Researchers create a periodic table of ecological niches

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Using the metaphor of the periodic table of elements, ecologists have started to create a table to organize ecological niches that shows the relationships between lizards and their environment.

Ecologist Robert H. MacArthur came up with the idea in the early 1970s and Eric Pianka, a UT professor of integrative biology, conceptualized it as a table. According to Pianka, at the time, many ecologists did not think this would ever be possible since ecological niches are so complex and encompass too many unique characteristics for each organism.

“A periodic table of niches is a scheme that organizes species or organisms based on their similarity as defined by a set of functional traits associated with various niche dimensions,” Texas A&M professor Kirk Winemiller said.

Recently, ecologists have become interested in organizing and developing classification systems for the relationships between a species’ functional traits and how they influence that species’ response to its environment, according to Winemiller.

For this table, five main niche dimensions were used: habitat, position on the food chain, life history, physiology and defense. Each dimension had its own subcomponents, according to Pianka.

“Scientists always search for generalizations and even ‘rules’ if they appear to exist — we do this by testing hypotheses,” said Laurie Vitt, professor emeritus at the University of Oklahoma.

The niches are defined by ecological data, life history, structure and size of the organism. The data was collected over a period of 50 years by Pianka and Vitt from fieldwork in Australia, North America and the Kalahari Desert in Africa. During this time, the researchers collected data from approximately 134 lizard species, according to Pianka. 

“Each cell in the table represents a set of ecological traits that would allow individuals of a species to live in that particular place at a particular time,” Vitt said. 

The concept behind the table applies globally and to all climate types and biomes, Vitt said. There is also a temporal component to table. 

“For example, a niche that is now filled by a particular lizard species could have been filled by an extinct dinosaur species historically,” Vitt said. 

The paper also included research analyses in multidimensional graphs, 3-D plots and cross-species comparisons displaying the complexities of the relationships between niches and the way they overlap.

Pianka, Vitt and Winemiller all said they hope more ecologists will collect data to add species to similar tables so that future tables encompass species within more diverse groups from vertebrates to microbes. 

Pianka also said he hopes that data can be collected from lizards in Southeast Asia soon — an area that often ends up neglected by ecologists — before the habitats there completely disappear. 

“(In the future), I hope to see innovative applications of periodic tables of niches to address issues such as invasive species, biocontrol, ecological restoration and environmental impact assessment using bioindicators,” Winemiller said. 

“I’m really excited about the reception we have gotten on this research,” Pianka said. “We hope that the table will only grow from here.”