Variation In Species Abundance Research Articles

Habitat attributes mediate herbivory and influence community development in algal metacommunities.

Understanding the drivers and impacts of spatiotemporal variation in species abundance on community trajectories is key to understanding the factors contributing to ecosystem resilience. Temporal variation in species trajectories across patches can provide compensation for species loss and can influence successional patterns. However, little is known about the underlying mechanisms that lead to patterns of species or spatial compensation and how those patterns may be mediated by consumer-resource relationships. Here we describe an experiment testing whether habitat attributes (e.g., structural complexity and spatial heterogeneity) mediate the effects of herbivory on tropical marine macroalgal communities by reducing accessibility and detectability, respectively, leading to variable trajectories among algal species at community (within patch) and metacommunity (i.e., among patch) scales. Reduced accessibility (greater habitat complexity) decreased the effects of herbivory (i.e., depressed consumption rate, increased algal species richness), and both accessibility and detectability (spatial heterogeneity) influenced algal community structure. Moreover, decreased accessibility at the community scale and a mosaic of accessibility at the metacommunity scale led to variation in community assembly. We suggest that habitat attributes can be important influencers of consumer-resource interactions on coral reefs, which in turn can increase species diversity, promote species succession, and enhance stability in algal metacommunities.

The impact of Traditional Chinese Medicine on mouse gut microbiota abundances and interactions based on Granger causality and pathway analysis.

The intestinal microbiota is essential in absorbing nutrients and defending against pathogens and is associated with various diseases, including obesity, type 2 diabetes, and hypertension. As an alternative medicine, Traditional Chinese Medicine (TCM) has long been used in disease treatment and healthcare, partly because it may mediate gut microbiota. However, the specific effects of TCM on the abundance and interactions of microbiota remain unknown. Moreover, using TCM ingredients and data detailing changes in the abundance of gut microorganisms, we developed bioinformatic methods that decipher the impact of TCM on microorganism interactions. The dynamics of gut microorganisms affected by TCM treatments is explored using a mouse model, which provided the abundance of 70 microorganisms over time. The Granger causality analysis was used to measure microorganism interactions. Novel "serial connection" and "diverging connection" models were used to identify molecular mechanisms underlying the impact of TCM on gut microorganism interactions, based on microorganism proteins, TCM chemical ingredients, and KEGG reaction equations. Codonopsis pilosula (Dangshen), Cassia twig (Gui Zhi), Radices saussureae (Mu Xiang), and Sijunzi Decoction did not cause an increase in the abundance of harmful microorganisms. Most TCMs decreased the abundance of Bifidobacterium pseudolongum, suggesting a Bifidobacterium pseudolongum supplement should be used during TCM treatment. The Granger causality analysis indicated that TCM treatment changes more than half the interactions between the 70 microorganisms, and "serial connection" and "diverging connection" models suggested that changes in interactions may be related to the reaction number connecting species proteins and TCM ingredients. From a species diversity perspective, a TCM decoction is better than a single herb for healthcare. The Sijunzi Decoction only significantly increased the abundance of Bifidobacterium pseudolongum and did not cause a decrease in the abundance of other species but was found to improve the alpha diversity with the lowest replacement rate. Because most of the nine TCMs are medicinal and edible plants, we expect the methods and results presented can be used to optimize and integrate microbiota and TCMs into healthcare processes. Moreover, as a control study, these results can be combined with future disease mouse models to link variations in species abundance with particular diseases.

Long-term monitoring dataset of fish assemblages in rocky tidepools on the southern coast of Taiwan

Long-term data of fish assemblages collected in the rocky intertidal zone provides a valuable resource for elucidating the temporal variations in species diversity and intertidal ecosystems. In this study, we describe a long-term time-series dataset of fish collected by counting the number of anesthetized fish at sampling stations in the rocky tidepools on the southern coast of Taiwan. The species assemblages were monitored seasonally at the two stations for 16 y (2000–2008 and 2012–2018). In total, 86 samples containing 5137 individuals belonging to 82 species were recorded. Our data can be used for elucidating the temporal variations in fish assemblages and intertidal ecosystems and as background information for the resilience of the fish community conservation in coastal areas. The current study presents valuable data for researchers to understand the temporal and spatial variations in species abundance, richness, diversity, and composition in relation to climate change, environmental factors, and human activities.

