Global warming 'altering genes'

The latter half of the 20th Century saw a rapid warming

		By Helen Briggs BBC News Online

Global warming is leading to changes in the genetic make-up of animals, say scientists.

They have found that mosquitoes have altered their genes in response to climate change.

According to biologists at the University of Oregon, US, many plants and animals are adapting to a warming environment by taking advantage of the longer seasons.

Evolution is happening and it is happening very fast

Dr William Bradshaw, University of Oregon

British birds now lay their eggs more than a week earlier than they did in the 1970s. And frogs are spawning about 10 days earlier. But the Oregon study is the first clear evidence that the genes of animals are changing.

In northern latitudes, warming has led to earlier springs, longer summers and milder winters. The shift in the seasons is linked to increasing global temperatures experienced in the second half of the 20th Century.

This has affected the life cycle of a tiny species of mosquito found on the eastern seaboard of North America, from the Gulf of Mexico to northern Canada.

Delayed dormancy

Dr William Bradshaw and Dr Christina Holzapfel studied populations of the mosquito, Wyeomyia smithii, in the laboratory.

They found that the insects are now entering their pupae 8-10 days later than they did in the 1970s.

A larger relative of the plant pitcher mosquito

Because the insects' life cycle is controlled by a genetic switch linked to the length of day, or photoperiod, it must be due to genes, the scientists say.

Dr Bradshaw told BBC News Online: "There is a genetic change in their response to daylight. We can detect this change over as short a time period as five years.

"Evolution is happening and it is happening very fast."

Complicated life cycle

The mosquitoes, the size of a grain of rice, occasionally bite people but prefer plants. They lay their eggs in a select environment: the foot of carnivorous plants called the purple pitcher.

The larvae swim and feed in water at the base of the plant, where they go through a complicated life cycle. To survive the winter, the mosquito must enter its dormant phase as a pupa.

To know when winter is coming, it takes its cues from the environment, in this case the length of the day.

The shift towards longer summers has meant that mosquitoes that enter their pupal stage later have an advantage. Thus, global warming is selecting for a certain genetic trait that, over the course of time, will be passed to the rest of the population.

A familiar British bird: Some species are now laying their eggs earlier

The implication, says Dr Bradshaw, is that there may be a genetic basis for seasonal changes seen in other animals.

Birds that lay their eggs slightly earlier in the year, along with the premature arrival of spring, may have a genetic advantage that they pass on to their offspring.

And, because of the complex interaction between predators and prey, the consequences are likely to be widespread.

"The broader implication is that the make-up of future communities in nature may depend critically on the ability of these species to adapt or evolve in their response to global warming," Dr Bradshaw told BBC News Online.

One species of British bird, the great tit, is already feeling the effects, he says. Some of the birds are running out of insects to feed to their chicks because they are nesting after caterpillars have developed into butterflies.