Reporting in the June 1 issue of the journal Nature, scientists from six institutions detail how male guppies with the most colorful -- and most rare -- patterns are more likely than their more commonly colored counterparts to survive in the wild.
"This study provides very solid support for frequency-dependent survival," said principal investigator Kimberly A. Hughes, an animal biologist at the University of Illinois at Urbana-Champaign. "We found that rare color patterns of these guppies had a highly significant survival advantage."
In evolutionary terms, frequency-dependent survival means that individuals with rare gene variants have a survival advantage relative to common variants, simply as a function of being rare. This process is important because it leads to the maintenance of many different variants (polymorphism) in the same population.
The same process could be important in the maintenance of genetic variants in humans, said Hughes, who also is a member of the Institute for Genomic Biology at Illinois. For example, she said, it has been hypothesized that genes involved in pathogen resistance (the Human Leukocyte Antigen or HLA genes) are highly polymorphic because pathogens are most successful at attacking individuals with common variants, and individuals with rare variants have higher survival.
However, the theory is difficult to test, and, in general, frequency-dependent survival has been difficult to document as an important process in nature, Hughes said.
The guppy system provided a way to test whether this kind of selection could really promote polymorphism in a natural setting, because guppies are highly
Contact: Jim Barlow, Life Sciences Editor
University of Illinois at Urbana-Champaign