Habitat Attributes Research Articles

Composition of non‐volant small mammals inhabiting a degradation gradient in a lowland tropical forest in Uganda

A study aimed at assessing the structure of rodent and shrew assemblages inhabiting a degradation gradient while considering rainfall patterns, was conducted in one of few remaining lowland tropical forests in eastern Africa. We collected a unique dataset of rodents and shrews, representing 24 species (19 rodents, 5 shrews). The most abundant species alternated in dominance as species abundance significantly fluctuated across the study period following a degradation gradient. While only generalist species were observed near the degraded forest edge, habitat specialists such as Deomys ferrugineus, Malacomys longipes and Scutisorex congicus, were observed in the primary forest interior suggesting a significant association between species and their associated habitats and habitat attributes. There was also an observed correlation between rainfall patterns and species abundance. Capturing more species in adjacent fallows and along the degraded forest edge suggests that many species are able to live in degraded habitats that offer a variety of food resources. The study has highlighted the importance of habitat heterogeneity through species associations and also recommend an assessment of the effect of habitat homogeneity due to the proliferation of paper mulberry on small mammal community.

A bioenergetics‐based index of habitat suitability: Spatial dynamics of foraging constraints and food limitation for a rare estuarine fish

AbstractObjectivesHabitat suitability models can guide restoration efforts in freshwater and estuarine ecosystems by synthesizing important habitat attributes in a single index. Several important elements of the foraging arena of Delta Smelt Hypomesus transpacificus, a small, zooplanktivorous fish, were quantified using a model that combined bioenergetics with physical habitat attributes. We applied the model to evaluate spatiotemporal variation in the suitability of Delta Smelt foraging habitat as indicated by growth potential.MethodsBioenergetics‐based estimates of daily potential growth, given constraints on daily foraging due to temperature, turbidity, day length, and prey availability, were compared to reference growth, estimated separately from length‐at‐age data. We defined suitable foraging arenas for Delta Smelt as times and places when potential growth equaled or exceeded reference growth.ResultAmong six contiguous regions of the upper San Francisco Estuary, temperature was consistently lowest and turbidity highest in the most seaward locations. As a result, predicted growth rates were greater there compared to landward, upstream regions that were warmer and less turbid.ConclusionSimulated habitat augmentation of prey and turbidity revealed that the effects of potential restoration actions could vary regionally as the factors limiting Delta Smelt foraging varied along longitudinal and seasonal gradients. Models of the spatiotemporal variation in Delta Smelt habitat may be substantially improved by directed laboratory studies; however, this research provided a data‐driven example of how dynamic estuarine habitat attributes interact to influence the suitability of foraging arenas experienced by a pelagic fish.

Sensitivity of fish habitat suitability to multi-resolution hydraulic modeling and field-based description of meso-scale river habitats

In-stream habitat models at the meso-scale are increasingly used to quantify the effects of hydro-morphological pressures in rivers. The spatial distributions of water depth and velocity represent key attributes of physical habitat. Choosing between field surveys, hydraulic modeling or their integration is made depending on available tools, technical skills, budget and time. However, the sensitivity to such choices of estimated habitat conditions suitable for biological organisms, such as fish, is poorly known.In this study, three commonly used approaches in hydraulic-habitat modeling were compared and tested on a mountain stream, the Mareta River (NE Italy). Two approaches were based on 2D hydraulic modeling, calculated on computational meshes with varying resolution and quality: (1) high-resolution meshes derived from topographical data obtained from Airborne Bathymetric LiDAR; (2) a mesh extrapolated from topographical cross-sectional profiles. The third approach (3) was based on in-stream surveys. From these, suitable channel-area for two fish species, the marble trout (juvenile and adult), and the European bullhead (adult), were estimated.Results showed that decreasing mesh resolution and quality affects the simulated water depth and velocity distributions, both in terms of their average and their standard deviation. The largest differences were found for the in-stream survey-based results. Morphologically complex unit types, such as steps, rapids and pools were more sensitive than simpler mesohabitats, such as glides and riffles. The most sensitive hydro-morphological unit types to the chosen approach were backwaters, glides being the least sensitive, also in terms of their suitability as mesohabitats. Despite that, a key finding is that errors are minimized when deriving habitat - streamflow rating curves at the reach scale, for which all approaches were largely able to reproduce the main characteristics of the curve, i.e. maxima, minima and inflection points.

