28 August 2009
Ant species goes female-only
by Kate Melville
It was thought that all social insect species could produce, when needed, a crop of males who would go forth and fertilize new queens, but US and Brazilian researchers now say the ant Mycocepurus smithii reproduces without fertilization and males of the species are nonexistent.
"Animals that are completely asexual are relatively rare, which makes this is a very interesting ant," says Christian Rabeling, from the University of Texas at Austin. "Asexual species don't mix their genes through recombination, so you expect harmful mutations to accumulate over time and for the species to go extinct more quickly than others. They don't generally persist for very long over evolutionary time."
Previous studies of M. smithii have pointed toward them being asexual, but specimens of male ants collected in Brazil in the 1960s were thought to possibly be males of M. smithii. However, Rabeling analyzed the males in question and discovered that they belonged to another closely related (sexually reproducing) species of fungus-farmer, Mycocepurus obsoletus, thus establishing that no males are known to exist for M. smithii.
He also dissected reproducing M. smithii queens from Brazil and found that their sperm storage organs were empty. Taken together with the previous studies of the ants, Rabeling and his colleagues have concluded that the species is very likely to be totally asexual.
Rabeling says he is using genetic markers to study the evolution and systematics of the fungus-gardening ants as this will help determine the date of the appearance of asexual reproduction.
Source: University of Texas at Austin