INDEPENDENT CHARACTER EVOLUTION IN LOWER CARBONIFEROUS GRANATOCRINID BLASTOIDS

There are many reasons to believe that certain morphological characters should evolve in a correlated manner. Character correlation may be expected when characters are related to one another due to functional and/or developmental constraints. In order to examine the pattern of character dependence in blastoids, 36 species of granatocrinid blastoids were scored for 43 binary characters. The character compatibility method described by O'Keefe and Wagner (2001) and the likelihood method described by Pagel (1994) were used to test for the correlation of these characters due to both functional and developmental association. Both tests show that there is no correlation among characters when grouped by function, development, or plate type. These results are not contingent on any one particular hypothesis of phylogeny. The character compatibility method assumes that a phylogenetic tree exists upon which characters can be mapped, but does not assume one particular topology. Several different tree topologies, retrieved from different tree reconstruction methods, were used to test for correlation of characters under the likelihood method showing that the independence of character change is not dependent upon tree topology for this dataset. Other Paleozoic blastozoans show a similar pattern of character change.