ROLE OF INTERSPECIFIC COMPETITION IN THE COEXISTENCE OF APODEMUS-ARGENTEUS AND A-SPECIOSUS (RODENTIA, MURIDAE)

Reciprocal-removal experiments with two replicates were conducted to t est for the role of interspecific competition in the coexistence of Ap odemus argenteus and A. speciosus. Population density, rate of appeara nce of new (unmarked) individuals, reproduction, survival rate and hab itat use were monitored during pre- and removal periods. In both remov al experiments, the removal of A. argenteus had little effect on A. sp eciosus, while that of A. speciosus affected several population charac teristics of A. argenteus. Namely, the removal of A. speciosus shifted the distribution of A. argenteus to the habitat with a denser shrub c over in one experiment. Also, the removal increased the population den sities and appearance rates of new individuals of A. argenteus in anot her experiment. Interspecific interactions between the two species app eared to be a one-way action from A. speciosus to A. argenteus. In rem oval periods in both experiments, the rates of appearance of new indiv iduals in each species were the highest on the grid where that species was removed. These results suggest that, though interspecific competi tion occurred between the two species, intraspecific competition had g reater effects than interspecific competition on the abundance and hab itat use of A. argenteus and A. speciosus. This implies that the funda mental niches of A. argenteus and A. speciosus differ potentially, whi ch may play an important role in the coexistence of the two species.