The tropics owe their stunning biodiversity to consistent year-round temperatures, not higher temperatures or more sunlight, according to a novel survey of insect diversity at different latitudes and at different points in the planet's history.
The finding, presented this week in the journal Paleobiology by researchers from Harvard University, Simon Fraser University, and Brandon University, may finally answer a question that has dogged scientists for centuries.
It also suggests, intriguingly, that the world is likely far less diverse today than it was tens of millions of years ago, when the entire Earth had consistent year-round temperatures, much like the modern tropics.
"The latitudinal diversity gradient has been recognized for 150 years as one of the most general observations in nature, and has produced more explanatory hypotheses than nearly any other observation," says co-author Brian D. Farrell, professor of biology at Harvard. "We show that when most of today's organisms were diversifying, up through the Eocene, the world lacked pronounced seasonality, more like today's tropics, even in areas where the temperature was low."
"It appears it's not the heat of the tropics that promotes diversity; it's the newer seasons of the temperate zone that depress diversity."
Scientists' explanations for tropical biodiversity have tended to focus on the greater heat and light found closer to the equator, and to a lesser extent the low seasonality of the tropics, where average temperature in the hottest and coolest months may vary by only a few degrees.
"These factors tend to change together as you travel away from the equator toward the poles, leaving it difficult to separate their individual effects on diversity," says lead author S. Bruce Archibald, a research associate at Simon Fraser University, Harvard's Museum of Comparative Zoology, and the Royal British Columbia Museum. Archibald conducted the research for his doctoral dissertation at Harvard, where Farrell was his advisor.
Farrell, Archibald, and colleagues engaged in a kind of time travel, invoking the fossil record to solve this conundrum. They compared modern insect diversity at the Harvard Forest in Petersham, Mass., and in a Costa Rican jungle against that seen at the 52.9-million-year-old McAbee fossil bed in British Columbia, noted for its exceptionally well preserved insects. At the time the McAbee fossils were created, Earth's climate was far less seasonal at all latitudes, allowing tropical species such as palm trees and crocodiles to live in what is now the high Arctic.
The scientists' discovery that the ancient Canadian site's insect diversity mirrors that of the modern Costa Rican jungle, despite a marked difference in latitude, suggests that it's seasonality, not heat or light, that drives biodiversity.
"Planet Earth and life have coevolved for well over a billion years, and this is yet additional evidence of the consequent intertwining of global physical and biological phenomena," Farrell says.
Farrell and Archibald's co-authors on the Paleobiology paper are William H. Bossert of Harvard's School of Engineering and Applied Sciences and David R. Greenwood of Brandon University. The work was funded by the Natural Sciences and Engineering Research Council of Canada, Harvard's Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, and the Maurice Pechet Foundation.
Steve Bradt | EurekAlert!
International network connects experimental research in European waters
21.03.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)
World Water Day 2017: It doesn’t Always Have to Be Drinking Water – Using Wastewater as a Resource
17.03.2017 | ISOE - Institut für sozial-ökologische Forschung
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy