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 Rüdiger 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.
