|SREL Reprint #0972|
Variation in Metamorphosis and Paedomorphosis in the Salamander Ambystoma
D. Semlitsch and J. Whitfield Gibbons
Phenotypic variation in metamorphosis and
paedomorphosis in the salamander Ambystoma talpoideum was examined
to determine its environmental or genetic basis. Eight artificial ponds were maintained, four at each of two
environmental treatments; constant water level, to simulate fish-free permanent
breeding ponds, and gradual drying out, to simulate temporary breeding ponds.
Two populations of salamanders were used, derived from two breeding ponds
having different frequencies of paedomorphosis.
The water level in the drying treatment was lowered
during the last 10 wk of the experimental period with no apparent differences in
water chemistry parameters between treatments and only a slight change in water
temperature during the last 2 wk. The
quality of the growth environment for larvae, as measured by body size and
survivorship, was the same in the four experimental treatments.
The frequency of metamorphosis was significantly higher in the drying
treatment than under constant water level, and also differed between
populations. The frequency of
paedomorphosis was significantly different between populations but not between
water level treatments.
The effects of water level were potentially
confounded by those of water temperature, density of larvae, and amount of food.
Population differences in the frequency of metamorphosis and
paedomorphosis could potentially represent genetic differences resulting from
the different selective regimes that individuals encounter in breeding ponds
varying in drying frequency. However,
phenotypic plasticity and nongenetic maternal effects cannot be dismissed
without further experimentation.
Ambystoma talpoideum; amphibian; metamorphosis; neoteny;
paedomorphosis; permanent pond; phenotypic variation; salamander; temporary
pond; water level
SREL Reprint #0972
Semlitsch, R.D. and J.W. Gibbons. 1985. Phenotypic variation in metamorphosis and paedomorphosis in the salamander Ambystoma talpoideum. Ecology 66:1123-1130.