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It is increasingly recognized that different genetic variants of hosts can uniquely shape their microbiomes. Invasive species often evolve in their introduced ranges, but little is known about the potential for their microbial associations to change during invasion as a result. We asked whether host genotype (G), microbial environment (E), or their interaction (G × E) affected the composition and diversity of host-associated microbiomes in Centaurea solstitialis (yellow starthistle), a Eurasian plant that is known to have evolved novel genotypes and phenotypes and to have altered microbial interactions, in its severe invasion of CA, USA. We conducted an experiment in which native and invading plant genotypes were inoculated with native and invaded range soil microbial communities. We used amplicon sequencing to characterize rhizosphere bacteria in both the experiment and the field soils from which they were derived. We found that native and invading plant genotypes accumulated different microbial associations at the family level in each soil community, often counter to differences in family abundance between soil communities. Root associations with potentially beneficial Streptomycetaceae were particularly interesting, as these were more abundant in the invaded range field soil and accumulated on invading genotypes. We also found that bacterial diversity is higher in invaded soils, but that invading genotypes accumulated a lower diversity of bacteria and unique microbial composition in experimental inoculations, relative to native genotypes. Thus variation in microbial associations of invaders was driven by the interaction of plant G and microbial E, and rhizosphere microbial communities appear to change in composition in response to host evolution during invasion. [ABSTRACT FROM AUTHOR]

Noise pollution is an unprecedented evolutionary pressure on wild animals that can lead to alteration of stress hormone levels and changes in foraging behavior. Both corticosterone and feeding behavior can have direct effects on gut bacteria, as well as indirect effects through changes in gut physiology. Therefore, we hypothesized that exposure to noise will alter gut microbial communities via indirect effects on glucocorticoids and foraging behaviors. We exposed captive white-crowned sparrows to city-like noise and measured each individuals' corticosterone level, food intake, and gut microbial diversity at the end of four treatments (acclimation, noise, recovery, and control) using a balanced repeated measures design. We found evidence that noise acts to increase corticosterone and decrease food intake, adding to a growing body of research indicating noise exposure affects stress hormone levels and foraging behaviors. We also found evidence to support our prediction for a causal, positive relationship between noise exposure and gut microbial diversity, such that birds had higher measures of alpha diversity during noise exposure. These results help to explain previous findings that urban, free-living white-crowned sparrows have higher bacterial richness than rural sparrows. However, noise appeared to act directly on the gut microbiome or, more likely, through an unmeasured variable, rather than through indirect effects via corticosterone and food intake. Altogether, our study indicates that noise affects plasma corticosterone, feeding behavior, and the gut microbiome in a songbird and raises new questions as to the mechanism linking noise exposure to gut microbial diversity. [ABSTRACT FROM AUTHOR]

Habitats are changing rapidly around the globe and urbanization is one of the primary drivers. Urbanization changes food availability, environmental stressors, and the prevalence of disease for many species. These changes can lead to divergence in phenotypic traits, including behavioral, physiological, and morphological features between urban and rural populations. Recent research highlights that urbanization is also changing the gut microbial communities found in a diverse group of host species. These changes have not been uniform, leaving uncertainty as to how urban habitats are shaping gut microbial communities. To better understand these effects, we investigated the gut bacterial communities of White-Crowned Sparrow (Zonotrichia leucophrys) populations along an urbanization gradient in the San Francisco Bay area. We examined how gut bacterial communities vary with the local environment and host morphological characteristics. We found direct effects of environmental factors, including urban noise levels and territory land cover, as well as indirect effects through body size and condition, on alpha and beta diversity of gut microbial communities. We also found that urban and rural birds' microbiomes differed in which variables predicted their diversity, with urban communities driven by host morphology, and rural communities driven by environmental factors. Elucidating these effects provides a better understanding of how urbanization affects wild avian physiology. [ABSTRACT FROM AUTHOR]

Gut microbial communities play critical roles in the biological functions of their host, such as mediating nutrient absorption, digesting food components the host cannot, and offering protection against enteric pathogens. Extensive research on gut microbial communities has been conducted on mammals, including humans and rodents, but much less work has been done in birds. Furthermore, much of the research on host–microbe interactions make use of faecal samples and rectal/cloacal swabs as a proxy for intestinal samples, which can be difficult to obtain directly. However, little is known about the overlap between the microbial communities of the gut, faeces and swabs, which limits interpretability of results based on faecal samples and swabs. To address this gap in knowledge, we compared the microbiome from five sample types – proventriculus, small intestine, large intestine, cloacal swabs and faeces – across individual Zebra Finches Taeniopygia guttata housed in constant conditions with a standardized diet. We compared diversity and community composition through 16S rRNA gene sequencing. Our results show that microbial communities from both cloacal swabs and faeces were distinct from proventriculus and small intestinal samples, but generally indistinguishable from large intestinal samples, indicating that these non‐lethal samples may be useful proxies for large intestinal bacterial communities. Gaining insight into non‐invasive sampling techniques for passerines has implications for studies of gut microbial diversity and abundance in wild bird populations. Furthermore, reliable non‐lethal sampling is necessary for experiments where repeated sampling is required. [ABSTRACT FROM AUTHOR]

Little is known about effects of salinity and flooding on plant symbionts, including baldcypress trees (Taxodium distichum), the dominant trees in many swamp ecosystems in the southeastern US. In this study, we characterize the culturable fungal and bacterial endophytes in the roots and leaves of baldcypress trees at four sites with varying levels of salinity and flooding regimes in southeastern Louisiana. Both salinity and flooding (water level) contributed to endophytic community composition of leaves and roots. We found that diversity and endophyte isolation frequency were higher in roots than in leaves, with leaf bacteria being almost negligible. Our study demonstrates a connection between environmental variables, plant symbionts, and a key restoration species. This work may help in predicting future outcomes of sea level rise for endophytes communities in baldcypress and other wetland plants. [ABSTRACT FROM AUTHOR]