Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida
Research Identifies Variety of Diamondback Terrapins
Diamondback terrapins (Malaclemys terrapin) are habitat specialists that adapted to exist in an estuarine environment along the U.S. coast from Massachusetts to Texas. Though the habitat in most of their range is salt marsh, a considerable quantity of their habitat in south Florida is mangrove waterways.
“Throughout this expansive range, their appearance or phenotype changes depending on the region they occur in even though they are all one species,” said SCCF Wildlife & Habitat Management Director Chris Lechowicz. “These brackish water species can tolerate a wide variety of salinities including hypersaline environments.”
Terrapins were divided into seven subspecies over the last couple of centuries, each representing its own phenotype in its own region. Florida is home to five of these seven subspecies with three of those being endemic to Florida — meaning they are only found in Florida.
The terrapins of Lee County, Florida have been labeled as ornate diamondback terrapins (M. t. macrospilota) and mangrove diamondback terrapins (M. t. rhizophorarum) in range maps, depending on the author.
“Through the research that SCCF biologists have conducted since 2013, we found that most terrapins processed resembled ornate diamondback terrapins,” said Lechowicz. “However, a low but consistent number of terrapins do more closely resemble the mangrove diamondback terrapin.”
With subspecies, there is an expansive blending of traits near the intersection of the two ranges which many refer to as intergrades, as opposed to a hybrid which is the mixing of two different species.
Over the last few years, researchers from around the state provided genetic samples to the Florida Fish & Wildlife Conservation Commission (FWC) for a genetic study to determine if the subspecies range maps, based on phenotypes, matched the genetics.
SCCF was one of the highest sample providers. Results of this genetic study moved the range of mangrove diamondback terrapins further up the west coast of Florida, a little north of Sarasota. So according to that taxonomy, Sanibel is home to mangrove diamondback terrapins according to genetics.
“We found that there are a variety of phenotypes in our population, some that do not resemble either subspecies, as well as examples that fit both very closely,” explained Lechowicz. “We have also found that island populations resemble one subspecies more than mainland populations. We have provided recent photos showing the diversity of coloration and patterning in our area.”
Please send any sightings and photos of diamondback terrapins to terrapin@sccf.org.