Five Questions for Carole Baldwin
Dr. Carole Baldwin never expected to find seven new species of fish among the Starskia blennies she was studying at the Smithsonian's National Museum of Natural History. "My research team was using barcoding to match larval stages of reef fishes to adults," she said. But when comparing the DNA of the larvae to the barcodes of the adult fish, discrepencies emerged.
After careful analysis of the fishes' morphology and DNA, the team found that what were thought to be three species of blenny–Starksia atlantica, Starksia lepicoelia, and Starksia sluiteri–are actually ten. Baldwin, a research zoologist and curator of fishes, was lead author of the paper describing her team’s discovery of the seven new species–all Starksia blennies from the Caribbean that were "hiding" within the three known species. The results raise intriguing questions about how many other new species are waiting to be discovered.
Can you explain what is meant by morphology?
Long before techniques were available to analyze DNA, scientists recognized species on the basis of morphology. In fishes, morphological examination typically involves comparing patterns of pigmentation (usually of preserved material in which colors have faded but also of fresh material when possible), numbers of rays in the fins, numbers of vertebrae, various counts or patterns of scales, and other features depending on the type of fish. For Starksia blennies, for example, we also looked at presence or absence of cirri above the eye, length of male genital papilla, and patterns of pores on the head.
Your findings seem to point to the need to use morphology as well as DNA to identify new species?
The new species of Starksia differ from certain previously known species only in minor ways–primarily small but consistent differences in patterns of pigmentation. Each of the new species was previously thought to be one of the known species, so you might say that the seven new species were previously “hiding” within three known species. It took DNA analysis combined with morphological examination to make them “visible.”
How reliable is DNA analysis?
My research team has analyzed DNA for more than 6,000 western Atlantic/Caribbean fish specimens, and the congruence between genetic lineages and currently recognized species is remarkable. So in general I trust the DNA. However, I would not recognize genetic lineages as new species based on DNA alone. In science in general, the more different kinds of data we can analyze to address a question the better, and identifying new species is no exception: it’s best to look at both DNA and morphology.
Scientists have used DNA barcoding before to identify new species, although it is not so common in fishes. I didn’t set out to identify new species using DNA barcoding. My research team was using barcoding to match larval stages of reef fishes to adults. That’s when we discovered that DNA may be useful in revealing new fish species.
Are there more species to discover in the Caribbean?
My current research suggests that there are many more unknown Caribbean reef-fish species still to be discovered, named, and described. And I’m talking about fishes that live in shallow waters that scientists have studied for more than 150 years. We scientists thought we were basically done with the Caribbean–in other words we thought there wasn’t much more to learn in terms of fish diversity, but we were wrong. And without DNA essentially guiding us to the new species, we most likely would not have discovered them. When the DNA results conflict with our current species classification (for example if there are more genetic lineages than known species as we found with Starksia), then we know we need to go back and look at the fish more closely. So far every time we have done that we have found information in the fish that supports the genetic data. So the DNA is showing us where to look to find new species.
What does the future hold?
I expect that we will find many more new species in shallow waters of the Caribbean, and if we apply this same molecular/morphological approach to other areas of the world, we will find huge numbers of new species. And that’s just in shallow water. We are only beginning to venture deeper, and my research team will be conducting deep-reef investigations in the southern Caribbean beginning this year. Other Smithsonian scientists working on various groups of invertebrate marine organisms also will participate in this deep-reef effort. We are living in a new age of discovery in terms of biological diversity, and just as in crime-scene investigations, DNA is playing a huge role.
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