Effects of increasing soil moisture on Antarctic desert microbial ecosystems.

Overgeneralization and a lack of baseline data for microorganisms in high-latitude environments have restricted the understanding of the microbial response to climate change, which is needed to establish Antarctic conservation frameworks. To bridge this gap, we examined over 17,000 sequence variants of bacteria and microeukarya across the hyperarid Vestfold Hills and Windmill Islands regions of eastern Antarctica. Using an extended gradient forest model, we quantified multispecies response to variations along 79 edaphic gradients to explore the effects of change and wind-driven dispersal on community dynamics under projected warming trends. We also analyzed a second set of soil community data from the Windmill Islands to test our predictions of major environmental tipping points. Soil moisture was the most robust predictor for shaping the regional soil microbiome; the highest rates of compositional turnover occurred at 10-12% soil moisture threshold for photoautotrophs, such as Cyanobacteria, Chlorophyta, and Ochrophyta. Dust profiles revealed a high dispersal propensity for Chlamydomonas, a microalga, and higher biomass was detected at trafficked research stations. This could signal the potential for algal blooms and increased nonendemic species dispersal as human activities increase in the region. Predicted increases in moisture availability on the Windmill Islands were accompanied by high photoautotroph abundances. Abundances of rare oligotrophic taxa, such as Eremiobacterota and Candidatus Dormibacterota, which play a crucial role in atmospheric chemosynthesis, declined over time. That photosynthetic taxa increased as soil moisture increased under a warming scenario suggests the potential for competition between primary production strategies and thus a more biotically driven ecosystem should the climate become milder. Better understanding of environmental triggers will aid conservation efforts, and it is crucial that long-term monitoring of our study sites be established for the protection of Antarctic desert ecosystems. Furthermore, the successful implementation of an improved gradient forest model presents an exciting opportunity to broaden its use on microbial systems globally.

Efectos del incremento de la humedad del suelo sobre los ecosistemas microbianos del desierto antártico Resumen La sobre generalización y la falta de datos de línea base de los microorganismos en los ambientes de latitudes elevadas han limitado el conocimiento de la respuesta microbiana al cambio climático, la cual es necesaria para establecer marcos de conservación en la Antártida. Para cerrar esta brecha analizamos más de 17,000 variantes de secuencias de bacterias y micro eucariontes de las regiones híper­áridas de las Colinas Vestfold y las Islas Windmill en el este de la Antártida. Usamos un modelo de gradiente de bosque extendido para cuantificar la respuesta de múltiples especies a la variación de 79 gradientes edáficos y así explorar los efectos del cambio y la dispersión eólica sobre las dinámicas comunitarias bajo las tendencias proyectadas de calentamiento. También analizamos un segundo conjunto de datos de la comunidad del suelo de las Islas Windmill para probar nuestras predicciones de los principales puntos de inflexión ambiental. La humedad del suelo fue el pronóstico más sólido para la composición del microbioma del suelo regional; las tasas más altas de rotación composicional ocurrieron con el 10­12% de humedad del suelo para los fotoautótrofos, como Cyanobacteria, Chlorophyta, y Ochrophyta. Los perfiles de polvo revelaron una alta tendencia de dispersión para Chlamydomonas, una microalga, y detectamos una biomasa más alta en las estaciones de investigación con tráfico. Esto podría significar un potencial para el brote de algas y un incremento en la dispersión de especies no endémicas conforme las actividades humanas incrementan en la región. El incremento pronosticado de la humedad disponible en las Islas Windmill estuvo acompañado de una abundancia elevada de fotoautótrofos. Hubo una declinación con el tiempo en la abundancia de taxones raros, como Eremiobacterota y Ca. Dormibacterota, las cuales tienen un papel importante en la síntesis química de la atmósfera. Que exista un incremento de taxones fotosintéticos junto con el incremento de la humedad del suelo bajo un escenario de calentamiento sugiere un potencial de competencia entre las estrategias primarias de producción, y por lo tanto un ecosistema con más factores bióticos, si es que el clima se vuelve más templado. Un mejor entendimiento de los detonadores ambientales ayudará a los esfuerzos de conservación, además que es importante que se establezca el monitoreo a largo plazo de nuestros sitios de estudio para la protección de los ecosistemas del desierto de la Antártida. Más aún, la implementación exitosa de un modelo de gradiente de bosque mejorado representa una oportunidad emocionante para ampliar su uso en los sistemas microbianos de mundo.

