Washington, May 28 : Who is responsible for flourishing lives in the tropics: temperature, or sunlight? Well, according to a new research, the explosion of species at the tropics has much more to do with warmth than with light.
"The diversity was unrelated to productivity (from photosynthesis), but it was strongly related to temperature," said University of Southern California biologist Jed Fuhrman, who led a group that analyzed bacterial samples from warm and cold oceans.
The research team found far greater diversity in samples taken near the equator. In particular, samples from low-productivity waters still contained many bacterial species, suggesting that photosynthesis has little influence on diversity.
Many researchers have tried to separate the influence of temperature and sunlight, Fuhrman said, but have found it hard to do by studying higher organisms.
He added that bacteria are ideal subjects because of their wide distribution and the recent availability of genetic fingerprinting.
The question of what drives diversity is important to biologists who seek to uncover the basic rules governing life.
"Is diversity ruled by fundamental laws, and if so, what is the basis of them?" Fuhrman asked.
The so-called kinetic law links the rates of metabolism, reproduction and many other biological processes to the motion of atoms and molecules. Such motion increases with temperature, presumably speeding up the biological processes.
Fuhrman calls this "the Red Queen runs faster when she is hot" hypothesis.
Productivity also is thought to promote diversity by increasing the food supply. This is "the larger pie can be divided into more pieces" hypothesis.
The two hypotheses may both be valid, Fuhrman said, but his group's results show that "the kinetics of metabolism, setting the pace for life, has strong influence on diversity."
Biologists have known for centuries that animal and plant biodiversity is greatest at the tropics, though they have not agreed on whether temperature or productivity was the cause.
The Fuhrman group is the first to show that bacteria follow the same pattern.
The study is published online in PNAS Early Edition.