Temporal Changes In Diversity Research Articles

Community Trait Variation Drives Selection on Species Diversity Through Feedback With Predator Density.

Identifying the processes underlying community assembly and dynamics remains a central goal in ecology. Although much research has been devoted to analyzing how environments affect species diversity, fewer studies have resolved the link between the fundamental process of ecological selection and species diversity. It has been suggested that identifying ecological selection by estimating changes in community-weighted variance (CWV) and mean (CWM) of functional traits may help to identify more general rules of community assembly. Here, we asked whether and how selection by predation and competition affect species diversity, and how this is determined by the initial CWV and CWM for traits governing species interactions, as in our case: Competitiveness and defense against a predator. We tracked experimental five-species phytoplankton communities in the presence and absence of a rotifer predator over time. We manipulated the initial community composition so that communities shared at least three of the five species but differed in CWV and CWM for defense against predation. We found that species diversity was highest with higher initial trait distributions and that temporal changes in diversity correlated with trait selection. The initial distributions determined the form of selection over time, with directional selection for defense and competitiveness, followed by reduced selection and an increase in niche availability when the initial trait distribution was low or high. For intermediate initial trait distributions, we observed directional selection in only one trait, followed by stabilizing selection. Differences and changes in selection for defense, competitiveness, and species diversity correlated with the changes in predator density over time. This suggests that the initial trait distribution determined species diversity through a feedback loop with changes in selection on traits and predator density. Overall, our study shows that identifying ecological selection on functional traits can provide a mechanistic understanding of community assembly.

Natural mega disturbances drive spatial and temporal changes in diversity and genetic structure on the toadfish Aphos porosus

Natural disturbances can modify extinction-colonization dynamics, driving changes in the genetic diversity and structure of marine populations. Along Chilean coast (36°S, 73°W), a strong hypoxic-upwelling event in 2008, and a mega earthquake-tsunami in 2010 caused mass mortality within the Aphos porosus population, which is a vulnerable species with low dispersal potential. We evaluated the effects of these two major disturbances on the diversity and spatial-temporal genetic structure of Aphos porosus in two neighboring areas that were impacted on different levels (High level: Coliumo Bay; Low level: Itata Shelf). Thirteen microsatellites (from 2008 to 2015) amplified in individuals collected from both locations were used to evaluate the effects of the two disturbances. Results showed that after the strong hypoxic-upwelling event and the mega earthquake-tsunami, Aphos porosus populations exhibited lower genetic diversity and less effective population sizes (Ne < 20), as well as asymmetries in migration and spatial-temporal genetic structure. These findings suggest a rise in extinction-recolonization dynamics in local Aphos porosus populations after the disturbances, which led to a loss of local genetic diversity (mainly in Coliumo Bay area impacted the most), and to greater spatial-temporal genetic structure caused by drift and gene flow. Our results suggest that continuous genetic monitoring is needed in order to assess potential risks for Aphos porosus in light of new natural and anthropogenic disturbances.

Assessing spatial and temporal changes in diversity of copepod crustaceans: a key step for biodiversity conservation in groundwater-fed springs