Structural complexity is a better predictor than single habitat attributes of understory bird densities in Andean temperate forests

Abstract The simplification of forest structural complexity, caused by anthropogenic land-use practices, is one of the main threats to understory specialist birds. We examined the association of both single structural attributes and structural complexity, with the density of 4 understory bird species in the Global Biodiversity Hotspot “Chilean Winter Rainfall-Valdivian Forests” of South America. Between 2011 and 2013, we surveyed habitat attributes and conducted bird point counts in 505 plots in Andean temperate ecosystems in Chile. In each habitat plot, we measured understory density, volume of coarse woody debris (CWD), number of snags, diameter at breast height (DBH) of trees, and leaf litter depth. With these attributes, we developed an index of stand structural complexity (ISC). On average, old-growth forests had higher values for understory density, CWD volume, DBH, and litter depth than secondary forests and open fields, and thus greater values of ISC. The density of understory birds was positively correlated with the ISC for the Rhinocryptidae Pteroptochos tarnii, Scelorchilus rubecula, and Scytalopus magellanicus. We also found a positive association between understory density and litter depth, with the density of the Furnariidae Sylviorthorhynchus desmursii. However, this latter species showed a negative association with the density of snags. Our results suggest the utility of using an index of structural complexity, rather than single or even additive habitat attributes, for determining the density of understory specialist birds. We recommend that management plans should promote the retention of habitat attributes that contribute to the structural complexity of temperate forests of South America and beyond.

Prey and habitat characteristics contribute to hotspots of distribution for an endangered coastal dolphin

IntroductionUnderstanding the characteristics of hotspots of species distribution provides opportunities for habitat-based management; a vital and often missing component in the conservation of mobile marine species. Correlates of species distribution derived from species distribution models (SDMs) are assumed to represent the characteristics of important habitat, which often include physical and biological (i.e., prey) components. In this study, we integrate surveys of Hector’s dolphin (Cephalorhynchus hectori) with in-situ data on environmental characteristics and prey to identify the statistical correlates of distribution and to assess ‘what makes hotspots unique’.MethodsBetween 2014 and 2017, ca. 300 surveys were carried out at hotspots and areas not routinely used by dolphins at Banks Peninsula on the east coast of New Zealand’s South Island. A broad range of prey and environmental variables were explored as drivers of dolphin distribution using generalized additive models, and principal component analysis was employed to determine a key environmental signature for hotspots.ResultsThe relative abundance of dolphins was strongly correlated with prey abundance and a range of environmental variables representing habitat type and oceanographic conditions. The combination of high prey abundance and sandy, shallow, high current and low turbidity habitat was strongly represented at hotspots.DiscussionThese characteristics are also likely attributes of habitat with high ecological value generally, being related to high biodiversity, productivity, naturalness and ecosystem function. This study showcases the importance of targeted investigations into the characteristics of species hotspots to better guide the management of important areas for the conservation of both species and ecosystems.

Spatiotemporal visual statistics of aquatic environments in the natural habitats of zebrafish

Animal sensory systems are tightly adapted to the demands of their environment. In the visual domain, research has shown that many species have circuits and systems that exploit statistical regularities in natural visual signals. The zebrafish is a popular model animal in visual neuroscience, but relatively little quantitative data is available about the visual properties of the aquatic habitats where zebrafish reside, as compared to terrestrial environments. Improving our understanding of the visual demands of the aquatic habitats of zebrafish can enhance the insights about sensory neuroscience yielded by this model system. We analyzed a video dataset of zebrafish habitats captured by a stationary camera and compared this dataset to videos of terrestrial scenes in the same geographic area. Our analysis of the spatiotemporal structure in these videos suggests that zebrafish habitats are characterized by low visual contrast and strong motion when compared to terrestrial environments. Similar to terrestrial environments, zebrafish habitats tended to be dominated by dark contrasts, particularly in the lower visual field. We discuss how these properties of the visual environment can inform the study of zebrafish visual behavior and neural processing and, by extension, can inform our understanding of the vertebrate brain.

