SREL Reprint #1870
THE EFFECT OF LARVAL DENSITY ON ADULT
DEMOGRAPHIC TRAITS IN AMBYSTOMA OPACUM
DAVID E. SCOTT
Drawer E, Savannah River Ecology Laboratory, Aiken, South Carolina 29801 USA
Abstract. Factors that affect traits of aquatic larvae of amphibians may have
long-lasting effects on terrestrial juveniles and adults. I manipulated larval
densities of marbled salamanders, Ambystoma opacum, in large-scale field
enclosures during 2 yr, released the juveniles that metamorphosed from these
enclosures, and tested for effects on adults that returned to the pond during 6-7
subsequent breeding seasons. Individuals from low larval density treatments
tended to have greater lipid stores at metamorphosis than those from high
densities and survived longer in a laboratory inanition study. In the field,
individuals that experienced low larval density returned for their first reproductive
bout as larger adults than those from high-density treatments. For 5-yr-old
females released in 1986, low larval density was linked to greater clutch size;
clutch size in 4-yr-old animals from the 1987 cohort did not differ between larval
treatment groups. Larval density also influenced age at first reproduction, as
animals reared at low densities returned to breed at younger ages. Averaged
across both cohorts, the proportion of animals that returned to breed at least
once was 21% for low-density groups compared to 6% for the high-density
groups. The larval environment exerted a strong influence on postmetamorphic
traits, and thus larval density likely plays an important role in population
regulation in both the aquatic and terrestrial phase of the life cycle.
Key words: age at maturity; Ambystoma opacum; amphibian; density
dependence,- fitness; phenotypic plasticity,- population regulation; reaction
norms; salamander; size at maturity,- southeastern U.S.; survival
SREL Reprint #1870
Scott, D.E. 1994. The effect of larval density on adult demographic traits in Ambystoma opacum. Ecology 75:1383-1396.
