Recently in Evolution Category

PNAS has put the proceedings of the Sackler Colloquium on 200 years of Darwin online. Nineteen papers, all free!

Via John Lynch.

The Darwin exhibit organized by the American Museum of Natural History in collaboration with the Museum of Science, Boston; The Field Museum, Chicago; the Royal Ontario Museum, Toronto, Canada; and the Natural History Museum, London, England that is currently touring North America will be at the Great Lakes Science Center in Cleveland from June 27 through September 18, 2009. From all reports this is a magnificent exhibition, well worth the drive to Cleveland. In addition, several Cleveland institutions will have related programs through the summer, including showings of Galapagos at the Omnimax theater in the Science Center.

How can anyone resist an article titled “Sexual Intercourse Involving Giant Sperm in Cretaceous Ostracode”? You can’t, I tell you. It’s like a giant brain magnet, you open the journal to the index, and there’s that title, and you must read it before you can even consider continuing on to anything else.

Some organisms have evolved immensely long sperm tails — Drosophila bifurca, for instance, has sperm cells that are about 60mm long, or 20 times longer than the length of the entire adult body. The excessively long sperm tail is obviously not a structure that has evolved for better swimming; instead, it is thought to act as a tangled barrier in the female reproductive tract to prevent other males from fertilizing the female, and there is also some very interesting evidence that sperm coevolves with the female reproductive tract, so some sexual selection at the level of the gametes is going on.

At the same time, sperm morphology is extremely diverse, and seems to evolve very rapidly. Perhaps these mega-sperm are a transient fad? Not all species of Drosophila exhibit the phenomenon, and those that do vary considerably from species to species. What we’d like to know is if there are any lineages that maintain these patterns of giant sperm over long periods of evolutionary time…so what do we need to do? We need to go spelunking for sperm in fossils!

Future Evolution (SSE+SSB+ASN) Meetings:

2010 Portland, Oregon (Portland State University)

2011 Norman, Oklahoma (University of Oklahoma)

2012 Ottawa, Ontario

Future SMBE Meetings:

2010 Lyon, France

I wonder if the politicians in Oklahoma will try to ban the evolution meeting like they tried to ban Dawkins. I bet you will see some bills trying to ban state funds for being used for the conference and others that demand an equally sized creationism conference. Good luck with that.

Prof. Steve Steve and I are currently wandering around the University of Idaho waiting for Evolution 2009 to start. And we are not alone.

The latest issue (July/August, 2009) of Discover Magazine had a handful of splendid articles, but what really caught my eye was a remarkably detailed image of a 100-million-year-old wasp that had been fossilized inside an opaque piece of amber (p. 39). I could not find the picture on the Discover website, but I easily tracked it to here, where you may see it along with a number of other images.

According to the Discover article, Paul Tafforeau and colleagues at the European Synchrotron Radiation Facility used a beam of x-rays to probe the interiors of bits of amber that are opaque to visible light. They found hundreds of fossilized beetles, ants, wasps, flies, and bits of plants, and made tomograms (or 3-dimensional reconstructions) of some of them. None of the trapped insects was bigger than a few millimeters, presumably because larger insects were not so easily trapped by the resin.

Discover notes that the team found more than 600 insects, none of which appears to be a modern species. It is not clear how many different species those insects represent, but Tafforeau says, “Each scan is a new discovery,” so I infer that they have discovered a great many new, ancient species - and that is among small insects only.

If you believe, with Lucretius and certain of our creationist colleagues, that species are not born but only die out, then all I can say is there must have been at one time one helluva lot of species.

Via Jerry Coyne, a special issue of Evolution: Education and Outreach devoted to transitional fossils. As Coyne notes, several of the papers include some very good teaching illustrations.

I will send an autographed copy of the book Why Evolution Works (and Creationism Fails), by me and Paul K. Strode, to the first person who can correctly find a quotation that accurately describes evolution by natural selection and predates Darwin, Wallace, and even Erasmus Darwin by hundreds of years. To enter, just post a comment. To win, you will have to state the quotation, its author, and the approximate year. I have a specific quotation in mind, but I will consider others, as long as they clearly describe natural selection.

For the table of contents and other information about the book, go here.

In a day or so, I will declare the winner and explain why the quotation is so interesting. In the meantime, below the fold, more about Why Evolution Works (and Creationism Fails).

The final chapter of my dissertation has finally been published in Molecular Ecology. I don’t have time to go into detail, so I’ll just cite the abstract that covers much of the motivation and large-scale results.

Abstract: Many self-incompatible plant species exist in continuous populations in which individuals disperse locally. Local dispersal of pollen and seeds facilitates inbreeding because pollen pools are likely to contain relatives. Self-incompatibility promotes outbreeding because relatives are likely to carry incompatible alleles. Therefore, populations can experience an antagonism between these forces. In this study, a novel computational model is used to explore the effects of this antagonism on gene flow, allelic diversity, neighborhood sizes, and identity-by-descent. I confirm that this antagonism is sensitive to dispersal levels and linkage. However, the results suggest that there is little to no difference between the effects of gametophytic and sporophytic SI on unlinked loci. More importantly both GSI and SSI affect unlinked loci in a manner similar to obligate outcrossing without mating types. This suggests that the primary evolutionary impact of self-incompatibility systems may be to prevent selfing, and prevention of biparental inbreeding might be a beneficial side effect.

The citation of the paper is

Cartwright RA (2009) Antagonism between local dispersal and self-incompatibility systems in a continuous plant population. Molecular Ecology 18:2327-2336. [doi:10.1111/j.1365-294X.2009.04180.x]

Unfortunately, there is not a free version available yet online. The research was partially funded by NIH, so a copy should show up in pubmed in several months. Until then, you can email me at [Enable javascript to see this email address.], and I’ll send you a reprint.

If you want to know how I fulfill the reprint requests, see this post on De Rerum Natura.

This essay is the third of a series authored by Dave Wisker, Graduate Student in Molecular Ecology at the University of Central Missouri.

In previous essays in this series, I have discussed two issues with the fusion that resulted in human chromosome 2: its dicentric nature, and the fusion’s possible effect on fertility. I showed how one extra centromere may not result in inevitable damage to the chromosome during meiosis and mitosis, and demonstrated that the fusion did not necessarily have to result in greatly decreased fertility. Either of those situations would have effectively prevented the fusion from rising in frequency and eventually becoming fixed in the human population. We are now in the position to consider the probability of such a fusion becoming fixed. This essay will examine the fixation probability of the fusion in a small subpopulation, or deme.

There is a wide array of resources on the web about evolution, ranging from public access to technical papers available via PubMed to the excellent Understanding Evolution site operated by the University of California Museum of Paleontology and the National Center for Science Education. The grand daddy of them all, of course, is the TalkOrigins Archive.

Now a new resource has been established by T. Ryan Gregory, evolutionary biologist and blogger at Genemicron. It’s called Evolver Zone, and is “a resource for students, teachers, and researchers with an interest in evolution.”

Evolver Zone is a collection of a wide range of resources on evolution, from online databases to software to teaching resources to multimedia (including games!). I haven’t browsed the whole site yet, but what I’ve seen looks to be very useful, particularly for advanced high school and undergraduate classes. Gregory tells us the site is a work in progress, so check back often for new additions.