Biology subjects

Härer, A.

Publications and source records attributed to Härer, A..

4 recordsLinked to original sources

bioRxiv2024

Host traits and environmental variation shape gut microbiota diversity in wild threespine stickleback

BackgroundDespite the growing recognition of the importance of gut microbiota in host ecology and evolution, our understanding of the relative contributions of host-associated and environmental factors shaping gut microbiota composition within and across wild populations remains limited. Here, we investigate how host morphology, sex, genetic divergence, and environmental characteristics influence the gut microbiota of threespine stickleback fish populations from 20 lakes on Vancouver Island, Canada. ResultsOur findings reveal substantial variation in gut microbiota composition and diversity among populations, with host traits exerting a stronger influence on bacterial alpha diversity than environmental characteristics. Host morphology, which is indicative of trophic ecology, was linked to gut microbiota divergence among populations, suggesting that dietary specialization may play a role in shaping the stickleback gut microbiota. Within and across populations, we only observed a weakly defined core microbiota and limited sharing of ASVs among hosts, indicating that gut microbiota composition is individualized. Additionally, we detected sex-dependent differences in microbial diversity, opening avenues for future research into the mechanisms driving this variation. ConclusionsIn sum, our study emphasizes the need to consider both host-associated and environmental factors in shaping gut microbiota dynamics and highlights the complex interplay between host organisms, their associated microbial communities, and the environment in natural settings. Ultimately, these insights enhance our understanding of host-microbiota interactions and their eco-evolutionary implications.

ecology↗

bioRxiv2023

A positive association between gut microbiota diversity and vertebrate host performance in a field experiment

The vertebrate gut microbiota is a critical determinant of organismal function, yet it remains unclear if and how gut microbial communities affect host fitness under natural conditions. Here, we investigate associations between growth rate (a fitness proxy) and gut microbiota diversity and composition in a field experiment with threespine stickleback fish (Gasterosteus aculeatus). We detected on average 63% more bacterial taxa in the guts of high-fitness fish compared to low-fitness fish (i.e., higher -diversity), suggesting that higher diversity promotes host growth. The microbial communities of high-fitness fish had higher similarity (i.e., lower {beta}-diversity) than low-fitness fish, supporting the Anna Karenina principle-- that there are fewer ways to have a functional microbiota than a dysfunctional microbiota. Our findings provide a basis for functional tests of the fitness consequences of host-microbiota interactions. Significance statementThe vertebrate gut microbiota is important for many aspects of their hosts biology--such as nutrient metabolism and defense against pathogens--that could ultimately affect host fitness. However, studies investigating the effects of gut microbiota composition on vertebrate host fitness under natural conditions remain exceedingly rare. We tested for associations between gut microbiota diversity and growth rate (a fitness proxy) in threespine stickleback fish reared in large outdoor ponds. We found evidence that a more diverse gut microbiota was predictive of higher growth rate and therefore increased host fitness. Notably, high-fitness fish had higher gut microbiota similarity to one another than did low-fitness fish, providing experimental evidence for the Anna Karenina principle--that there are fewer ways to have a functional microbiota than a dysfunctional microbiota--as it relates to host fitness.

evolutionary biology↗

bioRxiv2022

Validity of fecal sampling for characterizing temporal variation in threespine stickleback's gut microbiota

Diverse microbial communities associated with the guts of their hosts are crucial for many aspects of their hosts physiology, ecology, and evolution. The gut microbiota has been characterized for a broad range of species across the animal kingdom. Yet, for many host species we still dont have a good understanding of whether non-lethal sampling (e.g., fecal matter) can accurately capture the diversity of gut-associated bacterial communities, as estimated from lethal sampling of intestinal tissue. We further lack knowledge on whether such non-lethal sampling methods are suitable for studying temporal gut microbiota dynamics. Here, we addressed these questions in threespine stickleback fish, a model system in evolutionary ecology, by comparing bacterial communities based on 16S rRNA gene sequencing from intestinal tissue and feces. Despite some differences in community composition between the two sample types, we show that bacterial communities of feces and intestinal tissue largely overlap. Further, we were able to detect consistent and significant changes of fecal bacterial communities associated with an experimental diet shift. These results suggest that fecal sampling represents an adequate non-lethal method to characterize the gut microbiota of threespine stickleback. This allows for studying temporal gut microbiota dynamics at the individual level, which increases opportunities for future experimental gut microbiota research.

evolutionary biology↗

bioRxiv2022

Quantifying (non)parallelism of gut microbial community change using multivariate vector analysis

Parallel evolution of phenotypic traits is regarded as strong evidence for natural selection and has been studied extensively in a variety of taxa. However, we have limited knowledge of whether parallel evolution of host organisms is accompanied by parallel changes of their associated microbial communities (i.e., microbiotas), which are crucial for their hosts ecology and evolution. Determining the extent of microbiota parallelism in nature can improve our ability to identify the factors that are associated with (putatively adaptive) shifts in microbial communities. While it has been emphasized that (non)parallel evolution is better considered as a quantitative continuum rather than a binary phenomenon, quantitative approaches have rarely been used to study microbiota parallelism. We advocate using multivariate vector analysis (i.e., phenotypic change vector analysis) to quantify direction and magnitude of microbiota changes and discuss the applicability of this approach for studying parallelism. We exemplify its use by reanalyzing gut microbiota data from multiple fish species that exhibit parallel shifts in trophic ecology. This approach provides an analytical framework for quantitative comparisons across host lineages, thereby providing the potential to advance our capacity to predict microbiota changes. Hence, we emphasize that the development and application of quantitative measures, such as multivariate vector analysis, should be further explored in microbiota research in order to better understand the role of microbiota dynamics during their hosts adaptive evolution, particularly in settings of parallel evolution.

evolutionary biology↗