A TROPICAL forest ravaged by logging can recover, but the new growth will probably be much less genetically diverse. This makes it more vulnerable to threats such as disease and climate change.
In many tropical countries, "second-growth" forests now cover a greater area than old-growth forests. Uzay Sezen and his colleagues at the University of Connecticut in Storrs wanted to see how genetically diverse these regenerated patches are. They studied 20 hectares of forest in Costa Rica that was cleared for cattle ranching in the 1960s but has been left to recover since 1978.

Sezen's team picked a common canopy palm tree (Iriartea deltoidea) and took a DNA fingerprint from each individual in the second-growth forest to work out its parentage. There were 66 candidate parents, all mature trees from the old forest, but the scientists found that just two of them had produced more than half the offspring in the plot (Science, vol 307, p 891). "There are 64 other trees over there," says Sezen. "Why did these two trees go crazy?"
The palm flowers all year round so he suspects the unequal reproductive success was an accident of timing: those two trees produced seeds just as the cleared land was beginning to recover. The genetic diversity of other plant species with similar flowering patterns might also be reduced in the same way.