New research on lizards supports an old idea about how species can originate. Morphologically distinct types are often found within species, and biologists have speculated that these “morphs” could be the raw material for speciation. What were once different types of individuals within the same population could eventually evolve into separate species.
A new study conducted by researchers at the University of California, Santa Cruz, supports this idea. The study documents the disappearance of certain morphs of the side-blotched lizard in some populations. The researchers reported their findings in a paper published this week in the online early edition of Proceedings of the National Academy of Sciences (PNAS).
The side-blotched lizard, Uta stansburiana, has three morphs differing in color and mating behavior. Barry Sinervo, a professor of ecology and evolutionary biology at UCSC, has studied a population of side-blotched lizards near Los Baños, Calif., for over 20 years. Ammon Corl, now a postdoctoral researcher at Uppsala University in Sweden, led the new study as a graduate student at UCSC and is first author of the paper.
Previous work by Sinervo and his colleagues showed that competition among male side-blotched lizards takes the form of a rock-paper-scissors game in which each mating strategy beats and is beaten by one other strategy. Males with orange throats can take territory from blue-throated males because they have more testosterone and body mass. As a result, orange males control large territories containing many females. Blue-throated males cooperate with each other to defend territories and closely guard females, so they are able to beat the sneaking strategy of yellow-throated males. Yellow-throated males are not territorial, but mimic female behavior and coloration to sneak onto the large territories of orange males to mate with females.
“My goal when starting my Ph.D. thesis research was to understand how this fascinating mating system evolved,” Corl said. “We studied lizard populations from California to Texas and from Washington State down to Baja California Sur in Mexico.” …
Many aspects of the evolutionary history of these lizards are consistent with the theory that morphs can be involved in speciation, Corl said. Evolutionary theory predicts that new species could arise from particular morphs originally found in a population containing multiple morphs. Side-blotched lizards started off with three color morphs. If just one or two types occur in a population, they look just like the original morphs.
The theory was also supported by patterns in the formation of subspecies, which are the precursors to new species. Two subspecies of side-blotched lizard that originated from populations with three morphs now have only a single color morph. Thus, populations that lose morphs are not transitory, but can persist and eventually become a different species.
The study also found evidence to support the hypothesis that rapid evolutionary change occurs when particular morphs are lost from the system. “Imagine the three lizard morphs playing rock-paper-scissors,” Corl explained. “They have very specific adaptations for fighting one another. Now imagine that some morphs are lost, leaving a population of all rock morphs. Their adaptations for fighting the paper and scissors morphs are no longer useful. Therefore, rapid evolutionary change is expected in a population of rock morphs as they adapt to a new game in which they only fight other rock morphs.”
The study showed clear evidence of very rapid evolution of body size when morphs are lost from a population. “Such rapid evolution could eventually cause populations to evolve into distinct species. We are the first group to provide a statistical test of this hypothesis,” Corl said.
The idea of morphs being involved in speciation is an old one. Charles Darwin conducted experiments with different reproductive morphs in flowers to try to gain insight into the process of speciation. However, the new paper by Corl and colleagues is one of the first studies to use modern techniques to tackle the problem of morphs and speciation. …
Archive for February 18th, 2010
Posted by Xeno on February 18, 2010
Posted by Xeno on February 18, 2010
A pilot furious with the Internal Revenue Service crashed his small plane into an office building that houses federal tax employees in Austin, Texas on Thursday, setting off a raging fire that sent workers fleeing as thick plumes of black smoke poured into the air.
A U.S. law official identified the pilot as Joseph Stack and said investigators were looking at an anti-government message on the Web linked to him. The Web site outlines problems with the IRS and says violence “is the only answer.”
Federal law enforcement officials have said they were investigating whether the pilot crashed on purpose in an effort to blow up IRS offices. The Web site featured a long note dated Thursday denouncing the government and the IRS in particular and cited the Austin man’s problems with the agency.
All the officials spoke on condition of anonymity because the investigation is continuing.
At least one person who worked in the building was unaccounted for and two people were hospitalized, said Austin Fire Department Division Chief Dawn Clopton. She did not have any information about the pilot. About 190 IRS employees work in the building, and IRS spokesman Richard C. Sanford the agency is trying to account for all employees.
Flames shot out of the building, windows exploded and workers scrambled to safety after the blast. Thick smoke billowed out of the second and third stories hours later as fire crews battled the blaze.
“It felt like a bomb blew off,” said Peggy Walker, an IRS revenue officer who was sitting at her desk in the building when the plane crashed. “The ceiling caved in and windows blew in. We got up and ran.”
Federal Aviation Administration spokesman Lynn Lunsford initially said the plane was identified as a Cirrus SR22, but later said it might be a Piper Cherokee.
“It’s so destroyed that it’s hard to identify,” Lunsford said.
He said FAA has confirmed that the plane that took off from an airport in Georgetown, Texas, and that the pilot didn’t file a flight plan.
In a neighborhood about six miles from the crash site, a home listed as belonging to Stack was on fire earlier Thursday. Authorities in Austin would not comment on the house fire Thursday afternoon.
Good thing the steel supports in this building do not melt when exposed to burning aircraft fuel.
Posted by Xeno on February 18, 2010
This image provided by NASA shows the immense Andromeda galaxy, also known as Messier 31, captured in full in this new image from NASA’s Wide-field Infrared Survey Explorer, or WISE.
A glowing comet. A star-forming cloud. A new view of the Andromeda galaxy. A dense galaxy cluster.
NASA on Wednesday released the first images from its sky-mapping spacecraft, which captured a hodgepodge of cosmic targets two months after its launch on a mission to map the entire sky.
“We’ve got a candy store of images coming down from space,” principal investigator Edward Wright of the University of California, Los Angeles, said in a statement.
Since launching in December, the Wide-field Infrared Survey Explorer, or WISE for short, has sent back more than 250,000 raw images. NASA processed several of them for the public.
Orbiting some 325 miles above the Earth, WISE scans the sky in search of hard-to-see asteroids, comets, stars, galaxies and other celestial objects. One of its main tasks is to spot objects that may pose a danger to Earth.
Unlike optical telescopes, WISE is designed to detect objects that give off infrared light or heat.
The $320 million project is managed by NASA’s Jet Propulsion Laboratory.