INCUMBENT ADVANTAGE IN COMMON LIZARDS AND THEIR COLONIZING ABILITY

1. Settlement in a new environment is a key phase in effective dispers al. We investigated this phase in the common lizard (Lacerta vivipara Jacquin) by an experimental introduction of known individuals. 2. Intr oducing lizards in an already occupied environment revealed a prior-re sidence advantage and some differences in the ability of individuals t o face a new environment under conditions of high intraspecific compet ition. 3. Transplanted individuals (TI) died in larger numbers than re sident ones (RI) immediately after the introduction, except for juveni les. this prior-residence advantage could arise from the difference of familiarity with the local environment or from a dominant behaviour o f RI on TI. 4. TI which survived the first winter after the introducti on survived better than RI afterwards. However, surviving TI females p aid a cost in their reproduction. 5. Surviving TI were not a random su bset of the initial sample: smaller adult males and leaner adult femal es were selected. These selective responses arose from the transplanta tion since they were not observed in non-manipulated populations. 6. A comparison of characteristics between natural transient or immigrant individuals and TI survivors revealed: (i) TI male and yearling surviv ors may have been transients or immigrants in their site of origin; (i i) TI adult female survivors were not transients nor immigrants in the ir site of origin. The latter result questions the use of introduction experiments to test dispersal ability. Strictly. introduction experim ents only test settlement ability.