Despite the close attention springs have received from a hydrologic perspective and as biodiversity hotspots, the multiple dimensions of spring meiofaunal assemblage diversity are still poorly investigated. Knowledge of beta diversity patterns and drivers can inform and improve management decisions on biodiversity conservation. Here, we analyzed beta diversity of copepod assemblages in karst springs in Central Italy by focusing on: 1) relative contributions of turnover and nestedness components to taxonomic and phylogenetic beta diversity; 2) temporal variation of species richness and beta diversity within and between the target springs in conjunction with models of the influence of physical-chemical parameters on within-spring diversity changes; 3) expected risk of habitat loss due to variation in groundwater recharge under climate change. To this end, we gathered data from 168 samples collected in four karst springs from 2004 to 2016. Overall, we found 48 copepod species, 22 of which are obligate groundwater dwellers while the remaining 26 usually occur in surface freshwaters. All springs showed significant changes in taxonomic and phylogenetic beta diversity over time. Total beta diversity was high for both the taxonomic and phylogenetic dimensions, and turnover was the main component. Inter-site variability in dissolved oxygen explained a noticeable part of temporal variation in beta diversity, likely reflecting the role of microhabitat heterogeneity in shaping site-specific assemblages. However, most of the temporal variation in species richness and beta diversity remained unexplained, suggesting a major role of other factors, such as seasonal discharge variations. Modelling of recharge rates for all the four springs over 2001–2020 suggested a potential &amp;gt;40% recharge deficit under dry conditions. Moreover, Cellular Automata-based modelling of rainfall over the Gran Sasso-Sirente hydrogeologic unit (feeding three of the four springs) predicted an overall precipitation decrease in the 2081–2095 period. Such changes could produce severe effects on springs’ microhabitats and related communities. Our results indicate that partitioning beta diversity, monitoring its temporal changes and assessing its environmental drivers are critical to evidence-based conservation of springs. Particularly, the high species turnover we have observed suggests that conservation strategies should seek to preserve as many microhabitats as possible within and among karst springs.

Temporal Changes in Fecal Unabsorbed Carbohydrates Relative to Perturbations in Gut Microbiome of Neonatal Calves: Emerging of Diarrhea Induced by Extended-Spectrum β-lactamase-Producing Enteroaggregative Escherichia coli.

Early gut microbiota development and colonization are crucial for the long-term health and performance of ruminants. However, cognition among these microbiota is still vague, particularly among the neonatal dairy calves. Here, extended-spectrum β-lactamase-producing enteroaggregative E. coli (ESBL-EAEC)-induced temporal changes in diversity, stability, and composition of gut microbiota were investigated among the neonatal female calves, with the view of discerning potential biomarkers of this arising diarrhea cases in local pastures. Nearly, 116 newborn calves were enrolled in this time period study during their first 2 weeks of life, and a total of 40 selected fecal samples from corresponding calves were used in this study. The results revealed that differentiated gut microbiome and metabolome discerned from neonatal calves were accompanied by bacterial infections over time. Commensal organisms like Butyricicoccus, Faecalibacterium, Ruminococcus, Collinsella, and Coriobacterium, as key microbial markers, mainly distinguish “healthy” and “diarrheic” gut microbiome. Random forest machine learning algorithm indicated that enriched fecal carbohydrates, including rhamnose and N-acetyl-D-glucosamine, and abundant short-chain fatty acids (SCFAs) existed in healthy ones. In addition, Spearman correlation results suggested that the presence of Butyricicoccus, Faecalibacterium, Collinsella, and Coriobacterium, key commensal bacteria of healthy calves, is positively related to high production of unabsorbed carbohydrates, SCFAs, and other prebiotics, and negatively correlated to increased concentrations of lactic acid, hippuric acid, and α-linolenic acid. Our data suggested that ESBL-EAEC-induced diarrhea in female calves could be forecasted by alterations in the gut microbiome and markedly changed unabsorbed carbohydrates in feces during early lives, which might be conducive to conduct early interventions to ameliorate clinical symptoms of diarrhea induced by the rising prevalence of ESBL-EAEC.

Content bias in the cultural evolution of house finch song

We used three years of house finch, Haemorhous mexicanus , song recordings spanning four decades in the introduced eastern range to assess how individual level cultural transmission mechanisms drive population level changes in birdsong. First, we developed an agent-based model (available as a new R package called ‘TransmissionBias’) that simulates the cultural transmission of house finch song given different parameters related to transmission biases, or biases in social learning that modify the probability of adoption of particular cultural variants. Next, we used approximate Bayesian computation and machine learning to estimate what parameter values likely generated the temporal changes in diversity in our observed data. We found evidence that strong content bias, likely targeted towards syllable complexity, plays a central role in the cultural evolution of house finch song in the New York metropolitan area. Frequency and demonstrator biases appear to be neutral or absent. Additionally, we estimated that house finch song is transmitted with extremely high fidelity. Future studies can use our simulation framework to better understand how cultural transmission and population declines influence song diversity in wild populations. • We analysed house finch songs from three years spanning four decades in New York. • We compared real data against simulations to make inferences about cultural transmission. • Content bias, likely for syllable complexity, drives cultural evolutionary changes. • Frequency and demonstrator biases were absent and transmission fidelity was high.

