November 23, 2013
Possible Reasons For Increased Biodiversity In The Tropics Discovered
redOrbit Staff & Wire Reports - Your Universe Online
Biodiversity tends to be higher in the tropics, and new research appearing in the journal Molecular Ecology has an explanation as to why that region of the world is home to so many different types of plants and animals.
As part of their study, North Carolina State University geneticist Carlos Botero and his colleagues reviewed 2,300 species of mammals and 6,700 species of birds from all over the world. They found that, even though there are a greater number of species in the tropics, the harsher higher latitudes are home to a higher number of subspecies.
Subspecies are “potential stepping stones in the process by which one species becomes two,” the National Evolutionary Synthesis Center (NESCent) in North Carolina, which sponsored the research, said in a statement. The findings “suggest that the latitudinal diversity gradient may be due higher species turnover – a higher potential for speciation counterbalanced by a higher potential for extinction – towards the poles than near the equator.”
Experts have known for over a century that biodiversity increases in areas located closer to the equator. One of the many hypotheses that have been put forth to explain this phenomenon is that the tropical regions of the planet are especially fertile ground for the formation of new types of creatures. Another suggestion is that the species living in these so-called “cradles of diversity” are simply less likely to die off.
In their new study, Botero’s team compiled a set of climate data and weather patterns from all over the world, and combined that information with genetic data and other information for between 50 percent and 70 percent of all known living birds and mammals.
They found that, while the number of bird and mammal species increases closer to the equator, the number of subspecies (genetically distinct groups within each species) increases in higher latitudes – where the conditions tend to be colder, drier and more extreme, the investigators explained.
Animals living in these conditions are more likely to succumb to the extreme cold in the winter months or the more intense heat during the summer, according to Botero. The results are said to be consistent with previously published research suggesting that new species arise faster in temperate regions than in the tropics.
“If extreme weather events wipe out a population every now and then, but don't wipe out an entire species, the populations that survive will be geographically separated and could start to diverge from one another,” Botero said. “It may be that species come and go more frequently in the temperate zones.”
He went on to compare the diversity of the temperate zone and the tropics to the difference between pocket change and coins stored in a piggy bank. “There are usually more coins in your piggy bank than in your pocket,” Botero noted. “But you're always spending the coins in your pocket, and receiving new coins in the form of change. The coins in your piggy bank turn over less often, but over time they add up.”