Reproduction and life strategies in the Paleozoic tabulate coral Paleofavosites capax (Billings)

Abstract

Asexual and sexual modes of colony formation in a tabulate coral Paleofavosites capax are recognized from the early Silurian Gun River Formation of Anticosti Island. Québee. Colonies produced by asexual fragmentation comprise monospecific ‘clumped populations’. They are characterized by circular and concave bases, and lack a protocorallite origin of colony growth. Sexually produced colonies, where in situ, are always dispersed and characterized by conical bases with a definite protocorallite point origin of colony growth. Asexual colony formation by fragmentation in P. capax appears to have been an adaptation to a habitat of muddy substrates. Sexual reproduction in this species probably played a minor role but was necessary for the maintenance of gene diversity and long-distance dispersal. A comparison of corallite size distributions between populations demonstrates that intrapopulation variation in the ‘dispersed population’ and the conical colonies in ‘transported populations’ of P. capax is significantly larger than the variation in the ‘clumped populations’. It is suggested that this difference reflects the two modes of reproduction. The above observations are significant to systematic studies because they show that estimates of species morphologic parameters can he seriously biased even when based on a relatively large sample size from a well-defined population if that population is largely a result of asexual colony formation.