Coupling temperature-dependent spatial turnover of microbes and plants using the metabolic theory of ecology.

There is an urgent need to understand the coupled relationship between belowground microbes and aboveground plants in response to temperature under climate change. The metabolic theory of ecology (MTE) provides a way to predict the metabolic rate and species diversity, but the spatial scale dependence and connections between plants and microorganisms are still unclear. Here, we used two independent datasets to address this question. One is from comprehensive sampling of paddy fields targeting bacteria and microbial functional genes, and the other is a global metadata of spatial turnover for microorganisms (bacteria, fungi and archaea, n = 139) and plants (n = 206). Results showed that spatial turnover of bacterial communities and microbial functional genes increased with temperature and fitted MTE. Through meta-analysis, the temperature-dependent spatial scale pattern was further extended to the global scale, with the spatial turnover of microorganisms and plants being consistent with MTE. Belowground microorganisms and aboveground plants were closely linked with each other even when controlling for temperature, suggesting that factors other than shared relationships with temperature also contribute to their linkages. These results implied a broad application of MTE in biology and have important implications for predicting the ecological consequences of future climate warming.

Spatial patterns and ecological drivers of soil nematode ß-diversity in natural grasslands vary among vegetation types and trophic position.

Understanding biogeographic patterns of community assemblages is a core objective in ecology, but for soil communities these patterns are poorly understood. To understand the spatial patterns and underlying mechanisms of ß-diversity in soil communities, we investigated the ß-diversity of soil nematode communities along a 3,200-km transect across semi-arid and arid grasslands. Spatial turnover and nested-resultant are the two fundamental components of ß-diversity, which have been attributed to various processes of community assembly. We calculated the spatial turnover and nested-resultant components of soil nematode ß-diversity based on the ß-partitioning framework. Distance matrices for the dissimilarity of soil nematode communities were computed using the 'Sørensen' method. We fitted negative exponential models to compare the distance decay patterns in nematode community similarity with geographic distance and plant community distance in three vegetation types (desert, desert steppe and typical steppe) and along the whole transect. Variation partitioning was used to distinguish the contribution of geographic distance and environmental variables to ß-diversity and the partitioned components. Geographic distance and environmental filtering jointly drove the ß-diversity patterns of nematode community, but environmental filtering explained more of the variation in ß-diversity in the desert and typical steppe, whereas geographic distance was important in the desert steppe. Nematode community assembly was explained more by the spatial turnover component than by the nested-resultant component. For nematode feeding groups, the ß-diversity in different vegetation types increased with geographic distance and plant community distance, but the nested-resultant component of bacterial feeders in the desert ecosystem decreased with geographic distance and plant community distance. Our findings show that spatial variation in soil nematode communities is regulated by environmental processes at the vegetation type scale, while spatial processes mainly work on the regional scale, and emphasize that the spatial patterns and drivers of nematode ß-diversity differ among trophic levels. Our study provides insight into the ecological processes that maintain soil biodiversity and biogeographic patterns of soil community assemblage at large spatial scales.

Phylogenetic delineation of regional biota: A case study of the Chinese flora.

Biogeographical regionalization schemes have traditionally been constructed based on taxonomic endemism of families, genera, and/or species, and rarely incorporated the phylogenetic relationships between taxa. However, phylogenetic relationships are important for understanding historical connections within and among biogeographical regions. Phylogeny-based delineation of biota is a burgeoning and fruitful field that is expected to provide novel insights into the conservation of regional diversity and the evolutionary history of biota. Using the Chinese flora as an example, we compared regionalization schemes that were based on: (1) taxonomic endemism, (2) taxonomic dissimilarity, and (3) phylogenetic dissimilarity. Our results revealed general consistency among different regionalization schemes and demonstrated that the phylogenetic dissimilarity approach is preferable for biogeographical regionalization studies. Using the phylogenetic dissimilarity approach, we identified five phytogeographical regions within China: the Paleotropic, Holarctic, East Asiatic, Tethyan, and Qinghai-Tibet Plateau Regions. The relationship of these regions was inferred to be: (Paleotropic, ((East Asiatic + Holarctic) + (Tethyan + Qinghai-Tibet Plateau)).

