The tunnels of the London Underground are hot, dark, and damp. Crowds of warm-blooded humans congregate on the platforms. Stagnant pools of water collect beneath the tracks. The subterranean transit system is, in other words, a lovely home for a mosquito (or many thousands). At some point during the last 150 years or so, a small population of mosquitoes came to the same conclusion, settling into the interconnected tunnels of the world’s oldest underground railway. They became infamous pests, feasting on Londoners who took shelter in the tunnels during World War II and hassling modern-day maintenance crews.Although the insects look just like their aboveground counterparts, the common house mosquito Culex pipiens, their behavior is remarkably different. Unlike the street-level mosquitoes, the subterranean insects feed on mammals, are capable of breeding in confined spaces, do not require a blood meal before laying eggs, and do not go dormant during the dreary London winters. The two populations also have significant genetic differences and cannot interbreed. Together, these observations suggest that the mosquitoes that first colonized the tunnels have evolved, developing traits that better suit their underground environments. The subway, it seems, has birthed a brand new species.We are living, it is often said, in Anthropocene, an era in which humans are radically altering Earth’s ecosystems. As evidence of our impact, experts often point to the dismal extinction statistics: Nearly 800 plant and animal species are known to have gone extinct since 1500, a figure that is surely an underestimate, and current extinction rates may be 100 to 1,000 times higher than before Homo sapiens appeared on the evolutionary horizon. We may even be teetering on the precipice of a global mass extinction event—the sixth in the planet’s history. “The primary narrative that you’re hearing about biodiversity in the Anthropocene is a story about extinctions,” says Erle Ellis, an ecologist at the University of Maryland, Baltimore County.But human-induced extinctions are only part of the story. Our lifestyles and activities—the way we use the Earth’s land and exploit its resources—are also driving the evolution of new traits in organisms across the globe, and even, in some cases, the emergence of entirely new species. “It’s a counter narrative,” Ellis says. “Human-induced speciation.” This oft-overlooked phenomenon, the focus of a recent review paper, paints a more nuanced picture of the ways in which humans shape life on this planet—and exposes our need to reconsider how we measure biodiversity and exactly why we value it.“If our target is to prevent the loss of species and we are creating new species, then implicitly, we’re saying that we’re happy to end up in a world where we have the same number of species as now, but some of them are different species or ‘artificial’ species,” says Joseph Bull, a conservation biologist at the University of Copenhagen and one of the authors of the recent review. “Is that really the vision we have?”“If it’s not species numbers, which is the way it’s often framed in global conservation, what is it that we actually care about?”Humans have been driving evolution for millennia, often intentionally: Over the past 11,000 years, we’ve domesticated more than 700 plants and animals, turning the gray wolf into the toy poodle and the bland, bitter watermelon into a sweet, summertime snack. Among the 95 species that make up the world’s most important crops, at least six are human creations.But we also shape other species indirectly. Hunting, fishing, and harvesting, for instance, can lead to selection against the very traits that we prize. Consider a naturally occurring genetic variant that gives some red foxes iridescent, silver coats. Furs from these foxes fetched higher prices than the traditional rust-colored pelts, leading economically rational hunters to target the silver canids, removing them from the gene pool at disproportionate rates. In 1830 in Eastern Canada, silver foxes made up 16 percent of the population; a century later, that figure had declined to just 5 percent. Likewise, hunters’ hunger for trophy specimens has led to a decrease in horn size among Canadian bighorn sheep.We continuously reshuffle the planet’s species, moving organisms to foreign countries and continents, where they might interbreed with the native flora and fauna or develop traits that better suit their new homes; given enough time and separation from their parent populations, they may eventually become different species.Even when plants and animals stay put, we radically transform their habitats. We carve up landscapes, leaving isolated, fragmented populations to evolve away from each other in the islands of wilderness that remain. Thanks to deforestation in Central America, the giant helicopter damselfly appears to be splintering into multiple species . And we create entirely novel ecosystems, such as subway tunnels and li

Source: Are Humans Creating More Species Than We’re Killing? – The Atlantic