Changes In Species Richness Research Articles

Measured Effects of Anthropogenic Development on Vertebrate Wildlife Diversity

A major driver of the declining biodiversity is landcover change leading to loss of habitat. Many studies have estimated large-scale declines in biodiversity, but loss of biodiversity at a local scale due to the immediate effects of development has been poorly studied. California, in particular, is a biodiversity hotspot and has rapidly developed; thus, it is important to understand the effects of development on wildlife in the State. Here, we conducted reconnaissance surveys—a type of survey often used by consulting biologists in support of environmental review of proposed projects—to measure changes in the relative abundance and richness of vertebrate species in response to urban development. We completed 2 reconnaissance surveys at each of 52 control sites that remained undeveloped at the times of both surveys, and at each of 26 impact sites that had been developed by the time of the second survey. We completed the surveys as part of a before–after, control–impact (BACI) experimental design. Our main interest was the interaction effect between the before–after phases and the control–impact treatment levels, or the impact of development. After controlling for survey duration, we also tested for the effects of the number of years intervening the surveys in the before and after phases, project area size, latitude, degree of connectedness to adjacent open space, and whether the site was a redevelopment site, infill, or not infill. After development, the average number of vertebrate wildlife species we detected declined by 48% within the project area, and by 66% within the bounds of the project sites. Further, the average number of vertebrate animals we counted declined by 90% within the project area, and 89% within the bounds of the project sites. Development impacts measured by the mean number of species detected per survey were greatest for amphibians (−100%), followed by mammals (−86%), grassland birds (−75%), raptors (−53%), special-status species (−49%), all birds as a group (−48%), non-native birds (−44%), and synanthropic birds (−28%). Our results indicated that urban development substantially reduced vertebrate species richness and numerical abundance, even after richness and abundance had likely already been depleted by the cumulative effects of loss, fragmentation, and degradation of habitat in the urbanizing environment. Monitoring is needed in and around urbanizing areas to measure the cumulative effects of urbanization, and so are conservation measures to mitigate the effects of urbanization.

Rare Species Are Significant in Harsh Environments and Unstable Communities: Based on the Changes of Species Richness and Community Stability in Different Sub-Assemblages

To understand the contribution of different sub-assemblages (sub-communities) in the shrub and herb layers to the distribution patterns of community species richness and the stability of the Pinus massoniana Lamb. community, this study was carried out by using 160 shrub quadrats (5 m × 5 m) and 200 herb quadrats (1 m × 1 m). These quadrats were selected from 40 plots on six islands. In this study, common and rare species were classified according to the frequency, and “new communities” (sub-communities) were formed by adding or removing species. Then the changes of species richness and community stability in the “new communities” were analyzed. A redundancy analysis was also used to explore the factors affecting the size of the species richness in the understory of the Pinus massoniana community. The results showed the following: (1) The distribution patterns of both shrub and herb layer species frequencies in this area were plainly to the right, indicating a large proportion of non-common species (common species accounting for 37.87% in the shrub layer and 16.67% in the herb layer). (2) The higher the frequency of species, the greater their contribution to the pattern of species richness. Common species had a high frequency and were the most important contributors to the patterns of species richness in plant communities (64 common species and 41 most common species in the shrub layer and 10 common species in the herb layer each accounted for 95.72, 88.9, and 90.52%, respectively, of the species richness distribution pattern). However, rare species also made significant contributions to the species richness in regions with hard conditions (the (most) rare species in the herb layer explained more than 70% of the species richness distribution pattern, and the remaining species after removing the (most) common species explained more than 90%). (3) In relatively stable communities, rare species had relatively little influence on the stability of the community, which was mostly governed by the dominant species (common species (10 species) were more stable than rare species (38 species), Exc.-rare species (22 species) were more stable than except-common species (50 species), and Exc.-rarest species (35 species) were more stable than Exc.-most common species (55 species) in the herb layer). In less stable communities, the stability of the community gradually increased with the increase in species richness, which may be associated with the growth habit of the increased species (the stability of the herb layer was higher than that of the shrub layer, as shown by the Euclidean distance). The community stability was determined by not only the dominant species in the community but also the rare species that were important contributors to the stability of the communities. (4) The species richness of the shrub layer was considerably influenced (p-value < 0.05) by the soil pH, soil organic matter, and wind speed, whereas the species richness of the herb layer was significantly influenced (p-value < 0.05) by the soil pH. The greater the pH and wind speed, the greater the species richness in the island community. On islands, the soil stability was maintained in large part by the soil organic matter. The lack of soil organic matter can affect soil nutrients, destroy island habitats, and reduce species richness, all of which are harmful to the community stabilization.