Two independent allohexaploidizations and genomic fractionation in Solanales

Solanales, an order of flowering plants, contains the most economically important vegetables among all plant orders. To date, many Solanales genomes have been sequenced. However, the evolutionary processes of polyploidization events in Solanales and the impact of polyploidy on species diversity remain poorly understood. We compared two representative Solanales genomes (Solanum lycopersicum L. and Ipomoea triloba L.) and the Vitis vinifera L. genome and confirmed two independent polyploidization events. Solanaceae common hexaploidization (SCH) and Convolvulaceae common hexaploidization (CCH) occurred ∼43–49 and ∼40–46 million years ago (Mya), respectively. Moreover, we identified homologous genes related to polyploidization and speciation and constructed multiple genomic alignments with V. vinifera genome, providing a genomic homology framework for future Solanales research. Notably, the three polyploidization-produced subgenomes in both S. lycopersicum and I. triloba showed significant genomic fractionation bias, suggesting the allohexaploid nature of the SCH and CCH events. However, we found that the higher genomic fractionation bias of polyploidization-produced subgenomes in Solanaceae was likely responsible for their more abundant species diversity than that in Convolvulaceae. Furthermore, through genomic fractionation and chromosomal structural variation comparisons, we revealed the allohexaploid natures of SCH and CCH, both of which were formed by two-step duplications. In addition, we found that the second step of two paleohexaploidization events promoted the expansion and diversity of β-amylase (BMY) genes in Solanales. These current efforts provide a solid foundation for future genomic and functional exploration of Solanales.

CHARACTERIZING MODERN AND HOLOCENE BARRIER-ISLAND ENVIRONMENTS WITH FORAMINIFERAL ASSEMBLAGES: AN EXAMPLE FROM A WAVE-DOMINATED, MICROTIDAL BARRIER-ISLAND SYSTEM, NORTH CAROLINA, USA

Abstract Recent research has shown that sedimentological information in barrier-island settings may provide more detailed interpretations of some past coastal environments than interpretations based upon foraminifera. This research investigates whether targeted documentation of modern foraminifera in specific coastal environments can result in higher resolution micropaleontology-based paleoenvironmental reconstructions. Bear Island, North Carolina, characterized by little human disturbance, was chosen for detailed documentation of foraminifera in modern barrier-island-related environments. Modern sediments in all subenvironments were predominantly siliciclastic (< 30 % clastic carbonate debris) in composition: clastic carbonate allochems (e.g., mollusk shell fragments, echinoid spines) were admixed with fine- to medium-grained quartz sand. The hypothesis that modern foraminiferal assemblages of 26 modern coastal subenvironments can be distinguished based upon their foraminiferal assemblages was tested by discriminant analysis and resulted in the recognition of four environmental supergroups: shoreface, ebb-tidal delta, flood-tidal delta/inlet channel, and “barrier-combined” (foreshore, washover, dune, sandflat, spit, longshore bar, and trough). Holocene paleoenvironments represented by foraminiferal assemblages in 16 vibracores collected from the modern inner shelf, shoreface, ebb-tidal delta, and inlet environments of Bogue Banks, immediately adjacent to Bear Island, were interpreted, via discriminant analysis, based upon the modern dataset. Holocene and modern foraminiferal assemblages were similar but variations in species abundance and species diversity allowed for alternative paleoenvironmental classification of core samples at varying levels of probability. The methodology of this research is widely applicable to other coastal environments.

