Have any naturalists conducted serious studies in these isolated pockets to see if any new species or subspecies are emerging? There are several of these in So cal, Los Angeles area. We have one near my house that is about 200 acres, I am guessing, and has been an island for at least my lifetime, close to 80 years. Surrounded by oil refineries. The small animals that remain there are likely a very small gene pool.
(Not an expert in this at all, but interested in it.)
If you know the specific area (a map link, coordinates, place name, etc.), I’d be interested in looking to see if any studies have been done there. Or if anyone else knows, I’d love to hear.
Otherwise, as a slightly-educated wild-ass guess: 80 years isn’t a whole lot of time for meaningful divergence. It would take a “perfect storm” of environmental changes, genetic mutations, and individual behavior within that 80 years and 200 acres for a meaningful speciation to occur.
More often, Habitat fragmentation - Wikipedia just leads to extirpation (local extinction), which is why California and other places keep trying to build Wildlife corridor - Wikipedia instead. Populations trapped in these fragmented “habitat islands” can and do evolve into Endemism - Wikipedia and new species/subspecies, but that usually takes slow, gradual isolation over centuries or longer, and only under the right circumstances (i.e., there’s still enough remaining food, a relative dearth of predators, enough genetic diversity within that population so they don’t just die from hereditary diseases,etc.). It’s the exception, not the norm.
Bacteria, on the other hand… it’s much easier for them to quickly grow, reproduce, and develop into new strains. Probably not what you meant though.
For insect species, for example, this definitely can happen! Sometimes called “scrap wilderness”, these little bits of unbuilt environment can support a surprising variety of wildlife. The thing is that city streets aren’t necessarily as strong an isolation barrier as we might think.
One example I can think of is a population of common alligator lizards that I have only found in one vacant lot. I spent my entire life tromping around through fields and vacant lots and I have never seen this type anywhere else. I discovered this population when I was a kid and for many years I just assumed it was an older group of lizards that had time to mature without being disturbed but as the years went by I became more and more convinced that this was an isolated type as I have never seen anything close to it. The width of the body and head was at least double the typical size. I don’t know how long they could get because all of them were in some state of growing their tails back. They were very aggressive and I suspect they were eating each other’s tails. I know they fed of baby mice and that was most likely their primary source of protein. It was rare to see a small one so I strongly suspect they were cannibalistic.
That was a very good read and leads me to my primary interest in epigenetics. I was driving by one of our on-ramps yesterday and noticed it covered about 3 or 4 acres of land that was a little island. A nice big pond had developed, and cattails were growing, and a few ducks were swimming in it. I thought to myself that in 100 years it would be interesting to come back to this same spot, assuming it doesn’t change.
Not specifically related to micro-evolution, but the Don River Valley in Toronto is a good example of a wilderness pocket in an urban setting. The entire watershed covers an area of 36,000 hectares (350 km2). Some of the wildlife found within it:
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Mammals: Coyotes, red foxes, white-tailed deer, raccoons, beavers, muskrats, skunks, and opossums. Most of these creatures stay within the wildlife habitat. The raccoons do not!
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Birds: The area is a haven for over 300 species, including Great Blue Herons, Cooper’s hawks, red-tailed hawks, belted kingfishers, Baltimore orioles, many songbirds, and various owls
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Aquatic Life & Reptiles: Salmon run upstream in the fall. Turtles, toads, frogs, and snakes are present in the watershed