A Historical Floristic Inventory of Pine Rockland Fabaceae (Leguminosae)

The pine rocklands of southern Florida are an imperiled habitat as the higher, drier areas of land have been steadily developed over the last century. Little of the original extent of this unique ecosystem remains today, with much of it in remnant fragments affected by surrounding development. With this study, we sought to investigate temporal changes in diversity of pine rockland Fabaceae induced by anthropogenic factors. We provide a status update for Fabaceae taxa, a diverse and important group of plants in pine rocklands. Herbarium collections (1339 records) spanning 175 y (from 1830 to 2015) were used to analyze the species frequency and richness of plants collected. The results indicated temporal fluctuations in collection diversity with frequency of native species highest prior to the year 1920, and nonnative legume richness increasing with the decades. The accompanying species list resulting from the inventory included 119 Fabaceae species, in 52 genera, with an additional 18 species not previously listed for pine rocklands. Many other studies have documented the change in pine rockland cover and its extreme extent of habitat loss and fragmentation as the result of human development and population growth. The results of this study document the indirect effects of human habitation on remnant natural areas, as evidenced by collections from Miami-Dade County, with exotic invasives increasingly represented over time. The results also document the historical distributions of collections of Fabaceae species, helpful to conservation and restoration efforts in the globally imperiled pine rocklands of southern Florida.

Dynamics of Baltic Sea phages driven by environmental changes.

Phage predation constitutes a major mortality factor for bacteria in aquatic ecosystems, and thus, directly impacts nutrient cycling and microbial community dynamics. Yet, the population dynamics of specific phages across time scales from days to months remain largely unexplored, which limits our understanding of their influence on microbial succession. To investigate temporal changes in diversity and abundance of phages infecting particular host strains, we isolated 121 phage strains that infected three bacterial hosts during a Baltic Sea mesocosm experiment. Genome analysis revealed a novel Flavobacterium phage genus harboring gene sets putatively coding for synthesis of modified nucleotides and glycosylation of bacterial cell surface components. Another novel phage genus revealed a microdiversity of phage species that was largely maintained during the experiment and across mesocosms amended with different nutrients. In contrast to the newly described Flavobacterium phages, phages isolated from a Rheinheimera strain were highly similar to previously isolated genotypes, pointing to genomic consistency in this population. In the mesocosm experiment, the investigated phages were mainly detected after a phytoplankton bloom peak. This concurred with recurrent detection of the phages in the Baltic Proper during summer months, suggesting an influence on the succession of heterotrophic bacteria associated with phytoplankton blooms.

The Dynamics of Endophytic Bacterial Community Structure in Rice Roots under Different Field Management Systems

The structure of endophytic bacteria is important to plant health and stress tolerance, but little is known about the impacts of farming systems on temporal changes in diversity of endophytic bacteria. In this study, we investigated the endophytic microbiome in rice roots under organic and conventional farming systems at the seedling and tillering stages over two consecutive cropping seasons using 16S rRNA gene sequencing. Although the composition of the microbiome was significantly influenced by a field management system, growth stage, and interaction between the two factors, the growth stage alone explained more than 40% of variance. Soil pH and organic matter content also partially influenced the endophytic bacterial community composition. In addition, through indicator species analysis and the functional profiles predicted by phylogenetic analysis, we revealed the selection force of rice roots at the tillering stage to recruit endophytes, which are beneficial to plant growth. In summary, our data show that the dynamics of rice root bacterial composition are mainly influenced by the plant growth stage. Our findings offer new insights regarding the control of the root microbiome by host plants and the influence of farming systems.

Linking perturbations to temporal changes in diversity, stability, and compositions of neonatal calf gut microbiota: prediction of diarrhea.

