A new study that 2300 types of mammals and practically 6700 types of birds from across the globe helps describe why there space so many an ext species the plants and also animals in the tropics 보다 at higher latitudes. In a research supported by the nationwide Evolutionary Synthesis center in north Carolina, researchers found that when the tropics harbor a higher diversity that species, the number of subspecies -- potential stepping stones in the procedure by which one species becomes two -- is actually greater in the harsher environments typical of greater latitudes.
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The surprising results suggest that the latitudinal diversity gradient might be due greater species turnover -- a higher potential for speciation counterbalanced through a higher potential because that extinction -- towards the poles than close to the equator, the researchers say.
Scientists have actually known for an ext than a century that species diversity boosts towards the equator. Think tropical tropical -- which home two thirds that the world"s types -- teeming with buzzing insects, screeching birds and howling monkeys, matches the frigid tundra, where life is largely minimal to scattered trees and only a couple of dozen kinds of mammals, such together caribou and foxes.
Numerous hypotheses have been suggest to describe this pattern. One idea is that tropical areas harbor greater biodiversity since they are particularly fertile grounds because that the formation of new species -- i.e., "cradles the diversity." another idea is the biodiversity hotspots are less likely to shed the species they already have.
"There"s a many of dispute over what explains the global pattern that biodiversity," claimed lead writer Carlos Botero of phibìc Carolina State University.
In a study to show up in the November 22 issue of Molecular Ecology, Botero and also colleagues assembled a data collection of climate and weather patterns throughout the globe, and linked it with hereditary data other information for virtually 50% and also 70% of every mammals and also birds recognized to be lively today.
The team to be surprised to discover that while the variety of bird and also mammal species increases closer to the equator, the variety of genetically unique groups within each varieties -- well-known as subspecies -- is higher in the harsher environments typical of greater latitudes.
"These are atmospheres that are colder and drier, and where the differences between the hottest and also coolest months are much more extreme," Botero explained.
Animals in these atmospheres are more likely come freeze throughout cold winters or die throughout usually hot summers. "If excessive weather events wipe the end a population every now and also then, but don"t wipe out an entire species, the populations that make it through will it is in geographically separated and could begin to diverge indigenous one another," Botero said.
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The results are consistent with a 2007 examine by researchers at the college of brothers Columbia arguing that -- contrary to conventional wisdom -- types arise much faster in warm zones than in the tropics. "It might be that types come and also go much more frequently in the temperate zones," Botero said.
Comparing biodiversity in the temperate zones with that in the tropics is favor comparing the coins in your pocket through the coins in your piggy bank, he added. "There room usually an ext coins in her piggy financial institution than in her pocket. However you"re always spending the coins in her pocket, and also receiving new coins in the form of change. The coins in your piggy financial institution turn over much less often, but over time they add up."