Phylogenetically conservative trait correlation: Quantification and interpretation

Abstract Correlation across species between two quantitative traits, or between a trait and a habitat property, can suggest that a trait value is effective in sustaining populations in some contexts but not others. It is widely held that such correlations should be controlled for phylogeny, via phylogenetically independent contrasts (PICs) or phylogenetic generalized least squares (PGLS). A weakness of this idea is that a clade's traits tend to confer success in particular habitats or ways of life, and those niches in turn tend to select for the same traits to continue in the clade. This feedback mechanism can bind phylogeny and niche together as a unified cause for present‐day trait configurations. Accordingly, the phylogenetically conservative share of a trait correlation ought not to be excluded from consideration as potentially ecologically functional. Another weakness is that PGLS does not yield a complete or accurate breakdown of covariation between traits A and B because it corresponds to a generating model where B predicts variation in A but not the reverse, and phylogenetic signal in B is not modelled. Multi‐response mixed models using phylogenetic covariance matrices can quantify conservative trait correlation (CTC), a share of A‐B covariation that is phylogenetically conservative. Because the evidence is from correlative data, it is not possible to split CTC into causation by phylogenetic history versus causation by continuing reciprocal selection between A and B. Moreover, it is quite likely biologically that the two influences have acted in concert, through phylogenetic niche conservatism. Synthesis: The CTC concept treats phylogenetic conservatism as a conjoint interpretation alongside ongoing influence of other traits. CTC can be quantified via multi‐response phylogenetic mixed models.

Vegetation and soil ecology of threatened Himalayan Trillium habitats in Kashmir Himalaya

Understanding the vegetation and soil ecology of natural habitats harbouring threatened species is critical in conservation planning and restoration. The present study investigated the vegetation composition and soil physico‐chemical properties of natural habitats of Trillium govanianum – a threatened Himalayan endemic species. We laid 120 quadrats across eight randomly selected sites where the species was growing in the Kashmir Himalaya. We collected the soil samples from these sites and determined soil physico‐chemical properties using standard methods. Across all the sites, we found a total of 57 plant species with dominance of Rosaceae and Ranunculaceae. The importance value index (IVI) results revealed that Fragaria nubicola, Corydalis diphylla, Galium aparine, and Leucanthemum vulgare, were the dominant species in T. govanianum habitats. The density, abundance and IVI of three‐leaf vegetative plants was higher than one‐leaf vegetative and three‐leaf reproductive plants across all the study sites. We found that T. govanianum alone forms 23.5% positive, 0 negative, 76.4% random co‐occurrences with other associated species in its habitats. Our results reveal that the variations in vegetation composition among the sites was influenced by differences in soil properties. Principal component analysis (PCA) revealed that several soil properties such as organic carbon (OC), nitrogen, potassium, and sulphur were concentrated in five sites, namely Dara, Drung, Bangus, Gulmarg and Doodhpathri, which also showed the highest density, frequency, and abundance of T. govanianum. Overall, our study contributes quantitative information on the vegetation and soil ecology of T. govanianum‐habitats, which in turn can help in developing conservation strategies for this threatened species, and its sustainable management and habitat restoration.

