Lizards and Spartina grasses. Bald cypress trees and Roseau cane. Cyperus sedges and Beach Morning Glory. These living organisms are among the subjects of attention and scrutiny by scientists in the Tulane Department of Ecology and Evolutionary Biology. These species are not explored in isolation, however. They are studied for their connections within complex ecosystems. Four biologists share their research below:

PLASTICITY IN RESPONSE TO CHANGING TEMPERATURES

Alex Gunderson

“I study lizards,” said Alex Gunderson, an assistant professor of ecology and evolutionary biology, “but one of the things I’m trying to do is to use lizards as a model to understand what’s going to happen generally to organisms.” 

Among the principles that he’s studying is the plasticity for which lizards are known and, specifically, physiological plasticity or “an ability of an individual to change their physiology in response to a change in temperature. So, if it gets warmer, they might be able to adjust their physiology to better tolerate warmer conditions.”

Humans have a little bit of physiological plasticity. When we move to warm or cool conditions, our physiology changes somewhat to better tolerate rising and falling temperatures. 

Gunderson said that it has been proposed that animals, such as lizards, might be able to use plastic responses to temperature to buffer themselves from climate change. 

But there is a limit to this plasticity, said Gunderson. “What our research has shown is that plastic response is not very powerful. In some cases, it’s likely to help, but it’s not going to be a silver bullet that species are going to be able to plastically adjust to whatever is happening, and they’re going to be fine. Their plastic response is limited.”
 

Before he came to Tulane this year, Gunderson studied lizards in Puerto Rico and Florida, where he found that their tolerance for heat increases only about 10 percent. “Plasticity can’t compensate for the changes that are happening.”

A consequence of climate change is that some populations are decreasing, and species may vanish, said Gunderson. “For lizards, in particular, some of the estimates are, by the end of the century, up to 40 percent of lizard populations will go extinct.”

Gunderson is now turning his attention to two species of lizards in the genus Anolis that are found in New Orleans.

“We call them anoles [pronounced  -no-le],” said Gunderson. One, the green anole, is native to Louisiana. The other, the brown anole, is non-native and was introduced from Cuba.

The Cuban anole is considered an invasive species. It arrived in Louisiana about 20 years ago. “Its populations are going way up since it’s been introduced,” said Gunderson.
 

With the green anole population diminishing, and the brown anole on the rise, Gunderson and a team of his graduate and undergraduate students are starting to investigate why the invasive species is flourishing. 

“One of the hypotheses is that invasive species that are successful are more plastic. They can adjust to whatever they find and that helps them tolerate it better and then they can sort of take over,” said Gunderson.

“But we don’t have the answer to that yet. What we’re trying to do is understand what it is about how species interact with their environments that allows them to persist or causes them to perish.”

NOT ALL INVADERS ARE BAD 

Emily Farrer

“The climate is warming, sea levels are rising, storm intensities and frequencies are increasing, especially here in the Gulf Coast,” said Emily Farrer, assistant professor of ecology and evolutionary biology.

“My research is about how climate change affects ecosystems and how these effects might emerge in unexpected ways — mainly because species are all interacting with one another.”

When climate change “perturbs” a system, said Farrer, there can be chain reactions.

In her third year at Tulane (Farrer has also done research on California grasslands, Great Lakes marshes and Alpine tundra), she is interested in “how climate change might impact microbial communities and how this might then impact plant communities.”

Many microbes are “mutualists” that promote plant growth, others are pathogens that cause disease. If certain microbes increase or decrease with a changing climate, that will have implications for plants.

 As saltwater is moving inland and intruding on freshwater habitats, there can be an acute effect on organisms.

“Salinity impacts their physiology, their water uptake and stress levels,” said Farrer.

Also, like lizards, plants are categorized as either native or invasive. This distinction adds another layer of complexity to the ecosystem.

The invasive species that Farrer is currently studying is known as Roseau cane in Louisiana — although its genus is Phragmites, the name by which it’s called in states north of the Gulf Coast.

While technically not native to Louisiana, Roseau cane is not seen negatively by locals. In fact, they like it.

Farrer said that when she’s been at field sites on the Louisiana “bird’s foot” delta in Plaquemines Parish, south of Venice, she’ll ask people about Phragmites. They say to her, “Oh, that’s been there forever. It’s not invasive. It hasn’t gotten any bigger over the past couple of years.”

Hearing this different perspective on Phragmites — or Roseau cane — is interesting to Farrer. “It’s not all bad.”

Roseau cane, which has been coexisting with native vegetation for a long time, stands up well to storm events and does well in deep water. “It might actually be one of our last defenses against the land loss,” said Farrer. “This huge invasive species producing all this biomass could help build up the soil and reverse some of the land loss.”