Leaf traits and temperature shape the elevational patterns of phyllosphere microbiome

AbstractAimThe phyllosphere microbiome is central to plant health, distribution, and ecosystem function, yet, we lack a clear understanding of the drivers shaping their diversity in mountain ranges. Here, we examined how the endo‐ and epiphytic phyllosphere microbiomes of mountains simultaneously respond to climate and leaf functional traits.LocationTemperate forests of Changbai Mountain Natural Reserve, China.MethodsWe collected the leaves of dominant tree species along seven elevations from 800 to 1950. We investigated changes in species richness and Shannon diversity of endo‐ and epiphytic phyllosphere fungal and bacterial communities (using next‐generation sequencing of ITS2 and 16S) along an 1150 m elevational gradient. We also examined the direct and indirect effects of climate (mean annual temperature; MAT) and 13 leaf morphological and chemical traits on the microbiome of the phyllosphere.ResultsPhyllosphere microbiome declined monotonically with increasing elevation, contrasting with the hump‐shaped biodiversity patterns that are commonly reported. We observed a steeper decline in epiphytic bacterial diversity than in endophytic bacteria, whereas conversely endophytic fungi diversity declined more dramatically with increasing elevation than epiphytic fungi. Host plant traits – those involved in resource uptake and leaf surface temperature – predominantly shaped the elevational patterns of endophytic phyllosphere microbiome, whereas MAT mostly increased the richness and Shannon diversity of epiphytic organisms. We also observed weak, but significant indirect effects suggesting that host plant traits are important biotic drivers mediating climate effects on endophytic phyllosphere microbiome. Also, no covariation between bacteria and fungi was observed (neither for endophytic nor for epiphytic organisms), supporting neutral associations between bacterial and fungal communities, irrespective of the elevation.Main ConclusionsBoth direct and mediating effects of plant traits should be considered to better understand the drivers shaping the richness and Shannon diversity of endo‐ and epiphytic phyllosphere microbiomes, and more generally the plant–microbe associations. Our study also offers a trait‐based attempt to disentangle the effects of biotic and abiotic filters in shaping endo‐ and epiphytic phyllosphere microbiome along an elevational gradient.

Influence of the antibiotic nitrofurazone on community dynamics of marine periphytic ciliates: Evidence from community-based bioassays

Marine periphytic ciliates play a pivotal role in shaping coastal ecosystems dynamics, thereby acting as robust biological indicators of aquatic ecosystem health and functionality. However, the understanding of the effects of veterinary antibiotics on composition and structure of periphytic ciliate communities remains limited. Therefore, this research investigates the influence of the veterinary antibiotic nitrofurazone on the community dynamics of marine periphytic ciliates through bioassay experiments conducted over a one-year cycle. Various concentrations of nitrofurazone were administered to the tested ciliate assemblages, and subsequent changes in community composition, abundance, and diversity were quantitatively analyzed. The research revealed significant alterations in periphytic ciliate communities following exposure to nitrofurazone. Concentration-dependent (0–8 mg L−1) decrease in ciliates abundance, accompanied by shifts in species composition, community structure, and community patterns were observed. Comprehensive assessment of diversity metrics indicated significant changes in species richness and evenness in the presence of nitrofurazone, potentially disrupting the stability of ciliate communities. Furthermore, nitrofurazone significantly influenced the community structure of ciliates in all seasons (winter: R2 = 0.489; spring: R2 = 0.666; summer: R2 = 0.700, autumn: R2 = 0.450), with high toxic potential in treatments 4 and 8 mg L−1. Differential abundances of ciliates varied across seasons and nitrofurazone treatments, some orders like Pleurostomatida were consistently affected, while others (i.e., Strombidida and Philasterida) showed irregular distributions or were evenly affected (e.g., Urostylida and Synhymeniida). Retrieved contrasting patterns between nitrofurazone and community responses underscore the broad response repertoire exhibited by ciliates to antibiotic exposure, suggesting potential cascading effects on associated ecological processes in the periphyton community. These findings significantly enhance the understanding of the ecological impacts of nitrofurazone on marine periphytic ciliate communities, emphasizing the imperative for vigilant monitoring and regulation of veterinary antibiotics to protect marine ecosystem health and biodiversity. Further research is required to explore the long-term effects of nitrofurazone exposure and evaluate potential strategies to reduce the ecological repercussions of antibiotics in aquatic environments, with a particular focus on nitrofurazone.

