Darwin's Tree of Life to Become Multi-Dimensional
A reproduction of the first-known sketch by Charles Darwin of an evolutionary tree describing the relationships among groups of organisms will be featured in Darwin, the most in-depth exhibition ever mounted on this highly original thinker, November 19, 2005, through May 29, 2006, at the American Museum of Natural History.
Credit: © By permission of the Syndics of Cambridge University Library

The tree of life is about to go hyper-dimensional.

The two-dimensional tree of life that Charles Darwin first conceived over 150 years ago in his book "On the Origin of Species" should probably look more like a knotted, interlocking forest of trees, scientists argued.

The old-school tree of life, which separates living organisms into starkly divided kingdoms such as bacteria, fungi and plants, doesn't take into account that many genetically divergent organisms rely on each other to survive, said a study published online June 7 in the journal Trends in Ecology & Evolution.

"In our opinion, one should not classify the bacteria or fungi associated with a plant species in separate phylogenetic systems (trees of life), because they're one working unit of evolution," study co-author Debashish Bhattacharya, professor in the Department of Ecology, Evolution and Natural Resources at Rutgers University in New Jersey, said in a statement. "The goal is to transform a two-dimensional tree into one that is multidimensional and includes biological interactions among species." [Darwin Gallery: Darwin on Display]

Darwin originally constructed his tree of life to show how species were related. Organisms, such as dogs and wolves, that are closely related and share many similar features might be on neighboring twigs. Meanwhile, the more distantly related creatures — such as the major kingdoms of plants, animals, fungi, protists, archaebacteria and eubacteria — would be placed on the sturdy limbs at the base of the tree.

But in reality, microbes, viruses and fungi often interact with plants and animals in symbiosis, meaning the two divergent species are dependent on each other for survival. When these life-forms evolve together, they are called symbiomes, the new study said.

The new tree of life should incorporate data from these symbiomes, using a technique called symbiome phylogenetics (SYMPHY), the authors of the study argued. Categorizing and grouping life with this additional layer of information could help scientists better tackle issues like invasive species and sustainable agriculture, the researchers suggested.

"By connecting organisms to their microbial partners, we can start detecting patterns of which species associate under specific ecological conditions," Bhattacharya said.

As one example, if the same microbe tends to cling to the roots of very different plants, but in similar ecological conditions, such as nutrient-poor, high-salt soil, "then we have potentially identified a novel lineage that confers salt and stress tolerance and could be used to inoculate crop plants to provide this valuable trait," Bhattacharya said.

The new formulation could help scientists generally deduce how species and their symbionts interact in greater detail, the researchers said.

"We'd actually have trees interacting with trees, and that sort of network allows you to show connections across multiple different organisms and then portray the strength of the interactions between species," Bhattacharya said.

Originally published on Live Science.