METABOLIC AND MORPHOLOGICAL ADAPTATION TO HETEROGENOUS ENVIRONMENTS BY THE PACIFIC TREE TOAD, HYLA REGULA.

Abstract

Massive strides in the understanding of basic biological phenomena have been accomplished by the concentration on one or a few variables. The geneticist has considered the variable genotype in a constant environment, the ecologist a variable external environment on a constant genotype. The physiologist has emphasized the metabolic mechanisms involved in the relation between variable external and internal environments usually with a constant genotype. The developmental biologist has studied the changing phenotype in a relatively constant genotypic and external environment. These specializations have proven desirable-even necessary. The spectacular breakthroughs of the molecular biologist are indicative of the power of the method of concentration on a limited objective which ignores or standardizes or often uses as tools the other variables. The method works-a sufficient criterion for its continued use. These specialized approaches have led to naive considerations of the invariable components and, probably more important, have led to constricted visions of the whole system. Studies of the interaction of the several systems are hampered by the absence of adequate models subject to experimental test. Successful economic studies in agriculture use analysis of variance and multivariate analysis. These studies are based on the linear additive model and investigators usually are content to identify the relative magnitude of the interaction component when compared to the within-group variation. The nonlinearity of nature does not hamper this approach but may well limit its use in understanding the mechanism of interaction. A few holistic analyses have had variable successes. Birch (1960, and elsewhere) examined some aspects of the relation of genotype on numbers of organisms through the genetic variability of the components of the intrinsic rate of increase. Levins (1968, and elsewhere) used an optimum genotype and an optimum environment and analyzed the variation in terms of deviations from these optima. These models are logical outgrowths of earlier approaches including concepts presented within the terms adaptation, assimilation, stabilization, canalization, acclimatization, all of which must be considered as various ways of looking at the same phenomena. The necessity to use the holistic approach increases as the knowledge multiplies in each field and as the tools and data of other fields are required to understand the information obtained in specialized studies. This study attempts to examine the interrelation between internal and external environment and genotype in the life of the Pacific tree frog, Hyla regill. The study is subject to naive considerations and constricted vision and can merely claim to emphasize the role of these variables in the life of the frog. Prosser (1955) listed three kinds of variation of physiological and morphological characteristics: genetic, ontogenetic, and phenotypic. The genotype sets the limit for phenotypic variation. Physiological variation allows environmental limits to be set for each population of animals