Scenario planning and multispecies occupancy models reveal positive avian responses to restoration of afforested woodlands

Scenario planning is a powerful approach for assessing restoration outcomes under alternative futures. However, developing plausible scenarios remains daunting in complex systems like ecological communities. Here, we used Bayesian multispecies occupancy modeling to develop scenarios to assess woodland restoration outcomes in afforested communities in seven wildlife management areas in Arkansas, U.S.A. Our objectives were (1) to define plausible woodland restoration and afforestation scenarios by quantifying historic ranges of variation in mean tree cover and tree cover heterogeneity from 1986 to 2021 and (2) to predict changes in bird species richness and occupancy patterns for six species of greatest conservation need under two future scenarios: complete afforestation (100% tree cover) and woodland restoration (based on remotely sensed historic tree cover). Using 35 years of remotely sensed tree cover data and 6 years of bird monitoring data, we developed multispecies occupancy models to predict future bird species richness and occupancy under the complete afforestation and woodland restoration scenarios. Between 1986 and 2021, tree cover increased in all study areas—with one increasing 70%. Under the woodland restoration scenario, avian species richness increased up to 20%, and four of six species of greatest conservation need exhibited gains in occupancy probability. The complete afforestation scenario had negligible effects on richness and occupancy. Overall, we found decreasing tree cover to historic levels prior to widespread afforestation would provide community‐level benefits and would do little harm even to forest‐dependent species of conservation concern. Applying multispecies occupancy modeling within a scenario planning framework allows for comparing multiscale trade‐offs between plausible futures.

Synergistic effects between global warming and water quality change on modelled macrophyte species richness

Submerged freshwater macrophytes are crucial for the functioning of lakes. Their growth and survival follow environmental conditions like light, temperature, and nutrient availability. Hence, the impending increase in water temperature as well as changes of nutrients and turbidity will lead to changes in macrophyte geographic and depth distribution: Herein, we assess these potential changes. We apply an eco‐physiological macrophyte growth model to simulate biomass growth and survival of virtual species defined by random trait combinations within expert‐derived trait ranges for oligotraphentic, mesotraphentic, and eutraphentic species groups in deep lakes in Bavaria, Germany, which cover clear, moderate, and turbid lake conditions. The emergent potential species richness is compared with empirically observed species richness to evaluate general predictions for current conditions. Thereafter, we apply the model to scenarios of temperature increase and of turbidity and nutrient change to assess potential changes in species richness and the influence of species' traits on being an environmental change ‘winner' or ‘loser'. We find a cross‐lake, hump‐shaped pattern of potential species richness along depth. This largely reflects observed patterns, although mismatches were also detected and might be explained by missing processes and environmental heterogeneity within the lake. Rising temperature leads to increased richness of potential species in all lake types, species groups, and depths. Turbidity and nutrient change effects depend on depth and lake type. ‘Loser species' under increased turbidity and nutrient level are light consumptive and sensible to disturbances, while ‘winner species' have a high biomass production. These findings show that the hump‐shaped depth distributions of submerged macrophyte diversity can emerge solely considering eco‐physiology. The differential responses to environmental changes imply that management measures must account for lake type because those responses can have opposite trends depending on lake depth and type.

