The Effects of City Life On a Species’ Body

Species like the anole exist in natural and urban environments. So how does where they live affect their body shape? (Image Credit: RobinSings, CC BY-SA 4.0)

Linking locomotor performance to morphological shifts in urban lizards (2018) Winchell, K. et al., Proceedings of the Royal Society of Biological Sciences, 285, http://dx.doi.org/10.1098/rspb.2018.0229

The Crux

We know that human construction leads to displacement of many species, regardless of the ecosystem. But just because we put up a city, doesn’t mean that all the species that lived there go disappear. Some stay and adapt to their new surroundings. Understanding how certain types of organism respond to new environments is important when considering our impact on a species.

Today’s paper looks at the response of lizards, in this case anoles, to living in the city. The authors wanted to find out, among other things, whether individuals of the selected species showed different locomotive abilities on natural and man-made surfaces based on whether or not they came from the city or the forest, and whether these corresponded to morphological differences.

What They Did

The researchers collected over 120 Puerto Rican Crested Anoles from eight different sites, spread throughout urban and forest areas. They were prompted to sprint over bark, painted concrete, and aluminium sheeting at both a moderate and a steeper slope. Their speed, plus the number of times they slipped or stopped, was measured. Physical traits known to be associated with different forms of movement, including length of hind and forelimbs, size of toepads, width of pelvis, and number of lamellae (scales which improve grip) on the feet were also measured. These physical traits, as well as whether or not the lizards were from the city or the forest, were compared to the lizards speed of movement.

What They Found

Increases in several physical features corresponded to increases in speed and decreases in stops and slips, however these varied depending on the slope and the type of track. For instance, lizards with long forelimbs were faster on less steep slopes, yet were slower on the steeper tracks. This suggests that for speed in certain environments, lizards must trade speed in others.

As expected, lizards ran slower on the two man-made surfaces, as well as on the steeper track. On all tracks, the urban lizards were faster than the forested lizards, and generally displayed morphology better adapted for fast movement over flatter surfaces.

If a water dragon like this one evolves to move faster along city pathways, it may sacrifice quick movement through forests

If a water dragon like this one evolves to move faster along city pathways, it may sacrifice quick movement through forests (Image Credit: Stu’s Images, CC BY-SA 4.0)

Did You Know: Urbanisation in Ecology

One of the main tenets of ecology is its focus on interactions with organisms. So it would be foolish to ignore the interactions of organisms with humans, right? Well that used to be the case, according to Professor Mark Davis.

“30-40 years ago, most of the research was done in wilderness areas where there wasn’t much human activity. Now an awful lot of research involves some sort of human activity.”

Urban ecology is a discipline on the rise, and we expect it to grow in popularity in the coming decades.

So What?

The fact that across all surfaces, urban lizards performed better than forest lizards suggests that selection pressure on urban lizards has caused them to develop different morphological traits. The fact that lizards which had longer forelimbs (and thus were faster on less steep surfaces) were slower on steeper surfaces may suggest that urban lizards are required to run faster on open, less steep surfaces to avoid predation.

Basically, this study is a great example of the different ways that urbanisation can influence species morphology. Demonstrating a species ability to adapt like this paper does provides valuable insight into how urbanisation may affect other creatures and their ability to persist in our presence.

You can read more about Kristin’s research at https://kmwinchell.com/

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