Niche Dimensions Research Articles

Anthropogenic disturbances alter the trophic niche structure and ecological relationships of understory bat communities in the Ecuadorian Andean Chocó

Human disturbances have reduced the three basic niche dimensions for the survival of some mammalian species (space, time, and resources). Anthropic activities cause the extinction of ecological functionalities faster than species extinctions. In this study, we identified four types of habitats in the Ecuadorian Andean Chocó: primary forest (PF), secondary forest in natural regeneration (SF1), secondary forest in assisted regeneration (SF2), and pastures for cattle (P). The main objective was to determine the responses in the trophic niche and the ecological relationships of understory phyllostomid bat communities. We captured bats with mist nets and obtained fecal samples from 21 species. These were analyzed to quantify seeds, pollen, insects, and vertebrates consumed by each individual, with counts organized by species and habitat type. We conducted an ecological relationship analysis to understand the structure of bat–fruit networks and their dietary preferences. We calculated niche breadth and niche overlap to understand the trophic niche composition of each species. We applied null models to evaluate if there is evidence of trophic niche partitioning among these species. Despite a relatively small sample size, the results obtained are nevertheless interesting. While niche breadth was not useful for detecting the effects of human disturbances, niche overlap was significantly higher in disturbed habitats (SF1, SF2 and P), where ecological relationships were weaker. Most of the species were related to the consumption of seeds from the genus Piper. These results indicate that bat communities and their ecosystem services may be highly endangered due to anthropogenic disturbances. Network interactions in bats are highly variable in geographic space and time, and little is known about the community structure of bat–seed interactions. Studying mutualistic networks in bats and seeds is crucial because of their role in ecosystem support, supply, and regulation services that depend on them.

Can niche plasticity mediate species persistence under ocean acidification?

Global change stressors can modify ecological niches of species, thereby altering ecological interactions within communities and food webs. Yet, some species might take advantage of a fast-changing environment, allowing species with high niche plasticity to thrive under climate change. We used natural CO2 vents to test the effects of ocean acidification on niche modifications of a temperate rocky reef fish assemblage. We quantified three ecological niche traits (overlap, shift and breadth) across three key niche dimensions (trophic, habitat and behavioural). Only one species increased its niche width along multiple niche dimensions (trophic and behavioural), shifted its niche in the remaining (habitat) was the only species to experience a highly increased density (i.e. doubling) at vents. The other three species that showed slightly increased or declining densities at vents only displayed a niche width increase in one (habitat niche) out of seven niche metrics considered. This niche modification was likely in response to habitat simplification (transition to a system dominated by turf algae) under ocean acidification. We further showed that, at the vents, the less abundant fishes had a negligible competitive impact on the most abundant and common species. This species appeared to expand its niche space, overlapping with other species, which likely led to lower abundances of the latter under elevated CO2. We conclude that niche plasticity across multiple dimensions could be a potential adaptation in fishes to benefit from a changing environment in a high-CO2 world.

Mapping terrestrial mammals in China based on species richness of functional groups

Biodiversity loss is one of the most critical environmental issues globally. Functional diversity and functional groups, extending and expanding the concept of species richness, provide a more comprehensive understanding of biodiversity. By integrating mathematical indices calculation with classical geospatial statistical analysis and mapping techniques, we explored and visually illustrated the spatial patterns and regularities of functional diversity. This approach shed light on the functional diversity of China’s terrestrial mammals from a macroecological perspective. We found that in terms of overall quantity composition, underground-living mammals (UG groups) had the highest proportion (55.1%) in the vertical niche dimension, while nocturnal mammals (NO groups) dominated (58.6%) the in temporal niche dimension. Employing grid cells as fundamental units, in most grid cells, the proportion of UG and NO groups exceeded 50%, consistent with the overall quantity results. Examining the spatial distribution of functional group species richness from different perspectives reveals varying patterns. For instance, standard deviations of vertical and temporal niches showed different spatial clustering traits on either side of the Hu Huanyong Line. In a specific dimension of functional diversity, the numerical differences among functional groups are larger in grasslands with homogenous vegetation, while in forests with diverse vegetation types, these differences are minimized. Additionally, if there is a large disparity in species richness among functional groups in one dimension, there may be a smaller disparity in another. These findings offer a macroecological perspective for biodiversity research, providing insights for interdisciplinary studies in basic ecology, conservation biology, and geography, and offering scientific guidance for mammal conservation.

