Punctuated Equilibrium and the Validation of Macroevolutionary Theory 787
and places. Multivariate discriminant analysis assigned all but 9 of 507 offspring
into the same morphospecies as their maternal parent. The authors then used
electrophoretic methods to study enzyme variation in 402 colonies representing 8
species in the three genera. They found clear and complete correspondence
between genetic and morphometric clusterings, and also determined (p. 581) that
"genetic distances between morphospecies are consistently much higher than
between populations of the same morphospecies"; moreover, they found no
evidence for any cryptic division (potential "sibling species") within skeletally
defined morphospecies.
In a concluding and gratifying observation—indicating that paleontologists
9 - 8. Stasis in three genetically well-defined extant species of the gastropod Amalda from New
Zealand based on 662 fossil specimens. Mean values in multivariate expression based on all ten
variables fluctuate mildly through time, but never depart from the range of variation within
extant populations. From Michaud, 1989.