bioRxiv Science⌕ Search

SEARCH · bioRxiv Science

Results for “Ecology”

Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,333 records · Page 74Linked to original sources
bioRxiv2019

Temporal switching of species roles in a plant-pollinator network

Mutualistic networks are highly dynamic, characterized by high temporal turnover of species and interactions. Yet, we have a limited understanding of how the internal structure of these networks and the roles species play in them vary through time. We used six years of observation data and a novel statistical method (dynamic stochastic block models) to assess how network structure and species roles change across time in a quantitative plant-pollinator network from a dryland ecosystem in Argentina. Our analyses revealed a core-periphery structure persistent through seasons and years. Yet, species roles as core or peripheral were highly dynamic: virtually all species that played a core role in some seasons were also peripheral in other seasons, while many other species remained always peripheral. Our results illuminate our understanding of the dynamics of ecological networks and have important implications for ecosystem management and conservation.

ecology↗
bioRxiv2019

Assessing different components of biodiversity across a river network using eDNA

O_LIAssessing individual components of biodiversity, such as local or regional taxon richness, and differences in community composition is a long-standing challenge in ecology. It is especially relevant in spatially structured and diverse ecosystems. Environmental DNA (eDNA) has been suggested as a novel technique to accurately measure biodiversity. However, we do not yet fully understand the comparability of eDNA-based assessments to previously used approaches. C_LIO_LIWe sampled may-, stone-, and caddisfly genera with contemporary eDNA and kicknet methods at 61 sites distributed over a large river network, allowing a comparison of various diversity measures from the catchment to site levels and providing insights into how these measures relate to network properties. We extended our survey data with historical records of total diversity at the catchment level. C_LIO_LIAt the catchment scale, eDNA and kicknet detected similar proportions of the overall and cumulative historically documented species richness (gamma diversity), namely 42% and 46%, respectively. We further found a good overlap (62%) between the two contemporary methods at the regional scale. C_LIO_LIAt the local scale, we found highly congruent values of local taxon richness (alpha diversity) between eDNA and kicknet. Richness of eDNA was positively related with discharge, a descriptor of network position, while kicknet was not. C_LIO_LIBeta diversity between sites was similar for the two contemporary methods. Contrary to our expectation, however, beta diversity was driven by species replacement and not by nestedness. C_LIO_LIAlthough optimization of eDNA approaches is still needed, our results indicate that this novel technique can capture extensive aspects of gamma diversity, proving its potential utility as a new tool for large sampling campaigns across hitherto understudied complete river catchments, requiring less time and becoming more cost-efficient than classical approaches. Overall, the richness estimated with the two contemporary methods is similar at both local and regional scale but community composition is differently assessed with the two methods at individual sites and becomes more similar with higher discharge. C_LI

ecology↗
bioRxiv2019

Evaluating the stoichiometric trait distributions of cultured bacterial populations and uncultured microbial communities

Originality StatementThe ecological stoichiometry of microbial biomass has most often focused on the ratio of the biologically-important elements carbon (C), nitrogen (N), and phosphorus (P) and has primarily been examined at a resolution where the contribution of the individual is masked by the reported population or community average. However, reporting population or community averages makes it difficult to assess phenotypic plasticity and stochasticity and mask important information required to understand both the drivers and implications of microbial biomass stoichiometry in nature. One way to assess the diversity of individual microbial phenotypes is through the use of single-cell techniques such as energy dispersive spectroscopy (EDS). EDS reports cellular quotas for the majority of elements composing microbial biomass including C, N, and P. In this study, by measuring individual cells within a microbial community or population, we describe for the first time the stoichiometry of microbial biomass as a distribution instead of an average. Exploration of stoichiometric trait distributions (as presented here) has the potential to improve our understanding of how nutrients interact with individual microorganisms to structure the elemental content of bacterial biomass and better describe how bacterial community biomass affects the ecosystems within which these organisms exist. SummaryTo assess the potential for EDS to describe the stoichiometric variance within populations and communities we measured the stoichiometric trait distribution of cultured freshwater bacterial populations under different resource conditions and compared them to natural microbial communities sampled from three lakes. Mean biomass C:N:P values obtained by EDS matched closely to those obtained by bulk measures using traditional analytical techniques for each freshwater isolate. However, we observed pronounced differences in the stoichiometric trait distributions of freshwater bacterial isolates compared to the stoichiometric trait distributions of natural communities. The stoichiometric trait distribution of the environmental isolates changed with P availability, growth phase, and genotype, with P availability having the strongest effect. The distribution of biomass ratios within each isolate growth experiment were the most constrained during stages of rapid growth and commonly had unimodal distributions. In contrast to the population distributions, the distribution of N:P and C:P for a similar number of cells from each of the mixed lake communities had narrower stoichiometric distributions and more commonly exhibited multiple modes.

