Intraspecific variation of life history parameters in the terrestrial isopod, Armadillidium vulgare

Individual populations of the terrestrial isopod, Armadillidium vulgare, were studied in three Texas coastal prairie habitats: Chinese tallow forest, oak forest, and a Baccharis-grassland area. Time-specific life tables were compared for each population to determine intraspecific variation in life history parameters. Survivorship was greatest in the Baccharis area but density was lower and fluctuated less in this area than in the tallow or oak forests. Density in the oak forest was higher than in the tallow or Baccharis habitat. Density in the tallow and oak forests increased sharply during spring and summer and declined throughout the winter. Reproductive capacity of females in all three areas increased directly with body length but did not differ significantly between habitats. Density and reproductive performance of isopods in the tallow and oak forests was asynchronous with autumn leaf fall; this asynchrony may be a response to tannins leached from fallen leaves of these trees. Density and reproductive potential of isopods in the Baccharis-grassland, however, did not exhibit such marked fluctuations. Isopods in this latter habitat responded moderately to annual input of detritus during the fall.