You can also find them on Twitter @USGS
Scientists removed insects from fields of primrose for several years.
In just a few generations the primrose relaxed it’s defenses against insects and devoted more energy to competing for space and resources.
In the study, 16 identical plots were set up that contained the same relative numbers of 18 unique genotypes of native evening primrose. During each growing season, half the plots were treated biweekly with an insecticide; the other half were not.
The offspring of evening primrose are mostly clones of the parent due to self-pollination and other factors in primrose reproduction.
Of the genotypes that remained in the plots without insects, the researchers found more plants with relaxed defenses. By 2010 and even more in 2011, there was a shift toward plants that flowered earlier. When insects are present, later-flowering plants do better due to the timing of insect development, where larvae tend to eat the fruits of early flowering plants. Also, over time, there was a shift toward primroses with lower amounts of insect-deterring chemicals in the fruits, suggesting that in the wild, selection had been strongest for defense against flower and fruit eating insects.
Finally, without insects, primroses were better able to compete against dandelions – primrose genotypes that led to larger plants were favored when compared to the controls.
“The effects of insect pests can have immediate consequences for plant health and also sweeping consequences for evolution of entire communities,” Agrawal said.
This plant showed up of its own accord and grew to about 3′ in a month.
A bit of digging revealed it to be a Candle Bush. Since it was in the butterfly garden next to the driveway I thought I’d leave it a bit and see what happened.
It will grow 3′-4′ tall around here, I met someone who claims to have one 6′ tall in her garden. Flowers are yellow, spiky and attract bees, butterflies and hummingbirds. They do not winter over in cold years.
Like most butterfly attractor plants it does best with lots of sun.
Unfortunately they also attract fire ants, I had been warned of this and inspecting the plant last week I found several fire ants crawling around the base and a nest built right next to the trunk of the plant, so out it went.
It is supposed to be a good fungicide for ringworm and other skin fungal infections. It also well known as a laxative among other medicinal uses.
Like most plants here it is toxic, do not use it medicinally with out more research.
Native to east Africa.
Candle Bush at Dave’s Garden
“We show that exposing tomato plants to some level of caterpillar herbivory will increase resistance for future plants—it’s sort of like a plant vaccine,” says Sergio Rasmann, a biologist at the University of Lausanne in Switzerland.
Rasmann isn’t the only one seeing this effect. In a similar study, Ann Slaughter of the Universite de Neuchatel in Switzerland infected Arabidopsis thaliana plants with a benign strain of the bacteria Pseudomonas syringae (PstavrRpt2). The offspring were more resistant to disease than control groups, which were not infected in the first generation.
How does pest resistance get inherited? Researchers point to epigenetic mechanisms, which regulate gene expression and can be passed from one generation to the next without any changes to DNA sequences. The studies suggest known epigenetic factors like DNA methylation and histone modification mediate these effects, and are among the first to demonstrate siRNAs act as an epigenetic mechanism in plant defense responses.
Texas winters may seem mild to those who move here from farther north, but they can be hard to adjust to for immigrants from warmer climates. This is true not only for people but for ants too. A new study by biologists at Rice University and the University of Texas at Austin (UT) finds that the Texas leaf-cutter ant Atta texana, whose ancestors emigrated from the tropics, adapted to the relatively harsh Texas winters in an unusual way — through their food.
Like all leaf-cutter ants, A. texana cuts leaves but does not eat them.
“Leaf-cutters can’t digest the nutrients of leaves directly, so they use a fungus called Attamyces as a kind of external digestive system,” said co-author Scott Solomon, a lecturer in ecology and evolutionary biology at Rice. “It’s an example of a relationship that biologists call mutualism. The ants are completely reliant on the fungus, and the fungus — which only occurs in leaf-cutter colonies — is likewise reliant on the ants.”
The new study, which appears this week in the Proceedings of the National Academy of Sciences, found that leaf-cutter colonies in northern Texas and Louisiana, where winter temperatures regularly get below freezing, have found new ways to cope with the cold. Most leaf-cutter ant species are native to the predictably warm tropics, so the Attamyces fungus has adapted to a narrow range of temperatures. Previous studies have found the ants are attentive gardeners; they keep an ever-present watch on their subterranean gardens, and they are careful to regulate humidity in the gardens and to weed out anything that threatens the crop.
Leaf-cutters live in large colonies that contain up to 5 million members, and their subterranean nests have been found to extend almost 100 feet underground. Within these warrens, they dig thousands of tunnels that connect various chambers, where football-sized gardens of Attamyces are cultivated.
Over several years, Mueller’s team systematically mapped the range of the ants and collected samples of live Attamyces fungus from dozens of nests throughout the range. Tests in the lab revealed that the Attamyces in more northerly ant colonies resists cold better than samples from southern nests, where winters are milder. The studies also found that the ants aid the cold-tolerant fungi by moving them during the coldest months of the Texas winter into deeper garden chambers where conditions are milder.
The researchers were able to show that the fungus’s resistance to cold is based on genetic differences; this suggests that it has evolved during the several million years since the ants first arrived from the south with fungus in tow.
In addition to determining how leaf-cutter ants can survive outside the tropics, the study also found that the ants have been prevented from spreading farther north by the physical limitations of their fungal crop. According to Solomon, the finding that a species is limited by its mutualist is of particular interest to biologists.
“The range of the ants is not limited by their own tolerance to the cold but by the tolerance of the fungus,” Solomon said. “The range of one species is often influenced by the range of another — particularly harmful ones like predators or competitors — but it is really rare to find a case where a species’ range is completely dependent upon the evolution of a species that is helpful.”