M. J. Faber suggested the possibility of an environmental control
switch as an alternative to either genetic drift or reproductive
advantage, to explain the switch of a small isolated population of P
type to L type gastropods. Environmental switches of such kind are
likely to be more common than classically trained evolutionary
biologists have been willing to accept. There are a number of examples
across several phyla, of species that change their morphological form
depending on environmental conditions during early development. Some
retain their original genetic identity through the F1 and F2
generations; others do not, and the line between adaptive phenoplastic
response and heritable change is lately getting rather blurred.
Saxifragia saggitaria, Nemoria arizonaria), Salmo trutta, and Daphnia
lumholtz, for example, might be viewed as a continuum that lies on
either side of this line. This all sounds rather Lamarckian --and it
is-- but the arguments here lie at the heart of current epigenetics.
M.J. West-Eberhard has published a new book on the topic, which I for
one am anxiously awaiting ("Developmental Plasticity and Evolution,"
Oxford U Press., ISBN 0-19-512234-8).

Burton Vaughan
Biological Sciences
Washington State Univ-Tricities