Friday, 23 July 2010

Pandas don't like roads

Chinese geneticists make a sound case for panda corridors in some of the most fragmented panda habitat there is.

A paper published online today in the open-access journal BMC Genetics is another important milestone in the advance of panda science.

This is Figure 1 from the BMC Genetics paper, showing the Daxiangling (DXL) and
Xiaoxiangling (XXL) mountains and how the river and road carve them up into four effective fragments.

The belief that fragmented habitat is going to restrict gene flow might be intuitive but such intuition is not enough on which to base serious and expensive management decisions. In this study, a team of Chinese scientists, led by Professor Wei Fuwen of the Chinese Academy of Sciences, has a good go at providing the kind of evidence base that will be needed to construct meaningful habitat corridors between isolated pockets of bamboo forest.

When I was in China in March, interviewing scientists for my forthcoming book The Way of the Panda, Wei Fuwen gave me an hour of his time (I'll dig out the photo some time). As we began to talk, he was understandably wary of me, answering my sometimes difficult questions in generalities and frequently stopping the interview to pick up calls to his mobile phone with its implausibly snazzy ringtone or to light another cigarette. But after about 40 minutes, I think he decided I was someone he could trust and he opened up completely. By the end, he’d pulled me round his side of his strangely empty desk to show me a powerpoint presentation he’d just given at some closed meeting or other. He talked to me about the findings of the BMC Genetics study published today (you can get to the preprint PDF here).

He and his colleagues have sensibly homed in on the Daxiangling and Xiaoxiangling Mountains. These are the two most southerly regions in the panda’s range and are home to the smallest and perhaps most fragmented populations. This makes studying them pretty urgent, but the small population size also means that they had a chance of collecting data on most of the animals in the region. They probably got close.

They collected 192 panda scats (poos), got a genotype from 136 of them and resolved these into 53 different animals. This messy business is pretty much the only way to get good data on the population and distribution of pandas in the wild – I have heard of apocryphal stories of a PhD student going to study pandas in China and not seeing a single one for two years. In case you’re interested, this censusing approach was pioneered in the Wanglang Nature Reserve by Professor Wei and others in a paper in Current Biology in 2006. It is also, according to a Scientific American blog post, likely to be used in the Fourth Giant Panda Survey (which will begin next year).

Many of their findings make intuitive sense: pandas stick to bamboo forest; the Dadu River, which runs between the two mountain ranges, appears to have had a big role in keeping pandas from these two regions apart; and the National Route 108, which cuts its way from North to South through both of these ranges has further fragmented things. Still, though you could have predicted this might be the case, we now know it to be true and importantly we also now know just how small is the population size in each fragment, the genetic variation in each isolated population and where action is most urgently needed.

In conclusion, Wei and friends argue that “it is vital to connect currently fragmented habitats and increase the connectivity of bamboo resources within a habitat to restore population viability of the giant panda in these regions.” They also sign off with the idea that “for these small isolated populations reintroductions will be an effective strategy.”

No comments:

Post a Comment