ecology↗
bioRxiv2019

Rare Microbial Taxa Emerge When Communities Collide: Freshwater and Marine Microbiome Responses to Experimental Seawater Intrusion

Whole microbial communities regularly merge with one another, often in tandem with their environments, in a process called community coalescence. Such events allow us to address a central question in ecology - what processes shape community assembly. We used a reciprocal transplant and mixing experiment to directly and independently unravel the effects of environmental filtering and biotic interactions on microbiome success when freshwater and marine communities coalesce. The brackish treatment and community mixing resulted in strong convergence of microbiome structure and function toward the marine. Brackish exposure imposed a 96% taxa loss from freshwater and 66% loss from marine microbiomes, which was somewhat counterbalanced by the emergence of tolerant rare taxa. Community mixing further resulted in 29% and 49% loss from biotic interactions between freshwater and marine microbiomes, offset somewhat by mutualistically-assisted rare microbial taxa. Our study emphasizes the importance of the rare biosphere as a critical component of community resilience.

ecology↗
bioRxiv2019

Semi-quantitative characterisation of mixed pollen samples using MinION sequencing and Reverse Metagenomics (RevMet)

1. The ability to identify and quantify the constituent plant species that make up a mixed-species sample of pollen has important applications in ecology, conservation, and agriculture. Recently, metabarcoding protocols have been developed for pollen that can identify constituent plant species, but there are strong reasons to doubt that metabarcoding can accurately quantify their relative abundances. A PCR-free, shotgun metagenomics approach has greater potential for accurately quantifying species relative abundances, but applying metagenomics to eukaryotes is challenging due to low numbers of reference genomes. 2. We have developed a pipeline, RevMet (Reverse Metagenomics), that allows reliable and semi-quantitative characterization of the species composition of mixed-species eukaryote samples, such as bee-collected pollen, without requiring reference genomes. Instead, reference species are represented only by genome skims: low-cost, low-coverage, short-read sequence datasets. The skims are mapped to individual long reads sequenced from mixed-species samples using the MinION, a portable nanopore sequencing device, and each long read is uniquely assigned to a plant species. 3. We genome-skimmed 49 wild UK plant species, validated our pipeline with mock DNA mixtures of known composition, and then applied RevMet to pollen loads collected from wild bees. We demonstrate that RevMet can identify plant species present in mixed-species samples at proportions of DNA [≥]1%, with few false positives and false negatives, and reliably differentiate species represented by high versus low amounts of DNA in a sample. 4. The RevMet pipeline could readily be adapted to generate semi-quantitative datasets for a wide range of mixed eukaryote samples, which could include characterising diets, quantifying allergenic pollen from air samples, quantifying soil fauna, and identifying the compositions of algal and diatom communities. Our per-sample costs were {pound}90 per genome skim and {pound}60 per pollen sample, and new versions of sequencers available now will further reduce these costs.

ecology↗
bioRxiv2019

Future sea-level rise drives rocky intertidal habitat loss and benthic community change

Rocky intertidal ecosystems may be particularly susceptible to sea-level rise impacts but few studies have explored community scale response to future sea-level scenarios. Combining remote-sensing with large-area imaging, we quantify habitat extent and describe biological community structure at two rocky intertidal study locations in California. We then estimate changes in habitat area and community composition under a range of sea-level rise scenarios using a model-based approach. Our results suggest that future sea-level rise will significantly reduce rocky intertidal area at our study locations, leading to an overall decrease in benthic habitat and a reduction in overall invertebrate abundances, but increased densities of certain taxa. These results suggest that sea-level rise may fundamentally alter the structure and function of rocky intertidal systems. As large scale environmental changes such as sea-level rise accelerate in the next century, more extensive spatially-explicit monitoring at ecologically relevant scales will be needed to visualize and quantify the impacts to biological systems.

ecology↗
bioRxiv2019

Estimating the abundance of duiker (Cephalophus spp.) populations in African rainforests: an overview of relevant methods

