A Provisional Model of Demography in Desmognathus ocoee (Amphibia, Plethodontidae)
A provisional model of survival and demography in two populations of the salamander
Desmognathus ocoee
in the Cowee and Nantahala mountains of North Carolina was derived from existing data on growth, metamorphic timing, age at first reproduction, and fecundity. The model assumed stationary populations with stable age distributions (
R0
= 1.0,
r =
0), wherein observed ages at first reproduction in females were equal to optimal ages. Survivorship was partitioned into pre- and post-metamorphic phases, i.e., egg/larval survival and juvenile/adult survival. Premetamorphic survival estimates were fitted to the model to meet the requirement that
R0
= 1.0. Equivalence of optimal and observed age at first reproduction in females, as proposed, could reflect synergistic tradeoffs between (1) growth and reproduction, and (2) mortality and reproduction. The two populations show extreme similarity in life history and demography, in contrast to differences between the Cowee and Nantahala desmognathine assemblages.
Plots of ltmt versus age for postmetamorphic Desmognathus ocoee at Coweeta (Cow) and Wolf Creek (WC), based on the premise that the observed age at first reproduction in females equals the optimal age (t*). The latter is shown by the maxima of the curves, wherein dltmt/dt = 0. Expected lifetime fecundity is approximated by the shaded area under each curve.
Survivorship curves of Coweeta (Cow) and Wolf Creek (WC) postmetamorphic Desmognathus ocoee.
Contributor Notes
Associate Editor: D. S. Siegel.