Ant Species Diversity in the Central and Northern Parts of the Western Sichuan Plateau in China

Understanding how species richness changes along elevational gradients has attracted increasing attention from many researchers. The relationships between species richness and elevations were characterized by monotonic decreases or mid-elevational peaks. The western Sichuan Plateau is an important species diversity hotspot. However, there is little information available about the ant species diversity and distribution patterns of this region. In this study, we hypothesize that ant diversity will show a monotonic decrease from mid-elevation with increasing elevation. Here, the ant species diversity and distribution patterns of this region were investigated by plot surveys. A total of 22,645 ants were collected from eight elevational transects in the central and northern parts of the western Sichuan Plateau, which were identified as belonging to 40 species, 18 genera, and 4 subfamilies. We found a unimodal relationship between elevation and ant species richness, with the highest ant species richness occurring at mid-elevations. The similarity coefficient of ant communities in each elevational transect was at a moderate level of dissimilarity, indicating that the elevation difference and habitat heterogeneity had a great impact on ant communities in the central and northern areas of the western Sichuan Plateau.

La Niña‐related coral death triggers biodiversity loss of associated communities in the Galápagos

AbstractDuring a cold La Niña period (August 2007–January 2008) in the central Galápagos archipelago, 70% of Pocillopora branching corals were severely bleached across three long‐term monitoring sites, affording an opportunity to examine its impact on the persistence of these corals and their associated community of fish and mobile macroinvertebrates. Using a time series empirical approach, we tagged and tracked the fate of 96 coral heads and their associates. When surveyed in July 2008, recovered live and dead corals that were previously severely bleached supported similar levels of species richness (randomized observed and estimated Chao 1). By contrast, richness on the surviving live corals remained fairly stable, while Chao 1 estimated richness on dead corals underwent a nearly 50% increase between July and January 2009, thereafter declining to 50% of originally surveyed richness by February 2010. This nonlinear change in species richness was largely due to an influx and decline in opportunistic generalists including pencil urchin bioeroders, gastropod snails, and hermit crabs that colonized dead corals and fed on sessile invertebrates and algae that had initially recruited to dead and undefended coral substrate. Thus, dead corals retained high overall species richness until live corals had recovered, after which richness declined as dead corals eroded and disintegrated (July 2011). Live corals attracted a less speciose but stable assemblage of mutualistic xanthid crabs and fishes that increased in abundance over time with the recovery and growth of live coral tissue. Overall, coral status (live/dead), planar area and maximum branch length predicted the number of species associated with each colony. The delayed diversity loss of associated species following La Niña disturbance to a foundation species represents a local extinction debt of 32–49‐month duration. A better understanding of the scale of extinction debt in foundational marine ecosystems is needed to quantify the breadth of impacts of climate oscillations on biodiversity and ecosystem functioning.

Galling insect communities mediate the effects of fire on their associated parasitoid communities

Abstract Understanding fire effects on multitrophic levels is critical to the context of changes in fire regime and climate. Insects located at higher trophic levels, like parasitoids, are more vulnerable to habitat changes than insect herbivores because they need well‐established populations of their hosts to survive. Currently, fire effects on parasitoids and their interactions with their hosts are unknown. Our aim was to study the changes in abundance, richness and species composition, as well as the food web structure in a system involving parasitoids and galling insects under different fire scenarios. We asked whether potential changes in abundance, species richness and composition of parasitoid communities are explained by galled plant abundance, species richness and composition of galling insects, and how fire affects the structure of galling insect–parasitoid food webs. The highest parasitoid richness was found in the 9 years after fire scenario, whereas parasitoid abundance was not affected by fire. The parasitoid species composition in the 9 years after fire scenario was different from that in the unburned and 3 years after fire scenarios. Parasitoid communities were modulated by galled plant abundance, species richness and composition of galling insect communities. Vulnerability was significantly higher in 9 years after fire scenarios, but it increased with increasing network size. Fire affects the community of parasitoids through changes in their host communities. Differences in exclusivity to fire scenarios and diet specialisation of parasitoid species and galling insect richness may explain the patterns found. Our study supports evidence that fire creates habitats heterogeneous in the availability of hosts shaping the parasitoid communities, with a bottom‐up effect in food webs. Additionally, in burned areas were recorded unique galling insect–parasitoid interactions.

