Microbial ecosystems are dominated by specialist taxa

Abundance and specificity are two key characteristics of species distribution and biodiversity. Theories of species assembly aim to reproduce the empirical joint patterns of specificity and abundance, with the goal to explain patterns of biodiversity across habitats. The specialist‐generalist paradigm predicts that specialists should have a local advantage over generalists and thus be more abundant. We developed a specificity index to analyse abundance–specificity relationships in microbial ecosystems. By analysing microbiota spanning 23 habitats from three very different data sets covering a wide range of sequencing depths and environmental conditions, we find that habitats are consistently dominated by specialist taxa, resulting in a strong, positive correlation between abundance and specificity. This finding is consistent over several levels of taxonomic aggregation and robust to errors in abundance measures. The relationship explains why shallow sequencing captures similar β‐diversity as deep sequencing, and can be sufficient to capture the habitat‐specific functions of microbial communities.     

The biogeographic history of Phoenicurus redstarts reveals an allopatric mode of speciation and an out-of-Himalayas colonization pattern

Montane areas host high levels of diversity and endemism, and these features are tied to habitat stratification along an elevational gradient. As such, montane areas are often thought of as model systems in which sympatric speciation can occur. To test this idea, we selected Phoenicurus redstarts, an avian genus with an extensive distribution across Eurasia, as well as Northwest Africa; nine of the 14 species in the genus have distributions which include the Himalayas. We used sequences of the mtDNA ND2 and cytochrome-b genes and intron 9 of the Z chromosome specific ACO1 gene to reconstruct a phylogeny of the genus. The resulting trees were used to reconstruct a biogeographic history of Phoenicurus, and to date diversification events. We also analysed the relationship between node age and sympatry to determine the geographic mode of speciation in the genus. Our data suggest a very late Miocene, Himalayan origin for Phoenicurus. Diversification and colonization of other parts of Eurasia, as well as Northwest Africa, continued through the Pleistocene, with a rapid pulse of speciation in the late Pliocene. Allopatric speciation was the dominant mode of speciation in Phoenicurus, despite extensive distributional overlaps in the Himalayas where ecological conditions are amenable to speciation in sympatry. Our results, along with several other studies, suggest an emerging pattern where the Himalayas served as a source area for montane specialist avian lineages that subsequently colonized other Palaearctic regions.     

Influence of geographical extent on typology- and model-based assessments of taxonomic completeness of river macroinvertebrates

1. River InVertebrate Prediction and Classification System (RIVPACS)‐type predictive models are increasingly used to assess the biological condition of freshwaters, but management schemes may also be based on a priori groupings of similar water bodies (typologies) to control for natural variation in biota. The two approaches may lead to disagreements of the biological status of a site, depending on, for example, the spatial scale at which assessments are conducted. 2. We used data from 96 reference and 134 potentially impacted sites from Western and Central Finland to compare RIVPACS‐type models and a simple size‐based typology of rivers for the assessment of taxonomic completeness (the quotient of the Observed‐to‐Expected number of predicted taxa, O / E) of riffle macroinvertebrates. We specifically examined how geographical extent influences bioassessment performance (accuracy, precision and sensitivity to detect impact) of the two approaches. To fully examine the behaviour of the O / E‐index with the two approaches at differing spatial scales, we performed all assessments with a full range of thresholds for predicted taxa occurrence probabilities (p_t from 0+ to 0.9). 3. Both approaches performed consistently better than the corresponding null models. At the larger extent (i.e. assessment encompassing the whole study area), the RIVPACS‐approach performed in all aspects better than the typology‐approach. However, at the smaller extent (i.e. regional assessments) the RIVPACS‐type models and the typologies showed similar accuracy to predict the actual fauna (mean E), similar precision (SD) of cross‐validated O / E and similar sensitivity to detect sites with human impairment. 4. SD(O / E) decreased (i.e. precision increased) consistently with increasing p_t. However, both approaches were most sensitive at intermediate p_t:s (c. 0.2–0.6) when taxa with low predicted occurrence probabilities were excluded. 5. Our results show that RIVPACS‐type predictive models are less susceptible to variations in spatial scale, whereas the performance of a priori typologies increases with decreasing spatial extent. Thus, RIVPACS‐type models are more efficient for large‐scale bioassessments, but at restricted spatial scales, or with an otherwise biologically meaningful stratification, simple a priori classifications can be equally useful for the assessment of taxonomic completeness of river macroinvertebrates.     

NEW MURID RODENTS FROM THE LATE CENOZOIC OF YUSHE BASIN, SHANXI

<正> As scientific collaborators of the Chinese-American joint project "Neogene Rocks and Faunas, Yushe Basin, Shanxi, PRC", the present authors, with William R. Downs, Northern Arizona University, sampled the Yushe microfauna in the fall of 1987 and 1988. The fossil temains were retrieved by surface collection and by wet-sieving bulk quantities of sediment.     