Duikers are among the most sought after antelope species for bush meat in central Africa. Estimates of population abundance of duikers based on reliable methods is therefore of prime importance for their sustainable management. Here we retrieved 31 studies from the literature and compared methods used to estimate the abundance of duiker populations in African rainforests. Implemented methods all derived from seven main combinations of sampling designs and population abundance estimators. We then evaluated the relevance of those seven methods by scoring them based on eight criteria selected according to their pros and cons reported in the litterature for large-scale population management of wildlife. For management purposes, methods derived from distance sampling offer the best compromise between the implementation costs and the biological information collected. In particular, both diurnal and nocturnal distance sampling can be recommended. Hunter calls and drive-netting are less reliable, but can be used in association with other measurements in the framework of indicators of ecological changes, a monitoring approach that has been successfully used in temperate ecosystems for managing large herbivores. Funding informationMinistere de lEnvironnement et du Developpement Durable de la Republique Democratique du Congo, Campus France and Centre National de la Recherche Scientifique (CNRS). ResumeLes cephalophes sont parmi les especes dantilopes les plus recherchees pour la viande de brousse en Afrique centrale. Lestimation de labondance des populations de cephalophes revet donc une importance primordiale pour leur gestion durable et adaptative. Nous avons extrait 31 etudes de la litterature et compare les methodes utilisees pour estimer labondance des populations de cephalophes dans les forets tropicales africaines. Les methodes employees derivent de sept combinaisons principales de plans dechantillonnage et destimateurs dabondance. Nous avons evalue la pertinence de ces sept methodes sur la base de criteres selectionnes en fonction de leurs avantages et inconvenients pour une gestion a grande echelle de la population. Les methodes derivees de lechantillonnage par distance offrent le meilleur compromis entre les couts de mise en uvre et les informations biologiques collectees. Les methodes dechantillonnage diurne et nocturne se sont montrees les plus satisfaisantes. Les methodes dappel par les chasseurs et de battue au filet sont moins fiables, mais peuvent etre utilisees en association avec dautres mesures biologiques comme indicateurs de changements ecologiques, une approche qui a ete utilisee avec succes dans les ecosystemes temperes pour la gestion des grands herbivores. Mots-clesgestion durable, grands herbivores, indicateurs de changement ecologique, methode de recensement, viande de brousse

ecology↗
bioRxiv2019

High sampling effectiveness for non-bee pollinators using vane traps in both open and wooded habitats

O_LINon-bee insects are important for pollination, yet few studies have assessed the effectiveness of sampling these taxa using low cost passive techniques, such as coloured vane traps, among different habitat types. C_LIO_LIThis study sampled 192 sites--108 in wooded and 84 in open habitats within an agricultural region of southern Australia. Pairs of blue and yellow vane traps were placed at each site for a period of seven days during the austral spring. C_LIO_LIOverall, 3114 flies (Diptera) from 19 families and 528 wasps (non-bee and non-formicid Hymenoptera) from 16 families were collected during the study. This sampling was representative of the region, with vane traps equally or more likely to collect as many families from both taxa as those reported on the Atlas of Living Australia (ALA) database for the sampling area. C_LIO_LIBlue vane taps (BVTs) had greater average richness of both flies and wasps and greater abundance of individuals than yellow vane traps (YVTs). BVTs were particularly favoured by certain fly and wasp families known to pollinate flowers (e.g. Syrphidae, Bombyliidae and Scoliidae), whilst YVTs sampled some less common fly families, such as Acroceridae and Bibionidae that also provide additional ecosystem services to pollination. C_LIO_LIVane traps are an effective passive sampling technique for non-bee pollinators, such as flies and wasps. This study supports the use of vane traps as a component of the sampling protocol for ecological census and population monitoring within multiple habitat types, to effectively sample a more complete pollinator community. C_LI

ecology↗
bioRxiv2019

Facets of diazotrophy in the OMZ off Peru revisited: what we could not see from a single marker gene approach

