The tropics of Trinidad… the gleaming ice of the Arctic… as urban scientists, these are field sites we typically forgo for the sake of a short(ish) commute.
Studying what’s “close to home” certainly has its benefits. Not only can we study the evolutionary dynamics of our own neighborhoods’ wildlife, but we also engage in science that is especially suitable for outreach and public participation. With more than half the world’s population living in cities, our work holds immediate relevance.
While we do have some great benefits, a new branch of urban evolutionary ecology is opening up possibilities for research that is even more easily accessible, offers year-round field work, and eliminates commutes entirely.
Enter: The Indoor Biome
In their 2015 paper, Martin et al. define the indoor biome as “the ecological realm comprising species that reside and can (although do not necessarily always) reproduce in enclosed and semi-enclosed built structures”. Before diving into examples that illustrate the “rich but fragmented literature on evolution in the indoor biome”, the authors detail the origins of how different taxa construct “nests” to accommodate basic needs including sleep and reproduction, then wade into anthropological territory to describe how humans’ homes have developed over time.
Though the paper deserves a thorough read-through, here are three points raised that may make you do a double-take when you get home tonight.
1. Your home is a training ground for highly resilient flora and fauna
Thermostats and humidifiers keep our homes relatively stable in terms of temperature and humidity. However, your microscopic housemates experience extreme fluctuations in temperature and humidity on a regular basis, like when you turn on your shower or dishwasher. These resilient microbes and fungi may act as proof of selection for species that can withstand “episodically stressful conditions”.
2. Your domesticated housemates may share certain phenotypes & behaviors
Humans began building houses around 20,000 years ago. Researchers estimate that the ancestors of some of your biological cohabitants, like bed bugs (Cimex lectularius), were living in caves at this time. Similar conditions between caves and early human houses may have facilitated their transition from cave-dwellers to human housemates- which, as many of us are painfully aware, has persisted through the modern era.
Thus, these organisms’ morphologies may hearken back to their days living in caves.
For instance, the flat bodies of many indoor arthropods, including cockroaches and silverfish, assist them in fitting through tight spaces. House-bound populations of these species are also poor of vision but make up for it with longer antennae, which they use to navigate edges. The beetle Aglenus brunneus (Gyllenhal) is totally blind- it lacks eyes- yet it has also maintained a centuries-long plus relationship with humans by contentedly living in grain stores and barns. Perhaps owing to the reliability of a constant food source, this beetle and many other invertebrates that reside in barns are also wingless. Interestingly, though flightlessness is relatively rare among insects, indoor insects tend to exhibit a decreased dispersal ability. Bed bugs, camel crickets, and some roaches are examples of insects with low mobility. Furthermore, house-bound insects that can fly often do so poorly.
3. The outstanding questions about life in the indoor biome are fascinating
The remaining questions about the ecology and evolution of these creatures are incredibly wide-ranging: the authors write, “As a research field, the evolutionary biology of the indoor biome is interdisciplinary, situated at the intersections of evolutionary biology, ecology, anthropology, archaeology, engineering, architecture and design, human ecology, urban planning, environmental history, and political ecology.”
Here are some unsolved questions quoted directly from the article:
“Are houses similar enough to consider them a single biome or are they more akin to remote islands (multiple biomes)? Would one expect convergent or divergent evolution to appear across habitats in the indoor biome?”
“How many and which species are found exclusively in the biome?”
“Are populations of some indoor species genetically distinct within or among different types of structure (e.g., public kitchens versus private kitchens, bedrooms versus movie theaters)? In other words, what is the population structure of the inhabitants of the indoor biome? Does scale matter? Would we be more likely to find structured populations of, say, bacteria than mice?”
“What are the primary producers in the indoor biome?”
If you’ve been inspired to contribute to this nascent field, you don’t need to enter a graduate program; citizen science efforts are a simple yet effective way of increasing our knowledge of the critters that live with us. If you’re near NC State University, check out this iNaturalist page where you can add observations of organisms you find inside the campus buildings. You can also contribute to a worldwide effort started by the Dunn lab where everyone is encouraged to log sightings of indoor creatures, especially arthropods. Be sure to check out their iNaturalist page.
Read the full paper here: Martin, L. J., Adams, R. I., Bateman, A., Bik, H. M., Hawks, J., Hird, S. M., … Dunn, R. R. (2015). Evolution of the indoor biome. Trends in Ecology & Evolution, 30(4), 223–232. https://doi.org/10.1016/j.tree.2015.02.001
Featured Image “Loading the dishwasher” by m01229 is licensed under CC BY 2.0.
- Why Participate in Science Communication? + Urban Evolution Teaching Resource - June 9, 2020
- Urban Observation of the Week: Zombies! Brains! Fungi! - October 30, 2019
- What is the “Indoor Biome”? - September 3, 2019
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