Perturbations in early life gut microbiota can have long-term impacts on host health. In this study, we investigated antimicrobial-induced temporal changes in diversity, stability, and compositions of gut microbiota in neonatal veal calves, with the objective of identifying microbial markers that predict diarrhea. A total of 220 samples from 63 calves in first 8 weeks of life were used in this study. The results suggest that increase in diversity and stability of gut microbiota over time was a feature of “healthy” (non-diarrheic) calves during early life. Therapeutic antimicrobials delayed the temporal development of diversity and taxa–function robustness (a measure of microbial stability). In addition, predicted genes associated with beta lactam and cationic antimicrobial peptide resistance were more abundant in gut microbiota of calves treated with therapeutic antimicrobials. Random forest machine learning algorithm revealed that Trueperella, Streptococcus, Dorea, uncultured Lachnospiraceae, Ruminococcus 2, and Erysipelatoclostridium may be key microbial markers that can differentiate “healthy” and “unhealthy” (diarrheic) gut microbiota, as they predicted early life diarrhea with an accuracy of 84.3%. Our findings suggest that diarrhea in veal calves may be predicted by the shift in early life gut microbiota, which may provide an opportunity for early intervention (e.g., prebiotics or probiotics) to improve calf health with reduced usage of antimicrobials.

Biodiversity of Holothurians in Morella coastal waters, Central Maluku, Indonesia

The Holothurian is one of the echinoderms which has well known as the sea cucumber. The coastal communities in Maluku often harvest the sea cucumber for their livelihoods both for consumed and sold them. Recently, the number of sea cucumber has been decreased due to anthropogenic and environmental degradation. Therefore, the data of bio-ecology of the resources are needed to manage the resources for its sustainability. The objective of the study was to analyze the biodiversity of holothurians. Data were collected by purposive random sampling. The research was carried out from October 2017 to October 2018. The results showed that there were five species of holothurians found during this study. The abundance of holothurians ranged from 18 to 173 individuals which the highest abundance was found in March 2018 whereas the lowest abundance was found in November 2017. The diversity of species differed each month. The study indicated that there were temporal changes in diversity. The diversity index (H’) ranged from 0.733-1.346, meaning low species diversity. The evenness index showed that the abundance of each species had almost similar. So, that there were no predominance species. Nevertheless, three species have a high number or tend to be dominant later namely Bohadschia similis, Holothuria scabra and H. atra.

Lineages through space and time plots: Visualising spatial and temporal changes in diversity

Author(s): Skeels, Alex | Abstract: During the radiation of a clade, diversification rates can show temporal patterns such as a speedup or slowdown, which might relate to different ecological and evolutionary mechanisms. The temporal dynamics of diversification of whole clades are often visualised as a lineage-through-time (LTT) plot, which traces the number of reconstructed lineages at different time points. However, clades do not radiate evenly across space and may show different temporal dynamics in different regions. As such, a biogeographic approach is required to more completely understand temporal diversification dynamics. Here, I present a tool to extract temporal diversity information across different biogeographic regions from the output of commonly used ancestral range estimation models implemented in the R package BioGeoBEARS. The lineages through space and time (LTST) plot allows for visualisation of diversification dynamics in different regions, formatted in an accessible way which can be used for further quantitative analysis.

How can assemblage structure indices improve monitoring of change in bird communities using ongoing survey data?