In a recent greenhouse experiment led by Farrer, preliminary results show that “microbes from saline areas increase the growth of the Phragmites but suppress native plants.”

“This suggests that as saltwater intrusion increases in the future due to climate change, it may modify microbes in a way that favors invasive plants,” Farrer said.

She’s committed to studying more of the unknown connections of how climate change can impact ecosystems and to “understanding how climate change is affecting the system and how we can use this to predict what the system might do in the future.”

“I think these unknown connections are eye-opening. That’s why ecology is important.”

In the future, Farrer would like to expand her work to local, on-the-ground groups involved in restoration planting. “I’d like to incorporate some science — what we know about the system — into the plantings and have it inform the management of our coasts.”

This is a serious problem for the health of the tree, which is inextricably tied to coastal protection from land loss and storms.

A major component of the 2017 Coastal Master Plan of the Louisiana Coastal Protection and Restoration Authority is the restoration of forests devastated by sea-level rise and storm surge.

Van Bael is looking for bacteria and fungi that are saltwater-tolerant and could be used to inoculate the trees from salt­water stress in the future.

Van Bael is also beginning to work with the black mangrove tree to understand its tolerance to salinity. Often associated with the Florida Everglades, a species of mangrove — the black mangrove — “is creeping up out of Florida and into Mississippi, Alabama, Louisiana and Texas.”

The black mangrove tree “was probably here a long time ago,” said Van Bael. “So, we don’t necessarily think of it as an invasion.”

For her future research, Van Bael plans to stick with “studying coastal plants and trying to understand how bacteria and fungi can help them increase their growth and increase their stress resilience.”

ADAPTABILITY TO RAPID ENVIRONMENTAL CHANGE

Keith Clay

Increased salinity is the observable result of the rising sea along the Gulf Coast. This rising sea level and subsidence (sinking land) are evident in the erosion of the coast.

“The question is,” said Keith Clay, professor and chair of the ecology and evolutionary biology department, “whether the vegetation can move in concert with these environmental changes or whether it’ll be overwhelmed and suddenly plants and plant communities that used to be miles back are suddenly right on the shoreline.”

Like Farrar and Van Bael, Clay is interested in plant microbial interactions. He’s studied coastal plain and marsh vegetation, including several species of Cyperus sedges and the Beach Morning Glory. (His other area of research is arthropod vectors of disease, primarily ticks, and also mosquitoes.)

He’s interested in “microbial symbioses that help plants in terms of their ability to compete with other plant species, to tolerate stresses, and defend themselves against pests and pathogens.”

He sees potential for manipulating microbiome and plant interactions — or finding better partnerships — “to generate more robust and resilient plant communities that will be facing a lot of stresses in the not too distant future.”

Microbiomes are “microorganisms associated with larger organism, typically inside the larger organism.”

Clay, like Van Bael and Farrer, is a community ecologist. He joined Tulane after 32 years at Indiana University.

“In Indiana, they’re worried about agricultural impacts of global warming, greater storm severity, biological invasions, and more tropical and subtropical diseases that might be slowly working their way farther northwards by mosquito-borne pathogens.

“It’s all kind of theoretical in the Midwest. But here, it’s the real deal. These are actual threats, and people are being impacted.”

Earlier in his career in the 1980s, Clay was at Louisiana State University, and he’s revisiting some of his old study sites in Cameron Parish, now that he’s back in Louisiana. 

Everyone in Tulane’s ecology and evolutionary biology department has a lab aspect to their work. “But it’s combined or intimately connected to field-based research. We’re actually out in nature either collecting data, doing manipulations of environmental conditions or collecting samples. Nobody that I can think of is strictly a lab-based scientist.”

The department’s mission is to “understand how the world works — or at least how the living world works.”

The researchers’ work is becoming “more relevant all the time,” said Clay.

The living world “is constrained or dictated in part by the non-living world — the geology, climatology, hydrology, which are not directly biological processes.”

The processes that take place between organisms and their abiotic — that is, physical — environment are “the core focus of this department,” he said.

While he’s concerned about the effects of global warming or climate change on ecosystems, Clay said that as a biologist and ecologist, “I think life is resilient.”

Some predicted scenarios are dire, “but there will be organisms that survive and thrive,” said Clay. “It’s always been that way. Even after mass-extinction events, things survive.”

Main photo: Satellite image shows the Mississippi River "bird's foot" Delta in Louisiana on Nov. 14, 2018. (Photo by U.S. Geological Survey, LANDSTAT PROGRAM)