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.
Mutualisms, in which two or more species provide each other with services or resources that they can’t produce on their own, are everywhere you find living things. Mutualists offer protection, help transport pollen, and provide key nutrients.
Even when a mutualist’s services aren’t absolutely vital, they can help make stressful environments tolerable. That’s the insight behind a new study that finds the help from one group of mutualists could allow an unremarkable-looking species of grass to colonize more than 25,000 square kilometers (almost 10,000 square miles) of territory where it otherwise wouldn’t survive.
Macrobrachium ohione, by Clinton and Charles Robertson, via Flickr.
The Mississippi River that we know today is a creation of the army corps of engineers. Before they got to levying, dredging and damming it into submission, it was a wild and meandering thing that harbored great concentrations of wildlife. One component of that was a massively abundant shrimp with an amazing life cycle:
It turned out that in pre-colonial times the shrimp traveled all the way north into the upper reaches of the Mississippi’s main eastern tributary, the Ohio River, and back again – a 2,000-mile round trip. It was a journey more amazing than similarly epic migrators like salmon. For whereas adult salmon may have an equally long journey to their upstream spawning sites, it is the quarter-inch juvenile shrimp that swim and crawl 1,000 miles upstream against the strong currents of the Mississippi.
What happened to these shrimp? Go read the story to find out.
Sloths are weird critters. Cute, in a certain light, but mostly weird. They’re members—with armadillos and anteaters—in a superorder of mammals called the Xenarthra, which are united by a unique form of multi-jointed vertebrae. Their diet consists mostly of leaves, which are poor quality food, and hard to digest. Fortunately, they also have one of the slowest, lowest-energy lifestyles of any mammal, using heavily modified limbs to hang upside down from branches while they browse, their most recent meal fermenting in their guts.
David Attenborough got up close with a sloth—which he calls a “mobile compost heap”—in The Life of Mammals. He also observes one of the sloth’s weirdest behaviors: to answer the call of nature, it climbs all the way down to the ground.
Why do sloths go to all that trouble—and risk—just to poop? Well, according to a recent paper in Proceedings of the Royal Society, they do it to feed poop-eating moths that help cultivate nutritious algae in their fur. No, but really.
Here at Nothing in Biology Makes Sense, we’re fascinated by all the weird, baroque ways that living things influence and coevolve with each other—so Ed Yong’s new TED talk about mind-controlling parasites is right up our alley. Just like his writing—currently on display at National Geographic‘s Phenomena, among many other venues—it’s a compendium of nifty natural history punctuated with highly educational gross-outs and the occasional black-belt level pun.
Flowers that rely on animal pollinators
to remix their genetic material have evolved a tremendous diversity of strategies for attracting those pollinators—from beguiling scents
to elaborate visual displays
to pretending to be a lady pollinator
But there’s a downside to making a big, showy display to attract pollinators—you might also attract visitors who have less helpful intentions than gathering up some pollen and moving on to the next flower. Showy flowers might attract animals that steal the rewards offered to pollinators—or they might attract animals that eat the flowers themselves, or the developing seeds created by pollination. So the evolution of attractive floral displays might very well be a compromise between attracting the right visitors, and attracting the wrong ones.
Carlia longipes, looking right at home on a rock. Photo by berniedup.
Whether the weather be cold, or whether the weather be hot
we’ll be adapted whatever the weather, whether you like it or not.
Life is risky for a newly hatched lizard. You have to make your way in a habitat you’ve never seen before, full of all sorts of larger animals that think you’d make a decent snack, if maybe not a full meal. Wouldn’t it be nice if you could’ve been preparing for the conditions you’ll meet out there even before you crack through that shell?
Well, for one species of skinks, it looks like this may be exactly what happens. A recent paper in The American Naturalist makes the case that rainbow skinks (Carlia longipes) develop in their eggs to match the habitat conditions around their nest—based on the temperature of the nest.