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Date of Award
Master of Arts (M.A.)
John S. Tucker
To date the majority of the work on the ecological significance of embryonic temperature relationships has been with Eastern Frongs. The writer is aware of only two papers describing work of this nature with California frogs: Schechtmann and Oleson (1941) working with temperature tolerance in embryos of Hyla regilla, and the work of Zweifel (1955) on the Rana boylei species group.
For this reason it seemed desireable to study the effect of temperature on the growth rates of some frogs native to California and, since work of this nature has been done with the eastern Rana catesbeiana by Moore (1942b), it afforded an excellent opportunity for comparison to repeat the study using the California R. catesbeiana.
Although the California bull-frog has a considerable distribution, it is not native to this state but was introduced around 1905 (Storer, 1925). Very little work has been done with the life history of this species despite the opportunity it would seen to afford biologists interested in adaptational aspects of ecology. Storer (1925) stateed that, from the data available at the time, the seasonal schedule with regard to time of emergence from hibernation, time of spawning, and length of time required for larval development, conformed closely its calendar in the eastern states and had not, to that time, been modified to local conditions.
The relationship of the two native California frogs, Rana aurora draytonii and Rana boylei boylei, is one of close habitat partition. R. aurora is a pond frong and prefers permanent and relatively still water.R. boylei is primarily a stream frog and is found mostly along relatively small, gravelly watercourses. Although they seem to demonstrate a definite habitat preference some workers have observed these frogs in apparently sypatric relationship. (Stebbins 1951; Storer, 1925; Zwifel, 1955). By application of the inter-relationships as proposed by Moore, one could expect to find Rana aurora to have a more northerly distribution, a larger diameter egg, lower minimal and maximal temperature tolerance, lower temperature coefficient of development, and a higher developmental rate than the R. boylei. Rana aurora does in fact range much farther northwar than R. boylei, which occurs only in California and in Southern Oregon. (Although the subspecies, R aurora draytonii, dealh with here occurs almost exclusively in California. (Stebbins, 1951). The diameter of the egg deviates from the prediction slightly. The subspecies of R aurora that occurs in California (Rana auror draytonii) has almost the same sized egg, 2.06 - 2.50 mm. (Storer, 1925) as that of R. boylei, 2.2 mm. (Stebbins, 1951). If the distribution of the entire species is considered, the correlation is valid. The most northerly distributed R. aurora aurora has an egg 3.04 mm, in diameter (Ibid).
The present experiment was designed to test the remaining predictions.
Villeneuve, Donald Avila. (1960). The effect of temperature on the growth rates of several California frogs. University of the Pacific, Thesis. https://scholarlycommons.pacific.edu/uop_etds/1441