Elevated carbon dioxide accelerates the spatial turnover of soil microbial communities.

Although elevated CO2 (eCO2 ) significantly affects the α-diversity, composition, function, interaction and dynamics of soil microbial communities at the local scale, little is known about eCO2 impacts on the geographic distribution of micro-organisms regionally or globally. Here, we examined the ß-diversity of 110 soil microbial communities across six free air CO2 enrichment (FACE) experimental sites using a high-throughput functional gene array. The ß-diversity of soil microbial communities was significantly (P < 0.05) correlated with geographic distance under both CO2 conditions, but declined significantly (P < 0.05) faster at eCO2 with a slope of -0.0250 than at ambient CO2 (aCO2 ) with a slope of -0.0231 although it varied within each individual site, indicating that the spatial turnover rate of soil microbial communities was accelerated under eCO2 at a larger geographic scale (e.g. regionally). Both distance and soil properties significantly (P < 0.05) contributed to the observed microbial ß-diversity. This study provides new hypotheses for further understanding their assembly mechanisms that may be especially important as global CO2 continues to increase.

Measuring ß-diversity with species abundance data.

In 2003, 24 presence-absence ß-diversity metrics were reviewed and a number of trade-offs and redundancies identified. We present a parallel investigation into the performance of abundance-based metrics of ß-diversity. ß-diversity is a multi-faceted concept, central to spatial ecology. There are multiple metrics available to quantify it: the choice of metric is an important decision. We test 16 conceptual properties and two sampling properties of a ß-diversity metric: metrics should be 1) independent of α-diversity and 2) cumulative along a gradient of species turnover. Similarity should be 3) probabilistic when assemblages are independently and identically distributed. Metrics should have 4) a minimum of zero and increase monotonically with the degree of 5) species turnover, 6) decoupling of species ranks and 7) evenness differences. However, complete species turnover should always generate greater values of ß than extreme 8) rank shifts or 9) evenness differences. Metrics should 10) have a fixed upper limit, 11) symmetry (ßA,B  = ßB,A ), 12) double-zero asymmetry for double absences and double presences and 13) not decrease in a series of nested assemblages. Additionally, metrics should be independent of 14) species replication 15) the units of abundance and 16) differences in total abundance between sampling units. When samples are used to infer ß-diversity, metrics should be 1) independent of sample sizes and 2) independent of unequal sample sizes. We test 29 metrics for these properties and five 'personality' properties. Thirteen metrics were outperformed or equalled across all conceptual and sampling properties. Differences in sensitivity to species' abundance lead to a performance trade-off between sample size bias and the ability to detect turnover among rare species. In general, abundance-based metrics are substantially less biased in the face of undersampling, although the presence-absence metric, ßsim , performed well overall. Only ßBaselga R turn , ßBaselga B-C turn and ßsim measured purely species turnover and were independent of nestedness. Among the other metrics, sensitivity to nestedness varied >4-fold. Our results indicate large amounts of redundancy among existing ß-diversity metrics, whilst the estimation of unseen shared and unshared species is lacking and should be addressed in the design of new abundance-based metrics.

Phylogenetic Partitioning of Gansu Flora: Unveiling the Core Transitional Zone of Chinese Flora.

Floristic regions, conventionally established using species distribution patterns, have often overlooked the phylogenetic relationships among taxa. However, how phylogenetic relationships influence the historical interconnections within and among biogeographic regions remains inadequately understood. In this research, we compiled distribution data for seed plants in Gansu, a region of significant biogeographic diversity located in northwestern China.We proposed a novel framework for floristic regions within Gansu, integrating distribution data and phylogenetic relationships of genera-level native seed plants, aiming to explore the relationship between phylogenetic relatedness, taxonomic composition, and regional phylogenetic delineation. We found that (1) phylogenetic relatedness was strongly correlated with the taxonomic composition among floras in Gansu. (2) The southeastern Gansu region showed the lowest level of spatial turnover in both phylogenetic relationships and the taxonomic composition of floristic assemblages across the Gansu region. (3) Null model analyses indicated nonrandom phylogenetic structure across the region, where most areas showed higher phylogenetic turnover than expected given the underlying taxonomic composition between sites. (4) Our results demonstrated a consistent pattern across various regionalization schemes and highlighted the preference for employing the phylogenetic dissimilarity approach in biogeographical regionalization investigations. (5) Employing the phylogenetic dissimilarity approach, we identified nine distinct floristic regions in Gansu that are categorized into two broader geographical units, namely the northwest and southeast. (6) Based on the phylogenetic graphic regions of China across this area.

