Tuesday, April 9, 2013

Great Unanswered Questions – Advancing Taxonomic & Phylogenetic Infrastructure

The January 2013 issue of American Malacological Bulletin included eight papers from 11 presentations from the James H. Lee symposium, “Great Unanswered Questions in Malacology,” which was held at the 77th Annual American Malacological Society meeting in Pittsburgh, Pennsylvania, July 23-27 2011.  The organizers, Timothy Pearce and Charles Sturm, introduced each paper (Pearce and Sturm, 2013).  All the papers were quite interesting, but one that I would like to highlight further as the topic for this blog posting is entitled “Bivalvia – A discussion of known unknowns by R├╝diger Bieler, Paula M. Mikkelsen and Gonzalo Giribet (Bieler et al., 2013).  Although the subject was on bivalves, the conceptual issues they described are relevant to all mollusks and are worthy of broader consideration.  Bivalves, like other many other molluscan groups live in a range of habitat types, have an extensive amount of literature, and a rich fossil record.  However, bivalves, like other mollusks, are not used or even widely considered as model organisms, perhaps because that the term “model” has been used too narrowly, limited to studies of evolutionary genetics and experimentally-manipulative studies in ecology and evolution.  

To effectively use bivalves and other mollusks in studies of larger evolutionary questions, Bieler et al. (2013) identify three major components or basic tools of study:   (1) taxonomic infrastructure – an understanding of the valid species, their geographic distribution, and their geologic history; (2) monophyletic groups – the recognition and definition of clades above the species level; and (3) phylogenetic backbone – a robust phylogeny allowing discussion of evolutionary scenarios.  Taxonomic infrastructure is critical for asking even the most fundamental biological questions, but sadly there are too few taxonomic experts actively inventorying and describing most mollusk groups.  Many mollusk groups, however, have at least some rudimentary taxonomic infrastructure that would enable researchers to make some headway into establishing Bieler et al.’s (2013) numbers 2 (monophyletic groups) and 3 (phylogenetic backbone), which together, could simply be considered as “phylogenetic infrastructure.”  Phylogenetic infrastructure enables researchers to ask compelling questions with appeal to a wide range of evolutionary biologists, ecologists, behavioral biologists, and physiologists such as the evolution of active host-attraction strategies in the freshwater mussel tribe Lampsilini (Bivalvia: Unionidae) (Zanatta and Murphy, 2006) and the evolution of freshwater lineages within the gastropod superfamily Cerithioidea (Strong et al., 2011). 

Asking exciting research questions of broad evolutionary significance will attract new researchers (particularly students) to malacology.  Of course, for many mollusk groups, you can only take a phylogeny so far before you need to deal with unsolved taxonomic infrastructure.  It is important that the units of evolution (i.e., species) are identified and that they are carefully diagnosed, described and named.  Perhaps once students are engaged in evolutionary questions on mollusks, they may feel compelled to attempt to tackle the many taxonomic issues associated with the group, but this is easier said that done.  Hershler and his collaborators such as Hsiu-Ping Liu have long contributed to both the taxonomic and phylogenetic infrastructure of hydrobiids in North America, providing important information on the taxonomic diversity of the fauna and shedding light on the complicated biogeographic history of the western United States (see blog posting from March).  Of course, few molecular phylogeneticists possess the necessary skills for conducting taxonomic monography, so working with a taxonomist (if one is available) or receiving training from one would be most beneficial.  I would personally advocate training through workshops perhaps funded by the National Science Foundation (NSF) to stimulate such research activities within the discipline.  Although these have been done on some taxonomic groups through NSF PEET (Partnerships for Enhancing Taxonomic Expertise) awards on particular molluscan taxonomic groups, perhaps workshops to train and encourage phylogeneticists to venture into the taxonomic infrastructure realm would be beneficial.  Mollusks are fascinating creatures and there is much to learn.  Let’s think big and integrate taxonomy and phylogeny to advance the science. 

Literature Cited

Bieler, R., P. M. Mikkelsen, and G. Giribet.  2013.  Bivalvia-A discussion of known unknowns.  American Malacological Bulletin 31(1):123-133.
Pearce, T. A. and C. F. Sturm.  2013.  Introduction to the James H. Lee symposiu, “Great Unanswered Questions in Malacology,” 77th annual meeting of the American Malacological Society.  American Malacological Bulletin 31:105-107.
Strong, E. E., D. J. Colgan, J. M. Healy, C. Lydeard, W. F. Ponder, and M. Glaubrecht.  2011.  Phylogeny of the gastropod superfamily Cerithioidea using morphology and molecules.  Zool. Jour. Linnean Soc. 162:43-89.
 Zanatta, D. T., and R. W. Murphy.  2006.  Evolution of active host-attraction strategies in the freshwater mussel tribe Lampsilini (Bivalvia: Unionidae).  Molecular Phylogenetics and Evolution 41:195-208.