A Female-Centered Evaluation of Growth, Survival, Reproduction, and Demography in the Salamander Desmognathus quadramaculatus
In the present report, I evaluate life history and demography for two populations of the Black-bellied Salamander, Desmognathus quadramaculatus, in the Cowee and Nantahala Mountains, North Carolina, using published data on growth of females, fecundity, and larval growth and development to generate life tables and metabolic life histories for each population. I assumed that females in these populations reproduce biennially, beginning at ages 7–8 years and 8–10 years in Cowee and Nantahala populations, respectively. In deriving life tables, I posited stationary populations wherein net reproductive rate (R0) equaled 1.0 and population growth rate (r) equaled 0. Fecundity (mx column of the life table) was based on counts of ovarian follicles in gravid females. Survival values (lx column of the life table) were generated by an iterative process that yielded a value of R0 = 1.0. I projected the life spans in each population to 25 years. The demographic models developed by the procedure allowed comparison with those reported earlier for D. monticola and D. ocoee. Age at first reproduction and generation time are key contributors to variation in body size and life history in Desmognathus.
Representative life-history stages of Coweeta Creek/Nantahala River Desmognathus quadramaculatus. (A) Hatchling larva, ≈ 13 mm SL. (B) Second- or third-year larva, ≈ 30 mm SL. (C, D) Juvenile color morphs, each ≈ 60 mm SL. (E) Unsexed adult, ≈ 80 mm SL.
Gompertz growth curves fitted to the “female” Wolf Creek and Coweeta skeletochronological age estimates of unsexed larvae and small juveniles, and immature and mature females of Desmognathus quadramaculatus.
Plot of log-transformed values of number of yolked ovarian follicles versus standard length in gravid females of the Wolf Creek (red symbols) and Coweeta (blue symbols) populations of Desmognathus quadramaculatus. Least-squares regressions fitted to data of either population were non-significant (Bruce, 2013). Least squares regression equation fitted to the pooled data has a slight positive slope (ln fol = 1.392 + 0.585ln SL), but is non-significant (F = 1.517, df = 1,18, P = 0.234).
Metabolic life histories of Wolf Creek and Coweeta Desmognathus quadramaculatus. “Brood” is the complement of hatchling larvae that emerge from a single egg clutch (Bruce, 2018), and “brood mass” refers to the female component of the brood under a biennial cycle, i.e., number of deposited eggs/4. Mass values are based on wet weights (W) of living, anesthetized salamanders, ≈ 7 kJ/gram in energy density. (In the text, in the equation of the scaling function, dry body mass is designated K [= M of other authors] to avoid confusion with my use of M to designate mortality rate).
Contributor Notes
Associate Editor: D. S. Siegel.