Herself’s Houston Garden

From the unintended consequences dept. . .

Squirrels have bitten to death a stray dog which was barking at them in a Russian park, local media report.
Passers-by were too late to stop the attack by the black squirrels in a village in the far east, which reportedly lasted about a minute.

They are said to have scampered off at the sight of humans, some carrying pieces of flesh.

A pine cone shortage may have led the squirrels to seek other food sources, although scientists are sceptical.

The attack was reported in parkland in the centre of Lazo, a village in the Maritime Territory, and was witnessed by three local people. Read more Russian squirrel pack ‘kills dog’

More information:
Furious squirrels attack stray dog
The pack of mutant black squirrels that are giving Britain’s grey population a taste of their own medicine

The world is a cooler, wetter place because of flowering plants, according to new climate simulation results published in the journal Proceedings of the Royal Society B. The effect is especially pronounced in the Amazon basin, where replacing flowering plants with non–flowering varieties would result in an 80 percent decrease in the area covered by ever–wet rainforest.

The simulations demonstrate the importance of flowering–plant physiology to climate regulation in ever–wet rainforest, regions where the dry season is short or non–existent, and where biodiversity is greatest.

“The vein density of leaves within the flowering plants is much, much higher than all other plants,” said the study’s lead author, C. Kevin Boyce, Associate Professor in Geophysical Sciences at the University of Chicago. “That actually matters physiologically for both taking in carbon dioxide from the atmosphere for photosynthesis and also the loss of water, which is transpiration. The two necessarily go together. You can’t take in CO2 without losing water.”

This higher vein density in the leaves means that flowering plants are highly efficient at transpiring water from the soil back into the sky, where it can return to Earth as rain.

“That whole recycling process is dependent upon transpiration, and transpiration would have been much, much lower in the absence of flowering plants,” Boyce said. “We can know that because no leaves throughout the fossil record approach the vein densities seen in flowering plant leaves.”

For most of biological history there were no flowering plants—known scientifically as angiosperms. They evolved about 120 million years ago, during the Cretaceous Period, and took another 20 million years to become prevalent. Flowering species were latecomers to the world of vascular plants, a group that includes ferns, club mosses and confers. But angiosperms now enjoy a position of world domination among plants.

“They’re basically everywhere and everything, unless you’re talking about high altitudes and very high latitudes,” Boyce said.

Dinosaurs walked the Earth when flowering plants evolved, and various studies have attempted to link the dinosaurs’ extinction or at least their evolutionary paths to flowering plant evolution. “Those efforts are always very fuzzy, and none have gained much traction,” Boyce said.

Boyce and Lee are, nevertheless, working toward simulating the climatic impact of flowering plant evolution in the prehistoric world. But simulating the Cretaceous Earth would be a complex undertaking because the planet was warmer, the continents sat in different alignments and carbon– dioxide concentrations were different.

“The world now is really very different from the world 120 million years ago,” Boyce said. Read more

Read the paper
An exceptional role for flowering plant physiology in the expansion of tropical rainforests and biodiversity

The dilemma of plants fighting infections

Scientists from Tübingen reveal an evolutionary dilemma: plants that are more resistant to disease grow more slowly and are less competitive than susceptible relatives when enemies are rare

Individuals of one and the same plant species often differ greatly in their ability to resist pathogens: While one rose succumbs to bacterial infection, its neighbour blissfully thrives. Scientists from the Max Planck Institute of Developmental Biology in Germany have tracked down an explanation for this common phenomenon. Their conclusion: disease resistance can incur high costs. Especially resistant plants of mouse ear cress (Arabidopsis thaliana) produce fewer and smaller leaves, and have a competitive disadvantage in the absence of enemies. Whether it is better to invest in disease resistance or biomass is thus very much dependent on the unpredictable circumstances a plant may find itself in. Therefore both large, but vulnerable plants co-exist in nature with small, but well-protected ones (Nature, June 3rd 2010).

In the course of evolution, plants have invented many ways to defend themselves against enemies. Some produce smelly or bad-tasting ingredients, others develop thorns or have a particular effective immune response to viruses and bacteria. If selection pressure is sufficiently high, one would thus expect only those individuals to survive that are best protected. Pathogens, in turn, should have a difficult time. Everybody knows that this is not the case. Indeed, plants vary tremendously in their ability to defend themselves, and this is true not only for different species, but also for members of the same species.

The group of Detlef Weigel at the Max Planck Institute for Developmental Biology has now tracked down a variant of the ACD6 gene, which functions as a universal weapon in the fight against predators. With it, the plants both produce much more of a chemical that is directly toxic to microbes and more signalling molecules important in immunity. These enable mouse ear cress plants to combat a wide range of enemies, from bacteria and fungi to insects such as aphids. However, not all varieties have this variant. While it occurs throughout the area where mouse ear cress grows, from North Africa to Scandinavia, and from Central Asia to Western Europe, at any given place it is found in only about 20 percent of individuals. This already suggests that this variant might also confer some disadvantages.

“We could show that this gene makes plants resistant against pathogens, but at the same time it slows down the production of leaves and limits the size of leaves, so that these plants are always smaller than those that do not have this variant,” said Detlef Weigel. “But as soon as they are being attacked, the plants with the special ACD6 variant have a leg up compared to plants with the standard version. On the down side, at places or in years where there are few enemies, they are penalized and lose out compared to the larger fellow plants.” Smaller size eventually leads to reduced number of seeds and hence to fewer progeny. The conclusion of Weigel: “Just as in human society, there is no free lunch in nature.”

Original work:

M. Todesco, S. Balasubramanian, T. T. Hu, M. B. Traw, M. Horton, P. Epple, C. Kuhns, S. Sureshkumar, C. Schwartz, C. Lanz, R. A. E. Laitinen, Y. Huang, J. Chory, V. Lipka, J. O. Borevitz, J. L. Dangl, J. Bergelson, M. Nordborg, and D. Weigel
Natural allelic variation underlying a major fitness tradeoff in Arabidopsis thaliana.
Nature, June 3rd 2010

Source
Max Planck Institute Press Release