Phenotypic diversity of bamboo Schizostachyum lima (Blanco) Merr. population grown in several critical habitats on Lombok Island, Indonesia

Abstract. Aryanti E, Arumingtyas EL, Azrianingsih R, Arisoesilaningsih E. 2023. Phenotypic diversity of bamboo Schizostachyum lima (Blanco) Merr. population grown in several critical habitats on Lombok Island, Indonesia. Biodiversitas 24: 2788-2796. This study aims to analyze the phenotypic diversity among populations of Schizostachyum lima (Blanco) Merr. grown in several critical habitats on Lombok Island. Sampling was conducted to record clump growth and habitat properties of 38 sites grouped based on the clump density using PAST 4.11 and ArcGIS 10.8.2 software. Sampling was conducted to record clump growth and habitat properties of 38 sites grouped based on the clump density using PAST 4.11 and ArcGIS 10.8.2 software. The results showed that habitat 1 was the most critical land and had the lowest fertility, but it provided a qualified bamboo as a raw material for the artisanal straw industry. The results showed that habitat 1 was the most critical land and had the lowest fertility, but it provided a qualified bamboo as a raw material for the artisanal straw industry. Bamboo density reached 46 culms per clump and had the smallest culms diameter of 13 mm. Bamboo density reached 46 culms per clump and had the smallest culms diameter of 13 mm. The soil comprised 90% sand, with SOC 0.9 g.kg-1, total N 0.08 g.kg-1, and CEC 8.3 me.100 g-1. The soil comprised 90% sand, with SOC 0.9 g.kg-1, total N 0.08 g.kg-1, and CEC 8.3 me.100 g-1. Meanwhile, habitat 6 and habitat 7 were lesser critical, consisted of 66% of sand, showed the best soil fertility, and mean SOC 4.98 g.kg-1, total N 0.30 g.kg-1, CEC 27.23 me.100 g-1, density 151 culms, and biggest culms diameter 33 mm. Meanwhile, habitat 6 and habitat 7 were lesser critical, consisted of 66% of sand, showed the best soil fertility, and mean SOC 4.98 g.kg-1, total N 0.30 g.kg-1, CEC 27.23 me.100 g-1, density 151 culms per clump, and biggest culms diameter 33 mm. The other habitats varied in soil quality and bamboo growth properties. It was revealed that the high culms density, diameter, height, and internodal length were significantly increased in the high soil CEC, SOC, and total N. Furthermore, the SOC and total N content significantly correlated with the wall thickness.

Intraspecific variation in a predator changes intertidal community through effects on a foundation species.

Intraspecific variation is an important form of biodiversity that can alter community and ecosystem properties. Recent work demonstrates the community effects of intraspecific variation in predators via altering prey communities and in foundation species via shaping habitat attributes. However, tests of the community effects of intraspecific trait variation in predators acting on foundation species are lacking despite the fact that consumption of foundation species can have strong community effects by shaping habitat structure. Here, we tested the hypothesis that intraspecific foraging differences among populations of mussel-drilling dogwhelk predators (Nucella) differentially alter intertidal communities through effects on foundational mussels. We conducted a 9-month field experiment where we exposed intertidal mussel bed communities to predation from three Nucella populations that exhibit differences in size-selectivity and consumption time for mussel prey. At the end of the experiment, we measured mussel bed structure, species diversity, and community composition. While exposure to Nucella originating from different populations did not significantly alter overall community diversity, we found that differences in Nucella mussel selectivity significantly altered foundational mussel bed structure, which in turn altered the biomass of shore crabs and periwinkle snails. Our study extends the emerging paradigm of the ecological importance of intraspecific variation to include the effects of intraspecific variation on predators of foundation species.

Accelerated recovery of lake macroinvertebrates in the third decade since the reversal of acidification

