There are are couple of interesting pieces of research in the news. The first concerns tail shedding in island lizards. PhysOrg has the story:
The U-M-led team decided to test the long-held predator-pressure idea using a clever combination of laboratory experiments and field measurements made in mainland Greece and multiple offshore Aegean Sea islands inhabited by different combinations of predators.
Their conclusion? The predator-pressure hypothesis, while generally true, comes with an unexpected twist: Not all predators are created equal.
“The only predators that truly matter are vipers,” said U-M vertebrate ecologist Johannes Foufopoulos, co-author of a study published online this week in the journal Evolution.
This is how the study worked:
The U-M-led team looked for correlations between autotomy rates and the presence or absence of various types of lizard predators at the study’s 10 collecting sites. The autotomy rate is a measure of the ease with which lizards shed their tails. The higher the rate, the easier the tail separates from the body.
The only strong signal that emerged from the study was the link to vipers.
The team found that viper-free islands are home to lizards that have largely lost the ability to shed their tails. Conversely, all the locations where vipers have survived are inhabited by lizards with high autotomy rates.
The study involved more than 200 insect-eating lizards from 15 species, most measuring 5 to 8 inches from snout to tail-tip.
To measure autotomy rates, the researchers combined field observations and laboratory measurements. In the field, lizards that have shed their tails and grown new ones can be distinguished from lizards that retain their original tails.
In the laboratory, researchers used calipers to gently pinch lizards’ tails with a standardized level of pressure for 15 seconds. Laboratory autotomy rates for each species were expressed as the fraction of lizards that shed their tails during this procedure.
This new finding is consistent with an old theory, often discounted in science textbooks, that fins and (later) limbs evolved from the gills of an extinct vertebrate, Gillis added. “A dearth of fossils prevents us from definitely concluding that fins evolved from gills. Nevertheless, this research shows that the genetic architecture of gills, fins and limbs is the same.”
The research builds on the breakthrough discovery of the fossil Tiktaalik, a “fish with legs,” by Neil Shubin and his colleagues in 2006. “This is another example of how evolution uses common developmental programs to pattern different anatomical structures,” said Shubin, who is the senior author on the PNAS paper and Professor and Associate Dean of Organismal and Evolutionary Biology at the University of Chicago. “In this case, shared developmental mechanisms pattern the skeletons of vertebrate gill arches and paired fins.”
The paper can be found here. If some one with access could send them to me I would appreciate it. My email is firstname.lastname@example.org