'You don't define a chameleon by its color, but rather by its ability to change color'
~ Dr. Bewick's thoughts on exactly what it is that we study in the Bewick lab*
*Also, despite forays into herpetology, we do not study chameleons**
**Also, never say never
*Also, despite forays into herpetology, we do not study chameleons**
**Also, never say never
Inter-Individual Variation in Microbiomes
Animals, including humans, harbor large numbers of different microbes on and in their bodies - so called host-associated microbiota. While host-associated microbiota are critically important to host health, there is a surprising amount of variation in the microbiota on one host relative to another. How do these differences emerge? In particular, are these differences a result of nature (i.e., host genetics) or nurture (i.e., host environment)? Because most animals are genetically unique, it can be hard to determine whether inter-individual differences in host-associated microbiota are a result of host genetics, environment or both. In whiptail lizards, however, there are entire populations of genetically identical clones. What's more, these clones are closely related to other, sexually reproducing whiptail lizard species where each individual lizard is genetically unique. By comparing inter-individual variation in host-associated microbiota across different environments in clonal lizard populations versus sexually reproducing lizard populations, it is possible to assess the relative importance of both host genetics and environment on host-associated microbiota. This is part of a three year funded National Science Foundation (NSF) grant. |
Microbiomes of Hybrid Organisms
Hybridization between organisms from evolutionarily distinct lineages can have profound consequences on organism ecology, with cascading effects on fitness and evolution. Most studies of hybrid organisms have focused on organismal traits, for example various aspects of morphology and physiology. However, with the recent emergence of holobiont theory, there has been growing interest in understanding how hybridization impacts and is impacted by host-associated microbiomes. Better understanding of the interplay between host hybridization and host-associated microbiomes has the potential to provide insight into both the roles of host-associated microbiomes as dictators of host performance as well as the fundamental rules governing host-associated microbiome assembly. Recently, we developed an R package for analyzing the microbiomes of hybrid organisms with reference to their parent species. We are also conducting field experiments on... you guessed it... whiptail lizards! |
Every good model needs a field system where it can be tested. Living close to one of the most interesting and most imperiled metapopulations in North America, it only seems fitting that our field system should be green salamanders (Aneides aeneus) that inhabit the rock faces in the forests of Upstate South Carolina. It doesn't hurt that Megan Novak from the Barrett lab has already spent 3 years studying these metapopulations, which means she knows where the are... and will soon know how related each local population is to the others! We're excited to find out how related their microbiomes are to one another... and what this might mean for the spread of both commensals and pathogens in these awesome but threatened creatures that call our state home! |
Nested Metapopulations
Metapopulation theory has a long history in ecology, where it is used to describe the dynamics of organisms that frequent patchy and ephemeral habitats. Recently, metapopulation theory has been used to model host-associated microbiomes, with hosts acting as patches, and microbes as dispersing organisms. Extending this framework to scenarios where the hosts themselves exist as metapopulations gives what we term 'nested metapopulations' - systems where there is metapopulation structure at two distinct scales. Although similar 'patchy' models have been studied in epidemiology, the focus in disease literature is typically the effect of limited dispersal among patches and how this impacts the dynamics of disease spread. What is not considered, however, is the other key premise of ecological metapopulations - frequent extinction events at the patch scale. We are exploring models of nested metapopulations, focusing on how host-scale metapopulation structure and microbe-scale metapopulation structure interact to govern the distribution of microbes across both hosts and the habitat patches in which they live. |
Functional Redundancy in Microbial Communities
We are part of a five year National Science Foundation (NSF) funded Rules of Life (RoL) grant studying how functional redundancy varies with ecosystem complexity. Why is this important? Because humans tend to simplify every ecosystem that they touch - whether that's the tropical rainforest, or their own gut microbiomes. While we know this has a devastating impact on biodiversity, what is not as well understood is how this impacts ‘functional redundancy’ – the number of different species that can perform any given function. Functional redundancy is important, because it provides ecosystem insurance – in a redundant system, when one species goes extinct, there is another waiting to take its place. In the Bewick lab, we are building a series of predictive models to explore the mechanistic underpinnings of functional redundancy and the relationship between functional redundancy and ecosystem complexity. Specifically, we are using a metacommunity framework, and are examining how processes associated with local community assembly impact the scaling of functional redundancy with ecosystem complexity. Although these questions apply broadly across ecosystems at all scales, microbial communities are the perfect study system because it's much easier to define what microbes 'can' do (metagenomics) and what they 'do' do (metatranscriptomics)! For more information, please visit the project website. |
Host Biogeography and the Host-Associated Microbiomes
A fundamental question in macroorganism ecology is how individuals are distributed over geographic scales. Known as biogeography, the spatial distribution of a population can be limited by a range of factors, two of the most important being environmental conditions and dispersal limitation. These environmental and dispersal constraints tthen shapes the phylogenetic relationships among populations of a species across its range. Despite the importance of spatial distributions in macroorganism ecology most studies of host-associated microbiomes consider hosts that are sampled in the same location. Recently, researchers have begun to take a broader perspective and have started studying microbiome variation across a species range. Rarely, however, is this done within the context of host phylogeny and phylogenetic differentiation. This is an alarming oversight, especially given the impact of host phylogeny on host factors, for example host immune system function, that impact host-microbe interactions. We are using three unique systems, each comprising a host with substantial phylogenetic differentiation across its range, to study the impacts of host biogeography on the host-associated microbiome. Our first system - patch nosed salamanders - involves a host that experiences substantial dispersal limitation, but very little environmental variation across its range. Our second second system - Aphaenogaster rudis in Great Smoky Mountains National Park - involves a host species that experiences substantial environmental variation, but very little dispersal limitation across its range. Our third and final system - green salamanders - involves a species that experiences both dispersal limitation and environmental variation across its range. By studying how microbiomes vary in these three disparate systems, our goal is to begin understand how spatial processes combine with host evolution to influence the structure, diversity and spatial variation in host-associated microbiomes.
