So one of the big stories in evolutionary biology last week was this paper, which described the genome of the “marbled crayfish” (shown below), and which supported three important hypotheses:

  1. They are triploid organisms, most likely originating from the fertilization of a rare diploid egg of the slough crayfish (Procambarus fallax), a species found naturally in Georgia and Florida but also propagated in aquaria.
  2. They reproduce parthenogenetically, and thus their population is clonal.
  3. They have rapidly in Northern Europe and are now doing so in Madagascar.

From *Nature*

There are other questions that come up, such as whether the original event occurred in an aquarium situation and how parthenogenicity developed (A consequence of triploidy? Some other fortuitous mutation?), but what has fascinated me has been the science news coverage of it. The original paper (well written and well worth reading) was published in Nature Ecology and Evolution, a new open access journal that is part of the Nature empire, so perhaps first we should look at what they had to say about it:

Geneticists unravel secrets of super-invasive crayfish

Notice that the title is pretty neutral – while “unraveling secrets” and “super-invasive” may be a bit dramatic, the story is told in a fairly straightforward manner. Then there is Science:

An aquarium accident may have given this crayfish the DNA to take over the world

Now we are getting a bit more dramatic. The headline focuses on what is, at best, a speculative conclusion. Now let's turn to a national newspaper in the United States that overall has sound science coverage, The New York Times

This Mutant Crayfish Clones Itself, and It’s Taking Over Europe

Now this is actually a good article, written by Carl Zimmer, who is an excellent writer, especially about evolution (I taught from the textbook he coauthored for many years). But “clones itself”? “Taking over Europe?” Please. The article is overall sound, but the title is (to put in mildly) over the top.

Finally, all of the above (including the original paper) treat the marbled crayfish as a new species (Procambarus virginalis – don't you love the species name?). So it is worth it to read Jerry Coyne's take on this:

A “parthenogenetic” crayfish reproduces without sex: is it a new species?

Jerry is, of course, the coauthor of the best book on the subject of speciation, and he and his students have made tremendous contributions to the field over the years. In addition, he is a believer in the importance of skepticism in science. So it is not surprising that he has doubts about species status for this creature. I don't necessarily agree with him on this – his argument is that since they reproduce clonally, the Biological Species Concept can't be applied. So it is, of course, for most of the microbial world. But that gets to the heart of the question of what constitutes a “species”, and it's too late at night to pursue that in depth.

In any event, this has been a fun story to follow, and I'm glad to see lots of good science writing about it. The headlines may be hyperbolic, but the coverage has been sound.