Circadian rhythms of hosts and their gut microbiomes: Implications for animal physiology and ecology

Daily light–dark cycles shape the circadian physiology and behaviour of nearly all organisms, with variation in circadian phenotypes having cascading effects on individual fitness, species interactions and species co‐evolution. Recent evidence that circadian rhythms in host immunity and metabolism are synchronised by the gut microbiota suggest that the circadian dynamics of gut microbes are a crucial component of their function. However, there remains little knowledge or understanding of the diurnal dynamics of gut microbiomes in natural populations or the consequences for host physiology and ecology. Here, we summarise the hallmarks of gut microbiota oscillations reported to date and the mechanisms by which they synchronise rhythms in host immunity and metabolism. We outline the consequences for diverse biological processes such as host pathogen susceptibility and seasonal switches in metabolism, and discuss how the breakdown of these circadian interactions, for example during senescence or because of light pollution, may affect wildlife infection risk and disease. We also provide practical guidelines for the measurement of microbial oscillations in wildlife, highlighting that whilst faecal samples of wild animals are rarely available over a 24‐h period, characterising even parts of the gut microbial cycle can be informative. An improved understanding of how gut microbial diurnal rhythms manifest in wildlife is essential to fully comprehend their role in shaping variation in host circadian phenotypes and the consequences for host physiology and ecology. Read the free Plain Language Summary for this article on the Journal blog

Host- plasmid network structure in wastewater is linked to antimicrobial resistance genes

As mobile genetic elements, plasmids are central for our understanding of antimicrobial resistance spread in microbial communities. Plasmids can have varying fitness effects on their host bacteria, which will markedly impact their role as antimicrobial resistance vectors. Using a plasmid population model, we first show that beneficial plasmids interact with a higher number of hosts than costly plasmids when embedded in a community with multiple hosts and plasmids. We then analyse the network of a natural host-plasmid wastewater community from a Hi-C metagenomics dataset. As predicted by the model, we find that antimicrobial resistance encoding plasmids, which are likely to have positive fitness effects on their hosts in wastewater, interact with more bacterial taxa than non-antimicrobial resistance plasmids and are disproportionally important for connecting the entire network compared to non- antimicrobial resistance plasmids. This highlights the role of antimicrobials in restructuring host-plasmid networks by increasing the benefits of antimicrobial resistance carrying plasmids, which can have consequences for the spread of antimicrobial resistance genes through microbial networks. Furthermore, that antimicrobial resistance encoding plasmids are associated with a broader range of hosts implies that they will be more robust to turnover of bacterial strains

Emerging Infectious Disease leads to Rapid Population Decline of Common British Birds

Emerging infectious diseases are increasingly cited as threats to wildlife, livestock and humans alike. They can threaten geographically isolated or critically endangered wildlife populations; however, relatively few studies have clearly demonstrated the extent to which emerging diseases can impact populations of common wildlife species. Here, we report the impact of an emerging protozoal disease on British populations of greenfinch Carduelis chloris and chaffinch Fringilla coelebs, two of the most common birds in Britain. Morphological and molecular analyses showed this to be due to Trichomonas gallinae. Trichomonosis emerged as a novel fatal disease of finches in Britain in 2005 and rapidly became epidemic within greenfinch, and to a lesser extent chaffinch, populations in 2006. By 2007, breeding populations of greenfinches and chaffinches in the geographic region of highest disease incidence had decreased by 35% and 21% respectively, representing mortality in excess of half a million birds. In contrast, declines were less pronounced or absent in these species in regions where the disease was found in intermediate or low incidence. Also, populations of dunnock Prunella modularis, which similarly feeds in gardens, but in which T. gallinae was rarely recorded, did not decline. This is the first trichomonosis epidemic reported in the scientific literature to negatively impact populations of free-ranging non-columbiform species, and such levels of mortality and decline due to an emerging infectious disease are unprecedented in British wild bird populations. This disease emergence event demonstrates the potential for a protozoan parasite to jump avian host taxonomic groups with dramatic effect over a short time period

Stable isotope analysis provides new information on winter habitat use of declining avian migrants that is relevant to their conservation

Winter habitat use and the magnitude of migratory connectivity are important parameters when assessing drivers of the marked declines in avian migrants. Such information is unavailable for most species. We use a stable isotope approach to assess these factors for three declining African-Eurasian migrants whose winter ecology is poorly known: wood warbler Phylloscopus sibilatrix, house martin Delichon urbicum and common swift Apus apus. Spatially segregated breeding wood warbler populations (sampled across a 800 km transect), house martins and common swifts (sampled across a 3,500 km transect) exhibited statistically identical intra-specific carbon and nitrogen isotope ratios in winter grown feathers. Such patterns are compatible with a high degree of migratory connectivity, but could arise if species use isotopically similar resources at different locations. Wood warbler carbon isotope ratios are more depleted than typical for African-Eurasian migrants and are compatible with use of moist lowland forest. The very limited variance in these ratios indicates specialisation on isotopically restricted resources, which may drive the similarity in wood warbler populations' stable isotope ratios and increase susceptibility to environmental change within its wintering grounds. House martins were previously considered to primarily use moist montane forest during the winter, but this seems unlikely given the enriched nature of their carbon isotope ratios. House martins use a narrower isotopic range of resources than the common swift, indicative of increased specialisation or a relatively limited wintering range; both factors could increase house martins' vulnerability to environmental change. The marked variance in isotope ratios within each common swift population contributes to the lack of population specific signatures and indicates that the species is less vulnerable to environmental change in sub-Saharan Africa than our other focal species. Our findings demonstrate how stable isotope research can contribute to understanding avian migrants' winter ecology and conservation status

A Comparison of the Effects of Child Management and Planned Activities Training in Five Parenting Environments

This study compared the effects of two procedures designed to enhance the extra training effects of behavioral parent training. Twenty parents of oppositional children were randomly assigned to either a child management training condition or a combined child management plus planned activities condition. A further 10 non-problem children and their parents served as a social validation group. Observations of both parent and child behavior were conducted in each of five home observation settings (breakfast time, kindy (kindergarten) or school exit, a structured playtime, bathtime, and bedtime). Both training procedures resulted in changes in both child oppositional and parent aversive behavior in all observation settings. In addition, desired positive parenting behaviors also improved in all settings. Treatment effects were maintained in all settings at 3-month follow-up. Comparisons between oppositional children following treatment and children in the social validation group showed that they each displayed similarly low levels of oppositional behavior in all settings. The implications of the results for facilitating generalized changes in behavioral parent training are discussed

Earth security in the Indian Ocean region

Melissa Risely and Timothy Doyl

The essence of life - water security in the Indian Ocean

http://trove.nla.gov.au/work/827432