Wetenschap - 12 januari 2012

Ladybirds react to climate

Astrid Smit

Higher temperature seems disadvantage for black ladybird.

There has been a big fall in the number of black ladybirds in the Netherlands since the 1980s. Biologists at Wageningen UR and Leiden University have said in the scientific journal Heredity that they suspect a reaction to climate change.
Ladybirds are found in two colours: red with black spots and black with red spots. In the 1980s biologists discovered that in the Netherlands the red ladybird with black spots (Adalia bipunctata) was more common along the coast while the black species was more common inland. The researchers suspected a genetic adaption to the local climate. The black species absorbs heat more easily and more quickly, which is an advantage in the relatively cool local climate inland. Lab tests in the 1990s proved that black ladybirds are indeed at an advantage in an environment where temperatures are relatively low. And now the changing climate in the Netherlands seems to offer further confirmation of this genetic adaption. That is the conclusion of an article by entomologist Peter de Jong of Wageningen UR and biologist Paul Brakefield of Leiden University in the scientific journal Heredity.
The Dutch climate has been changing since the 1980s. The temperature inland has risen, especially in spring, and the number of black ladybirds has fallen sharply. After falling for fifty generations, the proportion of black ladybirds is now just as small as along the coast: ten to twenty percent. The researchers say the arrival of the dominant Asian ladybird (Harmonia axyridis) in the Netherlands does not invalidate this argument as it only really became prevalent from 2002. The link they have seen - climate change and fewer black ladybirds - could still be a coincidence but biologists have a strong suspicion that the changing climate is the cause.