Taylor's power law for freshwater fishes: Functional traits beyond statistical inevitability.

Taylor's power law (TPL) describes the expected range of parameters of the mean-variance scaling relationship and has been extensively used in studies examining temporal variations in abundance. Few studies though have focused on biological and ecological covariates of TPL, while its statistical inherences have been extensively debated. In the present study, we focused on species-specific features (i.e. functional traits) that could be influential to temporal TPL. We combined field surveys of 180 fish species from 972 sites varying from small streams to large rivers with data on 31 ecological traits describing species-specific characteristics related to three main niche dimensions (trophic ecology, life history, and habitat use). For each species, the parameters of temporal TPL (intercept and slope) were estimated from the log-log mean-variance relationships while controlling for spatial dependencies and biological covariates (species richness and evenness). Then, we investigated whether functional traits explained variations in TPL parameters. Differences in TPL parameters among species were explained mostly by life history and environmental determinants, especially TPL slope. Life history was the main determinant of differences in TPL parameters and thereby aggregation patterns, with traits related to body size being the most influential, thus showing a high contrast between small-sized species with short lifespans and large-bodied migratory fishes, even after controlling for phylogenetic resemblances. We found that life history traits, especially those related to body size, mostly affect TPL and, as such, can be determinants of temporal variability of fish populations. We also found that statistical effects and phylogenetic resemblances are embedded in mean-variance relationships for fish, and that environmental drivers can interact with ecological characteristics of species in determining temporal fluctuations in abundance.

Brocket deer niche breadth and overlap: spatial similarities limit species coexistence

AbstractUnderstanding species coexistence requires information about how species interact and partition their ecological niche. Niches of closely related species tend to be quite similar and thereby, when syntopic, overlap can result in competition when shared resources are limiting. Brocket deer of tropical forests are ecologically similar species due to convergence or relatedness. As a group, what little is known about their ecology suggests spatial and temporal niche separation while dietary differences among species remain largely unknown. The possibility of competition has been suggested, as it is rare for more than two species to co‐occur. If competition is important, then it may limit syntopy of more species and its importance should increase with relatedness between species. Based on analyses of faecal samples, camera traps, and stable isotopes and multidimensional analysis of niche space, we test spatial, temporal and dietary niche differences and compare niche breadth in two syntopic species pairs: Mazama rufa with M. nana (both of subtribe Odocoileina) and M. jucunda (Odocoileina) with Subulo gouazoubira (Blastocerina). In 2007–2008 and 2017–2019, 240 faecal samples and 375 records were collected in the Brazilian Atlantic Forest. Spatial partitioning among both species pairs was found, with S. gouazoubira and M. nana having greater niche breadth, which may permit or facilitate coexistence. Odocoileina tend to be nocturnal, while Blastocerina tend to be diurnal, which suggests that phylogeny may influence species coexistence. Furthermore, the species tended to overlap with respect to diet. These results suggest interference competition avoidance by niche partitioning at the level of habitat and time, allowing coexistence. Thereby, despite the morphological similarities, brocket deer species of evolutionarily convergent subtribes preserve differences in ecological niche dimensions that facilitate the coexistence of their populations.

Multi-dimensional niche differentiation of two sympatric breeding secondary cave-nesting birds in Northeast China using DNA metabarcoding.

Niche theory predicts that ecologically similar sympatric species should show differentiation in at least one of the main niche dimensions (time, space, and/or food). Here, we combined observations of breeding timing, nest site selection, and diet (the latter determined using DNA metabarcoding) to analyze the niche overlap and differentiation between two sympatric secondary cavity-nesting birds, the Japanese Tit Parus minor and the Yellow-rumped Flycatcher Ficedula zanthopygia. The results showed that (1) there were significant differences in the first egg laying date, length of the egg laying period, incubation date, and hatching date between tits and flycatchers, and the breeding time of flycatchers peaked later (about 30 days) than that of tits; (2) the two species had a large overlap in nest site selection, although the canopy coverage and shrub density of flycatchers were significantly higher than those of tits; and (3) the niche overlap in diet was minimal, with both species heavily relying on Lepidoptera (39.6% and 63.7% for tits and flycatchers, respectively), but with flycatchers consuming significantly higher percentages of Lepidoptera, Diptera, and Coleoptera than tits. The results indicate that these two sympatric secondary cavity-nesting species have significant niche differentiation in breeding time and diet, but little differentiation in nest site selection.

