Urbanization is one of the most dramatic changes humans make to natural habitats. Cities are concentrations of tall buildings, paved landscape, air pollution, and everything else that we do to make life easier for ourselves. But some living things do quite well in these highly altered conditions—think rats and cockroaches, but also red foxes and crows. As the Popular Science blog Eek Squad notes, there’s a new entry on that list: golden orb spiders, Nephila plumipes.
Lowe and colleagues found the city-dwelling arachnids were bigger than their country kin, and the most fertile spiders were found in neighborhoods with the highest socioeconomic status.
Why? The most likely explanation is that cities are warmer, which can lead to bigger invertebrates, and there’s more prey available. The latter is partly because of leaf litter and food for the prey, but it’s also because of a city-related scourge: Artificial light at night. Large spiders were found nearby, or living on, structures like light posts. Insects are drawn to sources of light at night, which could mean more meals for spiders living under bright lights in the big city.
Note that this isn’t necessarily an evolutionary change in response to urban habitats—the spiders probably just find conditions much more favorable in the city, and grow bigger as a result. But that change in resource availability could certainly lead to evolutionary changes over the long term. Go check out the whole Eek Squad post, and have a look at the original scientific article, which is freely available on PLOS ONE.