Chemical reversal from acidification has been progressing in European freshwaters since the late 1980s, responding to successful control of atmospheric pollution by acidifying emissions. However, biological recovery is often delayed after improvements in water composition. We studied macroinvertebrate recovery from acidification in eight glacial lakes in the Bohemian Forest (central Europe) between 1999 and 2019. The chemical composition of these lakes reflects a complex of environmental changes, dominated by a very steep decline in acid deposition and, currently, by elevated nutrient leaching following climate-induced tree dieback within their catchments. Temporal trends in species richness, abundance, species traits and community composition were evaluated with regard to water chemistry, littoral habitat properties and fish colonisation. The results showed accelerated recovery of macroinvertebrates following two decades of gradual improvement in water composition and slowly progressing biological rehabilitation. We observed a significant increase in macroinvertebrate species richness and abundance, coupled with distinct changes in community composition, the extent of changes varying between lakes, reflecting different littoral habitat properties (vegetated vs. stony) and water chemistry. Overall, the communities shifted toward more specialised (grazers, filterers, and phytophilous species) and acid-tolerant taxa at the expense of detritivorous, eurytopic and acid-resistant taxa. Where fish reappeared, open-water taxa declined greatly. Compositional changes were likely driven by the combined effects of water chemistry reversal, rehabilitation of habitat conditions and fish colonisation. Despite favourable trends, communities in recovering lakes still lack several biotic elements, particularly less vagile, acid-sensitive taxa and specialised herbivores known from the regional species pool. It is expected that future progress in lake recovery will be further promoted or inhibited by stochastic colonisation or disturbance events.

Integrating spaceborne estimates of structural diversity of habitat into wildlife occupancy models

Vegetation structure is a crucial dimension of wildlife habitat, responsive to global changes in human activities and ecosystem processes. NASA’s recent Global Ecosystem Dynamics Investigation (GEDI) provides an exciting opportunity to explore how spaceborne waveform observations can improve our ability to measure wildlife habitat and advance animal ecology in the Anthropocene. We tested the utility of GEDI data in univariate occupancy models to estimate habitat use in a remote mountain system in central Idaho, USA. We collected data from 49 camera trap stations from two surveys in 2018–2019 and modeled the occupancy for each of seven mammal species representing different trophic levels and feeding strategies: American black bear (Ursus americanus), deer (Odocoileus hemionus), elk (Cervus canadensis), moose (Alces alces), coyote (Canis latrans), wolf (Canis lupus), and mountain lion (Puma concolor). We first derived structural diversity indices (richness, evenness, and divergence) of GEDI-derived canopy height, plant area index, and foliage height diversity to represent different dimensions of vegetation structure. This spatial aggregation is necessary due to gaps in GEDI footprints and parallels commonly used functional diversity metrics applied to biological communities that are calculated using trait probability densities. We measured these indices across three spatial scales that reflect different species movement and habitat selection patterns. We found the structural diversity indices of canopy height, foliage height diversity, and plant area index had the strongest effects on the occupancy of most mammals compared to two-dimensional (2D) variables (e.g. tree cover, normalized difference vegetation index). The spatial extent of these indices also influenced the strength of response, highlighting the importance of selecting a scale large enough to capture sufficient GEDI footprints but small enough to reflect site-level variance. Compared to 2D covariates, our results suggest that GEDI variables allow researchers to generate more detailed inference on the forms of habitat that wildlife use. We discuss the implications of these findings for habitat management and future wildlife research from local to global scales.

Characterization of the physico-chemical properties of the natural habitat and in vitro culture effects on the biochemistry, proliferation and morphology of Lemna minuta

