The Distribution and Turnover of Bacterial Communities in the Root Zone of Seven Stipa Species Across an Arid and Semi-arid Steppe

The bacterial communities of the root-zone soil are capable of regulating vital biogeochemical cycles and the succession of plant growth. Stipa as grassland constructive species is restricted by the difference features of east–west humidity and north–south heat, which shows the population substituting distribution. The distribution, turnover, and potential driving factors and ecological significance of the root-zone bacterial community along broad spatial gradients of Stipa taxa transition remain unclear. This paper investigated seven Stipa species root-zone soils based on high-throughput sequencing combined with the measurements of multiple environmental parameters in arid and semi-arid steppe. The communities of soil bacteria in root zone had considerable turnover, and some regular variations in structure along the Stipa taxa transition are largely determined by climatic factors, vegetation coverage, and pH at a regional scale. Bacterial communities had a clear Stipa population specificity, but they were more strongly affected by the main annual precipitation, which resulted in a biogeographical distribution pattern along precipitation gradient, among which Actinobacteria, Acidobacteria, Proteobacteria, and Chloroflexi were the phyla that were most abundant. During the transformation of Stipa taxa from east to west, the trend of diversity shown by bacterial community in the root zone decreased first, and then increased sharply at S. breviflora, which was followed by continuous decreasing toward northwest afterwards. However, the richness and evenness showed an opposite trend, and α diversity had close association with altitude and pH. There would be specific and different bacterial taxa interactions in different Stipa species, in which S. krylovii had the simplest and most stable interaction network with the strongest resistance to the environment and S. breviflora had most complex and erratic. Moreover, the bacterial community was mainly affected by dispersal limitation at a certain period. These results are conducive to the prediction of sustainable ecosystem services and protection of microbial resources in a semi-arid grassland ecosystem.

An annotated checklist of groundwater Cyclopoida and Harpacticoida (Crustacea, Copepoda) from Romania with notes on their distribution and ecology

Romania, by its position in East-Central Europe has a complex geological history, high landscape heterogeneity and variable climatic conditions, ranging from temperate-continental in the northeast to sub-Mediterranean in the southwest. These conditions have created repeated waves of colonisation of groundwater by copepods, which raise particular interest in this group from a biogeographical perspective. The earliest investigations on groundwater copepods, dating back to the beginning of the 19th century, have resulted in a wealth of information on the richness of this group, making Romania one of the best studied regions from this perspective in Europe. Groundwater copepods in Romania are currently represented by 107 species and subspecies, of which 60 are harpacticoids (56%) and 47 are cyclopoids (43.9%). Of these, 50.5% are strict stygobites (32.7% harpacticoids and 17.7% cyclopoids). Among stygobite copepods 29 species (35 harpacticoids and 19 cyclopoids) are endemic to the country. Almost 86% of the species are single-site endemics (single cave, or single hyporheic or phreatic site) and the rest are restricted in distribution to a single aquifer or hydrographic basin. The aim of the present checklist represents a significant contribution to the knowledge of groundwater copepods in Romania and provides a sound baseline for future comparative faunal studies focused on the affinities and origins of copepods and the analysis of their biogeographical distribution patterns at regional and continental scales.

Seasonal cellular stress phenomena and phenotypic plasticity in land snail Helix lucorum (L.) populations from different altitudes

Temperature, a major abiotic environmental factor, regulates various physiological functions in land snails and therefore determines their biogeographical distribution. Thus, species with different distributions may present different thermal tolerance limits. Additionally, the intense reactivation of snail metabolic rate upon arousal from hibernation or aestivation may provoke stress. Land snails, Helix lucorum, display a wide altitudinal distribution resulting in populations being exposed to different seasonal temperature variations. The aim of the present study was to investigate the expression of heat shock proteins (Hsps), mitogen activated protein kinases (MAPKs) and proteins that are related to apoptosis (Bcl-2, ubiquitin), that have "cytoprotective" roles and are also considered to be reliable indicators of stress because of their crucial role at maintaining cellular homeostasis. These proteins were assessed in H. lucorum individuals from two different populations, one at Axios (sea level, 0m) and the other one at Kokkinopilos (Olympus, 1250 m), as well as after mutual population exchanges. Therefore, this study aimed to answer whether the different responses of these stress-related proteins depend solely on the environmental temperatures. The results of the present study showed seasonally altered levels in all studied proteins in the hepatopancreas and foot of snails, as much among different populations as between the same populations being exposed to varying altitudes. However, the changes between individuals of the same population acclimatized to a different habitat, showed a relatively similar pattern of expression supporting the induction of the specific proteins under the prism of the life history of each species.

Multisubstrate DNA stable isotope probing reveals guild structure of bacteria that mediate soil carbon cycling

Soil microorganisms determine the fate of soil organic matter (SOM), and their activities compose a major component of the global carbon (C) cycle. We employed a multisubstrate, DNA-stable isotope probing experiment to track bacterial assimilation of C derived from distinct sources that varied in bioavailability. This approach allowed us to measure microbial contributions to SOM processing by measuring the C assimilation dynamics of diverse microorganisms as they interacted within soil. We identified and tracked 1,286 bacterial taxa that assimilated 13C in an agricultural soil over a period of 48 d. Overall 13C-assimilation dynamics of bacterial taxa, defined by the source and timing of the 13C they assimilated, exhibited low phylogenetic conservation. We identified bacterial guilds composed of taxa that had similar 13C assimilation dynamics. We show that C-source bioavailability explained significant variation in both C mineralization dynamics and guild structure, and that the growth dynamics of bacterial guilds differed significantly in response to C addition. We also demonstrate that the guild structure explains significant variation in the biogeographical distribution of bacteria at continental and global scales. These results suggest that an understanding of in situ growth dynamics is essential for understanding microbial contributions to soil C cycling. We interpret these findings in the context of bacterial life history strategies and their relationship to terrestrial C cycling.