Autecology of the gecko Phyllopezus periosus (Squamata: Phyllodactylidae) inhabiting rock cliffs of a waterfall canyon from the semi-arid region of northeastern Brazil

Phyllopezus periosus is the largest phyllodactilid in Brazil, with a relictual distribution in the Caatinga Domain. Herein, we investigated the autecology of P. periosus, describing activity patterns, microhabitat use (spatial niche dimension), foraging mode, body temperature, reproduction, diet (trophic niche dimension), and temperature. Also, we tested the influence of seasonality and ontogeny on these biological aspects. Geckos (n = 116, 54 females, 33 males, and 29 juveniles) were sampled from October 2013 to September 2014. Phyllopezus periosus has an unimodal activity pattern, with peak activity in the early hours of the night. Males are more robust than females, and forelimbs in females are longer than in males. The body temperatures of this thermoconformer gecko are higher in the dry season. The reproductive season begins in the early dry season, with a fixed clutch of two eggs. Although we did not find evidence of more than one clutch per year, the studied population of P. periosus reproduces for an extended period throughout the dry season, as highlighted by the presence of juveniles all year. Phyllopezus periosus is saxicolous and presents a generalist diet composed mainly of arthropods, also including vertebrates such as frogs and lizards.

Alpine plant communities and current topographic microrefugia vary with regional climates

Topographic microrefugia on slopes are assumed to be critical for the persistence of alpine plant species and the maintenance of alpine plant community diversity in a warming climate. They create microclimates, some of which are cooler and/or wetter than others, which may buffer continuing climate change. However, the current relationship of plant communities to microtopography at individual slope scale could differ among regional climates, and if so resilience in new climates would also differ.Vegetation cover and topographic site characteristics at a fine scale were recorded in the field in three alpine regions of the Rocky Mountains, USA: Glacier National Park, MT, the Indian Peaks Area, CO, and Taos Ski Valley, NM. Elements of alpine slopes were identified and transformed into ordinal variables. Two indicators of insolation were calculated from slope angle, slope aspect, and latitude, and soil depth indicators and elevation were recorded. In each region, the contribution of these variables to the variation in the plant community composition were compared using nonmetric multidimensional scaling and random forest models.The partitioned variance explained by the topographic and topography-derived climatic variables differed among the three regions. Variables related to moisture conditions were more important in the snowiest, northern region and the central region, while those related to energy were more important in the southern region with higher radiation and temperature. Lower correlations of mesoscale variables set microrefugia in a hierarchical context.The more extreme regional topographically derived climatic variables better explain the differentiation of alpine plant communities. These variables may not play the same role in potentially novel future climates. Because topographic features mediate regional climates to niche dimensions, setting microrefugia in a multiscale framework can focus research on climate change impacts.

Niche dimensions in soil oribatid mite community assembly under native and introduced tree species.

Forest soils are a critical component of terrestrial ecosystems and host a large number of animal decomposer species. One diverse and abundant decomposer taxon is oribatid mites (Acari: Oribatida), whose species composition varies with forest type and tree species composition. We used functional traits that indicate different niche dimensions, to infer assembly processes of oribatid mite communities in monocultures and mixed forests of native and introduced tree species. We found that coexisting species differed more in the resource-related niche dimension, i.e., reproductive mode and trophic guild, than in the morphological dimension, e.g., body length and width, sclerotization and concealability. These results suggest that both filtering and partitioning processes structure oribatid mite communities. In native European beech forests, but not in non-native Douglas fir forests, oribatid mites were mainly structured by filtering processes acting via traits related both to environmental tolerance and to resources. Furthermore, oribatid mite trait diversity, but not phylogenetic diversity, differed significantly between monocultures and mixed forests, demonstrating that multidimensional diversity indices provide additional information on soil biodiversity. Overall, the study provides evidence that traits representing different niche dimensions need to be considered for understanding assembly processes in soil animal communities and thereby soil biodiversity.

