On the size of species’ ranges in the sediment-covered deep sea

David Thistle, Professor Emeritus in Biological Oceanography, Florida State University
Event Location: 
Event Date: 
Thursday, April 21, 2016 - 3:00pm
Event Type: 
SCMSS Seminar Series


According to some authors, metazoan species that inhabit the sediment-covered deep sea have ranges on the 100-km scale; others suggest that ranges are on the 1000-km scale. This ambiguity needs to be resolved because it makes it difficult for deep-sea ecologists to generalize their results and for policy makers to make good decisions about activities such as fishing and mining. At least part of the problem arises because most authors have used morphology alone to assess species’ ranges, but this approach does not separate closely related species reliably. As a way forward, we used both morphological and genetic data to investigate the ranges of harpacticoid copepod species; we chose harpacticoids because they appear to be poor dispersers and thus constitute a conservative test case.

Our material came from the continental rise along the west coast of the United States. We used morphology to combine individuals into nominal species. We then obtained gene-sequence data from the nuclear 18S ribosomal RNA gene and the mitochondrial cytochrome oxidase b gene from every individual in each nominal species. We considered individuals to belong to the same species when the morphological and genetic data agreed. We found 7 of 34 species (21%) to have 1000-km-scale ranges. Thus, many harpacticoid species in the deep sea have ranges much larger than 100 km, and we predict that deep-sea species that are better dispersers will have an even greater proportion of species with 1000-km-scale ranges. Our results also raise the question of how some harpacticoid species maintain genetic continuity over 1000-km-scale distances in the deep sea.

Speaker Information

Dr. David Thistle is a Professor Emeritus in Biological Oceanography at Florida State University in the Earth, Ocean, and Atmospheric Science department. 

More information about him and his work can be found here.