Adding pieces to the puzzle: insights into diversity and distribution patterns of Cumacea (Crustacea: Peracarida) from the deep North Atlantic to the Arctic Ocean

The Nordic Seas have one of the highest water-mass diversities in the world, yet large knowledge gaps exist in biodiversity structure and biogeographical distribution patterns of the deep macrobenthic fauna. This study focuses on the marine bottom-dwelling peracarid crustacean taxon Cumacea from northern waters, using a combined approach of morphological and molecular techniques to present one of the first insights into genetic variability of this taxon. In total, 947 specimens were assigned to 77 morphologically differing species, representing all seven known families from the North Atlantic. A total of 131 specimens were studied genetically (16S rRNA) and divided into 53 putative species by species delimitation methods (GMYC and ABGD). In most cases, morphological and molecular-genetic delimitation was fully congruent, highlighting the overall success and high quality of both approaches. Differences were due to eight instances resulting in either ecologically driven morphological diversification of species or morphologically cryptic species, uncovering hidden diversity. An interspecific genetic distance of at least 8% was observed with a clear barcoding gap for molecular delimitation of cumacean species. Combining these findings with data from public databases and specimens collected during different international expeditions revealed a change in the composition of taxa from a Northern Atlantic-boreal to an Arctic community. The Greenland-Iceland-Scotland-Ridge (GIS-Ridge) acts as a geographical barrier and/or predominate water masses correspond well with cumacean taxa dominance. A closer investigation on species level revealed occurrences across multiple ecoregions or patchy distributions within defined ecoregions.

New record of Myrmarachne melanocephala MacLeay, 1839 (Araneae: Salticidae) from Jharkhand, India and biogeographical implications of the co-occurrence of its ant model Tetraponera rufonigra Jerdon, 1851

We report the occurrence of the ant-mimicking jumping spider Myrmarachne melanocephala MacLeay, 1839 for the first time from Hazaribagh Wildlife Sanctuary, Jharkhand, India. Digital illustrations and descriptions of the spider, the female’s exuviae, and video records of a live male are also presented. The distribution pattern of M. melanocephala has not been studied in detail across India whereas its ant model, Tetraponera rufonigra Jerdon, 1851 is known to have a wide distribution. Co-occurrence of the mimic and the model implies a wider range of biogeographical distribution of these species in India.

Analysis of morphological characteristics and phenetic relationship of ebony (Diospyros spp.) in Indonesia

Rindyaastuti R, Hapsati L, Wibowo AT. 2021. Analysis of morphological characteristics and phenetic relationship of ebony (Diospyros spp.) in Indonesia. Biodiversitas 22: 2738-2753. Diospyros L. (Ebenaceae) is an economically important genus that covers over 500 plant species. Members of this group are known to produce hard, dark, high-quality timbers known as ebony trees, while other members are known as persimmon trees. There is limited information on the morphological characters and phenetic relationship of this genus from Indonesian archipelago. In this work, we reported the phenetic clustering of 14 species of Indonesian Diospyros, based on plant habit, stem, leaves, and fruit characters, which was analysed using UPGMA and Jaccard similarity index. The phenetic dendrogram divided the 14 species of Diospyros into two main clusters which separating Subgen. Maba and Eudiospyros. Further, subgen. Maba was clustered into a single cluster while subgen. Eudiospyros was divided into 3 sub-clusters as sister groups. The clustering in Eudiospyros was supported by low SI and bootstrap value, demonstrating the high morphological variation of the subgenus. The sectional separation of Diospyros spp. was considered as paraphyletic. In general, our phenetic clustering exhibited suitability and relevancy with previous classification. Fruit size and trichomes are very important in this phenetic clustering, especially to form Eudiospyros subgenus. Fruit trichomes were also special characters related to biogeographical distribution following the Wallace line theory.

Dominant associations of Ensifer medicae-Medicage polymorpha and Ensifer meliloti-Medicago lupulina in farmland and natural ecosystem

Aims The nitrogen-fixing rhizobia associated with Medicago polymorpha and M. lupulina in Yunnan, China have been poorly documented. This study aims to analyze the diversity of rhizobia isolated from these two Medicago species and investigate the impact of abiotic (soil properties) and biotic (plant hosts) factors on Medicago-associated rhizobia in this region. Methods 91 rhizobial isolates were characterized by RFLP of 16S rDNA and 16S–23S IGS, BOX-PCR fingerprinting, nodulation assays and phylogeny analyses based on housekeeping and symbiosis genes. The genetic diversity of the rhizobial isolates was assessed by the BOX AIR pattern and Shannon index. Additionally, the correlation of soil properties and rhizobial distribution was determined by the constrained analysis of principle coordinates (CAP) based on Bray-Curtis distance of presence/absence (PA) transformed species data. Results All the tested strains fell in the genus Ensifer and divided into two species, E. medicae and E. meliloti. Both host plants and soil properties contributed to the rhizobial diversity. For either E. meliloti or E. medicae, isolates from native host plants tended to be more genetically diverse than those of the same species from non-native hosts. The soil edaphic factor analysis elucidated that nitrogen, organic matter as well as Ca2+ and Na+ are the key factors to shape the biogeographical distribution of rhizobia. Conclusions This study evidenced the microsymbiont preference of M. polymorpha to E. medicae and M. lupulina to E. meliloti, but also revealed the considerable impacts of both plant hosts and soil factors on the rhizobial diversity and biodistribution.