Parallel clines in morphologic and genetic differentiation in a coastal zone marine invertebrate: the bryozoan Schizoporella errata

Genetic and morphologic differentiation in the bryozoan Schizoporella errata parallel each other over a distance of 102 km along the southern shore of Cape Cod. This is seen in the allele frequencies of two marker genes and in the length of the avicularium (a type of defensive polymorph of the bryozoan colony). These changes appear to be part of the continuing evolutionary adaptation to local environmental conditions, perhaps characteristic of marine species whose dispersal ability is very limited. The length scale of significant changes in allele frequencies at the two loci is as low as 10–11 km, and for avicularium length is 13 km.