11:15 AM - 11:30 AM
★ [MIS25-08] Comparison between morphological dissimilarity and morphological richness
Keywords:disparity, biodiversity, morphological dissimilarity, morphological richness
Morphological disparity, another look at biodiversity, has recently attracted attention of paleontologists in the context of mass extinction and recovery. The measure of disparity has commonly been based on morphological dissimilarity between objects, e.g., sum of variance, mean pairwise distance, range of variation etc. It is widely known that this sort of disparity is robust against sample size and is not seriously affected by a nonselective extinction, whereas selective extinctions should readily reduce the disparity. On the other hand, another aspect of disparity is morphological richness, which is assessed through compilations of the number of character states; e.g., number of pairwise character-state combinations and number of morphospace divisions occupied by observation. Unlike the morphological dissimilarity, the morphological richness appears to be fairly sensitive to nonselective extinctions as well as to selective ones. The comparison among the diversity measures based on the morphometric data obtained from the ammonoids revealed that the patterns of disparity change were totally different between dissimilarity and richness, while comparison within the same categories tended to indicate a consistent result. This result suggests that comparison between morphological dissimilarity and morphological richness provides a powerful tool to assess the selectivity of an extinction event.