Abundant Species Diversity and Essential Functions of Bacterial Communities Associated with Dinoflagellates as Revealed from Metabarcoding Sequencing for Laboratory-Raised Clonal Cultures.

Interactions between algae and bacteria represent an important inter-organism association in aquatic environments, which often have cascading bottom-up influences on ecosystem-scale processes. Despite the increasing recognition of linkages between bacterioplankton and dynamics of dinoflagellate blooms in the field, knowledge about the forms and functions of dinoflagellate-bacteria associations remains elusive, mainly due to the ephemeral and variable conditions in the field. In this study, we characterized the bacterial community associated with laboratory cultures of 144 harmful algal strains, including 130 dinoflagellates (covering all major taxonomic orders of dinoflagellates) and 14 non-dinoflagellates, via high-throughput sequencing for 16S rRNA gene amplicons. A total of 4577 features belonging to bacteria kingdom comprising of 24 phyla, 55 classes, 134 orders, 273 families, 716 genera, and 1104 species were recovered from the algal culture collection, and 3 phyla (Proteobacteria, Bacteroidetes, and Firmicutes) were universally present in all the culture samples. Bacterial communities in dinoflagellates cultures exhibited remarkable conservation across different algal strains, which were dominated by a relatively small number of taxa, most notably the γ-proteobacteria Methylophaga, Marinobacter and Alteromonas. Although the bacterial community composition between dinoflagellates and non-dinoflagellate groups did not show significant difference in general, dinoflagellates harbored a large number of unique features (up to 3811) with relatively low individual abundance and enriched in the potential methylotrophs Methylophaga. While the bacterial assemblages associated with thecate and athecate dinoflagellates displayed no general difference in species composition and functional groups, athecate dinoflagellates appeared to accommodate more aerobic cellulolytic members of Actinobacteria, implying a more possible reliance on cellulose utilization as energy source. The extensive co-occurrence discovered here implied that the relationships between these algal species and the bacterial consortia could be viewed as either bilaterally beneficial (i.e., mutualism) or unilaterally beneficial at least to one party but virtually harmless to the other party (i.e., commensalism), whereas both scenarios support a long-term and stable co-existence rather than an exclusion of one or the other. Our results demonstrated that dinoflagellates-associated bacterial communities were similar in composition, with enrichment of potential uncultured methylotrophs to one-carbon compounds. This work enriches the knowledge about the fundamental functions of bacteria consortia associated with the phycospheres of dinoflagellates and other HABs-forming microalgae.

Correlation of variations in species abundance of Atlantic forests regenerating on abandoned pastures with different environmental and spatial variables

The conversion of native forests into pastures is still a common practice in Brazil. Abandoned pastures have great potential for natural regeneration and therefore could play an important role in meeting the enormous demand for forest restoration. Few studies, however, have investigated the extent to which spatially-structured environmental variables and community structure are correlated with the variation in species abundance of regenerating forests on abandoned pastures. Therefore, we aimed to determine whether environmental and spatial variables were capable of explaining the variation in abundance of woody species on abandoned pastures in the subtropical Atlantic Forest. We systematically distributed 45 sample plots with size and inclusion criteria that changed according to the vegetation layer in three different abandoned pastures. In general, most of the variation in species abundance that our models were able to explain was correlated with spatially-unstructured physical-chemical soil properties. A smaller part of the variation was correlated with spatially-structured soil variables and topography-related variables. An even smaller portion of the variation was spatially-structured but was not correlated with spatially-structured environmental variables. Therefore, our results suggest that the variation in species abundance of regenerating subtropical Atlantic forests on abandoned pastures is more closely related to niche-based processes mediated by environmental variables than to stochastic spatial processes.

