The latest edition of Science Express (advance copies of papers that will be published in Science) has some interesting news about how one species of whitefly has been so successful. Basically, they succeed because they’re slutty.
“Asymmetric Mating Interactions Drive Widespread Invasion and Displacement in a Whitefly,” by Shu-Sheng Liu, Jing Xu, Jun-Bo Luan, Lian-Sheng Zang and Yong-Ming Ruan; P. J. De Barro ; and Fang-Hao Wan. Science DOI: 10.1126/science.1149887
” The role of behavioural mechanisms in animal invasions is poorly understood. Here we show that asymmetric mating interactions between closely-related but previously allopatric genetic groups of the whitefly Bemisia tabaci, a haplodiploid species, have been a driving force contributing to widespread invasion and displacement by alien populations….We found that the invader increased frequency of copulation and consequently production of female progeny and at the same time reduced copulation and female production in the indigenous genetic groups during invasion and displacement.”
Worse, these insects are capable of transmitting over 100 kinds of viruses that can cause additional damage to plants. And, just to make things more exciting, there are many different biotypes within this species, and some of them are extremely resistant to pesticides.
This study is a great example of how learning about the behavior of an animal can help us figure out how to control it. When these whiteflies arrive in a new area, they try to interbreed with local whiteflies. (Apparently whiteflies aren’t very good at telling species apart. Or, they really are slutty, and just don’t care.) The result of this interbreeding between types is lots of male whiteflies.
Why? It’s a quirk of genetics. Whiteflies are haplodiploid, which means that males are haploid (have half the regular amount of genetic material) and females are diploid (normal). A female that mates with the “wrong” male will lay unfertilized eggs, which develop into males.
The invasive females respond to this population full of males like they’ve arrived on the set of “Where the Boys Are.” They become more promiscuous, mate more often, and lay more female eggs. More females = more eggs being laid = more whiteflies.
Both males and females are also mating with the locals, and interrupting their reproduction–so the local biotype declines. Pretty soon, the invading whiteflies have taken over.
Hopefully, knowing more about how this particular group of whiteflies are such successful invaders will help us come up with better control methods.