speciation
grrlscientist | June 29, 2006
Wild specimen of the butterfly species, Heliconius heurippa.
Researchers recently demonstrated that this species is a naturally-occurring
hybrid between H. cydno and H. melpomene.
Image: Christian Salcedo / University of Florida, Gainesville.
Speciation typically occurs after one lineage splits into two separate and isolated breeding populations. But it is has been hypothesized that two "parental" species with overlapping ranges could hybridize, thereby giving rise to one new but reproductively isolated "daughter species" in the same area. However, this phenomenon has rarely been observed…
grrlscientist | June 6, 2006
Although these fish look similar and have the same genetic makeup, they
produce very different electrical signals (right) and will only mate with fish that produce
the same signals. Cornell researchers believe that these different electrical signals are the
fishes' first step in diverging into separate species. [Image: Carl Hopkins.]
The fishes depicted in the picture above are several types of mormyrids that are endemic to some tributaries of the Ivindo River in Gabon, Africa. These fishes produce weak electrical signals from a battery-like organ at the base of the tail to communicate…
evolgen | May 23, 2006Carl Zimmer has an article in the NYTimes Science section on how humans can interfere with diverging populations, increasing the frequency of hybrids and preventing speciation. He give two examples: three-spine sticklebacks in British Columbia, Canada and ground finches in the Galapagos. The sticklebacks colonized lakes on Victoria Island from the Pacific Ocean and became specialized populations in the new environment. Hybrids between different ecomorphs were selected against because of their intermediate phenotype. Zimmer reports that there are an excess of hybrids in recent samples taken…
evolgen | May 17, 2006
John Hawks reads the papers so that I don't have to. Here is Hawks's reply to the human-chimp speciation paper I mentioned in the previous post. The basic conclusion that Hawks reaches: Don't believe the hype. The data analysis in the paper is sound, but the conclusions the authors draw are designed explicitly for the sake of generating publicity. It's like Chuck D doing the data analysis, then Flavor Flav gettin' all janky with his big ol' clock around his neck screaming "Hybridization!" Hawks claims that there is no need to invoke the hybridization model to explain the data. He presents…
evolgen | May 17, 2006Humans and chimps did not undergo a speciation event. Some pair of species (one an ancestor of humans, the other of chimps) speciated. It was thought that this event occurred approximately 6.5-7.4 million years ago, based on fossil evidence. A new paper coming out in the week's issue of Nature, however, suggests that the speciation event was sloppy. The authors argue, based on differing amounts of divergence between humans and chimps in different parts of the genome, that there was some hybridization and the speciation event extended until 5.4 million years ago. You can read about the study…
evolgen | March 6, 2006If anyone thinks I have sold out to the Seed Gods, let this be my exhibit A against such opinions. Seed has published a review of Funk et al's ecological divergence and speciation PNAS paper. The scientific content is not all that bad, but it blows the implications of the study way out of proportion. My thoughts are below the fold.
The Seed article uses to the Funk paper to look at the role natural selection plays in speciation. The focus is put on whether allopatric speciation is a neutral process or if it depends on divergent selection in the two different environments. The article…
evolgen | February 11, 2006There's lots of cool stuff coming out in the speciation literature. The Questionable Authority has posted on two recent studies on sympatric speciation (see here and here). Nature, which published the two sympatric speciation papers, has a summary available here. I am of the opinion that most examples of sympatric speciation are actually allopatry with reinforcement (for more on this, see here). That is not to say that sympatric speciation is impossible, just extremely rare. In the end, some reproductive isolation is a requirement for speciation in sexually reproducing organisms (whether…
evolgen | February 2, 2006There are quite a few articles sitting around on my desktop waiting for me to write about them. It's gotten to the point where I just need to unload them on the blogosphere. Click through below the fold for some cool stuff from the scientific literature.
More on Neutrality from Laurence Hurst and Colleagues -- I just wrote about the nearly neutral theory, and here is an analysis of selection on silent sites in the human genome. Is this a coincidence or was this article subconsciously on my mind? From the abstract:
"At least in species with large populations, even synonymous mutations in…