Making new evolutionary innovations: butterfly study (Introduction)

by David Turell @, Wednesday, December 11, 2019, 18:38 (47 days ago) @ David Turell

Their so called species interbreed:

http://nautil.us/blog/do-butterflies-challenge-the-meaning-of-species

"Researchers recently analyzing the genomes of every butterfly species in the United States and Canada—845 in total—have revealed that at critical evolutionary intervals, butterfly species have crossed the reproductive barrier, mating with other species of butterfly and thereby transferring genes from one species to another. Hybridization, it turns out, plays a pivotal role in how life forms evolve. The tree of life may never look the same.

***

"Traditional taxonomy had outlined an ancestral tree for butterflies, discerning family, tribe, genus, and species based on the overall body shape of the butterfly and wing-pattern. By sequencing the genomes of all 845 butterfly species, Grishin and colleagues were able to work out a genomic family tree that in large part agreed with the existing one based on anatomy. But it also showed more. “People thought butterflies were closely related based on what they look like, but genomically, we saw something else.” Grishin’s group reclassified 40 species and suggested several new genus levels.

"Analyzing the genes of multiple species added a huge new dimension to the idea of “butterflies,” because it revealed not just the species themselves but also the relationships between them. Going back 70 million years, a burst of diversification ensued. Butterfly subfamilies appeared with major evolutionary inventions as a result of high positive selection (the tendency of beneficial traits to increase in a population), which is the overall driving force of adaptive evolution. Another burst, an explosive radiation in butterfly species, came about five million years ago

“'One surprise is that there are so many diversifications,” Grishin told me. “We see lots of rapid radiation in some groups—with many species forming in short periods of time. We didn’t understand the degree to which interbreeding was driving genetic transfer.” The hybridization tends to happen in “younger” species, many of which will eventually die off. Grishin explains it this way: “There are patterns of a cycle in butterfly evolution. Diversification, radiation, introgression, extinction, and repeat.” The timing, duration, and character of this pattern depend foundationally on geological change. “Butterflies exchange these genes and some of them can spread because they have beneficial genes” that aid in adapting to new conditions.

"It may be that the species paradigm needs a big overhaul if seemingly well-separated animals can actually interbreed. The revelations of butterflies are informing long-standing questions about Homo sapiens, for example. We have ancient DNA that may or may not have come by way of our ancestors mating with Neanderthals. “It’s possible we received genes from Neanderthals that enabled us to move out of Africa and into cooler climates,” Grishin said.

"As the picture of life gets longer and deeper thanks to genetic analysis, so too the humble arts play their part. Grishin and Cong are both computational scientists who work in the lab and not in the field. Yet Grishin credits Cong and colleagues with becoming stellar amateur lepidopterists in the course of their research. Instead of flying to conferences, they would drive, stopping by the side of the road to collect butterflies. Cong told me that their research adds to those with similar ambitions, “to obtain genomes of every species on Earth. These genomes are gifts from millions of years of evolution. Nature did the experiments, and we are trying to check the results.'”

Comment: We still do not understand speciation and morphological comparisons are not as good as genome studies in analyzing evolutionary relationships.


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