Density-dependent regulation of natural and
laboratory rotifer populations
T.W. Snell, B.J. Dingmann, M. Serra-2001
Hydrobiologia, 446/447:39-44
Abstract:
Density-dependent regulation of abundance is fundamentally important in the
dynamics of most animal populations. Density effects, however, have rarely
been quantified in natural populations, so population models typically have
a large uncertainty in their predictions. We used models generated from time
series analysis to explore the form and strength of density-dependence in
several natural rotifer populations. Population growth rate (r) decreased
linearly or non-linearly with increased population density, depending on the
rotifer species. Density effects in natural populations reduced r to 0 at
densities of 1–10 l^−1
for 8 of the 9 rotifer species investigated. The sensitivities of these
species to density effects appeared normally distributed, with a mean r=0
density of 2.3 l^−1
and a standard deviation of 1.9. Brachionus rotundiformis was the outlier
with 10–100× higher density tolerance. Density effects in laboratory
rotifer populations reduced r to 0 at population densities of 10–100 ml^−1,
which is 10^4
higher than densities in natural populations. Density effects in laboratory
populations are due to food limitation, autotoxicity or to their combined
effects. Experiments with B. rotundiformis demonstrated the absence of
autotoxicity at densities as high as 865 ml^−1,
a much higher density than observed in natural populations. It is,
therefore, likely that food limitation rather than autotoxicity plays a
major role in regulating natural rotifer populations.