Abstract Traditional monitoring of biodiversity has focused on the abundance or distribution of individual species, or on simple summary indices of average trends or diversity or species richness. Supplementing these approaches with an index system that measures subtle changes in assemblage structure is highly desirable and appears not to have been previously attempted. Subject to validation, such indices could inform sensitively about ecosystem health (defined as proximity to a stable or desired state) and the natural capital status or potential ecosystem service delivery. The available approaches for monitoring biological assemblages and the data to which they might be applied are reviewed, including consideration of sources of error. A particularly promising method is the calculation of ‘diversity profiles’ (Leinster & Cobbold, 2012), which present a ‘signature’ describing the range of biological variation, considering both species’ identities and their relative abundances. The diversity profile approach was tested using a long-term bird monitoring data set for woodland birds in the UK, applying species similarities based on phylogeny, habitat selection and ecological function (i.e. diet). Tests were conducted using three nested sets of species with different levels of specialization with respect to woodland. The influence of quantifiable sources of error was evaluated using bootstrapping. Profile shape and temporal changes in diversity varied in magnitude and pattern with the choice of similarity measure and species set, with the pattern of temporal change in diversity showing either an increase or a decline, depending on the choice of analysis. This shows that the profile approach has the potential to reveal subtle variations in assemblage structure, although careful application and interpretation of outputs are required. The bootstrapping results revealed that uncertainty in profile values was high, but that this was due chiefly to uncertainty in interspecific similarities, as opposed to sampled abundance values, but this relates to the specific application to the datasets tested, rather than to the method in general. Different approaches to quantifying differences between species (phylogenetic, habitat preference and dietary) revealed different aspects of assemblage variability. Combined with the calculation of reference levels of diversity for known assemblages or sets of conditions such that observed variation can be interpreted quantitatively, assemblage monitoring via diversity profiles could add valuable, quantitative inference to ongoing monitoring, and hence the assessment of ecosystem health, potentially bridging the gap between conservation and a purely economic valuation of the status of natural capital.

Temporal Changes in Diversity and Abundance of Mosquitoes (Insecta: Diptera: Culicidae) in a Small Ecological Preserve in North Carolina

We documented a changing diversity in mosquito species between 2 collection periods— 1994–1996 and 2013–2015—in a small (68-ha) ecological preserve in the piedmont of North Carolina. A short (22-y) ecological succession from abandoned farmland to developing forested wetland, and changes in precipitation clearly influenced differences in presence and abundance of species in the preserve. Thirty species were reported from the first period and 32 species in the second period. Of the 30 species found in 1994–1996, 3 species were not collected in the 2013–2015 period. Conversely, 6 species not reported previously were present in the 2013–2015 collections. From both periods, a total of 7172 mosquito specimens of 36 species were collected, representing 95% of species found in Rowan County, an area 2000 times larger than the Fred Stanback Jr. Ecological Preserve (FSJEP), and 54% of species recognized in North Carolina. These results demonstrate the advantages of studying mosquito diversity and abundance over time in small preserves, the impact of short-period environmental fluctuations and ecological succession on mosquito habitats, and the value of small wetland preserves for rare or uncommon species affected by habitat loss.

Increasing species richness but decreasing phylogenetic richness and divergence over a 320‐year period of urbanization

Summary Urbanization is increasing faster than ever, contributing to a global extinction crisis. Recently, scientists have debated whether species richness on local and regional scales is mostly declining, but long‐term changes in phylogenetic richness and divergence were largely disregarded. Space‐for‐time approaches revealed that plant phylogenetic divergence is lower in urban than in non‐urban areas. However, such approaches cannot fully disentangle the relative importance of the biotic processes that drive temporal changes in diversity. Using a unique European urban flora covering 320 years in seven time steps, combined with a comprehensive plant phylogeny, we examined (i) how species richness changed with urbanization over time; (ii) whether trends in phylogenetic richness and divergence parallel trends in species richness; and (iii) whether species extirpation or immigration is driving these changes. We found that over time urban species richness increased, but phylogenetic richness and divergence decreased. Extirpations of phylogenetically distinct native species and immigrations of phylogenetically common native and non‐native species caused a non‐random loss of phylogenetic diversity. Our analyses suggest that if future extirpations and immigrations continue to follow the patterns observed over history, this loss will continue. Synthesis and applications. Measures to protect phylogenetic diversity should combine the protection of threatened habitats and their species with the maintenance of habitats that mitigate heat and safeguard evolutionary history. Urban planners should consider a phylogenetically diverse set of species when designing green spaces.

Diversity of indoor fungi as revealed by DNA metabarcoding.

