Laboratory and field studies were initiated to study the life-history patterns of populations of Ambystoma gracile from three permanent lakes located at different altitudes in southwestern British Columbia. Laboratory studies indicated clear differences between low- and high-altitude populations with respect to larval growth, timing of metamorphosis, size at metamorphosis, and the incidence of neoteny. Field studies indicated that low-altitude neotenous females became sexually mature at a length of 7.1 cm (snout to vent length, SVL); but owing to the shorter seasons within higher altitude lakes, neotenous females required more seasons to attain sexual maturity. High- and low-altitude males attained sexual maturity at 7.4-cm SVL, but a few smaller, sexually mature males were discovered within the high-altitude lake. Neotenous females reproduced annually within the low-altitude lake, but high-altitude neotenous females did not reproduce during successive years. Possible genetic adaptations to low and high altitudes are discussed.
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Gerald W. Eagleson (1976) studied this question.