Biological dinitrogen (N2) fixation is the pathway making the large pool of atmospheric N2 available to marine life. Besides direct rate measurements, a common approach to explore the potential for N2 fixation in the ocean is a mining based on molecular genetic methods targeting the key functional gene nifH, coding for a subunit of the nitrogenase reductase. As novel sequencing and single cell techniques improved, our knowledge on the diversity of marine N2 fixers grew exponentially. However, to date one aspect of N2 fixation in the ocean is commonly left aside. This is the existence of two alternative types of nitrogenases, which are besides the Mo-Fe nitrogenase Nif, the Fe-Fe nitrogenase Anf, and the V-Fe nitrogenase Vnf, which differ with regard to their metal co-enzymes, as well as regarding their operon structure and composition. nifH-based studies may thus be biased, and alternative nitrogenases could not be recovered. Here, we screened a set of 6 metagenomes and -transcriptomes from a sulfidic water patch from the oxygen minimum zone off Peru for genes involved in N2 fixation. We identified genes related to all three nitrogenases, and generally increased diversity as compared to our previous nifH-based study from the same waters. While we could not confirm gene expression of the alternative nitrogenases from our transcriptomes, we detected additional diazotrophs involved in N2 fixation. We suggest that alternative nitrogenases may not be used under conditions present in those waters, however, depending on trace metal limitation in the future they may become active. Significance statementThis study addresses the important process of N2 fixation, based on a whole-metagenome and -transcriptome screening, reports an increased diversity of N2 fixing microbes in the sulfidic shelf water off Peru, as compared to previous target-gene based studies from the same waters. In addition to a generally higher diversity, genes encoding for alternative nitrogenases, which were previously not subject of any study on N2 fixation in oxygen minimum zones, were detected. The ecological meaning and evolutionary history of those alternative nitrogenases is subject of ongoing debates, however, their presence in OMZ waters would allow for N2 fixation at extreme anoxia, which may become important in a future ocean challenged by progressive deoxygenation.

ecology↗
bioRxiv2019

Insect herbivory and avian insectivory in novel native oak forests: divergent effects of stand size and connectivity

The value of novel native broadleaf woodlands for biodiversity conservation is important to consider for adequate forest management in rural landscapes. Passive reforestation has been proposed as a cost-efficient tool for creating networks of novel native forest stands that would help restoring biodiversity and associated ecosystem services. Yet to date the ecological functioning of such stands remains strongly understudied compared to forest remnants resulting from longer-term fragmentation. We assessed how the size and connectivity of newly established Pedunculate oak (Quercus robur L.) stands in rural landscapes of SW France affect rates of herbivory by different insect guilds as well as rates of avian insectivory and the abundance and richness of insectivorous birds. Comparing 18 novel forest stands along a gradient of size (0.04-1.15 ha) and cover of broadleaf forests in the surroundings (0-30% within a 500 radius), we found that even the smallest stands are colonised by leaf miners and chewers/skeletonizers, and that rates of herbivory are globally comparable to those reported from older and larger oak forests. The size of stands had a relatively minor effect on herbivory, whereas it increased the abundance of insectivorous bird. It also determined rates of avian insectivory as estimated by an experiment with plasticine caterpillars. These rates were however rather low and unrelated with the extent of herbivory in the stand. Overall, our study indicates that insect herbivores tend to react more rapidly to the establishment of novel native forests than their avian predators as the latter may depend on the development of larger patches of suitable habitat in the surrounding landscape. To favour a rapid build-up of diverse, and hence stable, trophic networks involving insect herbivores and their predators, woodland creation schemes should therefore primarily focus on habitat size and quality.

ecology↗
bioRxiv2019

Ammonia-oxidizing archaea release a suite of organic compounds potentially fueling prokaryotic heterotrophy in the ocean

Ammonia-oxidizing archaea (AOA) constitute a considerable fraction of microbial biomass in the global ocean, comprising 20-40% of the oceans prokaryotic plankton and thus play an important role in global nitrogen cycle. However, it remains enigmatic to what extent these chemolithoautotrophic archaea are releasing dissolved organic matter (DOM). A combination of targeted and untargeted metabolomics was used to characterise the exometabolomes of three model AOA strains of the Nitrosopumilus genus. Furthermore, we compared the composition of intra- and extracellular dissolved free amino acids (DFAA). Our results indicate that marine AOA exude a suite of organic compounds with potentially varying reactivity, dominated by nitrogen-containing compounds. A significant fraction of the released DOM consisted of labile compounds, which typically limit prokaryotic heterotrophic activity in open ocean waters, including amino acids, thymidine and B vitamins. In growing Nitrosopumilus cultures, hydrophobic amino acids were likely released as a result of passive diffusion corresponding to ammonia oxidation activity, while glycine was continuously released at high rates. Our results suggest that AOA release several ecologically and biochemically relevant metabolites, potentially fueling heterotrophic prokaryotes in the ocean.

ecology↗
bioRxiv2019

Niche partitioning and coexistence of two spiders of the genus Peucetia (Araneae, Oxyopidae) inhabiting Trichogoniopsis adenantha plants (Asterales, Asteraceae): a population approach

