Read Online The Darwin Awards Countdown to Extinction by Wendy Northcutt - Free Book Online Page B
Authors: Wendy Northcutt
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close relatives living in more appealing climates—lounging on beaches, soaking in tropical pools—who reproduce using sex.
In a marginal habitat, it pays to pass on to your children your proven genotype, unchanged. Only a few things can live where you live, and on balance, it’s best to stick with the tried and true. And saving energy with low-cost solo reproduction is a big help too.
Asexuals live where the environment allows natural selection to slow down.
#1 Reason for Sex: Aliens!
OK, then—since sex is a choice, why choose sex? 7
Field studies indicate that the number one reason for sex is biological interactions between species. Mainstream habitats are rich in predators, pathogens, and parasites. Sex, by shuffling genes, is especially good at protecting against parasites and disease. Studies in the lab—evolution in a bottle—show that those odd creatures that switch between sexual and asexual reproduction, like the water snail, Potomopyrgus antipodarum , get sexy when their parasites start hopping.
Japanese knotweed, Polygonum cuspidatum , a handsome but rather unwelcome invasive weed, is one of the first to colonize fresh lava fields in its native Japan. Its ability to flex sexual and non-sexual generations is its strength as a hardy colonizer. A single asexual clone of Japanese knotweed is now invading northern Europe. Although this clone would not stand a chance back home, far from its native pests and predators—the weed is nearly invincible—See Bailey, Bímová, and Mandák, “Asexual spread versus sexual reproduction and evolution in Japanese Knotweed,” Biological Invasions 11, no. 5 (2009).
You see, it’s the tiniest “predators” that evolve the fastest. Compare the life cycle of a flea (four weeks) to its prey, your cat, or compare a human life span to the two-week flu virus life cycle. Pathogens have many extra generations for natural selection to work, so they quickly hone in on the genetic weaknesses of, well, you. Prey must evolve, shift genetic profiles, to combat these enemies. Evolutionary biologists call this the “Red Queen Hypothesis” and liken the costly persistence of sexual reproduction to the Lewis Carroll character who had to keep running to stay in place.
Dandelions
Both sexual and asexual lifestyles have their niches, and a great example lives as close as your backyard.
In their native Eurasia dandelions grow as normal flowers, producing male pollen carried by bees to fertilize female ovules. But dandelions have also evolved asexual lines that clone themselves and send out seeds containing identical DNA. The “old sod” in Europe is golden with sexual dandelions, but it is the asexual ones that have blanketed the virgin continent of North America. They are a beautiful example of just when asexual reproduction is best. Far from their native pests and pathogens, sex-free dandelions have colonized every lawn in the USA because they are able to spread faster than their sexual relatives—even while wasting energy producing cheery yellow flowers that no bee will ever fertilize.
So the next time you’re in the mood to mate, stop and consider an alternative used by bananas, bacteria, lizards, and sharks. Maybe it is better to close the curtains and just do it yourself.
REFERENCES:
Crews, Grassman, and Lindzey, “Behavioral facilitation of reproduction in sexual and unisexual whiptail lizards,” Proc Nat Acad Sci USA 83 (1986), 9547-9550.
Juliet Eilperin, “Female Sharks Can Reproduce Alone, Researchers Find.” The Washington Post, http://tinyurl.com/2aaau4
Lively, Craddock, and Vrijenhoek, “Red Queen hypothesis supported by parasitism in sexual and clonal fish,” Nature 344 (1990), 864 -866.
Lively and Joleka, “Temporal and spatial distributions of parasites and sex in a freshwater snail,” Evolutionary Ecology Research 4 (2002), 219-226.
Thomas F. Savage, “A Guide to Recognition of Parthenogenesis in Incubated Turkey Eggs,” Oregon State
In a marginal habitat, it pays to pass on to your children your proven genotype, unchanged. Only a few things can live where you live, and on balance, it’s best to stick with the tried and true. And saving energy with low-cost solo reproduction is a big help too.
Asexuals live where the environment allows natural selection to slow down.
#1 Reason for Sex: Aliens!
OK, then—since sex is a choice, why choose sex? 7
Field studies indicate that the number one reason for sex is biological interactions between species. Mainstream habitats are rich in predators, pathogens, and parasites. Sex, by shuffling genes, is especially good at protecting against parasites and disease. Studies in the lab—evolution in a bottle—show that those odd creatures that switch between sexual and asexual reproduction, like the water snail, Potomopyrgus antipodarum , get sexy when their parasites start hopping.
Japanese knotweed, Polygonum cuspidatum , a handsome but rather unwelcome invasive weed, is one of the first to colonize fresh lava fields in its native Japan. Its ability to flex sexual and non-sexual generations is its strength as a hardy colonizer. A single asexual clone of Japanese knotweed is now invading northern Europe. Although this clone would not stand a chance back home, far from its native pests and predators—the weed is nearly invincible—See Bailey, Bímová, and Mandák, “Asexual spread versus sexual reproduction and evolution in Japanese Knotweed,” Biological Invasions 11, no. 5 (2009).
You see, it’s the tiniest “predators” that evolve the fastest. Compare the life cycle of a flea (four weeks) to its prey, your cat, or compare a human life span to the two-week flu virus life cycle. Pathogens have many extra generations for natural selection to work, so they quickly hone in on the genetic weaknesses of, well, you. Prey must evolve, shift genetic profiles, to combat these enemies. Evolutionary biologists call this the “Red Queen Hypothesis” and liken the costly persistence of sexual reproduction to the Lewis Carroll character who had to keep running to stay in place.
Dandelions
Both sexual and asexual lifestyles have their niches, and a great example lives as close as your backyard.
In their native Eurasia dandelions grow as normal flowers, producing male pollen carried by bees to fertilize female ovules. But dandelions have also evolved asexual lines that clone themselves and send out seeds containing identical DNA. The “old sod” in Europe is golden with sexual dandelions, but it is the asexual ones that have blanketed the virgin continent of North America. They are a beautiful example of just when asexual reproduction is best. Far from their native pests and pathogens, sex-free dandelions have colonized every lawn in the USA because they are able to spread faster than their sexual relatives—even while wasting energy producing cheery yellow flowers that no bee will ever fertilize.
So the next time you’re in the mood to mate, stop and consider an alternative used by bananas, bacteria, lizards, and sharks. Maybe it is better to close the curtains and just do it yourself.
REFERENCES:
Crews, Grassman, and Lindzey, “Behavioral facilitation of reproduction in sexual and unisexual whiptail lizards,” Proc Nat Acad Sci USA 83 (1986), 9547-9550.
Juliet Eilperin, “Female Sharks Can Reproduce Alone, Researchers Find.” The Washington Post, http://tinyurl.com/2aaau4
Lively, Craddock, and Vrijenhoek, “Red Queen hypothesis supported by parasitism in sexual and clonal fish,” Nature 344 (1990), 864 -866.
Lively and Joleka, “Temporal and spatial distributions of parasites and sex in a freshwater snail,” Evolutionary Ecology Research 4 (2002), 219-226.
Thomas F. Savage, “A Guide to Recognition of Parthenogenesis in Incubated Turkey Eggs,” Oregon State
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