THE MACROEVOLUTION OF INHERITANCE IN COLONIAL ORGANISMS (Invited Presentation)

Breeding experiments have shown that Stylopoma, a derived and complex colonial bryozoan, has a surprising pattern of inheritance: colonial traits are highly heritable among colonies but zooid traits lack heritability within colonies. Heritable traits are common in solitary organisms and because zooids are homologous to solitary organisms zooids should also have traits that are highly heritable. The loss of inheritance at the zooid level observed in Stylopoma is a clear marker of colony control over phenotypic evolution and something that is observable in the fossil record. I find that the Cretaceous genus Wilbertopora exhibits high heritability for traits among zooids. Wilbertopora colonies contain few zooids relative to colonies of Stylopoma. The first appearance of avicularia in cheilostomes is in Wilbertopora so the gain of polymorphism is not associated with the loss of heritability. Understanding the origins of colony control requires a macroevolutionary perspective to identify the covariation between inheritance patterns, growth from, degree of polymorphism, and colony size.