Hunting habits die hard: Conserved prey preferences in army ants across two distant neotropical rainforests

AbstractArmy ants are widely recognized as keystone species in neotropical rainforests due to their role as important arthropod predators. Their large‐scale raids involve thousands of workers scouring the forest floor in pursuit of prey, primarily capturing other invertebrates. Up to 20 species of army ants coexist in a rainforest, and dietary niche differentiation has been proposed as a mechanism to alleviate competition among them. Based on only a handful of study sites, however, our understanding of the precise dietary preferences and the extent of niche differentiation remains notably limited. In this study, we aimed to expand our knowledge of army ant communities by resolving an Ecuadorian predation network consisting of 244 prey species and 13 army ant species representing the five known neotropical army ant genera: Cheliomyrmex, Eciton, Labidus, Neivamyrmex, and Nomamyrmex. We collected 2156 prey items from 180 army ant raids/emigrations, and of these, we identified 1945 prey items to the family level, 1313 to the genus level, and 664 to the species level based on morphological identifications and DNA barcodes. Prey consisted primarily of other ants (1843 prey items; 153 ant species), to the largest part ant brood (N = 1726). Hence, most army ant species chiefly plundered the nests of other ants, while the three swarm raiding species, that is, Lab. praedator, Lab. spininodis, and Ec. burchellii, exhibited a relatively high proportion of non‐ant invertebrate prey in their diet. The predation network showed a high degree of specialization (H2′ = 0.65), characterized by little dietary niche overlap among sympatric species. We compared the Ecuadorian network with one previously studied in Costa Rica and found that, despite the large geographic distance, prey preferences remained remarkably similar. We discovered species‐specific preferences for captured ant genera and species, despite some species turnover in both army ants and prey. Additionally, army ants also exhibited consistent spatiotemporal raiding preferences across study sites. In conclusion, predation preferences within army ant communities exhibited consistency in multiple niche dimensions across two distant neotropical rainforests, suggesting a notable level of predictability within army ant predation networks.

Characterization of environmental drivers influencing the abundance of Anopheles maculipennis complex in Northern Italy

BackgroundIn Italy, malaria was endemic until the 1970s, when it was declared eradicated by WHO. Nowadays, with the persistence of competent mosquito populations, the effect of climate change, and increased possibility of importing malaria parasites from endemic counties due to growing migration, a malaria resurgence in Italy has become more likely. Hence, enhancing the understanding of the current distribution of the Anopheles maculipennis complex and the factors that influence the presence of this malaria vector is crucial, especially in Northern Italy, characterised by a high density of both human population and livestock.MethodsTo assess the presence and abundance of malaria vectors, a 4-year field survey in the plain areas of Lombardy and Emilia-Romagna region in Italy was conducted. Every sampling point was characterised in space by the land use in a 500-m radius and in time considering meteorological data collected in the short and long time periods before sampling. We combined the results of a linear regression model with a random forest analysis to understand the relative importance of the investigated niche dimensions in determining Anopheles mosquito presence and abundance.ResultsThe estimated normalised variable importance indicates that rice fields were the most important land use class explaining the presence of Anopheles, followed by transitional woodlands and shrubland. Farm buildings were the third variable in terms of importance, likely because of the presence of animal shelters, followed by urbanised land. The two most important meteorological variables influencing the abundance of Anopheles in our study area were mean temperature in the 24 h before the sampling date and the sum of degree-days with temperature between 18 °C and 30 °C in the 14 days before the sampling date.ConclusionsThe results obtained in this study could be helpful in predicting the risk of autochthonous malaria transmission, based on local information on land cover classes that might facilitate the presence of malaria vectors and presence of short- and medium-term meteorological conditions favourable to mosquito development and activity. The results can support the design of vector control measures through environmental management.Graphical

Living with voracious roommates: Factors that explain isotopic niche variation in a mixed colony of insectivorous bats.

Theory predicts that in resource-limited environments, coexisting species may overlap their niche dimensions but must differ in at least one to avoid competitive exclusion. Specifically, it has been suggested that the coexistence of competing species within a guild, could be sustained with mechanisms of resource partitioning, such as segregation along a trophic dimension. Among the most gregarious mammals are bats, which present diversification in their diet based on habitat choice and body size. Despite differences that could explain specialization in prey selection, there are insufficient studies that explore food overlap in mixed bat colonies and the factors that determine the selection of prey, both at intra- and inter-specific levels. To fill this gap, we analyzed the isotope signal (δ13C and δ15N) in feces collected in a mixed colony of Tadarida brasiliensis and Myotis chiloensis. To understand how several factors could influence these isotopic signals, intrinsic explanatory variables were analyzed, including body mass, body length, age, and sex. Also, extrinsic variables were analyzed, including monthly temporality and moonlight intensity. Our findings support age-dependent specialization in M. chiloensis, with a significant role of moonlight intensity and sex on δ15N. In T. brasiliensis, we identified a significant effect of size, sex, and ear length on δ15N. Our analysis indicates that both species of bats experience diverse degrees of overlap through austral summer months, affected by several factors that explain the variability in their fecal isotopic signals.