In this study, the ecological conditions of the natural habitat of Lemna minuta Kunth in Morocco were investigated, and the impact of five synthetic growth media (Murashige-Skoog (MS), Schenk-Hildebrand (SH), Hoagland medium (HM), 10X Algal Assay Procedure (AAP), and Swedish Standard Institute medium (SIS)) on the morphophysiological and biochemical parameters was analysed. The morphophysiological parameters included root length, frond surface area, and fresh weight, while the biochemical parameters included photosynthetic pigments, carbohydrates, and protein content. The study was conducted in vitro in two phases: an uncontrolled aeration system (Phase I) and a controlled aeration system (Phase II).The results showed that the pH, conductivity, salinity, and ammonium levels in the natural habitat were within the optimal range for duckweed growth. The measured orthophosphate concentrations were higher compared to previous observations, while the recorded chemical oxygen demand values were low. The study also revealed a significant effect of the culture medium composition on the morphophysiological and biochemical parameters of the duckweed. The fresh weight biomass, relative growth rate in fronds, relative growth rate in surface area, root length, protein content, carbohydrates, chlorophyll (a), chlorophyll (b), total chlorophyll, carotenoids, and the chlorophyll (a/b) ratio were all affected by the culture medium.The most accurate regression models described the growth index GI(F) based on time and in vitro culture conditions in both phases. In Phase I, the best models for MS, SIS, AAP, and SH media were linear, weighted quadratic, cubic, and weighted cubic, respectively. In Phase II, the best models for all growth media were linear. The time coefficients (in days) for Phase II were 0.321, 0.547, 1.232, 1.470, and 0.306 for AAP, HM, MS, SH, and SIS, respectively.Comparing the morphophysiological and biochemical parameters of fronds from different media and analysing the regression model results showed that the SH and MS media were the best among the tested media for the in vitro culture of L. minuta in controlled aeration conditions. However, further research is needed to develop new synthetic media that best promote the growth and maintenance of this duckweed in long-term culture.

Exploring sensitivities to hydropeaking in Atlantic salmon parr using individual‐based modelling

AbstractHydropeaking (the release of water pulses at hydropower plants) results in temporary reductions in river channel water‐covered area downstream, which may cause fish mortality through stranding. We used a mechanistic modelling approach to examine how both the form of the hydropeaking cycle and the characteristics of the affected fish control how hydropeaking may cause stranding mortality of fish. We modelled the response of Atlantic parr to hydropeaking in a regulated watercourse in central Norway (the River Nidelva) using an individual‐based population model designed explicitly to examine fish behaviour and stranding mortality during hydropeaking. A response to hydropeaking, involving migration from the riverbanks towards the mid‐channel on down‐ramping and a return to the riverbanks on up‐ramping, was based on individuals being parameterized to migrate to habitat properties that spatially changed throughout the hydropeaking cycle. We found that stranding mortality was strongly dependent on both the form of the hydropeaking cycle and on the fish response. Total stranding mortality was more dependent on the down‐ramping speed than the duration of the minimum flow period. Total stranding mortality was greatest when there was a low movement speed, leading to individuals being stranded, combined with a high probability of dying per unit of time when stranded. Given the sensitivity of mortality to the fish response and the lack of detailed field studies quantifying this, we conclude that this area requires further controlled studies for parameterizing models used to predict effects of hydropeaking on fish. Simulation‐based modelling, where there is a 100% control of and knowledge of fish characteristics, where a range of deterministic functions can be evaluated and in which boundary conditions can be easily controlled, may be a useful research tool to complement empirical studies.

The influence of habitat properties on sex determination in cavity-nesting Hymenoptera

Unravelling the relationships between insect population dynamics and habitat properties is often complex. Established theoretical concepts, which predict an influence of available resources on sex determination, have often not been tested with quantitative field data. Cavity-nesting Hymenoptera are suitable to assess the influence of habitat properties on reproductive parameters, as haplodiploidy enables direct responses to local conditions. We hypothesize that with increasing resource availability, the population sex ratio (share of females per site), sex allocation preference per individual offspring (the probability of producing either a male or a female offspring per brood cell) and resource allocation per individual offspring will be favouring towards females. We sampled offspring of Osmia cornuta, Osmia caerulescens and Trypoxylon figulus and their resource provisions using trap nests on 30 study sites in an agricultural landscape in southwest Germany, from March to August 2020. The potential influence of resource availability, landscape variables, temperature, seasonal progression, and nesting opportunities on sex and resource provisions was tested. Population sex ratio was not related to habitat properties. Sex allocation preference in the three species, however, depended on several variables including cavity size and seasonal progression, with pronounced differences amongst species. Individual resource provisioning mainly differed between sexes, as male larvae received less provisions than female larvae. As there was no influence of resource availability, we conclude that the sex ratio of established populations was balanced at the selected study sites by available resources in the landscape. At the individual scale, sex and resource allocation were influenced in species-specific ways. As such, sex determination and resource allocation are essential life history properties of sexually reproducing organisms.

