"We found that species extinction occurred more frequently and more rapidly between species of microorganisms that were more closely related, providing strong support for Darwin's theory, which we call the phylogenetic limiting similarity hypothesis," said Lin Jiang, an assistant professor in the School of Biology at Georgia Tech.
The study was published online on June 14, 2011 in the journal Ecology Letters. The work was supported by the National Science Foundation.
Jiang and his team -- Cyrille Violle, formerly a postdoctoral fellow at Georgia Tech currently at the Centre d'Ecologie Fonctionnelle et Evolutive in Montpellier, France, and Georgia Tech biology graduate student Zhichao Pu -- conducted experiments with 10 common ciliated protist species in artificial, simplified ecosystems called microcosms. Diana Nemergut, an assistant professor in the Institute of Arctic and Alpine Research and the Environmental Studies Program at the University of Colorado at Boulder, helped the team generate a family tree of the 10 microorganisms to determine how closely related the species were.
"We selected bacterivorous ciliated protist microorganisms for this study because they rapidly reproduce, allowing us to examine species co-existence over multiple generations in a closed system during a period of a few weeks, which wouldn't be possible if we were testing the hypothesis with plants or animals," said Jiang.
The researchers set up 165 microcosms that contained either an individual protist species or a pairing of two species, along with three types of bacteria for the organisms to eat. They collected weekly samples from each microcosm and examined them under a microscope, recording the presence or absence of species. After 10 weeks, the researchers estimated the density of the protist species in each microcosm.
The study results showed that all species survived until the end of the experiment when alone in a microcosm. However, in more than half of the experiments in which protists were paired together, one of the two species dominated, leading to the extinction of the other species.
The researchers found that the frequency and speed of this extinction process -- called competitive exclusion -- was significantly greater between species that were more closely related. In addition, in microcosms where both competitors coexisted for the duration of the experiment, the abundance of the inferior competitor was reduced more as the phylogenetic relatedness between the two competitors increased.
The study also showed that the frequency of competitive exclusion was significantly greater between species that had similar mouth sizes.
"We documented the mouth size of each species because there is some evidence that this morphological trait affects the selectivity and uptake rate of prey particles, and we thought that similarity in mouth size might translate into the exploitation of similar bacterial resources and result in competitive exclusion," said Jiang.
While they found that phylogenetic relatedness predicted the likelihood of coexistence better than mouth size, the results suggest that other traits involved in resource uptake may also be important predictors of the outcomes of competitive interactions in ecological communities.
"This study is one step toward a better understanding of how phylogenetic relatedness influences species interactions," said Jiang. "We hope our experimental validation of the phylogenetic limiting similarity hypothesis in microorganisms will encourage other ecologists to conduct additional studies with other types of organisms to further validate Darwin's hypothesis."
The phylogenetic limiting similarity hypothesis is just one of the many ideas Darwin published in his 1859 book called "The Origin of Species." In this book, Darwin introduced his scientific theory that populations evolve over the course of generations through a process of natural selection. The book presented a body of evidence that the diversity of life arose by common descent through a branching pattern of evolution.
This project is supported by the National Science Foundation (NSF) (Award No. DEB-0640416 and Ecosystems Award No. 0922267). The content is solely the responsibility of the principal investigator and does not necessarily represent the official views of the NSF.
Abby Robinson | EurekAlert!
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences