could be a good single predictor of soil microbial assemblage in temperate steppe. β-Diversities are more explained by combined effect of local environmental variables based on variation partitioning analysis, reflecting the community assemblage is more likely driven by species sorting through environmental filtering.

Testing the Validity of Age-Size Reconstructions in Cohort Species, UsingCarnegiea gigantea

Abstract Age-size relationships of a species in any given population are variable due to local environmental and genetic variations across individuals. The aim of this study is to test an age-size model for the keystone Carnegiea gigantea (saguaro, Cactaceae), that establishes in cohorts, to assess its accuracy in reconstructing those cohorts. Monte Carlo simulation is used to generate a Carnegiea gigantea population based on parameters selected and then applies the age-size model to the population to ascertain its effectiveness. Individuals in a cohort of different sizes are generated, as would be expected in the real world, and a simulated empirical dataset is created. Variation in growth over time incorporates two sources of variability, (1) individual variability (e.g. genetic or microsite variations) as well as (2) population-wide variability (such as fluctuations in rainfall from year to year). Generally, older cohorts are more difficult to accurately estimate, but all cohorts are identifiable. Resu...