The influence of scale-dependent geodiversity on species distribution models in a biodiversity hotspot.

Improving models of species' distributions is essential for conservation, especially in light of global change. Species distribution models (SDMs) often rely on mean environmental conditions, yet species distributions are also a function of environmental heterogeneity and filtering acting at multiple spatial scales. Geodiversity, which we define as the variation of abiotic features and processes of Earth's entire geosphere (inclusive of climate), has potential to improve SDMs and conservation assessments, as they capture multiple abiotic dimensions of species niches, however they have not been sufficiently tested in SDMs. We tested a range of geodiversity variables computed at varying scales using climate and elevation data. We compared predictive performance of MaxEnt SDMs generated using CHELSA bioclimatic variables to those also including geodiversity variables for 31 mammalian species in Colombia. Results show the spatial grain of geodiversity variables affects SDM performance. Some variables consistently exhibited an increasing or decreasing trend in variable importance with spatial grain, showing slight scale-dependence and indicating that some geodiversity variables are more relevant at particular scales for some species. Incorporating geodiversity variables into SDMs, and doing so at the appropriate spatial scales, enhances the ability to model species-environment relationships, thereby contributing to the conservation and management of biodiversity. This article is part of the Theo Murphy meeting issue 'Geodiversity for science and society'.

Wide ecological niches ensure frequent harmful dinoflagellate blooms

Harmful algal blooms (HABs) and their consequences cause multiple devastating effects in various freshwater, brackish and marine ecosystems. However, HAB species at moderate population densities have positive ecological roles as primary producers of organic matter and food for zooplankton and fish. They also enhance benthic-pelagic coupling and participate in the biogeochemical cycles. The consequences of HABs are transported across the conventional environmental boundaries by numerous cascade effects in the food webs and beyond. Meanwhile, forecasts of bloom events are still limited, largely because of scarcity of reliable information on ecological niches of the bloom-forming algae. To fill up this knowledge gap, this study focused on dinoflagellates, a diverse group of mostly photosynthesizing protists (unicellular eukaryotes) capable of mixotrophy, since they play a key role in primary production and formation of blooms in marine and brackish waters worldwide. In this study, ecological niches of 17 abundant bloom-forming dinoflagellate species from coastal regions of the southern Baltic Sea were identified for the first time. It was hypothesized that wider ecological niches ensure more frequent dinoflagellate blooms compared to the species with narrower niches. This hypothesis was verified using the long-term (44 years) database on phytoplankton abundance and physical-chemical characteristics of the environment. It were analyzed 4534 datasets collected from 1972 to 2016. Fourteen abiotic parameters (water temperature, salinity, Secchi depth, pH, Chl a, and concentration of basic nutrients) were considered as ecological niche dimensions. The Principal Component Analysis presented the dissolved inorganic nitrogen, total nitrogen, Chl a, and temperature as principal niche dimensions of dinoflagellates. The algal bloom criteria were refined. It was for the first time proved statistically that HAB frequency of dinoflagellate species robustly correlated with the width of their ecological niches.

Habitat partitioning among sympatric tinamous in semiarid woodlands of central Argentina.

Sympatric, phylogenetically related and morphologically similar species that overlap in their distributions at a regional scale display different patterns of co-occurrence at local assemblages. Occurrence of each species at local scales might be the result of interspecific competition for limiting resources. However, these patterns could also arise from species-specific habitat preferences along the abiotic or land use gradients. To assess the role of these mechanisms, we investigated niche partitioning among sympatric tinamou species occurring in semiarid woodlands of central Argentina. We used occupancy models incorporating habitat characteristics and interspecific interactions, while accounting for detectability, to examine the spatial overlap among elegant crested tinamous (Eudromia elegans), brushland tinamous (Nothoprocta cinerascens), and nothura tinamous (Nothura darwinii and N. maculosa) across a wide regional scale. In addition, we investigated time partitioning among these species by estimating the degree of overlap in their daily activity patterns. The regional distribution of the three species was influenced by the gradient in plant productivity and vegetation structure, in agreement with their broad habitat requirements. We also found that the occurrence of each species was presumably affected by the presence of one or two predator species. Models including interactions among tinamou species found weak negative and positive interactions among species pairs, suggesting that co-occurrence patterns were mainly driven by species-specific habitat use rather than interspecific competition. The three species were diurnal, showing two main peaks of activity, and overlapped widely in their overall diel activity, although subordinate species tended to shift their activity patterns to reduce encounters with the dominant tinamou species, suggesting some segregation in this niche dimension. Projected changes in rainfall seasonality and warmer conditions in this region could benefit elegant crested tinamous over the other two species, although climate and land use changes will likely have a negative impact on all tinamou species.

