What does the new species of hammerhead mean for shark science and conservation?
In the year 2000, Dr. William Driggers, now of the National Marine Fisheries Service’s Southeast Fisheries Science Center in Mississippi, was sampling for sharks in South Carolina. Dr Driggers recalls that “at the time I was collecting samples from various species of sharks for life history studies and also collecting tissues for Dr. [Joseph] Quattro’s genetics work.” Dr. Quattro, a professor at the Marine Science Program and Department of Biological Sciences at the University of South Carolina, had been working on a project to characterize the population genetics of fish in South Carolina by “working my way down river systems to the coast,” he told me. “Even sturgeons were showing population differentiation, so I thought the next animal would be marine, but estuarine dependent – sharks.” Analysis of the samples Dr. Driggers collected led to a surprising result.
“I was asked “what are the chances that I would misidentify a ‘scalloped hammerhead’ and answered that there was no chance as they are very morphologically distinctive (looks like I was wrong),” Dr. Driggers told me. “I was then informed that genetic sequences indicated that some of the specimens I had labeled as ‘scalloped hammerhead’ were distinctly different from known S. lewini sequences. At Dr. Quattro’s request, I began bringing back whole specimens so they could be archived and morphometric analyses conducted. The first whole specimen that was vouchered and shown to be the new species was collected in Bulls Bay in July of 2001.”
In 2006, Dr. Quattro and his team published a paper entitled “Genetic evidence of cryptic speciation within hammerhead sharks,” showing that there may be a previously-unknown species hiding within scalloped hammerheads. When genetic samples of scalloped hammerheads, great hammerheads, and bonnethead sharks were phylogenetically mapped, the team found an unexpected result. Dr. Quattro, told me that “while doing the population genetics of this animals, we found two divergent genetic lineages within what were morphologically scalloped hammerheads. We gathered sequences and specimens from other known species and didn’t find a match – that’s what got us on the whole cryptic species [defined by Bickford et al. 2007 as “two or more distinct species erroneously classified and hidden under one species name”] thing.”