Spatial turnover of core and occasional bacterial taxa in the plastisphere from a plateau river, China.

Plastic surfaces in the environment are a comparatively new niche for microbial colonization, also known as the "plastisphere". However, our understanding of the core and occasional bacterial taxa in the plastisphere is limited. Here, environmental plastic, water, and sediment samples were collected from 10 sites in a plateau river (Lhasa River, China) in September of 2019. The composition and spatial turnover of core and occasional bacterial taxa in the plastisphere were revealed via 16S rRNA gene sequencing and compared with water and sediment. The results indicated that deterministic processes dominated the habitat specialization that shaped the formation of core and occasional taxa in the plastisphere, water, and sediment of the Lhasa River because the decline in zeta diversity in the plastisphere, water, and sediment was more fitted to a power-law form rather than an exponential form. Proteobacteria (65.9%), Bacteroidetes (16.0%), and Cyanobacteria (11.7%) dominated the plastic core taxa. Core taxa rather than occasional taxa in the plastisphere had a lower (21.7%) proportion of OTUs and a higher (81.7%) proportion of average relative abundance than water and sediment, which were dominant in plastic bacterial communities. The spatial turnover of core and occasional bacterial taxa in the plastisphere was governed by abiotic as well as biotic factors. Specifically, the spatial turnover of core taxa in the plastisphere with high connectivity but low functional redundancy was easily affected by geographical distance, altitude, and heavy metals. Furthermore, strong drug resistance was found in the spatially persistent core taxa in the plastisphere. This study provides empirical support for the spatial turnover (species variation) and potential ecological mechanisms of bacterial communities in the plastisphere from river ecosystems.

Functionally explicit partitioning of plant ß-diversity reveal soil fungal assembly in the subarctic tundra.

Metabarcoding technologies for soil fungal DNA pools have enabled to capture the diversity of fungal community and the agreement of their ß-diversity with plant ß-diversity. However, processes underlying the synchrony of the aboveground-belowground biodiversity is still unclear. By using partitioning methods for plant ß-diversity, this study explored the process driving synchrony in tundra ecosystems, in which drastic vegetation shifts are observed with climate warming. Our methods based on Baselga's partitioning enabled the division of plant ß-diversity into two phenomena and three functional components. Correlation of fungal ß-diversity with the components of plant ß-diversity showed that the spatial replacement of fungi was promoted by plant species turnover, in particular, plant species turnover with functional exchange. In addition, spatial variety of graminoid or forbs species, rather than shrubs, enhanced fungal ß-diversity. These results suggest the importance of small-scale factors such as plant-fungal interactions or local environments modified by plants for the fungal community assemblage. The process-based understanding of community dynamics of plants and fungi allows us to predict the ongoing shrub encroachment in the Arctic region, which could weaken the aboveground-belowground synchrony.

Plant-Soil Feedbacks and Temporal Dynamics of Plant Diversity-Productivity Relationships.

Plant-soil feedback (PSF) and diversity-productivity relationships are important research fields to study drivers and consequences of changes in plant biodiversity. While studies suggest that positive plant diversity-productivity relationships can be explained by variation in PSF in diverse plant communities, key questions on their temporal relationships remain. Here, we discuss three processes that change PSF over time in diverse plant communities, and their effects on temporal dynamics of diversity-productivity relationships: spatial redistribution and changes in dominance of plant species; phenotypic shifts in plant traits; and dilution of soil pathogens and increase in soil mutualists. Disentangling these processes in plant diversity experiments will yield new insights into how plant diversity-productivity relationships change over time.

Seasonality in Spatial Turnover of Bacterioplankton Along an Ecological Gradient in the East China Sea: Biogeographic Patterns, Processes and Drivers.

