M. Zimmer et W. Topp, Species-specific utilization of food sources by sympatric woodlice (Isopoda : Oniscidea), J ANIM ECOL, 69(6), 2000, pp. 1071-1082
1. In long-term laboratory studies, the influence of different food materia
ls on parameters of population dynamics was compared in the sympatric woodl
ice, Porcellio scaber and Oniscus asellus, as a measure of interspecific di
fferences in the utilization of food.
2. Freshly fallen leaf litter of different tree species had been acidified
and microbially inoculated prior to the experiments. By analysing the influ
ence of pH level, density and activity of litter-colonizing microbiota and
several physico-chemical characteristics of the leaf litter, we obtained in
formation on those factors that determine food quality.
3. The studied species responded similarly to different leaf litter species
in that both P. scaber and O. asellus performed better on litter with low
C:N ratio. Overall, both isopod species reproduced more successfully on lit
ter with higher pH levels, containing half the levels of tannins and other
phenolics.
4. Interspecific differences were obvious with respect to the significance
of litter-colonizing microbiota, and the dependence of juveniles on particu
lar food parameters. While the performance of adult P. scaber was influence
d by both litter-colonizing microbiota and physico-chemical characteristics
of the leaf litter, adult O. asellus were influenced by leaf litter charac
teristics, but not by litter-colonizing microbiota. Juvenile mortality was
affected by the tested food parameters in O. asellus, but not in P. scaber.
Growth rates of juveniles of both species were influenced by physico-chemi
cal characteristics of the leaf litter. Additionally, leaf litter microbiot
a had a significant influence on growth rates in juvenile P. scaber, but no
t in juvenile O. asellus.
5. Reasons for, and consequences of, similarities and differences between t
he observed sympatric species, and intraspecific differences between ontoge
netic stages, are important aspects of soil ecology and may help explain th
e sympatric coexistence of two species belonging to the same guild of sapro
phagous soil animals.