Biodiversity Challenge: The Marriage of Morphological and Molecular Methodology (3 Comments)

Big_Nose_George

Who knows how many this guy is smuggling

When you hear the words “new species,” what comes to mind? Many of you probably imagine cute-faced primates, exotic amphibians, or prehistoric fish hidden deep away from human exploration.  My point is that we typically associate these discoveries with excursions to far away places, when in fact there are undescribed species right under our noses.  Many organisms remain new to science because either they are so tiny that we need high-magnification microscopes just to find them, or that previous identifications were incorrect.  When the latter happens, multiple species that appear similar can be mistakenly grouped into a single species by even the most meticulous of researchers.  This notion can seem confusing to many of us who were taught growing up that a species’ name is a permanent, definitive term.  The truth is that the classifications of organisms are constantly changing, reflecting the best available knowledge at any given time.  As new methods of study become available, our understanding of animal populations and their classification, especially in marine environments, can drastically change.

An example of this phenomenon is in an article by Schulze et al from 2012.  The authors examined three species of Pacific sipunculans, a group of small, unsegmented marine worms, which had previously been described only on their phallic-like anatomy. Each individual was taken from either the eastern or western coast, representing populations separated by more than 5,000 miles. By comparing the DNA of each species, the researchers were able to get a better idea of how genetically dissimilar these distant populations are.  Using the Biggie-Tupac scale, they found that the east/west divergence among each species was surprisingly high.  Though their anatomy remained similar, the genetic differences between the populations were about three times greater than would be needed to classify a difference in species.  The study concluded that instead of three species with distinct east and west populations, there might be up to six potentially different species in the region; three confined to the east Pacific and three to the west.

These sorts of studies highlight the importance of combining molecular data with earlier taxonomic research, since many of our traditional taxonomy studies still rely on strictly morphological data. The problem with this is that we cannot get the complete picture of species distributions, community structure, or other demographic information using only one method of study. Think of using both morphological and molecular data as a “discount double-check” for taxonomists.  It’s a way to make sure that we aren’t being fooled by appearances, as they can often be misleading.

Besides simply being good practice, this method of research has implications far beyond classification.  According to Schulze et al., “a solid taxonomic framework is necessary for interpreting population-level genetic data, but genetic data are also crucial for establishing a taxonomic framework.”  Now that we have the technology to analyze large amounts of genetic data, it is important that we do so when studying marine populations.  We don’t always appreciate the methodology behind describing and defining species, but fisheries, conservation organizations, ecotourism-based companies, and independent researchers all use this “basic” information to make critical decisions facing the future of our oceans.  Therefore, it’s important that we recognize how valuable the thoroughness of these studies are, no matter the scale.  One of the essential yet often overlooked steps in measuring biodiversity is determining what constitutes a species, and studies like this help us understand how complex that question can be.

29 October, 2013

October 29, 2013

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  • I cannot agree with this sentiment enough. Most of the time taxonomy is more or less good enough: sure we can recover finer scale relationships, collapse a taxa here and there, but by and large, two centuries of careful measurements and observations have, in my opinion, gotten us pretty darn close. Its a shame to ignore this resource in favor of molecular methods, especially when taxonomy is frequently used to both build (think Bayesian) and correct molecular phylogenies. Well put

  • I’m glad you agree, Jon. With all the resources taxonomy has available to it today, it would be a shame not to use both methods (i.e. morphological and molecular) whenever possible. The field certainly has come a long way and hopefully will continue to play a large role in future biological research.

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