Why are tropics more diverse

In a study supported by the National Evolutionary Synthesis Center in North Carolina, researchers found that while the tropics harbor a greater diversity of species, the number of subspecies -- potential stepping stones in the process by which one species becomes two -- is actually greater in the harsher environments typical of higher latitudes.

The surprising results 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, the researchers say. Scientists have known for more than a century that species diversity increases towards the equator. Think tropical rainforests -- which house two thirds of the world's species -- teeming with buzzing insects, screeching birds and howling monkeys, versus the frigid tundra, where life is largely limited to scattered trees and only a few dozen kinds of mammals, such as caribou and foxes.

Numerous hypotheses have been proposed to explain this pattern. One idea is that tropical regions harbor greater biodiversity because they are especially fertile grounds for the formation of new species -- i.

The team was surprised to find that while the number of bird and mammal species increases closer to the equator, the number of genetically distinct groups within each species -- known as subspecies -- is greater in the harsher environments typical of higher latitudes. Animals in these environments are more likely to freeze during cold winters or die during usually hot summers. Most of the species that invade disturbed areas in the American tropics are pioneer species. On small-scale plots 20 X 20 m such pioneers will increase the diversity if there has been a disturbance such as a tree fall within these plots.

However, these species are extremely common and widespread. Therefore, they will increase the diversity of a plot where disturbance occurs, but they will not increase the number of species occurring at the landscape level. Intermediate levels of disturbance will not increase the diversity of local endemic species in a mature forest because these species have adapted over the millennia to the conditions of a mature forest. Intermediate disturbance will increase diversity due to immigration of common pioneer species.

Diversity can be high in a disturbed area following the invasion of pioneer species in a mature or "climax" community Whittaker Conservationists are generally more concerned with preserving species endemic to mature communities. Pioneer species are rarely considered endangered species.

Logging, shifting cultivation, and other anthropogenic disturbances ensure the survival of pioneer species, often considered to be weeds. In the end, there is little agreement on the reasons for high diversity in the tropics. Perhaps the Eurocentric perspective of scientists caused them to look at the problem from the wrong viewpoint. Perhaps more progress could have been made on the diversity question had there been a scientist from the tropics who, while traveling in Europe or North America, would have asked, "Why are there so few species at high latitudes?

Diversity is highest where stress is least, that is, where temperatures are optimum year round, rainfall is adequate, and nutrients are plentiful and well balanced. Continue reading here: Defense Against Pests and Diseases. Survive Global Water Shortages. Ecology Center Alternative Energy current. Backyard Revolution Solar System. Free Power Secrets. Water Freedom System. Miracle Farm Blueprint. The researchers found that the warmer the temperature, the greater the diversity of plants and animals.

The researchers believe this study reveals significant evidence supporting the hypothesis that temperature is the most important factor for distribution patterns of species. News coming your way. The biggest news about our planet delivered to you each day. About Us. Privacy Policy. Terms of Service. The year-old naturalist had expected to find the same level of diversity of plants and animals as he had left behind in the higher latitudes of Plymouth, England. Instead, on the balmy Galapagos Islands, he found a multitude of strange and diverse creatures thriving together.

He wondered: How was it possible that the tropics seemed to hold so much more diversity than the more northerly forests of Europe? Shouldn't these tightly packed creatures have battled it out to extinction long ago? Darwin never found out the answer to that particular mystery after all, he had a lot on his mind , and so the question persisted for another century.

Finally, in the early s, two ecologists independently came up with the same hypothesis to explain the mysterious phenomenon—at least with trees.

Daniel Janzen and Joseph Connell put forth a seemingly counterintuitive explanation.