Ecology & Evolutionary Biology

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May 2024

Archives for May 2024

Suissa Study Has High Hopes For Plant-Ant Partnerships

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Ants crawling on a green stem

by Randall Brown

Collaborations across research disciplines can lead to unexpected breakthroughs and discoveries. Collaborations across species lead to unexpected evolutionary paths of mutual benefit.

For example, some plants have managed to recruit ant bodyguards. They produce sugary nectar on their leaves that attracts the ants, then these very territorial and aggressive ant mercenaries patrol “their” plant and sting or bite herbivores that try to eat it.

These relationships are well-documented in flowering plants, but they also occur in non-flowering ferns. This is weird news for researchers, as it has long been thought that ferns lack the nectaries for such complex biotic interactions.

Jacob Suissa, assistant professor in the UT Department of Ecology and Evolutionary Biology, worked with colleagues at Cornell University, including fern expert Fay-Wei li and ant expert Corrie Moreau, to investigate how this phenomenon developed over the millennia. They recently published findings in Nature Communications about the evolutionary timeline and underlying factors of this interspecies partnership.

“The new elements of this work are twofold,” explained Suissa. “First, we discovered that nectaries—the structures that produce sugary nectar to attract ant bodyguards—evolved in ferns and flowering plants around the same time.”

This happened some 135 million years ago, coinciding with the rise of plant-ant associations in the Cretaceous period. 

“This timing is quite spectacular given that it is very late in fern evolutionary history, nearly 200 million years after their origin,” said Suissa. “But it’s very early in flowering plant evolutionary history, nearly at the start of their origin in the Cretaceous.”

The second new element is how it all happened. Ferns originally flourished as terrestrial plants, growing on the forest floor. They transitioned in a major way in the Cenozoic Era, around 60 million years ago, becoming epiphytic, or tree dwelling, plants.

They learned some new habits on their way up.

“We discovered that as ferns left the forest floor and moved into the canopies, either as epiphytes, climbers, or tree ferns, they tapped into the existing ant-flowering plant interactions and evolved nectaries,” said Suissa.

This presents a curious dynamic in the ecological and evolutionary history of these two plant lineages. Ferns and flowering plants diverged from a common ancestor more than 400 million years ago, but then hit their stride in parallel with their nectary evolution and the mutually beneficial ant-plant tradeoff.

“This suggests that there may be some ‘rules of life’ governing the evolution of non-floral nectaries and ant-plant mutualism,” said Suissa. “This work can help future investigations by providing the evolutionary framework or backdrop for ecological, developmental, or genomic analyses.”

Read Suissa’s full paper, “Convergent evolution of nectaries in ferns facilitated the independent recruitment of ant-bodyguard from flowering plants,” in Nature Communications.

UT Researchers Dig Up Good News For Microbial Studies

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UT Researchers Dig Up Good News For Microbial Studies

by Randall Brown

Post-doctoral researcher Joe Edwards and graduate student Sarah Love, both in the Department of Ecology and Evolutionary Biology, published findings this spring that can save fellow researchers a lot of time and energy when storing soil samples for later study of their microbial content.

The preferred method for storing soil samples for the study of microbes has long been to freeze them to keep the DNA intact for studies that might need to extract information years down the road. The downside is the need to power these freezers and maintain facilities to house them.

Headshot photo of Sarah Love outdoors with mountains behind her
Outdoor headshot photo of Joe Edwards

Edwards and Love examined a wide array of soil samples in a project funded by the National Science Foundation and the US Forest Service. Their analysis indicates that soil stored under refrigerated or air-dried conditions can still retain the needed information for understanding microbial community composition and structure for many years.

“We wanted to show that these air-dried soils were still useful for understanding soil microbial communities,” said Edwards. “We’re using dried soil microbes from an archived national database to look at long-term, continent-wide spatial patterns in fungal communities and compare those with forest census data from all of those same plots.”

This soil database stores a history of the ecological changes in an area over long periods of time. Researchers want to study these soils with relatively new methods to build a timeline of ecological changes in fungi at the microbial level.

“This microbial sequencing technology has only been around for maybe the last 10 to 15 years or so,” said Edwards. “We don’t have very long-term trajectories for these microbiomes. The cool thing about these archives is that they were sampled more than once, so we have multiple resampling. We can look at how much of that community changes over time and get historical patterns for them, which is something really nobody has done yet.”

The results that Edwards and Love found show that dry-storage soil samples can be extremely useful for studying how soil properties and fungal communities change over longer periods, potentially up to decades. 

“What we were saying in the paper is a little nuanced,” said Edwards. “We managed to maintain the environmental variance that was explained in the microbial community. The method isn’t quite as reliable if you’re just trying to track specific taxa of fungi across time. But for looking at broad patterns in community diversity and community composition, it’s useful. We can get a good idea of the overall shape of these communities as they change over space and time.”

Knowing the reliability of available archived information can help future researchers know that their samples will give them the accurate data they need. 

Edwards and Love will apply the findings themselves to the next phase of their own soil research: sequencing thousands of air-dried soils from across the country. The information they find can offer important new understanding of long-term, global patterns of change.