Bringing light onto the Raunkiæran shortfall: A comprehensive review of traits used in functional animal ecology.

Trait-based approaches elucidate the mechanisms underlying biodiversity response to, or effects on, the environment. Nevertheless, the Raunkiæran shortfall-the dearth of knowledge on species traits and their functionality-presents a challenge in the application of these approaches. We conducted a systematic review to investigate the trends and gaps in trait-based animal ecology in terms of taxonomic resolution, trait selection, ecosystem type, and geographical region. In addition, we suggest a set of crucial steps to guide trait selection and aid future research to conduct within and cross-taxon comparisons. We identified 1655 articles using virtually all animal groups published from 1999 to 2020. Studies were concentrated in vertebrates, terrestrial habitats, the Palearctic realm, and mostly investigated trophic and habitat dimensions. Additionally, they focused on response traits (79.4%) and largely ignored intraspecific variation (94.6%). Almost 36% of the data sets did not provide the rationale behind the selection of morphological traits. The main limitations of trait-based animal ecology were the use of trait averages and a rare inclusion of intraspecific variability. Nearly one-fifth of the studies based only on response traits conclude that trait diversity impacts ecosystem processes or services without justifying the connection between them or measuring them. We propose a guide for standardizing trait collection that includes the following: (i) determining the type of trait and the mechanism linking the trait to the environment, ecosystem, or the correlation between the environment, trait, and ecosystem, (ii) using a "periodic table of niches" to select the appropriate niche dimension to support a mechanistic trait selection, and (iii) selecting the relevant traits for each retained niche dimension. By addressing these gaps, trait-based animal ecology can become more predictive. This implies that future research will likely focus on collaborating to understand how environmental changes impact animals and their capacity to provide ecosystem services and goods.

Measuring habitat quality for waterbirds: A review.

Quantifying habitat quality is dependent on measuring a site's relative contribution to population growth rate. This is challenging for studies of waterbirds, whose high mobility can decouple demographic rates from local habitat conditions and make sustained monitoring of individuals near-impossible. To overcome these challenges, biologists have used many direct and indirect proxies of waterbird habitat quality. However, consensus on what methods are most appropriate for a given scenario is lacking. We undertook a structured literature review of the methods used to quantify waterbird habitat quality, and provide a synthesis of the context-dependent strengths and limitations of those methods. Our search of the Web of Science and Scopus databases returned a sample of 666 studies, upon which our review was based. The reviewed studies assessed habitat quality by either measuring habitat attributes (e.g., food abundance, water quality, vegetation structure), or measuring attributes of the waterbirds themselves (e.g., demographic parameters, body condition, behavior, distribution). Measuring habitat attributes, although they are only indirectly related to demographic rates, has the advantage of being unaffected by waterbird behavioral stochasticity. Conversely, waterbird-derived measures (e.g., body condition, peck rates) may be more directly related to demographic rates than habitat variables, but may be subject to greater stochastic variation (e.g., behavioral change due to presence of conspecifics). Therefore, caution is needed to ensure that the measured variable does influence waterbird demographic rates. This assumption was usually based on ecological theory rather than empirical evidence. Our review highlighted that there is no single best, universally applicable method to quantify waterbird habitat quality. Individual project specifics (e.g., time frame, spatial scale, funding) will influence the choice of variables measured. Where possible, practitioners should measure variables most directly related to demographic rates. Generally, measuring multiple variables yields a better chance of accurately capturing the relationship between habitat characteristics and demographic rates.