In the present study, we conducted DNA metabarcoding (the nuclear ITS2 region) for indoor fungal samples originating from two nursery schools with a suspected mould problem (sampling before and after renovation), from two university buildings, and from an old farmhouse. Good-quality sequences were obtained, and the results showed that DNA metabarcoding provides high resolution in fungal identification. The pooled proportions of sequences representing filamentous ascomycetes, filamentous basidiomycetes, yeasts, and other fungi equalled 62.3%, 8.0%, 28.3%, and 1.4%, respectively, and the total number of fungal genera found during the study was 585. When comparing fungal diversities and taxonomic composition between different types of buildings, no obvious pattern was detected. The average pairwise values of SørensenChao indices that were used to compare similarities for taxon composition between samples among the samples from the two university buildings, two nurseries, and farmhouse equaled 0.693, 0.736, 0.852, 0.928, and 0.981, respectively, while the mean similarity index for all samples was 0.864. We discovered that making explicit conclusions on the relationship between the indoor air quality and mycoflora is complicated by the lack of appropriate indicators for air quality and by the occurrence of wide spatial and temporal changes in diversity and compositions among samples.

The genetic underpinnings of population cyclicity: establishing expectations for the genetic anatomy of cycling populations

Despite extensive research into the mechanisms underlying population cyclicity, we have little understanding of the impacts of numerical fluctuations on the genetic variation of cycling populations. Thus, the potential implications of natural and anthropogenically‐driven variation in population cycle dynamics on the diversity and evolutionary potential of cyclic populations is unclear. Here, we use Canada lynx Lynx canadensis matrix population models, set up in a linear stepping‐stone, to generate demographic replicates of biologically realistic cycling populations. Overall, increasing cycle amplitude predictably reduced genetic diversity and increased genetic differentiation, with cyclic effects increased by population synchrony. Modest dispersal rates (1–3% of the population) between high and low amplitude cyclic populations did not diminish these effects suggesting that spatial variation in cyclic amplitude should be reflected in patterns of genetic diversity and differentiation at these rates. At high dispersal rates (6%) groups containing only high amplitude cyclic populations had higher diversity and lower differentiation than those mixed with low amplitude cyclic populations. Negative density‐dependent dispersal did not impact genetic diversity, but did homogenize populations by reducing differentiation and patterns of isolation by distance. Surprisingly, temporal changes in diversity and differentiation throughout a cycle were not always consistent with population size. In particular, negative density‐dependent dispersal simultaneously decreased differences in genetic diversity while increasing differences in genetic differentiation between numerical peaks and nadirs. Combined, our findings suggest demographic changes at fine temporal scales can impact genetic variation of interacting populations and provide testable predictions relating population cyclicty to genetic variation. Further, our results suggest that including realistic demographic and dispersal parameters in population genetic models and using information from temporal changes in genetic variation could help to discern complex demographic scenarios and illuminate population dynamics at fine temporal scales.

Dispersal in the desert: ephemeral water drives connectivity and phylogeography of an arid‐adapted fish

AbstractAimWe examine landscape processes shaping the range‐wide phylogeography of a dispersal‐limited, desert‐dwelling fish (the desert goby, Chlamydogobius eremius) in arid Australia.LocationSouth‐western Lake Eyre Basin, central Australia.MethodsWe obtained sequence data for the mitochondrial cytochrome b gene (n = 513 individuals) and nuclear genetic markers (51 allozyme loci; n ≥ 128 individuals) to investigate the phylogeographic relationships among 51 populations. Sampling spanned multiple habitat types (permanent desert springs, ephemeral rivers) and sub‐catchments, and the entire distribution of C. eremius and representatives of its sister species, Chlamydogobius japalpa. Phylogeographic analyses (genetic diversity, AMOVA, Tajima's D, WST, mismatch distribution) were used to explore the distribution and partitioning of mtDNA variation; principal coordinates analysis and neighbour‐joining tree networks were used to explore allozyme variation.ResultsThree main genetic groups exist across C. eremius/C. japalpa populations. The geographical distributions of these groups reflected the historical and current confluence point of major rivers in the region. Surprisingly, permanent desert springs did not contain higher genetic diversity than ephemeral rivers.Main conclusionsGenetic structuring of Chlamydogobius populations revealed unanticipated levels of connectivity, indicating that the ephemeral waters of Lake Eyre have allowed gene flow across drainage boundaries and large distances. Phylogeographic breaks reveal that connectivity relies on temporary surface water, while rapid temporal changes in diversity highlight flood‐driven dispersal as the main means of gene flow between localities and habitats. Dispersal pathways reveal that ecological context (life history and tolerance of extreme conditions) has played a key role in shaping observed patterns.