Gut microbiome resilience of green-lipped mussels, Perna canaliculus, to starvation

Host gut microbiomes play an important role in animal health and resilience to conditions, such as malnutrition and starvation. These host-microbiome relationships are poorly understood in the marine mussel Perna canaliculus, which experiences significant variations in food quantity and quality in coastal areas. Prolonged starvation may be a contributory factor towards incidences of mass mortalities in farmed mussel populations, resulting in highly variable production costs and unreliable market supplies. Here, we examine the gut microbiota of P. canaliculus in response to starvation and subsequent re-feeding using high-throughput amplicon sequencing of the 16S rRNA gene. Mussels showed no change in bacterial species richness when subjected to a 14-day starvation, followed by re-feeding/recovery. However, beta bacteria diversity revealed significant shifts (PERMANOVA p-value < 0.001) in community structure in the starvation group and no differences in the subsequent recovery group (compared to the control group) once they were re-fed, highlighting their recovery capability and resilience. Phylum-level community profiles revealed an elevation in dominance of Proteobacteria (ANCOM-BC p-value <0.001) and Bacteroidota (ANCOM-BC p-value = 0.04) and lower relative abundance of Cyanobacteria (ANCOM-BC p-value = 0.01) in the starvation group compared to control and recovery groups. The most abundant genus-level shifts revealed relative increases of the heterotroph Halioglobus (p-value < 0.05) and lowered abundances of the autotroph Synechococcus CC9902 in the starvation group. Furthermore, a SparCC correlation network identified co-occurrence of a cluster of genera with elevated relative abundance in the starved mussels that were positively correlated with Synechococcus CC9902. The findings from this work provide the first insights into the effect of starvation on the resilience capacity of Perna canaliculus gut microbiota, which is of central importance to understanding the effect of food variation and limitation in farmed mussels.

Geographical trends of soil‐associated biodiversity changes due to tree plantations in South America: Biome and climate constraints revealed through meta‐analysis

AbstractAimTo evaluate the interaction between climate and biome structure when explaining changes in species richness of soil‐associated communities due to tree plantations developed in different biomes. Compare the response of plants, soil invertebrates and soil microorganisms, and to test whether they should be considered sensitive‐coupled biotas.LocationContinental South America.Time Period1996–2023.Major Taxa StudiedPlants, soil invertebrates and soil microorganisms.MethodsThrough a meta‐analysis, the change in species richness (i.e. response ratio) associated with tree plantations was evaluated in 127 points of study across South America, considering soil‐associated communities of plants, invertebrates and microorganisms. The influence of biome structure (open vs. closed habitats) on the response ratio, and its interaction with the actual evapotranspiration (AET) and temperature seasonality was evaluated. Differentiated responses of different taxa were tested by comparing models with and without an interaction term referring to the taxon studied. The regional agricultural cover and plantation age were considered as anthropogenic variables.ResultsModels containing the AET were better at explaining the trend of change in species richness than those with temperature seasonality. The response of the change in species richness was oppositely related to the AET in open and closed biomes. Plants presented a higher loss in species richness than soil invertebrates and microorganisms. The three taxa were positively associated with AET, while seasonality was not relevant in any case. Both anthropogenic variables significantly lessened the change in species richness in all models.Main ConclusionsThe structural contrast between the anthropogenic habitat and the biome where it is developed is a key factor influencing the response of soil‐associated communities to tree plantations. Nevertheless, its influence must be assessed together with climatic and anthropogenic variables given that their interaction can explain different geographical trends in the change in species richness across regions.

