http://www.sciencedaily.com/releases/2005/01/050111164858.htm

ScienceDaily (Jan. 15, 2005) — Findings reported this week reveal how an evolutionary innovation involving the sharing of genes between two ant species has given rise to a deep-seated dependency between them for the survival of both species populations. The new work illustrates how genetic exchange through interbreeding between two species can give rise to a system of interdependence at a high level of biological organization--in this case, the production of worker ants for both species.

Millions of years before the first modern humans evolved, ants were practicing many of the social innovations we consider to be our own: division of labor, agriculture, and even slavery. Indeed, these traits have been taken to their extreme in many ant species, such as the case of slavemaker ants, which have become so specialized for raiding food from the colonies of other ants that they can no longer feed themselves or raise their younger siblings. Recent work on ants suggests that we may need to add genetic engineering to the list of innovations ants have evolved to employ. In two species of harvester ants, populations have been discovered in which queens mate with males of another species to produce genetically novel hybrid workers. In a new study, Dr. Sara Helms Cahan and colleagues demonstrate that both of the species involved have effectively given up the ability to produce pure-species workers in favor of the hybrids, thereby becoming completely dependent on one another for survival.

Female ants are generally found in two forms: reproductive queens and sterile workers. The role, or caste, of an individual is determined for life at a certain stage in her development. In virtually all ant species, it is the environment in which a female is raised, rather than a genetic predisposition, that determines which caste she will adopt. However, in two harvester ant populations in southern New Mexico, queens and workers from the same colonies are genetically very different; in both species at the site, only the queens are genetically derived from a pure species-specific lineage, whereas all the workers are hybrids that possess a combination of genes from the two species in a single individual. It is not currently known whether the ants benefit from having hybrids do the work, but, as is evident from the researchers' own attempts at selective breeding and genetic engineering, combining genomes is an easy way to produce novel characteristics that may be highly advantageous for growth, environmental tolerance, or disease resistance. Regardless of the specific advantages, however, it is clear that these ants have committed themselves to the hybrid workforce strategy. When the researchers prevented queens from mating with males of the other species, very few succeeded in making any workers at all, a handicap that would lead to certain population failure in the field. The new findings suggest that specialization involving reliance on interspecific hybrid workers has left these species unable to survive independently of one another.

Sara Helms Cahan, Glennis E. Julian, Steven W. Rissing, Tanja Schwander, Joel D. Parker, and Laurent Keller: "Loss of Phenotypic Plasticity Generates Genotype-Caste Association in Harvester Ants"

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The other members of the research team include Glennis E. Julian of University of Texas, Austin; Steven W. Rissing of The Ohio State University; and Tanja Schwander, Joel D. Parker, and Laurent Keller of University of Lausanne. This work was supported by grants from the Durfee Foundation (administered by the Earthwatch Institute), the Swiss Society of Naturalists (ASSN), and the Swiss National Science Foundation.

Publishing in Current Biology, Volume 14, Number 24, December 14, 2004, pages 2277–2282.

ScienceDaily (Mar. 25, 2008) — It turns out ants, like humans, are true farmers. The difference is that ants are farming fungus.

Entomologists Ted Schultz and Seán Brady at the Smithsonian's National Museum of Natural History have been providing new insight into the agricultural abilities of ants and how these abilities have evolved throughout time. Using DNA sequencing, the scientists were able to construct an "evolutionary tree" of fungus-growing ants, which revealed a single pioneering ancestor that discovered agriculture approximately 50 million years ago.

In the past 25 million years, four different specialized agricultural systems have evolved, leading to the most recently evolved and best-known fungus-growing ant species--"leaf-cutter ants." The ants do not eat the leaves; they grow their fungus gardens on them and then eat the fungus. By studying the agricultural evolution of leaf-cutter ants, as well as various other species, scientists may be able to develop improved human agricultural and medical methods.

