Study Reveals New England is Key to Survival of Diamondback Terrapins

Study: New England is key to survival of diamondback terrapins

A new peer-reviewed study led by researchers at Brown University in partnership with the Rhode Island Department of Environmental Management revealed that diamondback terrapins (Malaclemys terrapin), iconic turtles of America’s salt marshes, face heightened risks at the northern edge of their range in New England.

First large-scale genetic study of diamondback terrapins across their northern range highlights urgent conservation needs as federal endangered species listing is considered.

Diamondback terrapin. Photo: Amanda Lyons

The Science is Clear: Terrapin Need Regional Protection

The study, published in Journal of Heredity, shows that while Rhode Island is the only New England state to officially list the terrapin as endangered, its populations are part of a broader pattern of declining genetic diversity and increasing isolation as the species extends northward from the mid-Atlantic. These findings arrive as NOAA Fisheries weighs a petition to list the terrapin under the federal Endangered Species Act.

Diamondback terrapins are a keystone predator in salt marshes, helping maintain the balance of these ecosystems. This study shows that Rhode Island and other coastal states in New England are at the front lines of terrapin conservation — what happens here will have ripple effects for the species across its range.

Lead author, Amanda Lyons '21 MSc, '20 B.S. Honors, worked tirelessly with community members and the Kartzinel Lab to connect a widely-recognized conservation need with the cutting-edge technologies emerging to help address it.

The team analyzed DNA from more than 100 terrapins across 18 sites, from New Jersey to Massachusetts, using state-of-the-art genomic methods. The results are clear:

• Genetic diversity declines steadily with latitude, making northern populations more vulnerable.
• Populations in Narragansett Bay and Cape Cod are genetically distinct and relatively isolated.
• Despite severe habitat loss, Rhode Island’s populations still maintain moderate genetic diversity, meaning conservation action here can have outsized benefits.

Next Steps for Policy & Management

Salt marshes are under immense pressure from sea-level rise and development

The study provides timely evidence for upcoming conservation decisions that will have consequences for the future of diamondback terrapins and salt marsh ecosystems more generally. This important dataset can be used to:

• Identify genetically distinct populations that need special protection.
• Plan habitat restoration and coastal corridor projects to improve connectivity.
• Weigh the risks and benefits of translocations to counteract isolation without causing genetic mismatches.

Protecting terrapins isn’t just about saving a charismatic turtle — it’s about protecting the health of coastal ecosystems across New England and the Eastern Seaboard more generally.

Rhode Island is both a stronghold and a test case for regional conservation action. Results clearly show that genetic diversity declines sharply with latitude, potentially leaving northern populations at greater risk. But Rhode Island’s populations still maintain moderate genetic diversity — meaning action here could tip the scales for the entire region. Steps taken in the region may directly shape whether terrapins gain federal endangered species protection in the years ahead.

Funding provided by:

• Voss Undergraduate Research Fellowship from the Institute at Brown for Environment and Society
• The Diamondback Terrapin Working Group
• Sophie Danforth Conservation Biology Fund from the Roger Williams Park Zoo
• Rhode Island Department of Environmental Management Cooperative Agreement

More like this

• Find all conservation genomics happening in the Kartzinel Lab
• See the fieldwork behind the paper in our 2019 post