MORPHOLOGICAL DATA PARTITIONS POSSESS DIFFERENT LEVELS OF PHYLOGENETIC SIGNAL FOR THE EVOLUTIONARY RELATIONSHIPS OF THE REEF CORAL FAMILIES MERULINIDAE, MONTASTRAEIDAE, DIPLOASTRAEIDAE, AND MUSSIDAE (CNIDARIA: ANTHOZOA: SCLERACTINIA)

Coral reefs are the most diverse of all marine ecosystems, and among the most threatened in the modern biosphere. A robust phylogenetic framework including fossils is crucial for studying macroevolutionary questions such as patterns of morphological evolution, paleobiogeography, and temporal diversification. The fidelity of morphological data for resolving coral relationships, however, has been questioned. In this study, we test the strength of phylogenetic signal in two datasets of 40-50 morphological characters on phylogenetic trees constructed from molecular data. Each character was partitioned by type as macromorphological (observable through binocular microscope), micromorphological (scanning electron microscopy scale), and microstructural (transverse thin-section scale). Three common metrics, the parsimony-based Slatkin-Maddison test, Blomberg’s K statistic, and Pagel’s lambda, were used to test for phylogenetic signal in morphological characters on the molecular-derived trees. The majority of characters possess significant phylogenetic signal, with the micromorphological and microstructural characters showing stronger agreement with the molecular phylogenies according to the Blomberg’s K and Pagel’s lambda results. Inaccurate primary homology assessment in the macromorphological characters may be a contributing factor to their lower phylogenetic signal, but this can now be addressed with existing molecular phylogenies. All of the characters will still be useful in incorporating fossil data in future phylogenetic analyses. This work represents an important stepping-stone to using morphological data from fossil species to reconstruct phylogenetic relationships in scleractinian corals, which is crucial to understanding broader questions about macroevolutionary patterns in the group in the context of ongoing global change.