Colonization of high-elevation lakes by long-toed salamanders (Ambystoma macrodactylum) after the extinction of introduced trout populations

We surveyed high-elevation lakes for long-toed salamander (Ambystoma macrod actylum) larvae and trout in the northern Bitterroot Mountains of Montana, U.S.A., in 1978, 1997, and 1998. Our objectives were to (i) test whether tr out exclude salamander populations; (ii) determine whether lakes in which t rout have gone extinct have since been colonized by salamanders; and (iii) estimate the rates of population extinction and colonization in lakes never stocked with trout. In agreement with previous work on the interactions be tween trout and long-toed salamanders, trout effectively excluded salamande r populations from lakes. Somewhat surprisingly, however, salamanders manag ed to colonize lakes after the extinction of trout populations despite evid ence of low levels of interpopulation dispersal in these salamander populat ions. In lakes never stocked with trout there was no evidence of a decline in salamander populations; 2 of these lakes were colonized and no populatio ns went extinct.