Bird community effects on avian malaria infections

In community assembly processes, interspecific interactions play an important role in shaping community diversity, especially at the local scale. Changes in species richness or abundance can modify local infectious disease dynamics, either reducing or increasing the risk of transmission within the community. This study evaluates the effects of bird community on avian haemosporidians infections in a Neotropical region. Bird samples were collected from areas surrounding three dams, and molecular analysis were performed to identify blood-parasitic haemosporidia infecting the birds. Generalized linear models were used to analyze the relationships between the bird community and the prevalence, number of infections, and richness of avian haemosporidian lineages. Non-significant effects of bird community dominance and richness on the prevalence of avian parasites and the number of infections of Haemoproteus were found. However, there was evidence of an amplification effect. Host dominance was associated with the total number of infections, the number Plasmodium infections and the expected richness of Plasmodium lineages, while the expected richness of Haemoproteus lineages was associated with the richness of bird species. These findings highlight the role of host community dominance and richness in the dynamics of parasite infections, potentially influenced by the availability of competent hosts. This study contributes significantly to our understanding of blood parasite diversity in tropical birds within a relatively understudied region of South America.

Effects of warming and nitrogen addition on soil fungal and bacterial community structures in a temperate meadow.

Soil microbial communities have been influenced by global changes, which might negatively regulate aboveground communities and affect nutrient resource cycling. However, the influence of warming and nitrogen (N) addition and their combined effects on soil microbial community composition and structure are still not well understood. To explore the effect of warming and N addition on the composition and structure of soil microbial communities, a five-year field experiment was conducted in a temperate meadow. We examined the responses of soil fungal and bacterial community compositions and structures to warming and N addition using ITS gene and 16S rRNA gene MiSeq sequencing methods, respectively. Warming and N addition not only increased the diversity of soil fungal species but also affected the soil fungal community structure. Warming and N addition caused significant declines in soil bacterial richness but had few impacts on bacterial community structure. The changes in plant species richness affected the soil fungal community structure, while the changes in plant cover also affected the bacterial community structure. The response of the soil bacterial community structure to warming and N addition was lower than that of the fungal community structure. Our results highlight that the influence of global changes on soil fungal and bacterial community structures might be different, and which also might be determined, to some extent, by plant community, soil physicochemical properties, and climate characteristics at the regional scale.

Study on the succession of plant communities under the influence of drought

Drought has a strong impact on the growth of plant populations, and the number of different species in a plant community plays an important role in the drought adaptation of the community's progeny. In this paper, a mathematical model is developed to analyze how the number of different species in a plant community under a long-term irregular drought cycle is adaptive to drought in future generations, and thus how the plant community benefits from it. This paper uses biomass to quantify the growth of plant populations and changes in plant communities, and uses a large amount of visual data for visual analysis. First, a logistic growth model of plant population biomass change is developed based on temperature accumulation, precipitation and interspecific competition as influencing factors. The correlation coefficients were then obtained using the collected plant population biomass to predict the changes in total plant biomass and species richness, and the interspecific competition model was then used to calculate the values of total community biomass after final stabilization based on logistic, and the system of differential equations was solved using the Runge-Kutta Methods was finally concluded that the biomass of the community after final stabilization showed a positive correlation with the number of species and species type, and showed a strong positive correlation with species type and a weak positive correlation with species number.

Shifting of nutrient limitation dominates the recovery of aboveground net primary productivity of mixed forests in northeastern China after selective logging