Soil nitrogen mediates the effect of climatic distance on herbivory rates in a tropical herb

AbstractThe center‐periphery hypothesis predicts that species are most abundant at the center of their distribution range. Differential herbivory rates between center and periphery populations can explain this variation in species abundance. However, if the geographic center of a species distribution coincides with its ecological optimum, the resource availability hypothesis predicts higher herbivory rates and tolerances at the center compared to the periphery. Biogeographical studies on herbivory have treated these two mechanisms separately, limiting our mechanistic understanding of the role of herbivory in shaping species range limits. We analyzed the role of resource availability on herbivory variation from center to periphery using data collected across the distribution of Thunberbia atacorensis, a range‐limited species of West Africa. We used two types of distances: geographic distance (the distance from each plot to the geographic center of all populations) and climatic distance (the distance from each plot to the preferendum of the species). We found no increase in herbivory toward the periphery of the climatic and geographic ranges. However, herbivory rates increased with soil nitrogen. Soil nitrogen decreased from the center to the periphery of the climatic range. Phylogenetic diversity and competition from surrounding plants did not affect herbivory rates. Our study provides insights into how nutrient limitation can shape species center‐periphery distribution by altering spatial variation in herbivory rates.

Drivers of avian diversity and abundance across gradients of human influence

ContextIdentifying factors driving patterns of species communities in heterogenous human-dominated landscapes remains elusive despite extensive research. Biodiversity is thought to decrease with habitat modification, as sensitive species are lost. Conversely, diversity has also been shown increase at moderate levels of landscape modification where greater habitat heterogeneity supports a diverse suite of species.ObjectivesWe explore patterns of avian diversity and abundance in heterogenous landscapes using a novel integration of multiple dimensional gradients of human-mediated modification.MethodsWe attempt to identify aspects of landscape heterogeneity driving patterns of avian diversity and abundance in agro-urban–rural systems. Specifically, we utilize an intuitive multi-dimensional gradient distinguishing between two axes of human-influence, variation in the built environment (hard–soft) and in agricultural development (green–brown). We use these as covariates in community N-mixture models to describe variation in species abundance and diversity.ResultsAvian richness was greatest in more heterogeneous regions of the landscape. Responses of individual species were variable, with sensitive species declining, while generalist species increased, leading to higher overall diversity in human-dominated regions.ConclusionsSpecies abundance and diversity is maximized in more heterogeneous parts of landscape mosaics. By characterizing distinct axes of human influence that capture spectrum of land use, we can identify differential effects confounded in traditional landscape metrics. Critically, we demonstrate that multi-dimensional landscape gradients provide a more nuanced understanding of how patterns of biodiversity emerge. Acknowledging that biodiversity is not always negatively impacted by habitat modification offers encouraging insight to guide conservation and management in human-dominated landscapes.

Resource partitioning among freshwater congeneric fishes (Loricariidae: Hypostomus): trophic, spatial, and temporal dimensions

ABSTRACT Resource partitioning is essential for coexistence of phylogenetically related species in altered environments, where changes in biotopes can limit resources and change ecological strategies. We investigated resource partitioning between two congeneric catfishes (Hypostomus affinis and H. luetkeni) in three niche dimensions (trophic, spatial, and temporal) in a Neotropical reservoir. We tested the hypothesis that the use of different mesohabitats (spatial dimension) is more relevant for the coexistence of species, and that morphological differences between the species confer different advantages in the mesohabitats occupation. We evaluated species morphology, diet composition and abundance along a spatial-temporal gradient. A high dietary overlap and a low temporal variability in species abundance were found, indicating that these two dimensions play a minor role in the species distribution. However, a strong spatial segregation modulated apparently by morphological differences was observed. Hypostomus luetkeni has a larger oral disk area, and a flatter body that confer advantages in the occupation of lotics habitats, whereas H. affinis has relatively larger fins that provide more efficient displacements in lentic habitats. Spatial partitioning was the main driver modulating mechanism for the coexistence of these species and differences in the occupation of the mesohabitats probably have been amplified in this altered environment.

Is There Any Linkage between Interstellar Aldehyde and Alcohol?

