Comparison and cost benefit analysis of different data sets used for determining mollusc evolution: a case study of the cryptobranch nudibranch Halgerda (Mollusca: Gastropoda)

Abstract

-Several approaches to examining the evolution of organisms have been tested over the past several decades. Specifically, morphological and molecular (DNA sequences) data sets are the most widely used methods to test a phylogenetic hypothesis. A cost benefit analysis of previously published studies of nudibranch mollusc phylogeny is presented. The previous studies utilized different types of data sets to derive hypotheses of relationships. The present cost benefit analysis examines the usefulness of the different data sets to verify an existing species level phylogeny. The existing hypothesis had been derived from morphological data only. Results of the present analysis indicate that two of the four data sets used, DNA sequence data and morphological characters, are the most effective when measured in terms of robustness of the resultant phylogeny and considering cost and time spent on the analysis. The other two data sets: sperm morphology and natural product chemistry were found to be valuable at higher taxonomic levels. Conclusions from the cost benefit analysis indicate that combinations of data can provide valuable insight into evolutionary relationships, allowing the researcher to further examine a hypothesis from various perspectives. Those perspectives include the molecular evolution of the organism, morphological character evolution, chemical evolution and reproductive evolution at a cellular level. Using a multidisciplinary approach to systematics reveals the complexities of evolution.