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Photo credit: Ben Camper
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Zoraptera Microbiomes
Photo credit: Daniel Malagon
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Zoroptera are, quite possibly, the coolest insects in the world! Colloquially known as 'angel insects', members of this seemingly species poor order (there is a single family, and only 44 extant species) are generally scarce and have been called 'one of the most enigmatic insect groups'. A big questions is the phylogenetic placement of Zoraptera within the higher systematics of insects - a conundrum known as the 'Zoraptera Problem'. But it's not just their weird relationship to other insects, or general mysteriousness that makes Zoraptera awesome. Zoraptera live in small colonies in highly emphemeral habitat under rotting wood. And what's more, they actually engage in social behavior, including communal grooming.
Despite their general rarity, the Bewick Lab has successfully located multiple Zoraptera colonies in and around Upstate South Carolina. We are currently conducting 16S rRNA and shotgun metagenomic sequencing on these colonies to determine what weird and wonderful microbes are associated with these weird and wonderful arthropods. We are particularly interested in microbiome variation across colonies in what is, essentially, a metapopulation system. But who knows! Maybe learning about Zorapteran microbiomes will shed light on the 'Zoraptera Problem' as well! |
Seven Forms of Rarity of Southeastern Salamanders Following the classic work of Rabinowitz et al. (1986), we are trying to characterize rarity across Southeastern salamanders. This means understanding how different species of salamanders are differentially distributed across three largely independent axes of rarity: (1) local abundance (2) geographic range (3) habitat or niche breadth If species are independently common or rare along each of these axes, then there are eight possible combinations, seven of which involve rarity along at least one dimension. This leads to Seven Forms of Rarity. We want to know how many different salamanders fall into each form of rarity, and whether different forms or rarity are more or less likely depending on species phylogeny or species traits. To assess geographic range and niche breadth, we are using the USGS Gap Analysis Project. To assess local abundance, we are polling expert opinion. If you're an expert who would like to get involved and contribute your knowledge of salamander ecology to our project, please consider taking our survey. |
Pseudoscorpions of the Southern Appalachians
If zoroptera are the coolest insects in the world, pseudoscorpions are, without question, the coolest arachnids. Like zoroptera, the phylogenetic placement of pseudoscorpions is murky at best. But that's not the only aspect of pseudoscorpion biology that makes them awesome! Like spiders, pseudoscorpions make silk... and venom. And what's more, unlike snake venoms - which have been studied ad nauseam (sorry Parkinson Lab) - arachnid venoms are relatively poorly characterized. Further, of all the poorly studied arachnid venoms (spiders, ticks, scorpions, etc.) out there, which do you think have been studied the least? You guessed it... pseudoscorpions! Oh, and here's one more cool factoid about these crazy creatures - pseudoscorpions are basically backwards spiders... they spin their silk from their chelicerae (mouth parts) but inject their venom through their pedipalps (claws). |
photo credit: Simon Dunn
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photo credit: Simon Dunn
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So what aspect of pseudoscorpion biology does the Bewick Lab study? Can I join the Bewick Lab to explore the chemistry of pseudoscorpion venom? Sadly, no... if you want to study venom, at least at Clemson University, you're still going to need to join the Parkinson Lab. Instead, the Bewick Lab is currently focused on understanding the biodiversity and distribution of litter-dwelling pseudoscorpions in the Southern Appalachians. Amazingly, despite their adorable resemblance to little lobsters, and their overall phylogenetic and natural product coolness, pseudoscorpions are understudied. Currently, for example, we don't even know which species are found in the Southern Appalachians - let alone where (habitat types, elevation) these different species occur! So that's what were trying to figure out. And while this work doesn't involve any microbes (yet!), we still think it's ok... because pseudoscorpions are pretty 'micro' for a study of macroecology! |
Ok.... so I know I said that pseudoscorpions were understudied, and that's 100% true. But you know what's even harder to find than a scientific journal article on pseudoscorpions? A song! That's right... for reasons we are still trying to understand, almost no one writes songs about pseudoscorpions. Fortunately, Simon Dunn, of the Bewick Lab has worked to rectify this situation. So please enjoy what almost certainly holds the Guinness World Record for the longest and most scientifically factually correct song about pseudoscorpions.