Unique study reveals arms race between the sexes in diving beetles
Johannes Bergsten, Umeå Uniersity, shows in his dissertation that females and males among aquatic diving beetles constitute an example of an evolutionary arms race between the sexes. Such arms races have been predicted theoretically, but only in a group of true bugs (hemiptera) has anyone managed to demonstrate it until now.
"It is well known that the females and males of many insects can have opposing interests regarding various aspects of mating. But it is highly controversial for this conflict actually to lead to evolutionary arms races between the sexes of one and the same species,” says Johannes Bergsten.
The bodily structures of the diving beetles involved in this arms race are the suction-cupped front and medial feet of the male and various modifications of the dorsal side of the female. The male uses his suction cups to grab hold of the female during mating by pressing them against the female’s back, neck shield, or wing sheaths. But precisely in the places the male tries to fasten his suction cups, the female diving beetle has different sculpted areas in the form of furrows, warts, tufts of hair, etc. that make it impossible for the male to get a grip. To establish an evolutionary process spanning millions of years, it is necessary to look back in history with the aid of a family tree.
Work to determine a family tree for the group of diving beetles that Johannes Bergsten has studied took him to China, Japan, Russia, Canada, the U.S., Portugal, and Sardinia, among other places, for the collection of materials. The materials collected were used to sequence DNA from three different genes that were used, together with similarities and differences in body structure, to set up a family tree. Moreover, these travels led to the discovery of new species of diving beetles in China and the U.S., one of which is described in the dissertation.
Bergsten has also devoted a great deal of time to a special problem that can occur in family-tree analyses of DNA data. Family tree analyses are used to understand the origin of life, including the place of humans in the tree of life, which comprises all living organisms on earth.
The molecular revolution in biology has created incredible potential for family-tree analysis using DNA sequences, but it has also entailed new difficulties and traps. Understanding just when and how these analyses can go awry is crucial in all research based directly or indirectly on family trees.
The problem of “Long-Branch Attraction” involves the grouping together of branches despite the fact that they are not closely related. This problem is well known on theoretical grounds, but how or whether it actually affects family-tree analyses has been called into question.
Johannes shows how common the problem is, how it can be discovered, and how to get around it. One example of incorrect conclusions caused by the LBA problem is the fact that the hedge hog was seen as belonging to the oldest line of placental mammals and as being not at all related to the mole and the shrew, and that the guinea pig was seen as not being a rodent, like the rat and the mouse.
On Friday, June 3, 2005, Johannes Bergsten, Department of Ecology and Environmental Science, Umeå University, will publicly defend his dissertation titled Taxonomy, Phylogeny, and Secondary Sexual Character Evolution of Diving Beetles, Focusing on the Genus Acilius.
Johannes Bergsten can be reached at:Phone: (home) +46 90-13 07 85, (work) +46 90-786 64 59 E-mail: Johannes.email@example.com