Talk about a royal scandal. When a termite king and queen have been in power for some time, the king begins mating with his royal daughters to populate the colony. Now, researchers report that one termite species has found a way around this incest: The queen produces offspring that have only her genes. That way, when the king mates with a daughter, he's effectively still having sex with the queen.
A termite colony starts when a king and queen pair up during an annual mating flight and settle down to start a family. At first, the couple produces worker and soldier termites that care for the nest. When the colony gets big enough, the king and queen start making alates--winged termites that leave home to find mates and start colonies of their own. Finally, late in the queen's life, she lays several eggs that become secondary queens to replace her--and those queens start mating with the king to produce more workers, soldiers, and alates. This inbreeding reduces the offspring's genetic diversity and thus the colony's ability to adapt to environmental stress.
But it turns out that at least one termite species has adopted an alternative. In the Japanese termite Reticulitermes speratus, the founding queen bears her junior queens through a process called parthenogenesis, a form of asexual reproduction that produces offspring with duplicates of half of mom's genes. Some ant queens also asexually reproduce, but the resulting queens head off to start their own colonies.
Figuring out Reticulitermes's strategy wasn't easy. Entomologist Kenji Matsuura of Okayama University in Japan and colleagues first collected termites from 30 colonies at five different sites. Then they analyzed the genes of kings, queens, and other castes. The worker genomes held the real surprise: They appeared to come from only one queen despite the presence of several in the nest. Further analysis showed that the secondary queens lacked any genetic input from the king, meaning that the primary queen produced them on her own, the researchers report in today's issue of Science.
By creating these genetic representatives that are untainted by the king, the queen boosts her reproductive output, because there are dozens to well over 100 secondary queens doing her job. At the same time, she prevents incest, says entomologist and co-author Ed Vargo of North Carolina State University in Raleigh, ensuring the genetic diversity of the workers. Even when the queen dies, she maintains her genetic contribution to the colony. "This gives genetic momentum to the expression 'Long live the queen,' " says entomologist Barbara Thorne of the University of Maryland, College Park, who was not involved in the study.
Laurent Keller, an evolutionary biologist at the University of Lausanne in Switzerland who has done similar studies in ants, says that until recently, researchers have failed to recognize these bizarre forms of reproduction, and more studies like this are needed to find out how common they are. "My guess is that many more [cases of unusual reproduction] will come up soon when people look more carefully."