Barks of Three Wild Pyrus Taxa: Phenolic Constituents,Antioxidant Activity,and in Vitro and in Silico Investigations of α-Amylase and α-Glucosidase Inhibition

Dry MeOH extracts of the twig barks of Pyrus communis subsp. pyraster, P. spinosa and their hybrid P.×jordanovii nothosubsp. velenovskyi, collected in wild in Serbia, were analyzed. By LC/MS, the contents of arbutin (99.9–131.0 mg/g), chlorogenic acid (2.2–6.3 mg/g), catechin (1.0–5.3 mg/g) and total dimeric and trimeric procyanidins (42.2–61.3 mg/g), including procyanidin B2 (8.9–17.2 mg/g), were determined. Colorimetrically, high contents of total phenolics (436.2–533.4 mg GAE/g) and tannins (339.4–425.7 mg GAE/g), as well as strong total antioxidant activities (FRAP values 4.5–5.9 mmol Fe²⁺/g), and DPPH (SC₅₀=6.6–7.1 μg/ml) and hydroxyl radical (SC₅₀=447.1–727.7 μg/ml) scavenging abilities were revealed. In vitro, all extracts exhibited notable inhibition of α-amylase (IC₅₀=310.8–617.7 μg/ml) and particularly strong inhibition of α-glucosidase (IC₅₀=2.1–3.7 μg/ml). Molecular docking predicted that among identified compounds procyanidin B2 is the best inhibitor of these carbohydrate-digesting enzymes. Obtained results showed that the barks of investigated Pyrus hybrid and its parent taxa have similar composition and bioactivity.     

Scaphidiidae (Coleoptera) of Fiji

Abstract

This paper describes 12 new species of Scaphidiidae from Fiji based on a collection made in October 1977 on the two main islands, Viti Levu and Vanua Levu. Three genera and 23 species are now known from Fiji: Baeocera Erichson (parallela n.sp., vanuana n.sp., plana n.sp., ovalis n.sp., kuscheli n.sp., gnava n.sp., ignobilis n.sp., kuscheliana n.sp., reducta n.sp., plus two species left unnamed); Scaphisoma Leach (kuscheli n.sp., liliputanum Löbl, distans Löbl, aequatum Löbl, zimmermani Löbl, debile n.sp., mucronatum n.sp., fijianum Löbl, alienum Löbl); and Scaphoxium Löbl (ventrale Löbl, malekulense Löbl, vitianum Löbl). Keys are given to genera and species.     

Some new African Milichiidae (Diptera: Cyclorrhapha) having pronounced sexual dimorphism of the frons

Enigmilkhia dimorphka gen. et sp. nov. and Milkhia distinctipennis, fumicoslata, savannaticola and sylvicola spp. nov. are described from tropical Africa. These forms, though belonging to different subfamilies, exhibit a very similar sexual dimorphism in the shape and chaetotaxy of the frons. Such a dimorphism is unknown within the Milichioidea.     

Nucleotide composition and CpG and CpNpG content of ITS1, ITS2, and the 5.8S rRNA in representatives of the phylogenetic branches melanthiales-liliales and melanthiales-asparagales (Angiospermae,Monocotyledones) reflect the specifics of their evolution

The nucleotide composition and the contents of CpG and CpNpG in internal transcribed spacers 1 and 2 (ITS1 and ITS2) and the 5.8S rRNA gene of the nuclear genome were studied in two phylogenetic lineages of monocotyledonous angiosperms. The evolutionary advance of taxa by morphological characters proved to positively correlate with an increase in the contents of C, CpG, and CpNpG, contrasting the views that genome evolution in vertebrate and higher plants tends to decrease or, at least, preserve the amount of CpG and CpNpG, potentially subject to methylation, in nuclear DNA. Cryptaffinity taxa, which are intermediates between morphologically distinct taxonomic groups, displayed higher contents of CpG and CpNpG as compared with neighboring taxa. Changes in the contents of these elements in the regions of cryptaffinity taxa are intricate, suggesting a reciprocating character for their accumulation. Cryptaffinity taxa and their close phylogenetic relatives from the ancestral and descendant groups were assumed to reflect the key macroevolutionary changes and to correspond to saltatory periods separating the periods of gradual evolution.     

A new pachyosteomorph arthrodire (Pisces: Placodermi) from the Upper Frasnian of the Central Devonian Field,Russia

A new genus and species of pachyosteomorph arthrodire, Omalosteus krutoensis gen. et sp. nov. from shallow-water marine deposits of the Evlanovo Regional Stage (Upper Frasnian, Upper Devonian) of the Central Devonian Field is described. It is tentatively referred to the family Trematosteidae Gross, 1932, which was earlier believed to be endemic to central Europe. The new genus is characterized by a rounded, dorsoventrally compressed cross section of the pectoral region and smooth head shield and postcranial membrane bones. The centrale is elongated, forming a narrow lateral lobe. The praeorbitale, postorbitale, and centrale come in contact in the center of the orbital region. The mediodorsale is wide, its carinal process projects considerably posteriorly. The anterior margin of the anterior ventrolaterale lacks articular facets for the interlaterale.