Intra-population variability in energy parameters of the salamander Plethodon Cinereus

Summary

Mean values of energetic parameters are used in ecosystem studies because only crude estimates are possible when dealing with a large scope. However, when the focus is at the population level, finer resolution is possible and thus potential ontogenetic differences should be examined. Analysis of energetic parameters of a population of terrestrial salamander, Plethodon cinereus, was undertaken in order to determine ontogenetic differences.

Digestive efficiency does not differ significantly between age classes, nor is it correlated with energy intake. Adult males and non-gravid females have virtually identical mean efficiencies. Thus it is probably meaningful to calculate energy flow through the population using a mean digestive efficiency value. Percent water content decreases significantly with increasing age whereas percent ash content increases significantly. Thus when estimating energy tied up in standing crop, correction must be applied for ontogenetic differences in water and ash content. Once these corrections have been made, the AFDW-specific energy content is not significantly different between age groups (with the exception of gravid females which is higher). Salamanders accumulate energy in their tissues with increasing age, although immatures are not significantly different from non-gravid adults. Since gravid females have significantly more joules/mg wet weight than other groups, separate energy density values must be calculated for these individuals if a meaningful standing crop energy estimate is to be obtained from wet weight biomass.