Some marine species have had the same jobs for millions of years

For years, scientists have asked whether fossils record how ocean ecosystems actually worked, not just which species were there. A new study answers that question with a careful field test along the North Carolina coast.

The researchers found that the functional makeup of marine communities can be read from the fossil record with surprising accuracy. In other words, many marine species have performed the same jobs for millions of years.

That result matters because managers often need a trustworthy baseline for restoration in places that have been altered for centuries. If fossils preserve which ecological jobs were present, then restoration targets can be set with more confidence.

Functional diversity of marine species

The study was led by Carrie L. Tyler of the University of Nevada, Las Vegas (UNLV), with collaborators from the University of Florida.

Tyler’s group focused on functional diversity, the variety of ecological roles in a community, such as feeding modes and mobility, rather than only species lists.

Across ecology, evidence suggests that functional information can sharpen how we judge stability, productivity, and resilience. The emerging field of conservation paleobiology uses geologic archives to set realistic baselines and to guide restoration in today’s stressed ecosystems.

Scientists did not reach this point overnight. Decades of work comparing living seafloor communities to their nearby accumulations of shells and hard parts, called a death assemblage, showed that these remains often mirror local diversity patterns.

That line of work helped build trust that nearshore fossils can serve as credible yardsticks of past conditions.

“Most of what we know, in terms of biases in the fossil record, is based on mollusks. We designed our study to determine whether those biases are consistent when you include many types of organisms, not just mollusks,” said Tyler.

Testing fossils against living species

The team surveyed 51 coastal sites in Onslow Bay, North Carolina. They sampled the live benthic community, the sympatric death assemblage on the seafloor, and the subset of species known to occur as fossils in the region.

The researchers cataloged more than 200 species spanning six major invertebrate groups. For each species, they recorded traits that drive ecosystem processes, including feeding type, motility, and where an animal lives relative to the sediment.

From those traits, they computed a set of widely used functional metrics. These included how much trait space is occupied by the community, how evenly that space is filled, and how many unique functions are covered by one species versus many.

The researchers then asked a simple question. Do the dead and fossil subsets recover the same functional structure as the living community in the same places and habitats?

Marine species kept their jobs

The answer was yes, and not by a hair. Functional groups present in the living community were also present in the death and fossil samples, and the pattern of how many species filled each function was closely aligned.

The correlations between live, dead, and fossil functional groupings were strong, with reported rank concordance exceeding 0.85 and with P values far below 0.001 in formal tests.

Functional richness, evenness, divergence, and dispersion were highly congruent across assemblages, with only modest contraction in the fossil subset.

Importantly, the traits that matter for ecosystem processes were retained. Suspension feeders, burrowers, and predators each maintained their footprint in trait space, which means trophic structure and sediment interaction roles were not washed out by preservation filters.

The team also evaluated functional vulnerability. When they treated functions with two or fewer species as vulnerable, the fossil subset approximated the vulnerability seen in the live community – a practical detail for risk assessment.

Why it matters for conservation

Modern baselines are often shifted by centuries of harvesting, pollution, and warming. Functional reconstructions drawn from the youngest fossil archives can show which ecological roles have been lost and, crucially, which roles still have redundancy to buffer change.

This trait focus is powerful for setting restoration goals that match how systems actually work. It helps managers ask not only which species are missing, but which functions are absent and need reintroduction or support.

Independent syntheses point in the same direction. Previous reviews have outlined how geohistorical data can clarify extinction risk, recovery windows, and the feasibility of rebuilding ecosystem functions in coastal habitats.

Study limitations and next steps

No single study can cover all settings. Communities dominated by soft-bodied organisms, or places with unusually patchy preservation, may show lower functional fidelity and need case by case checks.

The authors also caution about abundance weighting at small habitat scales. In their data, heavy weighting by a few abundant taxa suppressed some evenness metrics in specific habitats, so presence absence trait analyses may often be the more robust first pass.

There is room to expand these tests into reef, delta, and deep shelf systems where trait distributions differ. Applying the same framework can reveal where fossil baselines are reliable enough to guide restoration targets.

“There are no pristine ecosystems left on the planet, so when you are trying to restore an ecosystem that can be a difficult and challenging task without having any idea of what it looked like before,” said Tyler.

“It hasn’t been free of human impacts or pristine for thousands of years, so we don’t have records of what that ecosystem is ‘supposed’ to look like. This study shows the fossil record can be used to give us an idea of what that ecosystem used to look like, and what functions are needed to keep it healthy.”

The study is published in Proceedings of the National Academy of Sciences.

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