Abstract It is speculated that there might be some linkage between interstellar aldehydes and their corresponding alcohols. Here an observational study and astrochemical modeling are coupled together to illustrate the connection between them. The ALMA cycle 4 data of a hot molecular core, G10.47+0.03, are utilized for this study. Various aldehydes (acetaldehyde, propanal, and glycolaldehyde), alcohols (methanol and ethylene glycol), and a ketone (acetone) are identified in this source. The excitation temperatures and column densities of these species were derived via the rotation diagram method assuming local thermodynamic equilibrium conditions. An extensive investigation is carried out to understand the formation of these species. Six pairs of aldehyde–alcohol are considered for this study: (i) methanal and methanol, (ii) ethanal and ethanol, (iii) propanal and 1-propanol, (iv) propenal and allyl alcohol, (v) propynal and propargyl alcohol, and (vi) glycolaldehyde and ethylene glycol. One pair of ketone–alcohol (acetone and isopropanol) and ketene–alcohol (ethenone and vinyl alcohol) are also considered. Two successive hydrogenation reactions in the ice phase are examined to form these alcohols from aldehydes, ketone, and ketene, respectively. Quantum chemical methods are extensively executed to review the ice-phase formation route and the kinetics of these species. Based on the obtained kinetic data, astrochemical modeling is employed to derive the abundances of these aldehydes, alcohols, ketone, and ketene in this source. It is seen that our model could successfully explain the observed abundances of various species in this hot molecular core.

Predicting species abundance by implementing the ecological niche theory

Species are not uniformly distributed across the landscape. For every species, there should be few favoured sites where abundance is high and many other sites of lower suitability where abundance is low. Consequently, local abundance could be thought of as a natural expression of species response to local conditions. The correlation between abundance and environmental suitability has been well documented, and a recent meta‐analysis has suggested that this relationship could be a generality. Despite the importance and potential implication of the abundance–suitability relationship, its predictive power for meaningful extrapolations has been surprisingly poorly explored. In this study, we showed how a highly predictable trend can be extracted from the abundance–suitability relationship, accurately predicting the variation in species abundance at a high spatial resolution. We produced high‐quality environmental suitability estimations for 50 endemic species in the Australian Wet Tropics. Environmental suitability derived from species distribution models was related to observed abundance estimated using data from 29 years of uninterrupted monitoring effort. We used the fitted relationship to accurately predict abundance at a fine scale across the species range. Our results showed that the abundance–suitability relationship was strong for endemic species in the Australian Wet Tropics. The predictive power of our models was high, explaining, on average, 55% of the deviance across taxa. Despite interspecific variation in the strength of the abundance–suitability relationship associated with potential intrinsic estimation biases, our approach provides a powerful tool for predicting abundance across the species range at a fine scale. The potential for robust abundance predictions from occurrence‐based species distribution models shown in this study are numerous, and it could have a significant impact in enhancing species conservation and management decisions.

Where nothing stands still: quantifying nomadism in Australian arid-zone birds

ContextNomadism is a movement strategy in response to non-seasonal environmental variability. Knowledge of nomadic species movements is poor but is necessary to understand life histories and develop appropriate conservation strategies.ObjectivesWe provide a first quantification of nomadism among Australia’s arid bird community, which is presumed to be highly nomadic, by measuring variation in species’ occurrence and abundance among years to determine whether there are clear nomadic and non-nomadic strategists.MethodsWe surveyed birds annually from 2012 to 2016. We measured how many years each species was present at a site and estimated inter-annual variability in species abundance, using both measures to infer species movement patterns. We used results to inform existing movement classifications.ResultsMost arid species showed low site persistence, with species detected at the same site, on average, 1.8 out of the five survey years. Movement varied along a continuum rather than grouping into distinct nomadic and non-nomadic groups. Species classified as nomadic showed higher variation in abundance and lower site persistence than species classified as resident. Our method of quantifying nomadism closely replicated existing expert-derived movement classifications of arid zone bird species.ConclusionsRather than a fixed attribute, movements of many species in our study can be heavily environment-dependent, and individuals of a single species can display a continuum of movements in different times and places. This complicates the conservation of species, but the growing recognition of the complexity of species movements offers opportunities for a more nuanced understanding of the relationship between species and environment.