Seasonal succession in bacterioplankton is a common process in marine waters. However, seasonality in their spatial turnover is largely unknown. Here, we investigated spatial turnover of surface bacterioplankton along a nearshore-to-offshore gradient in the East China Sea across four seasons. Although seasonality overwhelmed spatial variability of bacterioplankton composition, we found significant spatial turnover of bacterioplankton along the gradient as well as overall seasonal consistency in biogeographic patterns (including distance-decay relationship and covariation of community composition with distance to shore) with subtle changes. Bacterioplankton assembly was consistently dominated by deterministic mechanisms across seasons, with changes in specific processes. We found overall seasonal consistency in abiotic factors (mainly salinity and nitrogen and phosphorus nutrients) shaping bacterioplankton composition, while phytoplankton showed a similar influence as abiotic factors only in spring. Although key taxa responsible for bacterioplankton spatial turnover showed certain season-specificity, seasonal switching between closely related taxa occurred within most dominant families. Moreover, many close relatives showed different responding patterns to the environmental gradients in different seasons, suggesting their differences in both seasonally climatic and spatially environmental preferences. Our results provide insights into seasonal consistency and variability in spatial turnover of bacterioplankton in terms of biogeographic patterns, ecological processes, and external and internal drivers.

Dramatic impact of metric choice on biogeographical regionalization.

For a quantitative biogeographical regionalization, the choice of an appropriate dissimilarity index to measure pairwise distances is crucial. Several different metrics have been used, but there is no specific study to test the impact of metric choice on biogeographical regionalization. We herein applied a hierarchical cluster analysis on the mean nearest taxon distance (MNTD) and the phylogenetic turnover component of the Sørensen dissimilarity index (pßsim) pairwise distances to generate two schemes of phylogenetic regionalization of the Chinese flora, and then evaluated the effect of metric choice. Floristic regionalization based on MNTD was influenced by richness differences, but regionalization based on pßsim can clearly reflect the evolutionary history of the Chinese flora. We provided a brief description of the five regions identified by pßsim, and the regionalization can help develop strategies to effectively conserve the taxa and floristic regions with different origins and evolutionary histories.

Plant species richness and composition of a habitat island within Lake Kastoria and comparison with those of a true island within the protected Pamvotis lake (NW Greece).

Lake Kastoria is one of the potentially "ancient" Balkan lakes that has a great environmental importance and ecological value, attracts high touristic interest and is under various anthropogenic pressures. It belongs to a Natura 2000 Special Protection Area and a Site of Community Interest. The city of Kastoria is located at the western part of the lake and just next to it, towards the centre of the lake, is a peninsula, a habitat island. In the framework of research concerning the flora of lake islands of Greece, one of the main objectives of the present study is to fill a gap concerning plant species richness of the habitat island within the protected Lake Kastoria, which is surrounded by the lake except for its north-western part where the border of the city of Kastoria is located. Floristic analysis of the habitat island of Lake Kastoria is in large measure accounted, concerning chorology with emphasis on Balkan endemics (8.7%), life forms, by hemicryptophytes (36.1%), therophytes (33.2%), phanerophytes (16.4%) and geophytes (10.9%) and, for habitats, by taxa preferring agricultural and ruderal ones (53.3%). Another objective is to compare its floristic composition to the one of the island within the protected urban Lake Pamvotis - one of the very few lake islands in Greece - focusing on the influence of urbanisation. The α- and ß- diversity are measured in order to reveal floristic differences. Beta diversity partitioning in turnover and nestedness showed that the ß-diversity is mostly expressed as compositional turnover. The role of the society in combination with long-term programmes for the study of plant species richness, functional diversity and patterns of species assemblages over time are necessary for the effective management and protection of protected areas, including lake insular areas.

Patterns and drivers of species richness and turnover of neo-endemic and palaeo-endemic vascular plants in a Mediterranean hotspot: the case of Crete, Greece.