Sediment prokaryote communities in different sites of eutrophic Lake Taihu and their interactions with environmental factors.

To investigate the temporal variation of the sediment prokaryote communities and their relation with the rapid increase of algae population in Taihu, a shallow eutrophic freshwater Lake, water and surface sediments were sampled from seven sites in different stages of algal bloom. The physicochemical characterization revealed positive correlations among the nutrient (N, P) parameters in the water and sediments, as well as TN/TP ratio 30.79 in average in water and 0.13 in sediments, demonstrating that P content was the limit factor for bloom in Taihu and sediment was an important nutrient resource for the water body. T-RFLP analysis of 16S rRNA genes revealed a diversity decrease of sediment prokaryotic communities along the bloom. The bacterial communities in sediments were more sensitive and shaped by the temporal changes, while archaea were more sensitive to the trophic level. The pyrosequencing data showed clear spatial and temporal changes in diversity of sediment bacteria. Betaproteobacteria was the most abundant group in all the samples, following by Delta-, Gama- and Alpha-proteobacteria, Acidobacteria, Chlorobi, Chloroflexi etc. At the genus level, Thiobacillus and Sulfuricurvum were the most dominant groups in the sediments, and the increase of Thiobacillus abundance in February might be used as bioindicator for the subsequent bloom. In addition, NO3 (-)-N was evidenced to be the main factor to regulate the bacterial community structure in the sediments. These results offered some novel and important data for the evaluation and predict the algal bloom in Taihu and can be reference for other shallow fresh water lakes.

Decomposing changes in phylogenetic and functional diversity over space and time

The α, β, γ diversity decomposition methodology is commonly used to investigate changes in diversity over space or time but rarely conjointly. However, with the ever-increasing availability of large-scale biodiversity monitoring data, there is a need for a sound methodology capable of simultaneously accounting for spatial and temporal changes in diversity.Using the properties of Chao's index, we adapted Rao's framework of diversity decomposition between orthogonal dimensions to a multiplicative α, β, γ decomposition of functional or phylogenetic diversity over space and time, thereby combining their respective properties. We also developed guidelines for interpreting both temporal and spatial β-diversities and their interaction.We characterised the range of β-diversity estimates and their relationship to the nested decomposition of diversity. Using simulations, we empirically demonstrated that temporal and spatial β-diversities are independent from each other and from α and γ-diversities when the study design is balanced, but not otherwise. Furthermore, we showed that the interaction term between the temporal and the spatial β-diversities lacked such properties.We illustrated our methodology with a case study of the spatio-temporal dynamics of functional diversity in bird assemblages in four regions of France. Based on these data, our method makes it possible to discriminate between regions experiencing different diversity changes in time. Our methodology may therefore be valuable for comparing diversity changes over space and time using large-scale datasets of repeated surveys.

Spatial and temporal variability in subtidal macroinvertebrates diversity patterns in a management and exploitation area for benthic resources (MEABRs)

Diversity and biological variability are key attributes to maintain a viable life system in the marine benthic zone and this balance is heavily affected by human activities. In Chile, Management and Exploitation Areas for Benthic Resources (MEABRs) are coastal areas administrated by local fishermen, which regulate the extraction of species of commercial of commercial importance (e.g. Concholepas concholepas, Fissurella spp. Loxechinus albus), key components of food webs. Both spatial and temporal impacts these species have on the structure and dynamics of the subtidal community are poorly understood. In one of the oldest MEABRs of Chile we evaluated spatial and temporal effects of controlled extraction of commercial species on subtidal macro invertebrate's diversity. Our results indicate that in a spatial scale MEABRs showed increased species richness, and important temporal changes in diversity and species composition from bivalves, ascidians and gastropods to cnidarians, sponges and bryozoans. We discuss possible mechanisms associated with the combined effects of fishery management and predation by key species on temporal composition variation in the subtidal macro invertebrate assemblage in this regulated area.