Combining multi-target regression deep neural networks and kinetic modeling to predict relative fluxes in reaction systems

The strong nonlinearity of large and highly connected reaction systems, such as metabolic networks, hampers the determination of variations in reaction fluxes from variations in species abundances, when comparing different steady states of a given system. We hypothesize that patterns in species abundance variations exist that mainly depend on the kernel of the stoichiometric matrix and allow for predictions of flux variations. To investigate this hypothesis, we applied a multi-target regression Deep Neural Network (DNN) to data generated via numerical simulations of an Ordinary Differential Equation (ODE) model of yeast metabolism, upon Monte Carlo sampling of the kinetic parameters. For each parameter configuration, we compared two steady states corresponding to different environmental conditions. We show that DNNs can predict relative fluxes impressively well even when a random subspace of input features is supplied, supporting the existence of recurrent variation patterns in abundances of chemical species, which can be recognized automatically.

Diversity partitioning and distance-decay relationship of saprophytic flies (Insecta: Diptera) in the western Brazilian Amazon

Studying beta-diversity patterns of biological communities and how species are organized in space is central to understanding the processes that maintain species diversity. Furthermore, knowledge on beta-diversity patterns is key for the protection and conservation planning of regional diversity. Insects represent the terrestrial animal group with the largest global biomass and a great body of information about spatial diversity patterns of megadiverse orders such as hymenopterans, lepidopterans, and coleopterans is available. However, studies dedicated to understanding these patterns in dipterans are scarce. Here, we aim to characterize the spatial variation of the assemblage of phytosaprophytic flies in the Amazon forest by investigating its distribution across hierarchies of spatial scales and the effect of geographical distance. The study site is located in the Direct Influence Area of the Belo Monte hydroelectric dam, Pará state, Brazil. Sampling followed the Rapid Assessments for Long Term Ecological Research experimental design. Fly assemblages were not uniform across most of the spatial scales investigated. The larger scale (from 10 to 100 km) contributed more to the gamma diversity of the region than the smaller ones (approximately 1 km). The beta diversity with a Shannon index of over 60 % of γ taxonomic diversity was influenced by the diversity within transects (α-diversity). Pairwise dissimilarity showed no significant relationship between geographical distance and Sorensen dissimilarity, turnover, nestedness, balanced variation in species abundances, or abundance gradient components. The absence of stochastic processes in the formation of the assemblages of phytosaprophytic flies indicates that environmental filters are more important to its structuring than neutral processes. Thus, studies on larger scales can provide more robust evidence on the assemblages distribution, both in preserved and highly impacted environments. Our study considered this wide-scale and our finding revealed some patterns in the assembly rules of the flies community Amazon.

The influence of abiotic and spatial variables on woody and herbaceous species abundances in a woodland–grassland system in the Eastern Terai of India

AbstractThe environmental factors that influence tree–grass abundances in tropical savanna and grasslands are not well understood, particularly for woodland–grassland mosaics in humid zones. We studied the effects of abiotic and spatial variables on woody and herbaceous species distributions in a Terai ecosystem of northeastern India. We evaluated the importance of climatic and non-climatic factors that maintain variable tree–grass ratios across the landscape, and also accounted for spatial connectivity and dispersal. We measured species abundances of woody and herbaceous plant species in 134 plots with each 30 m × 30 m in a 519 km2 protected Terai habitat, and derived several climatic and non-climatic environmental factors. We constructed variables based on different models of spatial connectivity among sites, to test their influence on species abundances. We then used redundancy analyses and variation partitioning to quantify the importance of environmental variables and spatial structure on variation in tree–grass abundances. We found that environmental variables including rainfall, fire, water stress, topography and soil nutrients had statistically significant effects on species abundance and tree–grass ratios. Spatial structure was significant, and the best spatial model was an inverse distance-weighted model with linkage extending to 23.5 km, indicating weak dispersal limitation. About 21% of the variation in species abundance was explained by the selected environmental and spatial factors. The results indicate that dynamic plant communities in which spatial–temporal variation in environmental factors may drive stochasticity in species distribution and abundance, thus dominantly influencing on the vegetation mosaic.

