For spiders, raccoons, and such? Big, high-tech cities are new and different. But you don’t get remarkable results from these independent theatres of evolution. That’s clear from a recent long article, well worth reading, mostly for the fascinating information but also for the need, so common these days, to assert that something is happening which obviously isn’t:
Whatever the dynamics of the effect, these results are helping to confirm that the structure of city environments has profound evolutionary implications for its inhabitants. “The specifics will vary from species to species,” says Luc De Meester, an evolutionary ecologist at the Katholieke Universiteit Leuven in Belgium. “But there are generalities.” While most research has focused on species of conservation concern, “even species that tend to be abundant . . . are very strongly impacted by city life,” he adds. Given this potential for urbanization to influence the genetic structure of populations, some researchers have posited that cities could act as hotspots for the evolution of new species. Especially in small or fragmented populations, the breakdown of gene flow can help promote speciation. “It’s a tantalizing idea,” says Munshi-South. But there’s a long way to go before scientists can point to a specific case with certainty, he says. “Even in the few cases that have been talked about as potential examples of urban speciation, there are a lot of unresolved questions.” CATHERINE OFFORD, “Cities can serve as cauldrons of evolution” at The Scientist
Sums it up: “there’s a long way to go before scientists can point to a specific case with certainty” Of course, one factor is surely that the species that get involve with cities are highly adaptable to begin with and are likely to merely specialize rather than “evolve.”
Here’s an example from the article:
Compared to raccoons (Procyon lotor) in rural areas or in the city zoo, Toronto’s street raccoons are bulkier—some being almost a meter long and weighing up to 15 kilograms (33 pounds). Last summer, researchers documented signs of hyperglycemia in city populations of the nocturnal animals, a condition not observed in rural raccoons (Conserv Physiol, 6:coy026, 2018). The likely cause: a diet of high-fat, sugary food from the city’s garbage cans. Researchers have also reported diet changes in other urban mammals, birds, and even some invertebrates. A 2015 study found that Manhattan’s pavement ants (Tetramorium sp.) showed isotope signatures in their tissues consistent with increasing consumption of human fast foods (Proc R Soc B, 282:20142608). CATHERINE OFFORD, “Cities can serve as cauldrons of evolution” at The Scientist
I (O’Leary for News) remember those bruiser Toronto raccoons well. They are “evolving” — into urban raccoons. Come back a century from now and they will be plodding around at twilight, fatter than ever.
(Note: The racoons are not “becoming smarter,” such that that they can now manipulate latches where they couldn’t before. They were always able to use their hand-like front paws like that but the Toronto garbage bins did not used to have that kind of handle. In the past, raccoons have needed their kind of dexterity to pry off roof tiles, etc., so as to spend the winter in the attic insulation between food waste garbage days.
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