East and West of the Carpathian Arc: Evidence of postglacial ecological and morpho-logical divergence of Phytoecia tigrina metapopulations (Coleoptera, Cerambycidae)

Phytoecia tigrina Mulsant (1851) is recognized as a species under strict protection EU Habitat Directive, it represents a focal point for conservation efforts across Europe. However, the dearth of comprehensive understanding regarding its biology, ecology, and geographical distribution poses formidable challenges to conservation endeavors. In the current study, we have delineated eight European and two Asian distinct metapopulations of Ph. tigrina across its geographic range, with a particular emphasis on elucidating its dispersion within the Circum-Carpathian region. This delineation serves to underscore the species' distribution, niche dimensions and limits of ecological tolerance that illuminate its adaptation capacity to diverse environmental conditions within the range. Our study has unveiled notable differentials in both morphological and ecological traits among Ph. tigrina metapopulations, notably between those located on the eastern and western flanks of the Carpathian Arc. Such differentials suggest the influence of divergent evolutionary trajectories, likely influenced by historical climatic changes during the Late Pleistocene and Holocene epochs. Significantly, specimens derived from eastern metapopulations exhibit morphological features of sufficient magnitude to warrant the proposition of a distinct subspecies, Phytoecia (Pilemia) tigrina podillica ssp. nov. This taxonomic delineation underscores the taxonomic complexity inherent within the Ph. tigrina species complex. Our investigations have further illuminated the historical dynamics of the species distribution, indicating the presence at least of two refugia during the Last Glacial Maximum (LGM). These refugial enclaves, situated in the Sea of Marmara/Eastern Aegean Sea region and the Pannonian Plain, likely played pivotal roles in shaping contemporary distributional patterns. Moreover, our ecological niche modeling endeavors have elucidated rapid expansions of suitable habitat for Ph. tigrina during post-glacial epochs, notably the Preboreal and Boreal periods. These expansions aligned with the rapid dispersion of its host plant Cynoglottis barrelieri supplying colonization of new territories in the face of the fast-changing post-glacial environment. Our study underscores the intricate interplay between evolutionary history, environmental dynamics, and imperatives for conservation Ph. tigrina. By elucidating these complexities, we endeavor to furnish a robust foundation for future conservation initiatives aimed at safeguarding this emblematic species and its associated habitats.

Spatial and temporal patterns of phytoplankton community succession and characteristics of realized niches in Lake Taihu, China

Understanding the dynamics and succession of phytoplankton in large lakes can help inform future lake management. The study analyzed phytoplankton community variations in Lake Taihu over a 21-year period, focusing on realized niches and their impact on succession. The study developed a niche periodic table with 32 niches, revealing responses to environmental factors and the optimal number of niches. Results showed that the phytoplankton in Lake Taihu showed significant spatial and temporal heterogeneity, with biomass decreasing as one moved from the northwest to the southeast and expanding towards central lake area, and towards autumn and winter. Different phytoplankton groups in Lake Taihu occupied realized niches shaped by temperature, nitrate, and phosphate. To predict the response of eutrophic freshwater lake ecosystems to human activities and climate change, it is critical to interpret the law of phytoplankton bloom and niche succession.

Differences in functional niche hypervolume among four types of forest vegetation and their environmental determinants across various climatic regions in China.