Niche theory suggests that the coexistence of ecologically similar species at the same site requires some form of resource partitioning that reduces or avoids interspecific competition. Here, we investigated the temporal and spatial niche differentiation of two sympatric congeneric spiders, Peucetia rubrolineata and P. flava, inhabiting Trichogoniopsis adenantha (Asteraceae) plants along an altitudinal gradient in various shaded and open areas in an Atlantic forest in Serra do Japi, SP, Brazil. In theory, the coexistence of two Peucetia species could be explained by: (1) temporal segregation; (2) differential use of the branches of the plant; (3) differential use of specific parts of the branches of the plant; (4) differential distribution in shaded and open areas; and (5) differential altitudinal distribution of the two Peucetia species. With respect to temporal niche, we observed that the two spider species had a similar age structure and similar fluctuation in abundance throughout the year. With respect to micro-habitat use, in both species, different instars used different plant parts, while the same instars of both species used the same type of substrate. However, the two Peucetia species segregated by meso-habitat type, with P. rubrolineata preferring T. adenantha plants in shaded areas and P. flava preferring those in open areas. Our results support the hypothesis of niche partitioning begetting diversity, and highlight the importance of analysing habitat use at multiple scales to understand mechanisms related to coexistence.

ecology↗
bioRxiv2019

Effect of time-series length and resolution on abundance- and trait-based early warning signals of population declines

Natural populations are increasingly threatened with collapse at the hands of anthropogenic effects. Predicting population collapse with the help of generic early warning signals (EWS) may provide a prospective tool for identifying species or populations at highest risk. However, pattern-to-process methods such as EWS have a multitude of challenges to overcome to be useful, including the low signal to noise ratio of ecological systems and the need for high quality time-series data. The inclusion of trait dynamics with EWS has been proposed as a more robust tool to predict population collapse. However, the length and resolution of available time series are highly variable from one system to another, especially when generation time is considered. As yet it remains unknown how this variability with regards to generation time will alter the efficacy of EWS. Here we take both a simulation- and experimental-based approach to assess the impacts of relative time-series length and resolution on the forecasting ability of EWS. We show that EWS performance decreases with decreasing length and resolution. Our simulations suggest a relative time-series length between ten and five generations and a resolution of half a generation are the minimum requirements for accurate forecasting by abundance-based EWS. However, when trait information is included alongside abundance-based EWS, we find positive signals at lengths and resolutions half of what was required without them. We suggest that, in systems where specific traits are known to affect demography, trait data should be monitored and included alongside abundance data to improve forecasting reliability.

ecology↗
bioRxiv2019

The restoration species pool for restoring tropical landscapes: assessment of the largest Brazilian supply chain

Brazil has been committed to fulfill international restoration goals and to enforce environmental legislation that will require private landowners to undertake ecological restoration of 21 million hectares of degraded and deforested landscapes. To support a broad range of restoration practices, a consolidated supply chain able to represent regional plant diversity is essential. This study investigated the restoration species pool in native plant nurseries in Sao Paulo state, southeastern Brazil and evaluated their geographic distribution, similarity of their plant stocks and the proportion of species represented from regional floras. Despite the lack of technical assistance and the large presence of non-native species (126 species, average 7.5 species/nursery), we found still more impressive native species richness in plant nurseries (561 species, average 86.4 species/nursery) from both the Atlantic Forest and Cerrado domains, representing 38 to 44% of regional floras. There was a huge bias toward tree and shrub species (96.6%) and absence or underrepresentation of other growth forms, as well as of savanna specialists, animal-dispersed and threatened species. The great dissimilarity of species offered in the nurseries surveyed underscores the importance of regional seed collection practices. Effective assistance and capacitation are essential to address issues related to misidentification of species, underrepresentation of most functional plant groups, and the presence of non-native species, as well as to support the supply chain, currently undergoing market downturn.\n\nAuthor contributions CYV and RRR conceived and designed the research. CYV performed data compilation; CYV and RPN analyzed the data; CYV and RAGV led the writing of the manuscript; all authors contributed to the drafts and gave final approval for publication.\n\nImplications for practiceO_LIPlant nurseries collecting propagules from the surrounding vegetation provide an adequate - but limited - restoration species pool, with very dissimilar plant stocks available among plant nurseries.\nC_LIO_LIPlant nurseries concentrate their production on shrub and tree species and sub-represent other growth forms and some functional groups such as animal-dispersed and threatened species.\nC_LIO_LIThe diversity of the restoration species pool is the basis to support a broad range of restoration practice, being essential to boost restoration initiatives that complement and support the conservation of remaining diversity in human modified landscapes.\nC_LIO_LIEffective assistance and capacity building should be provided to address issues related to misidentification, underrepresentation of functional groups and the presence of exotic and invasive species, as well as to support the supply chain, currently under market downturn\nC_LI

ecology↗
bioRxiv2019

Distinct defense strategies allow different grassland species to cope with root herbivore attack

