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+--- Thread: Article Hybrids between two species can produce “swarms” that flourish (/thread-16274.html)
Hybrids between two species can produce “swarms” that flourish - C C - Jul 31, 2024
https://arstechnica.com/science/2024/07/how-hybrid-swarms-can-break-down-species-boundaries-and-take-over-habitats/
INTRO: There are no wild ligers. Indeed, hybrids were once thought to be rare in nature—and of little consequence in an evolutionary sense. But now we know they can play an important role in speciation—the creation of new, genetically distinct populations.
As it turns out, hybridization in nature is quite common. Some 25 percent of plant species hybridize and some 10 percent of animals do the same.
“Hybridization as an event is rare,” said Jeremie Fant, a conservation scientist with the Chicago Botanic Garden who has worked on plant hybridization. “But in evolutionary history, it's been very common. Hybrids in the plant kingdom are everywhere. They are scattered through most lineages. When hybridization does occur, it can have important evolutionary impacts.”
Often, crosses between two species are evolutionary dead ends. They may be infertile, or they may simply be absorbed into populations of one of the parent species, leaving only a few spare genes from their oddball parent drifting in the gene pool. But in a number of rare but significant cases, hybridization events can significantly alter the trajectory of evolution.
When two related species overlap geographically, they may form what are called “hybrid zones.” Some of the most obvious hybrid zones occur at the boundaries of divergent ecosystems. A plant species adapted to one soil type may exchange genes with a related plant adapted to another, and their offspring thus develop a population that thrives in an intermediate area with characteristics of both soil types.
These hybrid zones are often quite stable over time, with insignificant introgression, or breeding back, to the parent populations. That’s because the genes that serve the organisms in the hybrid zone may not be particularly useful to those outside of it, so they do not spread more widely.
Sometimes, however, hybridization events become something more. They turn into swarms. The first instance of the term “hybrid swarm” occurred in 1926 in a Nature article about New Zealand flora.
“As far as biologically defining the difference between that zone and a swarm, I've been struggling to find a nice, clean definition,” Fant said.
“A hybrid swarm is the ultimate erosion of two species into some other thing that's a combination of both,” suggested Scott A. Taylor, an associate professor at the University of Colorado who has worked on hybridization in chickadees... (MORE - details)