Species take care of each other in ecological communities

November 30, 2005

Unspoken rules of existence in tropical rain forests mean no one species will take up too much space and squeeze others out, says new research conducted in part at the University of Alberta that shows how ecological communities regulate themselves.

Dr. Fangliang He is part of a research team that studied fundamental questions plaguing scientists since Darwin's time: why are some species so common while others are rare? How do common and rare species interact? And how do hundreds, even thousands, of tree species coexist in a limited space in the tropics?

He, along with Igor Volkov and Jayanth Banavar, from Pennsylvania State University, Stephen Hubbell from the University of Georgia and Amos Maritan from the Universita di Padova in Italy, offer a new theory to explain why tropical rain forests are so species rich and how species are assembled in a community. Their work is published in the current edition of "Nature".

Species must meet certain conditions to live in a community. Understanding the rules that make up community assemblages is one of the most challenging scientific questions facing scientists today. Niche theory, which assumes species differ from one another in various aspects, has been traditionally used to explain community assemblages. However, this theory offers little to predict community assemblage patterns - the way species share a limited space.

He's work attempts to address community assembly rules based on Hubbell's recently developed neutral theory. "The basic idea of the neutral theory is that community membership is determined by five fundamental processes: birth, death, immigration, speciation and random drift. Furthermore, the theory assumes that every individual in the community, regardless of species identity, has the same rates of birth, death, immigration and mutating into a new species," said He, who is a Canada Research Chair from the Department of Renewable Resources.

The research team modified this theory by arguing that the birth rate and mortality rate are not identical across species, but there is a "density-dependent" probability of birth and death. The more abundant species have lower birth rates and higher mortality rates. "The consequence is that when a species becomes rare, its birth rate will increase and death rate will reduce," said He. In other words, species will regulate themselves to make room for each other if they follow the membership rules. "If not, they're out."

The scientists tested their model using data from six tropical rain forests--these tiny areas can accommodate more than 1000 tree species--across the world. "Our theory offers a better understanding of why tropical rain forests are so species rich," said He. "This rare species advantage regulates dynamics and therefore permits the coexistence of many species in a community."
-end-


University of Alberta

Related Immigration Articles from Brightsurf:

Why do white Americans support both strict immigration policies and dream act?
White Americans support strict immigration policies while at the same time favor the DREAM Act that would grant legal status to some immigrants who were brought to the United States as children, a contradiction linked to racial resentment and the belief that equality already exists, according to a Rutgers-led study.

Empathy exacerbates discussions about immigration
Discussions about immigration are heated, even antagonistic. But what happens when supporters and opponents undertake to show more empathy?

UB study finds no apparent link between undocumented immigration and crime
An analysis by a University at Buffalo-led team using two estimates of undocumented immigration suggests that, on average, this population reduced or had no effect on crime in 154 U.S. metropolitan areas studied, including places such as New York City, Chicago and Las Vegas.

Increase in immigration has little impact on the wages of US citizens
A new study in Review of Economic Studies suggests that a large increase in the stock of immigrants to the United States would have little impact on the wages of native US citizens.

Journal maps intersection of immigration and aging
A new special issue of the journal The Gerontologist from The Gerontological Society of America explores how contemporary trends in immigration, migration, and refugee movement affect how people age and how societies care for aging people.

Older refugees have high levels of depression even decades after immigration to Canada
A new study of Canadians aged 45-85, released this week, found that refugees were 70% more likely to suffer from depression than those born in Canada when age, sex and marital status were taken into account -- even decades after immigration.

Immigration and transition: Emerging trends in spina bifida care
In this collection of articles in the Journal of Pediatric Rehabilitation Medicine (JPRM) experts highlight the emerging trends in spina bifida care in response to challenges faced by spina bifida patients and their physicians due to demographic shifts in age and ethnicity and other societal factors.

Arrival of refugees in Eastern German communities has no effect on voting behavior, attitudes on immigration
The arrival of refugees in eastern German communities has had no effect on local residents' voting behavior or on their attitudes toward immigration, finds a new study of citizens in more than 200 regional municipalities.

Attitudes toward race, immigration underscored vote switching in 2016 election
It's estimated that around 9% of voters who supported Barack Obama in 2012 crossed party lines to endorse Donald Trump in 2016 -- but why?

Vanished classmates: The effects of immigration enforcement on school enrollment
Partnerships between Immigration and Customs Enforcement (ICE) and local police departments designed to enforce immigration laws reduced the number of Hispanic students in US public schools in adopting counties by 10 percent after two years.

Read More: Immigration News and Immigration Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.