IMPLICATIONS OF INTRACOLONIAL VARIATION IN A PALEOZOIC BRYOZOAN

Relative differences between environmentally controlled variation and genetically controlled variation are important when investigating morp hologic variation in general, especially when establishing species con cepts. The colonial nature of bryozoans provides a means for distingui shing between the two sources; variation can be partitioned into withi n-colony (microenvironmental) and among-colony (environmental + geneti c) components. For the Paleozoic order Cryptostomata, biologically and taxonomically significant morphologic characters are well defined and methods for recognizing morphotaxa are well established. The importan ce of within-colony variation to the morphometric treatment of fenestr ate species was assessed after the discovery of a large specimen of He mitrypa sp. Variation within the colony was compared to variation amon g and within two congeneric species. The distribution of study segment s across the colony allowed assessment of variation both along the gro wth axis and laterally between segments of approximately equivalent ge nerational age. Repeatability of methods was assessed using data measu red independently from identical segments by three workers. Variation within the large colony is less than variation among congeneric specie s, indicating that genetic differences among species exceed variation resulting from combined phenotypic and genotypic sources within specie s. Neither astogenetic nor ontogenetic morphologic gradients are recog nized. Variation between data collected from identical segments by pai rs of workers falls within the range of variation for the entire colon y. Thus, multiple workers can reproduce data to the finest level of me aningful resolution. Cryptostome morphospecies concepts are validated. The potential for partitioning genotypic versus environmental variati on in reduced, multidimensional morphospace is reinforced. Studies of microevolution and speciation may be designed that account for these f actors.