Functional traits play an important role in studying the functional niche in plant communities. However, it remains unclear whether the functional niches of typical forest plant communities in different climatic regions based on functional traits are consistent. Here, we present data for 215 woody species, encompassing 11 functional traits related to three fundamental niche dimensions (leaf economy, mechanical support, and reproductive phenology). These data were collected from forests across four climatic zones in China (tropical, subtropical, warm-temperate, and cold-temperate) or sourced from the literature. We calculated the functional niche hypervolume, representing the range of changes in the multidimensional functional niche. This metric quantifies how many functional niche spaces are occupied by existing plants in the community. Subsequently, we analyzed differences in functional niche hypervolume and their associated environmental factors across different types of forest vegetation. The results indicate that the functional niche hypervolume and the degree of forest vegetation overlap decrease with increasing latitude (e.g., from tropical rainforest to cold temperate coniferous forest). The total explanatory power of both climate and soil factors on the variation in functional niche hypervolume was 50%, with climate factors exhibiting a higher explanatory power than soil factors. Functional niche hypervolume is positively correlated with climate factors (annual mean temperature and annual precipitation) and negatively correlated with soil factors (soil pH, soil organic matter content, soil total nitrogen content, and soil total phosphorus content). Among these factors, annual mean temperature, soil pH, and soil total nitrogen content most significantly affect the difference in functional niche hypervolume among forest vegetation. Our study emphasizes the significant variation in the functional niche hypervolume among typical forest vegetation in China.

Spatial, temporal and trophic resource partitioning among the four egret species (Aves: Pelecaniformes: Ardeidae) in a tropical wetland ecosystem, India

The diversity of micro-habitats in tropical wetlands allows the coexistence of several species. These sympatric species interact with each other, either directly or indirectly, to optimally use the available resources. They achieve this through niche separation or minimal overlap to avoid competition. India’s wetland ecosystems are home to various sympatric species, such as the Great Egret Ardea alba (GE), Median Egret Ardea intermedia (IE), Little Egret Egretta garzetta (LE) and Cattle Egret Bubulcus ibis (CE). These egret species are closely related, and as a result, have similar niche requirements, which could lead to high intra-specific competition. However, there have been few studies on how these species utilize resources. This study aims to understand the possible mechanisms that enable the coexistence of these species in a tropical wetland. We have examined habitat characteristics, feeding behaviour, timings of seasonal and daily activities, and spacing patterns to evaluate possible models of species coexistence. We discovered that these four sympatric egret species have differences in microhabitat selection, activity patterns, both daily and seasonally, and feeding preferences. The study further indicates that there is a relationship between the niche dimensions, but it is only partially dependent on each other.

Ecological niches of bloom-forming cyanobacteria in brackish Baltic Sea coastal waters

Cyanobacterial blooms occur regularly during summer and fall in various freshwater and brackish environments worldwide causing harm to aquatic flora, fauna, and water quality in natural ecosystems as well as in aquaculture. They also interfere with industrial fisheries, tourism, and human health. Meanwhile, up to date limited knowledge exists about these detrimental phenomena in brackish waters, and patterns of their expansion across the freshwater-to-marine continuum remain unclear. In this study, we analyzed long-term (1972–2016) dynamics of cyanobacterial harmful algal blooms (cyanoHABs) in the brackish southern Baltic Sea coastal waters, refined the cyanoHAB criteria, and for the first time measured ecological niches of the dominant bloom-forming cyanobacteria. The ecological niches of selected cyanoHAB species were determined considering a set of abiotic parameters as niche dimensions: water temperature, salinity, and concentrations of basic nutrients (PO43−, SiO44−, dissolved inorganic nitrogen – DIN, total phosphorus – TP, total nitrogen – TN, and TN/TP ratio), with special emphasis on salinity. We hypothesized that in highly variable brackish environments, the cyanobacterial species with broader ecological niches occur and bloom more often compared to those with narrower niches. For testing this hypothesis, we evaluated the effects of ecological niche width on the occurrence of the dominant cyanoHAB species and frequency of their blooms. The results revealed a pronounced statistically significant (p < 0.05) positive correlation between salinity-niche width and frequency of cyanoHABs. Moreover, the occurrence of cyanoHAB species with wider DIN and PO43− concentration-niches was substantially higher than that of the species with narrower nutrient-concentration niches. The effect of temperature-niche width on the occurrence of cyanoHAB species, on the contrary, was negligible and statistically insignificant. The latter result concurs with the fact that most of these cyanobacteria are highly thermophilic: on average, they bloom at temperatures above 21 °C, and their realized temperature niches in the southern Baltic coastal waters are relatively narrow.