MORPHOMETRIC NETWORK ANALYSIS OF INTEGRATION IN MORPHOLOGICALLY CONSERVATIVE MOLLUSCAN CLADES
We tested the utility of morphometric network analysis using several morphologically conservative molluscan clades: the corbulid bivalves Bothrocorbula and Caryocorbula, the venerid Lirophora, and the gastropod family Naticidae. For some of these taxa, previous attempts to use morphometric data to detect morphospecies has met with limited success. In fact, Lirophora has resisted traditional morphological description, with single species names being applied to temporally and geographically distant taxa. For naticids, the new source of characters provided by geometric morphometrics and integration are invaluable to the phylogenetic placement of problematic fossil taxa. In the two corbulid genera, species-level phylogenies are hampered by few discrete characters. In these clades, species differ primarily in valve outline shape, which is difficult to deconstruct into character states appropriate for phylogenetic analyses. In addition, strong interspecific allometry in Caryocorbula indicates that constraint channeled its morphologic evolution. We found that for most taxa the use of morphometric network analyses greatly increased our ability to distinguish taxa, recognize modularity in shape variation, and parse out overall shape differences into character states of use in phylogenetic analyses.