Protist diversity on a nature reserve in NW England − with particular reference to their role in soil biogenic silicon pools

Soil protists play fundamental roles in many earth system processes, yet we are only beginning to understand the true diversity of the organisms involved. In this study we used conventional (microscopy-based) methods to characterise the diversity and estimate protist population sizes in soils from a variety of distinct habitats within Mere Sands Wood nature reserve in NW England. We produced population size data for over ninety soil protists belonging to two major eukaryotic functional groups: testate amoebae (TA) and diatoms, adding substantial ‘cryptic diversity’ to the nature reserves recorded biota. From these population size data we estimated relative contributions of TA and diatoms to soil biogenic silicon (BSi) pools and found significant correlations between taxon richness and the TA and diatom Si pool. This could indicate that protist functional diversity can influence terrestrial BSi pools, especially in early successional plant communities where TA and diatoms can potentially increase Si mineralisation and/or create Si ‘hot spots’ and hence, the biological availability of this element for subsequent plant uptake. TA were particularly abundant in mor humus type soils further supporting the idea that they could be important players in nutrient cycling in such soils. Overall, we demonstrate this is a useful approach in order to start to attempt to estimate the role of protists in the Si cycle and other ecological processes

The Mass-Radius(-Rotation?) Relation for Low-Mass Stars

The fundamental properties of low-mass stars are not as well understood as those of their more massive counterparts. The best method for constraining these properties, especially masses and radii, is to study eclipsing binary systems, but only a small number of late-type (M0 or later) systems have been identified and well-characterized to date. We present the discovery and characterization of six new M dwarf eclipsing binary systems. The twelve stars in these eclipsing systems have masses spanning 0.38-0.59 Msun and orbital periods of 0.6--1.7 days, with typical uncertainties of ~0.3% in mass and 0.5--2.0% in radius. Combined with six known systems with high-precision measurements, our results reveal an intriguing trend in the low-mass regime. For stars with M=0.35-0.80 Msun, components in short-period binary systems (P<1 day; 12 stars) have radii which are inflated by up to 10% (mean=4.8+/-1.0%) with respect to evolutionary models for low-mass main-sequence stars, whereas components in longer-period systems (>1.5 days; 12 stars) tend to have smaller radii (mean=1.7+/-0.7%). This trend supports the hypothesis that short-period systems are inflated by the influence of the close companion, most likely because they are tidally locked into very high rotation speeds that enhance activity and inhibit convection. In summary, very close binary systems are not representative of typical M dwarfs, but our results for longer-period systems indicate that the evolutionary models are broadly valid in the M~0.35-0.80 Msun regime.Comment: Accepted to ApJ; 21 pages, 10 figures, 8 tables in emulateapj format. The full contents of Table 4 are included in the submission as tab4.tx

Constructing the first comorbidity networks in companion dogs in the Dog Aging Project

Comorbidity and its association with age are of great interest in geroscience. However, there are few model organisms that are well-suited to study comorbidities that will have high relevance to humans. In this light, we turn our attention to the companion dog. The companion dog shares many morbidities with humans. Thus, a better understanding of canine comorbidity relationships could benefit both humans and dogs. We present an analysis of canine comorbidity networks from the Dog Aging Project, a large epidemiological cohort study of companion dogs in the United States. We included owner-reported health conditions that occurred in at least 60 dogs (n = 160) and included only dogs that had at least one of those health conditions (n = 26,614). We constructed an undirected comorbidity network using a Poisson binomial test, adjusting for age, sex, sterilization status, breed background (i.e., purebred vs. mixed-breed), and weight. The comorbidity network reveals well-documented comorbidities, such as diabetes with cataracts and blindness, and hypertension with chronic kidney disease (CKD). In addition, this network also supports less well-studied comorbidity relationships, such as proteinuria with anemia. A directed comorbidity network accounting for time of reported condition onset suggests that diabetes precedes cataracts, elbow/hip dysplasia before osteoarthritis, and keratoconjunctivitis sicca before corneal ulcer, which are consistent with the canine literature. Analysis of age-stratified networks reveals that global centrality measures increase with age and are the highest in the Senior group compared to the Young Adult and Mature Adult groups. Only the Senior group identified the association between hypertension and CKD. Our results suggest that comorbidity network analysis is a promising method to enhance clinical knowledge and canine healthcare management

Do Female Dogs Age Differently Than Male Dogs?