The primary productivity of temperate forests is commonly limited by nitrogen (N) supply, which may be aggravated by the removal of trees. After selective logging, whether and the mechanism by which the N limitation can be alleviated by the rapidly increasing nutrient turnover during the recovery processes, which is important for improving carbon sequestration in temperate forests, remain unclear. We investigated the effect of nutrient limitation (leaf N:Pcom: the leaf N:P ratio at the community level) on plant community productivity by selecting 28 forest plots including seven forest recovery periods (at the sites logged 6, 14, 25, 36, 45, 55, and 100 years ago) following low-intensity selective logging (13–14 m3/ha) and one unlogged treatment by measuring the soil N concentration, soil phosphorus (P) concentration, leaf N concentration, leaf P concentration, and the aboveground net primary productivity (ANPP) of 234 plant species. The plant growth in temperate forests was limited by N, but the P limitation was observed at the sites logged 36 years ago, which showed a transition pattern of plant growth from N limitation to P limitation during the forest recovery process. Meanwhile, a robust linear trend in the community ANPP was observed with the increase in the community leaf N:P ratio, which suggests the enhancement in community ANPP with the release of N limitation after selective logging. Nutrient limitation (leaf N:Pcom) had a significant direct effect (56.0 %) on the community ANPP and showed a higher independent contribution (25.6 %) to the variation in the community ANPP than the soil nutrient supply and even the changes in species richness. Our results suggested that selective logging alleviated the N limitation, but a shift toward P limitation should also be highly regarded in learning the changes in carbon sequestration during the recovery processes.

Flood changed the community composition and increased the importance of stochastic process of vegetation and seed bank in a riparian ecosystem of the Yellow River

Changes in riparian plant community composition and species richness are anticipated as a result of future projected increases in the risk of flood disasters in riparian ecosystems, but the extent and direction of these changes remain uncertain. In this study, we established four blocks comprising six plots in each block to investigate communities of vegetation and seed banks before and after flooding the middle and lower reaches of the Yellow River to investigate how flood influenced the indicator species, alpha diversity, community composition, and community assembly process. The study found that Symphyotrichum subulatum and Rumex acetosa were the indicator species for pre- and post-flood vegetation, as well as for the seed bank. Furthermore, there was a significant increase in all three alpha diversity indices (Shannon-wiener Index; H, Simpson diversity index; D, and Species richness; S) for both the vegetation and seed bank following the flood event. Our analysis of community assembly revealed that the flood event had a notable effect on the relative importance of different processes driving vegetation and seed bank dynamics. Specifically, according to the species composition assembly analysis, we observed a significant increase in the relative importance of stochastic process but decreased in determined process in vegetation. However, the results of multiple regression on matrices indicated the environmental filtering can hardly explain the deterministic process which the patterns of pre-flood vegetation composition were largely controlled by biological interactions, particularly competition among species. Therefore, the reduction of competitive pressures accompanied with the uncertainty of upstream seed banks make local riparian ecosystem more vulnerable to ecological invasions (after the recorded flood event, the invasive species Bidens pilosa was observed to successfully establish). This vulnerability highlights the need for effective protection and management strategies to ensure the long-term sustainability of riparian ecosystems in the middle and lower reaches of the Yellow River.

How to fill the biodiversity data gap: Is it better to invest in fieldwork or curation?

Data gaps and biases are two important issues that affect the quality of biodiversity information and downstream results. Understanding how best to fill existing gaps and account for biases is necessary to improve our current information most effectively. Two current main approaches for obtaining and improving data include (1) curation of biological collections, and (2) fieldwork. However, the comparative effectiveness of these approaches in improving biodiversity data remains little explored. We used the Flora de Bogotá project to study the magnitude of change in species richness, spatial coverage, and sample coverage of plant records based on curation versus fieldwork. The process of curation resulted in a decrease in species richness (synonym and error removal), but it significantly increased the number of records per species. Fieldwork contributed to a slight increase in species richness, via accumulation of new records. Additionally, curation led to increases in spatial coverage, species observed by locality, the number of plant records by species, and localities by species compared to fieldwork. Overall, curation was more efficient in producing new information compared to fieldwork, mainly because of the large number of records available in herbaria. We recommend intensive curatorial work as the first step in increasing biodiversity data quality and quantity, to identify bias and gaps at the regional scale that can then be targeted with fieldwork. The stepwise strategy would enable fieldwork to be planned more cost-effectively given the limited resources for biodiversity exploration and characterization.