BACKGROUND: Exploring species richness and turnover patterns and their drivers can provide new insights into underlying mechanisms shaping community assembly, with significant implications for biodiversity conservation. Here, we explored diversity patterns of non-endemic, neo-endemic and palaeo-endemic vascular plants in Crete, Greece, a Mediterranean hotspot of plant richness and endemism. We evaluated the relationship between α-diversity and environmental (bioclimatic variables, topography), and anthropogenic variables by Generalized Additive Models, after accounting for spatial autocorrelation. Then, we quantified turnover using the novel concept of zeta diversity (the number of shared species by multiple sites), a framework which allows to explore the full spectrum of compositional turnover, the contribution of rare and widespread species to observed patterns and the underlying processes shaping them. Finally, we explored the abiotic and biotic effects, i.e. how well one category of species (non-endemics, palaeo-endemics, neo-endemics) predicts the patterns of the other categories, on zeta diversity by multi-site Generalized Dissimilarity Modelling. RESULTS: We found a strong correlation between neo-endemic and palaeo-endemic α-diversity, with climate, topography, and human impact driving species richness. Zeta diversity analysis revealed a sharper decrease of shared palaeo-endemic species, followed by neo-endemics, and then by non-endemics with the number of sites considered to estimate compositional turnover. Perhaps, the narrow distributions of palaeo-endemics as relict species and often habitat specialists, thus persisting locally, and of neo-endemics that may have not reached yet their potential geographical range, resulted in the observed zeta diversity decline pattern. Deterministic processes controlled species turnover of rare non-endemic and neo-endemic species, while deterministic and stochastic processes contributed similarly to palaeo-endemic turnover. However, stochasticity dominates in the case of widespread species in all occasions. The environmental and anthropogenic variables were poor predictors of compositional turnover, especially of widespread species. However, the non-endemic species composition was correlated to rare palaeo-endemics and neo-endemics, highlighting the importance of biotic effects in driving turnover patterns. CONCLUSIONS: It seems that centers of neo-endemism of vascular plants coincide with centers of palaeo-endemism in Crete, but species richness and species turnover are shaped by different drivers.

Longitudinal changes of clavarioid funga (Basidiomycota) diversity in the tundra zone of Eurasia.

The study deals with certain variations of the diversity level of clavarioid funga in the 33 localities (100 km2 each) inside seven longitudinal sectors (100,000 km2) situated along the gradient of the climatic continentality of the Eurasian tundra zone. As continentality increases, from the maritime climate of Fennoscandia to the continental climate of Yakutia, α-diversity and γ-diversity decrease considerably. On the other side, spatial turnover of species, or ß-diversity, grows in the direction of continental areas. This paper uses the following methods to assess the spatial turnover: Whittaker's index and mean Jaccard similarity index, as well as by several other parameters. In addition, our data show that the genus Typhula is richest in the tundra, and its share in the structure of the clavarioid funga grows as the studied area decreases, as well as when the environmental conditions become more severe (continentality of the climate). Also, the paper discusses the issue of newly emerging taiga fungi species in the European Arctic, which is connected with climatic warming followed by ″greening″ of the tundra. Note that in the cryo-semiarid continental climate of Yakutia, where climatic changes are just as pronounced, no new taxons have been discovered so far.

Are all species necessary to reveal ecologically important patterns?

While studying ecological patterns at large scales, ecologists are often unable to identify all collections, forcing them to either omit these unidentified records entirely, without knowing the effect of this, or pursue very costly and time-consuming efforts for identifying them. These "indets" may be of critical importance, but as yet, their impact on the reliability of ecological analyses is poorly known. We investigated the consequence of omitting the unidentified records and provide an explanation for the results. We used three large-scale independent datasets, (Guyana/ Suriname, French Guiana, Ecuador) each consisting of records having been identified to a valid species name (identified morpho-species - IMS) and a number of unidentified records (unidentified morpho-species - UMS). A subset was created for each dataset containing only the IMS, which was compared with the complete dataset containing all morpho-species (AMS: = IMS + UMS) for the following analyses: species diversity (Fisher's alpha), similarity of species composition, Mantel test and ordination (NMDS). In addition, we also simulated an even larger number of unidentified records for all three datasets and analyzed the agreement between similarities again with these simulated datasets. For all analyses, results were extremely similar when using the complete datasets or the truncated subsets. IMS predicted ≥91% of the variation in AMS in all tests/analyses. Even when simulating a larger fraction of UMS, IMS predicted the results for AMS rather well. Using only IMS also out-performed using higher taxon data (genus-level identification) for similarity analyses. Finding a high congruence for all analyses when using IMS rather than AMS suggests that patterns of similarity and composition are very robust. In other words, having a large number of unidentified species in a dataset may not affect our conclusions as much as is often thought.