Plant Seeds Adapt to City Life

A species of plant found in cities has evolved rapidly in order to adapt to the challenges of surviving in the concrete jungle, a study suggests.

Crepis sancta growing in urban areas produces heavy seeds that fall to the ground rather than lighter seeds that are dispersed by the wind.

Wind-blown seeds are less likely to germinate because most end up on concrete surfaces, scientists say.

The findings appear in Proceedings of the National Academy of Sciences.

Researchers from the Centre d’Ecologie Fonctionelle et Evolutive (CEFE), based in Montpellier, estimate that the change in the way the plant disperses its seeds has taken place in as little as five to 12 generations (five to 12 years).

Co-author Pierre-Oliver Cheptou said the team was surprised by the speed of the change.

“Logic would assume that this sort of evolutionary trait would develop more slowly, which is probably the case in less fragmented situations,” he told BBC News.

“However, at the same time, it is consistent with the estimation we had for the trait in a fragmented urban situation.”

Risky business

The team collected seed samples from the weed, which grows on wasteland or next to roadside trees, from various locations around the French city.

They then grew them in a greenhouse. Compared with specimens taken from the countryside, the urban samples produced far fewer of these seeds.

The researchers said “dispersing” seeds had a lower chance of germinating because the majority ended up on concrete surfaces.

The heavier seeds were at an evolutionary advantage because they would fall down into the patch of soil that had supported the previous generation of the plant.

They added that their findings supported “cost of dispersal” theories.

“When dispersal is passive (wind or water transport) and habitat choice is random, the probability of settling in a suitable site is dependent upon the frequency of suitable sites in the landscape,” they wrote.

“Many empirical studies have reported a reduction in dispersal structures in organisms that live on islands, such as plants or insects.”

Dr Cheptou said that their study showed the same also applied to plants in urban areas, where suitable soil was widely fragmented by buildings, pavements and roads.

He explained that such a strategy, while increasing the odds of survival for the next generation, could have drawbacks.

“We can hypothesize that in fragmented situations, the evolution towards lower dispersal leads to more isolated populations, increasing the risk of extinction.”

Answer the following questions:

1. What does a study suggest?

2. What do researchers think about this plant?

3. What did researchers say about “dispersing” seeds?

4. What seeds are less likely to germinate?

5. What did Dr Cheptou say about the empirical studies?

Article 5

“Bizarre” New Mammal Discovered

A new species of mammal has been discovered in the mountains of Tanzania, scientists report.

The bizarre-looking creature, dubbed Rhynochocyon udzungwensis, is a type of giant elephant shrew.

The cat-sized animal, which is reported in the Journal of Zoology, looks like a cross between a miniature antelope and a small anteater.

It has a grey face, a long, flexible snout, a bulky, amber body, a jet-black rump and it stands on spindly legs.

“This is one of the most exciting discoveries of my career,” said Galen Rathbun, from the California Academy of Sciences, who helped to confirm the animal was new to science along with an international team of colleagues.

Despite its name, the creature, along with the 15 other known species of elephant shrew, is not actually related to shrews.

Dr Rathbun told the BBC News website: “Elephant shrews are only found in Africa. They were originally described as shrews because they superficially resembled shrews in Europe and in America.”

In fact, the creature is more closely related to a group of African mammals, which includes elephants, sea cows, aardvarks and hyraxes, having shared a common ancestor with them about 100 million years ago.

The new species was first caught on film in 2008 in Ndundulu Forest in Tanzania’s Udzungwa Mountains by Francesco Rovero, from the Trento Museum of Natural Sciences in Italy.

Dr Rathbun said: “I got these images, and said to myself: “Boy, these look strange.” But you can’t describe something new based just on photographs, so, we went back in and collected some specimens.”

Flashy creatures

He told the BBC that it quickly became apparent that the creatures were new to science.

He said: “Elephant shrews are almost all distinguished by distinctive color patterns.”

“They are all quite flashy - one species has a bright golden rump, another checkers along the rump.”

“And this one, with its grey face and black rump, was pretty different.”

As well as its distinctive coloring, the new species is also larger than other species of giant elephant shrew, weighing 700 g and measuring about 30 cm in length.

It uses its long, flexible nose and tongue to flick up insects, such as termites, and it is most active in daylight.

Dr Rathbun added: “They are behaviorally fairly simple - they are not like a dog or cat you can interact with - but they are so bizarre-looking and so unique and interesting, you kind of get wrapped up with them.”

The scientists say there is still much to learn about the Rhynochocyon udzungwensis, but they hope further research will help to answer questions about how many of the animals exist, their range and how closely the animals live together.

Tanzania’s Udzungwa Mountains are biodiverse-rich. In addition to this new species, a number of other new animals have been found there, including the Udzungwa partridge, the Phillips’ Congo shrew, and a new genus of monkey known as Kipunji as well as several reptiles and amphibians.

Answer the following questions:

1. How can you describe a new mammal?

2. Is it true that the creature is more closely related to a group of African mammals? Why?

3. For what reason does this creature use its long, flexible nose and tongue?

4. Where was a new species of mammal been discovered?

5. What do you think about this creature?

Article 6

Date: 2016-04-22; view: 1070