Biodiversity time series are biased towards increasing species richness in changing environments

The discrepancy between global loss and local constant species richness has led to debates over data quality, systematic biases in monitoring programmes and the adequacy of species richness to capture changes in biodiversity. We show that, more fundamentally, null expectations of stable richness can be wrong, despite independent yet equal colonization and extinction. We analysed fish and bird time series and found an overall richness increase. This increase reflects a systematic bias towards an earlier detection of colonizations than extinctions. To understand how much this bias influences richness trends, we simulated time series using a neutral model controlling for equilibrium richness and temporal autocorrelation (that is, no trend expected). These simulated time series showed significant changes in richness, highlighting the effect of temporal autocorrelation on the expected baseline for species richness changes. The finite nature of time series, the long persistence of declining populations and the potential strong dispersal limitation probably lead to richness changes when changing conditions promote compositional turnover. Temporal analyses of richness should incorporate this bias by considering appropriate neutral baselines for richness changes. Absence of richness trends over time, as previously reported, can actually reflect a negative deviation from the positive biodiversity trend expected by default.

Community context mediates effects of pollinator loss on seed production

AbstractA critical goal for ecologists is understanding how ongoing local and global species losses will affect ecosystem functions and services. Diversity–functioning relationships, which are well‐characterized in primary producer communities, are much less consistently predictable for ecosystem functions involving two or more trophic levels, particularly in situations where multiple species in one trophic level impact functional outcomes at another trophic level. This is particularly relevant to pollination functioning, given ongoing pollinator declines and the value of understanding pollination functioning for single plant species like crops or threatened plants. We used spatially replicated, controlled single‐pollinator‐species removal experiments to assess how changes in bumble bee species richness impacted the production of fertilized seeds in a perennial herb—Delphinium barbeyi—in the Rocky Mountains of Colorado, USA. To improve predictability, we also assessed how traits and abundances in the plant and bumble bee communities were related to D. barbeyi reproductive success. We hypothesized that trait‐matching between pollinator proboscis length and D. barbeyi's nectar spurs would produce a greater number of fertilized seeds, while morphological similarity within the floral community would dilute pollination services. We found that the effects of pollinator removal differed depending on the behavioral patterns of pollinators and compositional features of the plant and pollinator communities. While pollinator floral fidelity generally increased D. barbeyi seed production, that positive effect was primarily evident when more than half of the Bombus community was experimentally removed. Similarly, communities comprising primarily long‐tongued bees were most beneficial to D. barbeyi seed production in tandem with a strong removal. Finally, we observed contrasting effects of morphological similarity in the plant community, with evidence of both competition and facilitation among plants. These results offer an example of the complex dynamics underlying ecosystem function in multitrophic systems and demonstrate that community context can impact diversity–functioning relationships between trophic levels.

Species richness, vegetation structure, and floristic composition of woody plants along the elevation gradient of Mt. Meru, Tanzania

AbstractUnderstanding the change in vegetation composition along elevational gradients is critical for species conservation in a changing world. We studied the species richness, tree height, and floristic composition of woody plants along an elevation gradient of protected habitats on the eastern slope of Mount Meru and analyzed how these vegetation variables are influenced by the interplay of temperature and precipitation. Vegetation data were collected on 44 plots systematically placed along five transects spanning an elevational gradient of 1600 to 3400 m a.s.l. We used ordinary linear models and multivariate analyses to test the effect of mean annual temperature and precipitation on woody plant species richness, tree height, and floristic composition. We found that species richness, mean tree height, and maximum tree height declined monotonically with elevation. Models that included only mean annual temperature as an explanatory variable were generally best supported to predict changes in species richness and tree height along the elevation gradient. We found significant changes in woody plant floristic composition with elevation, which were shaped by an interaction of mean annual temperature and precipitation. While plant communities consistently changed with temperature along the elevation gradient, levels of precipitation were more important for plant communities at lower than for those at higher elevations. Our study suggests that changes in temperature and precipitation regimes in the course of climate change will reshape elevational gradients of diversity, tree height, and correlated carbon storage in ecosystems, and the sequence of tree communities on East African mountains.