O_LIRoot-feeding insect herbivores are of substantial evolutionary, ecological and economical importance. Plants can resist insect herbivores through a variety of tolerance and resistance strategies. To date, few studies have systematically assessed the prevalence and importance of these strategies for root-herbivore interactions across different plant species.\nC_LIO_LIHere, we characterize the defense strategies used by three different grassland species to cope with a generalist root herbivore, the larvae of the European cockchafer Melolontha melolontha.\nC_LIO_LIOur results reveal that the different plant species rely on distinct sets of defense strategies. The spotted knapweed (Centaurea stoebe) resists attack by dissuading the larvae through the release of repellent chemicals. White clover (Trifolium repens) does not repel the herbivore, but reduces feeding, most likely through structural defenses and low nutritional quality. Finally, the common dandelion (Taraxacum officinale) allows M. melolontha to feed abundantly but compensates for tissue loss through induced regrowth.\nC_LIO_LISynthesis: Three co-occurring plant species have evolved different solutions to defend themselves against attack by a generalist root herbivore. The different root defense strategies may reflect distinct defense syndromes.\nC_LI

ecology↗
bioRxiv2019

Conserving unprotected important coastal habitats in the Yellow Sea: shorebird occurrence, distribution and food resources at Lianyungang

The authors have withdrawn their manuscript since this preprint contain errors which have been corrected in the version published in the journal Global Ecology and Conservation (doi: 10.1016/j.gecco.2019.e00724). Therefore, the authors do not wish this preprint to be cited as reference for the project. If you have any questions, please contact the corresponding author.

ecology↗
bioRxiv2019

Changes in the Physicochemical Properties and Microbial Communities of Rhizospheric Soil after Cassava/Peanut Intercropping

Cassava/peanut intercropping is a popular cultivation method in southern China and has the advantages of apparently increased yield and economic efficiency compared with monoculture, however, the ecological benefits of this method are poorly understood. This study aimed to investigate the effects of intercropping on the physicochemical properties and microbial community structures of soil. Field trials were performed to determine the effects of cassava/peanut intercropping on rhizospheric soil nutrient content, enzyme activities, microbial quantity and microbial community structure. The microbial community was characterized by 16S rRNA tag-based high-throughput sequencing on the Illumina MiSeq platform. Results showed that cassava/peanut intercropping could improve the physicochemical properties of rhizospheric soil by increasing the available nutrient content, pH, bacterial quantity, and some enzyme activities and by altering the microbial community structure. 16S rRNA gene sequencing demonstrated that the microbial community structure varied between the intercropping and monoculture systems. Nitrospirae, Verrucomicrobia and Gemmatimonadetes were more abundant in the intercropping system than in the monocultures. Redundancy analysis (RDA) revealed that the abundances of DA101, Pilimelia and Ramlibacter were positively correlated with environmental parameters such as available nitrogen and pH, and these were dominant genera in the rhizospheric soil of the intercropped peanut plants.

ecology↗
bioRxiv2019

An experimental manipulation of species’ phenologies overturns competitive hierarchies

Ecological theory produces opposing predictions about whether differences in the timing of life history transitions, or phenology, promote or limit coexistence. Phenological separation is predicted to create temporal niche differences, increasing coexistence, yet phenological separation may competitively favour one species, increasing fitness differences and hindering coexistence. We experimentally manipulated relative germination timing, a critical phenological event, of two annual grass species, Vulpia microstachys and V. octoflora, to test these contrasting predictions. We parameterized a competition model to estimate within-season niche differences, fitness differences, and coexistence, and to estimate coexistence when among-year fluctuations of germination timing occur. Increasing germination separation caused parallel changes in niche and fitness differences, with the net effect of weakening within-year coexistence. Both species experienced a competitive advantage by germinating earlier, strongly enough to allow the generally inferior competitor to exclude the other with at least a four day head start. The overall consequence of germination separation was to limit coexistence within a given year, although among-year variation in relative timing of germination was sufficient to support long-term coexistence. Our results clarify how phenological differences structure competitive interactions, and highlight the need to quantify among-year variation in these differences to better understand species coexistence.

ecology↗