The relationships between the physical and chemical properties of an aquatic environment and the floristic specificity of pleustonic communities in northern Poland

A comparative phytosociological and habitat analysis of 84 pleustonic phytocoenoses in northern Poland was carried out in order to determine the scale of their floristic distinctiveness and to obtain an answer to the question whether and to what extent the floristic differentiation of pleustonic communities corresponds to the differentiation of their habitat conditions. Based on phytosociological studies, it was shown that the investigated phytocoenoses are not random groups of species, but well differentiated in terms of floristic composition and phytocoenotic structure by communities. It was shown that the studied phytocoenoses represent the following separate associations in phytosociological terms: Salvinio natantis-Spirodeletum polyrhizae, Lemno-Spirodeletum polyrhizae, Riccietum fluitantis and Ricciocarpetum natantis. Hydrochemical studies showed that the floristic distinctiveness of these communities is largely confirmed by the differentiation of properties of the water habitat. Salvinio natantis-Spirodeletum polyrhizae is characterised by the deepest waters (mainly 0.7–1.2 m), alkaline, of a low colour, rich in ions (Mg2+, Na+, Cl−) and therefore characterised by the highest electrolytic conductivity, poor in dissolved organic matter, NO3− and total iron. Lemno-Spirodeletum polyrhizae is characterised by medium deep waters (mainly 0.3–0.8 m), mostly alkaline, of a low colour, less rich in ions (Ca2+, Na+, Cl−) and relatively low in dissolved organic matter and NO3−. Riccietum fluitantis is characterised by shallow waters (mainly 0.2–0.4 m), most often slightly acidic, of a quite high colour, low in cations and Cl−, and relatively rich in total iron, NO3−, and dissolved organic matter. Ricciocarpetum natantis is characterised by the shallowest waters, (mainly < 0.3 m), most often acidic, of the highest colour, low in ions, and rich in total iron, dissolved silica, NO3− and dissolved organic matter. By demonstrating habitat distinctiveness, the studied pleustonic communities may have significance as indicators of various types of aquatic environment.

The Diversity of the Brains of Ray-Finned Fishes

Brains are very plastic, both in response to phenotypic diversity and to larger evolutionary trends. Differences between taxa cannot be easily attributed to either factors. Comparative morphological data on higher taxonomic levels are scarce, especially in ray-finned fishes. Here we show the great diversity of brain areas of more than 150 species of ray-finned fishes by volumetric measurements using block-face imaging. We found that differences among families or orders are more likely due to environmental needs than to systematic position. Most notable changes are present in the brain areas processing sensory input (chemosenses and lateral line vs. visual system) between salt- and freshwater species due to fundamental differences in habitat properties. Further, some patterns of brain volumetry are linked to characteristics of body morphology. There is a positive correlation between cerebellum size and body depth, as well as the presence of a swim bladder. Since body morphology is linked to ecotypes and habitat selection, a complex character space of brain and body morphology and ecological factors together could explain better the differentiation of species into their ecological niches and may lead to a better understanding of how animals adapt to their environment.

Deterministic versus stochastic control in β-diversity, abundance and co-occurrence patterns of a soil nematode assemblage living in a Mediterranean soil

In this paper we studied the determinism-stochasticity trade-off affecting the structure of a soil nematode assemblage. Specifically, in a field experiment that lasted six months, the soil temperature and moisture conditions were manipulated in 14 plots. The generic composition of the soil nematode assemblage was explored by estimations of β-diversity, its turnover and nestedness components and by fitting rank abundance models. Further the associative aspects between the assemblage members and between them and habitat attributes were accounted for by analyzing the niche overlap based on Pearson correlation coefficients. Using variation partitioning and null models, we found that the generic diversity of the assemblage was more strongly determined by non-registered lateral experimental factors (stochastic control). By contrast, the deterministic control—less strong than the stochastic counterpart—was exerted both in synchronization with the changes in habitat characteristics and/or with a time delay. The network analysis showed that, under favorable habitat conditions in July, September and October, reduced network modularity and enhanced connectivity were favored, which probably led to a niche-based deterministic selection that outperformed stochasticity. Conversely, under changing experimental conditions in August and lower temperature in November and December, stochasticity would be superior to niche identity, leading to enhanced modularity and relatively loose networks.