Abstract
The demography of Porcellio spinicornis was modelled using growth, survival, and reproduction parameters modified by temperature, humidity, and day length. Growth rates were temperature-dependent (0.0 below 10 °C, increasing to a maximum at 30 °C, and decreasing to 0.0 above 35 °C). Survival rates were both temperature-dependent and size-dependent. Small animals (prejuveniles) survived between 10 °C and 35 °C with maximum survival at 25 °C. Medium-sized animals (juveniles) and adults survived between 0° and 35 °C with maximum survival at 25 °C. Females were able to reproduce between 17.5 °C and 27.5 °C, and the number of young produced increased with female size. P. spinicornis exhibited narrow humidity tolerances (95% RH ± 3% RH) but were able to search out and remain in microhabitats containing the correct humidity conditions. Day length had no detectable demographic effects.Simulations using the laboratory-based demographic model and field temperatures for 1971 and 1972 suggested that a P. spinicornis population should slowly increase in numbers. But when the 1971–1972 temperatures were decreased by art average of 0.77 °C, the simulated population decreased. This suggests that minor temperature fluctuations could regulate the numbers of P. spinicornis; and inspection of field temperature data from 1957–1973 indicates sufficient year to year temperature fluctuation to maintain stable P. spinicornis populations in Southern Ontario.
Published Version
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