Pseudacris Maculata Research Articles

Genetic Changes in a Population of Boreal Chorus Frogs (Pseudacris triseriata) Polymorphic for Color

A 3-year study of color polymorphism in a population of boreal chorus frogs revealed that nearly all characteristics studied con- cerning the composition of the population were similar to those of an idealized population. The sex ratio was 1 : 1, there was no evidence of interaction between color phenotype and sex, and mating was random with respect to color phenotypes. Changes in the frequency of background colors did not follow any detectable pattern, while changes in the frequen- cy of spot colors did. The frequency of green-spot genotypes and pheno- types was lowest in juveniles, somewhat higher in yearlings, and highest in adults. Individuals having the highest coefficients of survival in the aquatic phase were brown-spotted, but were green-spotted in the terres- trial phase. Spot color polymorphism in the population is probably balanced. It is conceivably maintained by differential selection pressures in the aquatic and terrestrial phases of the life cycle.

COMPARATIVE REPRODUCTIVE BIOLOGY OF MONTANE AND PIEDMONT CHORUS FROGS

Sub-units of a species living in contrasting environments may respond to differences in their respective habitats by developing differentially adaptive traits. For example, Moore (1942, 1946, and 1949) has demonstrated differences in both developmental temperature tolerances and coefficients between northern and southern populations of R. pipiens. Also, Ruibal (1955) has shown that populations of R. pipiens from different elevations in Mexico exhibit different rates of development at all temperatures tested. Embryos from higher elevations develop more slowly than their lowland counterparts. Ruibal suggests that this difference may be due to a history of selection for rapid development in the lowland localities resulting from greater interspecific competition in the larval stage. This phenomenon, called special adaptation by Brown (1958), may be most conveniently elucidated by comparing different conspecific local populations which are geographically proximate, thus minimizing the effects of differentiation due to isolation by distance. An opportunity to study this mechanism under near optimal conditions is afforded by populations of the boreal chorus frog, Pseudacris triseriata (Weid), in northern Colorado. In this area populations of P. triseriata occur at elevations from less than 4900 ft to above 10,000 ft. A presumed result of this elevation gradient has been the development and maintenance of numerous differences between montane and and piedmont chorus frogs. Variations in body size, adult temperature tolerance, and metabolism have been described in a previous paper (Pettus and Spencer, 1964). The purpose of this paper is to report our observations on variations in the eggs of these frogs and the results of a series of experiments designed to reveal differences in temperature effects during development. Both Moore (1949) and Ruibal (1955) have reported geographic variation in egg size of Rana pipiens. Moore's data show, with one striking reversal, a correlation between increased egg diameter and increased latitude. Ruibal reported only minor variation in egg diameters in spite of the fact that his samples were drawn from populations over a wide range of elevations.

The Boreal Chorus Frog in Northern Saskatchewan

The Boreal Chorus Frog in Northern Saskatchewan

Additional Records and a Correction of the Type Locality for the Boreal Chorus Frog in Northwestern Ontario

Additional Records and a Correction of the Type Locality for the Boreal Chorus Frog in Northwestern Ontario