Importance Index of Mangrove Ecosystems in Kampung Baru Village, Penajam District, North Penajam Paser Regency

Mangroves are plants that grow between tidal lines. Mangrove forests have very important ecological and economic functions, but are very vulnerable to damage if they are not wise in maintaining, conserving and managing them. This research was conducted in Kampung Baru Village, Penajam District, Penajam Paser Utara Regency, East Kalimantan Province. The purpose of this study was to identify the types of mangroves and to determine the ecological conditions of mangrove forest vegetation in the mangrove ecosystem of Kampung Baru Village. The method used is the Transect Line Plot method. The data obtained were then processed by community structure analysis. The types of mangroves found in four stations in the mangrove ecosystem of the Kampung Baru, consist of nine types of mangroves, namely: Rhizopora mucronata, Rhizopora apiculata, Ceriops decandra, Avicennia marina, Nypa, Avicennia alba, Avicennia officinalis, Avicennia rumphiana, Sonneratia alba, and from four families, namely: Rhizophoraceae, Sonneratiaceae, Canthaceace and Arecaceace. The highest density value was Rhizophora mucronata, namely 1.04 ind/m 2 , with a relative density of 149.8%. The highest frequency value for Rhizophora mucronata was 400. The highest value for closure was Avicennia alba (100.12 m 2 ). Importance value index of Rhizophora mucronata (151.82%), the lowest analysis of all stations were Ceriops decandra and Nypa species and had very abundant species diversity.

Caution Is Needed When Using Niche Models to Infer Changes in Species Abundance: The Case of Two Sympatric Raptor Populations.

Simple SummaryThis study focuses on sympatric populations of hen harrier (Circus cyaneus) and Montagu’s harrier (Circus pygargus) breeding in mountain heathlands in the NW Iberian Peninsula. These populations have been affected by habitat loss caused by land-use change. Despite the mounting evidence supporting positive relationships between species abundance and habitat suitability, the capacity of ecological niche models to capture variations in population abundance remains largely unexplored. This study shows that habitat suitability predicted from niche models was significantly correlated with the relative abundance for hen harrier and, to a lesser extent, for Montagu’s harrier. However, the temporal variation in local population abundance was not significantly explained by habitat suitability changes predicted by the niche models. These findings call for caution in the use of niche models to infer changes in population abundance. The positive relationship between species abundance and habitat suitability supports the use of niche models to estimate abundance but does not guarantee the ability of these models to predict temporal variations in species abundance. These findings highlight (1) the need to include other possible biotic or abiotic factors involved in population abundance dynamics into niche models and (2) the need to establish specific monitoring protocols for tracking population dynamics.Despite the mounting evidence supporting positive relationships between species abundance and habitat suitability, the capacity of ecological niche models (ENMs) to capture variations in population abundance remains largely unexplored. This study focuses on sympatric populations of hen harrier (Circus cyaneus) and Montagu’s harrier (Circus pygargus), surveyed in 1997 and 2017 in an upland moor area in northwestern Spain. The ENMs performed very well for both species (with area under the ROC curve and true skill statistic values of up to 0.9 and 0.75). The presence of both species was mainly correlated with heathlands, although the normalized difference water index derived from Landsat images was the most important for hen harrier, indicating a greater preference of this species for wet heaths and peat bogs. The findings showed that ENM-derived habitat suitability was significantly correlated with the species abundance, thus reinforcing the use of ENMs as a proxy for species abundance. However, the temporal variation in species abundance was not significantly explained by changes in habitat suitability predicted by the ENMs, indicating the need for caution when using these types of models to infer changes in population abundance.