Humans, as well as their closest ancestors, the higher African primates, exhibit female-biased survival and multiple sex differences in causes of death. However, the effects of sex on aging and longevity in an excellent model of human health, the companion dog, have not been well explored. Using two large independent databases on companion dog longevity and causes of death, we performed the most extensive analysis of sex differences in dog aging to date. Unlike the findings in humans, we observed only a small effect of sex on canine longevity. When broken down by neutering status, we discovered a small male advantage in survival among intact dogs but a clear female survival advantage among neutered dogs. Overall, the effect of neutering on life span was greater than the effect of sex. However, we found few sex differences in causes of death in either intact or neutered dogs. The results of this study suggest limited sex effects on either longevity or causes of death in the companion dog. Our analysis suggests that the majority of apparent sex differences in the wider canine populations may be due to the effects of neutering

Microbial diversity of a nature reserve: eukaryotic microorganisms of Mere Sands Wood in N.W. England

The idea of incorporating eukaryotic microorganisms into biological surveys is a new idea in nature conservation. Using Testate amoebae and Diatoms as model organisms, this study aimed at expanding the Wildlife Trust’s knowledge of biodiversity at its Mere Sands Wood Nature Reserve by describing and quantifying microbial diversity and distribution using traditional protist taxonomy based on morphology. The methods employed were similar to that adopted in the studies of macroscopic organisms, allowing for a comparison between the diversity of microscopic and previously studied macroscopic organisms.The results of this study highlighted the dramatic increase in species richness estimates by incorporating just two groups of eukaryotic microorganisms. Species richness was a useful measure of diversity and these results were largely consistent with diversity indices. Terrestrial soil and lake sediment microhabitats supported distinct assemblages of testate amoebae and diatom communities which enabled inferences to be made about the potential factors influencing microbial diversity and distribution in terrestrial and aquatic habitats. Lower microbial diversity was found in lake sediment associated with invasive aquatic plants and native monocultures. Taxon richness and diversity varied between different microhabitats and also at the replicate scale within a 1m2 quadrat, further highlighting the small-scale variability in microbial communities. The lack of correlation between different microbial groups demonstrated the complexities in understanding the structure of microbial communities. The relationship between species and genus richness highlighted the potential for using surrogate measures for future rapid biodiversity surveys.The use of evolutionary life strategies in protists is an area for future study which may provide useful insights into nature conservation management for microscopic organisms in habitats prone to disturbance and stress. This study illustrates the potential for incorporating eukaryotic microorganisms into biodiversity surveys. It would be useful to extend this research to other nature reserves and representative habitats using a nested design, facilitating replication and randomisation

Control of subsidiary HRM Policies by Multi-national Corporate Headquarters: The Role of Institutional Differences and Labor Unions

There is a lack of clarity about the institutional sources of variation in the control of multi-national enterprise (MNE) subsidiaries by corporate headquarters (CHQ). Applying comparative institutional theory, we focus on the control of HRM policies by CHQ. First, we argue that when there are substantial home-host institutional differences in national employment protection regulation the dissimilarity in CHQ-subsidiary mindsets increases the likelihood of CHQ control. Second, we argue that union influence within the subsidiary amplifies that effect. We analyze a sample of 708 MNE subsidiaries in 32 countries with CHQs distributed across 39 countries. Unlike some prior work on subsidiary autonomy, we account for the multi-level nature of country and firm-level data. The evidence for the first of our arguments is mixed. However, in that we find a significant three-way interaction effect of CHQ control on home country and host country employment protection regulation and union influence, the second argument finds suppor

The Past, Present and Future of Soil Protist Ecology

This essay introduces the special issue of this journal on the ecology of soil protists. This issue marks approximately the first 100 years of soil protistology as a discipline as some of the first studies to show that protozoa were an important part of soil ecology took place at Rothamsted, in southern England, towards the end of the first decade of the twentieth century. Much of the work on soil protists – and indeed the papers in this special issue – concentrate on traditional protozoa. In addition it is now realised that slime molds (Eumycetozoans) can potentially make an important contribution to the numbers and diversity of soil amoebae. We also argue that diatoms and other algae are likely important in soils and in need of more detailed study. By its nature microbiology (including soil protist ecology) is a science limited by technology – for example the subject could not really exist before the invention of the microscope. We suggest ways in which newer technologies (molecular methods, stable isotopes etc) may contribute to future studies on the ecology of soil protists

Testate amoebae as functionally significant bioindicators in forest-to-bog restoration

In north-west Europe, large areas of open peatland have been drained and planted with spatially homogenous stands of non-native conifers. The detrimental impact of afforestation on peatland carbon and biodiversity have led to large-scale attempts to restore these landscapes back to their open, tree-less form. The responses of dominant microbial consumers - testate amoebae - to peatland forest-to-bog restoration are largely unexplored. We studied changes in testate amoebae with forest-to-bog restoration in the largest expanse of blanket bog in the UK and compared testate amoeba communities in relatively undisturbed open bog with forested and forest-to-bog restoration sites. Forested areas contained testate amoeba communities which were functionally different from open bog, characterised by a lack of mixotrophic taxa known to contribute to primary production. Seventeen years after restoration management, the microbial communities in the forest-to-bog sites remained more similar to forested areas than to the open bog community. Our results suggest that afforestation has reduced the trophic level of testate amoeba communities, which are only beginning to recover post-restoration in the wettest areas where Sphagnum has re-colonized. This study also highlights the need to consider a wide-range of reference sites to encompass the natural variability within ombrotrophic blanket bog. We conclude that testate amoebae have the potential to act as functionally-significant bio-indicators in peatlands undergoing forest-to-bog restoration