In the long run sex always wins

Carl Zimmer has an incredible piece up, This Mutant Crayfish Clones Itself, and It’s Taking Over Europe:

All the marbled crayfish Dr. Lyko’s team studied were almost genetically identical to one another. Yet that single genome has allowed the clones to thrive in all manner of habitats — from abandoned coal fields in Germany to rice paddies in Madagascar.

In their new study, published in the journal Nature Ecology and Evolution, the researchers show that the marbled crayfish has spread across Madagascar at an astonishing pace, across an area the size of Indiana in about a decade.

Basically, it looks like a crayfish mutated and now is able to reproduce clonally. That is, it’s asexual. Also, because of its chromosomal structure, it’s no longer inter-fertile with the species from which it emerged.

As it happens there are a fair number of lineages which have sexual and asexual species. Asexual species seem to be much younger. The implication then is that they’re going extinct and emerging over and over again.

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6 thoughts on “In the long run sex always wins

  1. I understand why clonal species might tend not to last long. What I’ve never understood is why we don’t see more hermaphroditic species. That would seem to combine the best of both worlds: the genetic recombination of sex; plus every individual is a baby making machine. Any thoughts about why this isn’t more common?

    Here is a speculative idea: because gametes are asymmetric, in a hermaphroditic species every individual will want to take the free riding male role, fertilizing as many other individuals as possible with small cheap sperm, while avoiding the production of large expensive eggs. This makes the arrangement unstable, and the end result is that you get sperm specialists and egg specialists (i.e., male and female), even though from the point of view of being fruitful and multiplying this isn’t the optimum solution. If animals had only one type of gamete rather than two — let’s say just a medium sized mobile gamete that would swim around looking for a mate of the same type — then all animals would be hermaphrodites.

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  2. Richard Lenski shows that sex isn’t so beneficial.

    in bacteria.

    (also, lenksi’s experiments are great because they are so long-term that sometimes they overturn each other, so there’s no point in citing ONE paper as definitive; they rarely are)

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  3. “… because gametes are asymmetric, in a hermaphroditic species every individual will want to take the free riding male role, fertilizing as many other individuals as possible with small cheap sperm, while avoiding the production of large expensive eggs.”

    In a primarily hermaphroditic Caenorhabditis nematode species (C. briggsae), genes that would promote fertility in that species’ residual males appear to have been actively selected against and therefore lost. Moreover, this negative selection against male-fertility genes can be observed as independently occurring events in three different hermaphroditic lineages. In other words, the negative selection is powerful enough to have recurred convergently.

    (However, if you transgenically restore a male-fertility gene to C. briggsae from its male-female sibling species C. nigoni, you get much more vigorous males. So, up to a point, the negative selection in favor of wimpy males can be artificially reversed…)

    http://science.sciencemag.org/content/359/6371/55

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