2nd of two parts
Editor’s note: Reporting for this project was supported by a grant from the Knight Center for Environmental Journalism at Michigan State University.
By Ashley Han and Olivia Watters
Can two animals look the same, act the same, even share a mother and yet be two different species?
You can find an answer in a very particular kind of salamander which resides in the Skyline High School wetlands: the LJJ unisexual hybrid salamanders.
These salamanders are akin to legend in this Ann Arbor school’s halls. Ask around and you’ll get a dozen different answers to what these creatures are, why they matter –and where they’ve gone.
When they were discovered early on during Skyline’s construction, herpetologists originally thought that they were hybrids.
However, they never were a species to begin with.
The key point which sets these salamanders apart is their unique genetic makeup.
The term most people know the salamanders by is “silvery salamander.” Reports and local online newsletters produced around the time of Skyline’s construction record the animals under that name.
Today, herpetologists consider that name to be inaccurate.
“It’s an obsolete name and bad science,” says George Hammond, a biologist with the city of Ann Arbor. The label has “not been used by scientists for many years.”
Using the name “silvery salamander” implies that these groups of salamanders are a species when they really aren’t.
The correct name is LJJ unisexual hybrid salamanders, with those letters representing the true species that contribute to the hybrids’ genetic makeup.
- “L” for one set of chromosomes from Ambystoma laterale (blue-spotted salamanders)
- “J” for two sets of chromosomes from Ambystoma jeffersonianum (Jefferson salamanders)
How can they reproduce?
The method of reproduction between these organisms is complex. The process begins after the first spring rainfall as the salamanders migrate back to the wetland where they were born.
The male species of Abstomya salamanders leave sperm packets on the ground, which the females collect and use to fertilize their eggs. This stimulates the development of the embryo.
But the male’s DNA isn’t always incorporated into the female’s embryo.
When that occurs, the offspring have DNA only from the mother. That’s how clones of the female salamander are produced because they are made solely with the DNA of the female.
Occasionally, the male’s DNA is incorporated in the embryo, resulting in many combinations of genomes. This process is called kleptogenesis.
Why aren’t they a species?
Because of their varying, complex genetic composition, these salamanders don’t neatly fit into the definition of a “species.” Their internal makeup depends heavily on contributions from other Ambystoma species since they use sperm donors and don’t reproduce completely independently.
They were first thought to be hybrids, said Katy Greenwald, a professor of biology and environmental science at Eastern Michigan University.
“In other words, that a blue-spotted and Jefferson salamander could reproduce and create a unisexual,” Greenwald said.
“We now know this is never the case — none of the sexual species breed with each other in the wild. The unisexuals are a unique 5-million-year-old lineage. They are, in fact, a ‘species complex’ and not a species,” she said.
Species complexes are a group of closely related organisms that look the same, act the same and are genetically tied, but cannot be grouped under one name because of each one’s different genetic material.
Since the sperm’s genetic material may or may not be incorporated into the developing embryo, it creates a wide variety of salamanders.
That’s why herpetologists no longer group all these salamanders under the name “silvery salamander.”
Ashley Han and Olivia Watters are Skyline High School students.