"Agriculture is very rare in the animal world," said Schultz. "We only know of four animal groups that have discovered agriculture: ants, termites, bark beetles and humans. By studying certain fungus-growing ants, which our study indicates are almost like 'living fossils,' we might be able to better understand steps involved in the evolution of ant agriculture."

To complete their research, scientists spent more than 15 years assembling a comprehensive array of specimens, which included 91 ant species, 65 of which were fungus-growing ant species representing all different groups of fungus-growing ants. Researchers then used DNA sequencing, combined with a variety of state-of-the-art computer algorithms, to construct an evolutionary tree of fungus-growing ants. Dominican amber fungus-growing ant fossils were used to calibrate time intervals on the evolutionary tree.

From this evolutionary tree, scientists were able to determine that fungus-growing ants are all descended from a common ancestor that pioneered agriculture 50 million years ago during a period of global warming. The researchers also determined that in the past 25 million years, four different specialized agricultural systems emerged.

Each of these systems has its own unique set of cultivated fungi. For example, approximately 20 million years ago one group of fungus-growing ants discovered "higher agriculture," meaning they cultivated their fungi to produce specialized "fruits" that the ants would harvest and eat for food. Leaf-cutter ants, which belong to this group, originated recently--less than 10 million years ago. Finally, it also was discovered that there are certain fungus-growing ant species living in South America today that are "missing links" in evolution.

This research was published in the March 24 issue of the journal Proceedings of the National Academy of Sciences.

ScienceDaily (Mar. 23, 2008) — In a study of New Zealand's "living dinosaur" the tuatara, evolutionary biologist, and ancient DNA expert, Professor David Lambert and his team from the Allan Wilson Centre for Molecular Ecology and Evolution recovered DNA sequences from the bones of ancient tuatara, which are up to 8000 years old. They found that, although tuatara have remained largely physically unchanged over very long periods of evolution, they are evolving - at a DNA level - faster than any other animal yet examined.

"What we found is that the tuatara has the highest molecular evolutionary rate that anyone has measured," Professor Lambert says.

The rate of evolution for Adélie penguins, which Professor Lambert and his team have studied in the Antarctic for many years, is slightly slower than that of the tuatara. The tuatara rate is significantly faster than for animals including the cave bear, lion, ox and horse.

"Of course we would have expected that the tuatara, which does everything slowly -- they grow slowly, reproduce slowly and have a very slow metabolism -- would have evolved slowly. In fact, at the DNA level, they evolve extremely quickly, which supports a hypothesis proposed by the evolutionary biologist Allan Wilson, who suggested that the rate of molecular evolution was uncoupled from the rate of morphological evolution."

Allan Wilson was a pioneer of molecular evolution. His ideas were controversial when introduced 40 years ago, but this new research supports them.

Professor Lambert says the finding will be helpful in terms of future study and conservation of the tuatara, and the team now hopes to extend the work to look at the evolution of other animal species.

"We want to go on and measure the rate of molecular evolution for humans, as well as doing more work with moa and Antarctic fish to see if rates of DNA change are uncoupled in these species. There are human mummies in the Andes and some very good samples in Siberia where we have some collaborators, so we are hopeful we will be able to measure the rate of human evolution in these animals too."

The tuatara, Sphendon punctatus, is found only in New Zealand and is the only surviving member of a distinct reptilian order Sphehodontia that lived alongside early dinosaurs and separated from other reptiles 200 million years ago in the Upper Triassic period.

Journal reference: Lambert et al.:"Rapid molecular evolution in a living fossil." Researchers include Jennifer M. Hay, Sankar Subramanian, Craig D. Millar, Elmira Mohandesan and David M. Lambert, Trends in Genetics. March 2008. (http://dx.doi.org/10.1016/j.tig.2007.12.002)

LINDYY

It is indeed unsettling to not fully understand the changes that are constantly taking place around us.

I guess that is perhaps one part of the reason I seek out this kind of information . . . I figure the more I know . . . the less unsettling it will be.

Just thought Id share some science news and events with my fellow JSH'ers