Functional Traits Are Good Predictors of Tree Species Abundance Across 101 Subtropical Forest Species in China.

What causes variation in species abundance for a given site remains a central question in community ecology. Foundational to trait-based ecology is the expectation that functional traits determine species abundance. However, the relative success of using functional traits to predict relative abundance is questionable. One reason is that the diversity in plant function is greater than that characterized by the few most commonly and easily measurable traits. Here, we measured 10 functional traits and the stem density of 101 woody plant species in a 200,000 m2 permanent, mature, subtropical forest plot (high precipitation and high nitrogen, but generally light- and phosphorus-limited) in southern China to determine how well relative species abundance could be predicted by functional traits. We found that: (1) leaf phosphorus content, specific leaf area, maximum CO2 assimilation rate, maximum stomata conductance, and stem hydraulic conductivity were significantly and negatively associated with species abundance, (2) the ratio of leaf nitrogen content to leaf phosphorus content (N:P) and wood density were significantly positively correlated with species abundance; (3) neither leaf nitrogen content nor leaf turgor loss point were related to species abundance; (4) a combination of N:P and maximum stomata conductance accounted for 44% of the variation in species’ abundances. Taken together, our findings suggested that the combination of these functional traits are powerful predictors of species abundance. Species with a resource-conservative strategy that invest more in their tissues are dominant in the mature, subtropical, evergreen forest.

Unravelling tidal effect on zooplankton community structure in a tropical estuary.

The variability in zooplankton density and species composition in response to tidal oscillations were investigated in the lesser saline upper reaches (E1) and higher saline lower reaches (E2) of the Mahanadi Estuary, located at the mouth of the third largest river in Indian Peninsula. This is the first of its kind high frequency observation over the tidal cycle ranging from highest high tide to lowest low tide in this estuary revealing dynamic variability of zooplankton assemblages. Zooplankton abundance was higher during high tide in comparison to low tide, irrespective of salinity regimes. On the diurnal scale, it was higher at night in comparison to the day at both E1 and E2. The higher abundance of zooplankton groups such as Copepoda, Cladocera, and planktonic larvae during the night at E1 as well as E2 indicating an upward migration. Many of the zooplankton taxa (e.g., Pseudodiaptomus serricaudatus, Pseudodiaptomus sp., Acartia danae, Acrocalanus longicornis, Oithona sp., Corycaeus andrewsi) migrated towards E1 due to tidal effect during high tide and maintained their position even during low tide. In contrast, the prevalence of limnetic taxa (e.g., Brachionus rubens, Polyarthra vulgaris, Bosminopsis deitersi, Moina micrura, Heliodiaptomus sp.) at E2 during low tide indicated a predominant riverine source. The tidal variability of Brachyura (zoea and megalopa) revealed different emergence times that indicated dispersal of zoeas to the adjacent Bay of Bengal and the return of magalopa to the Mahanadi Estuary. Species diversity index was higher during high tide, and prominent at E2. At E1, marine, fresh, marine-brackish, and marine-brackish-fresh zooplankton species dominated during high tide, while brackish-fresh taxa dominated during low tide. Differently, E2 was enriched with marine, marine-brackish, and marine-brackish-fresh taxa during high tide, whereas fresh, brackish-fresh, and marine-fresh dominated during low tide. Salinity and suspended matter influenced the dominant zooplankton taxa at E2 and E1, respectively. Zooplankton assemblages exhibited a pattern of prominent diurnal-spatial variation in comparison to the tidal scale in the Mahanadi Estuary. Overall, this study documented a very high zooplankton diversity (92 taxa belonging to 13 groups) and significant variations in species abundance which highlighted the importance of carrying out sampling over the tidal cycle at contrasting salinity regimes.