Evolution of Certain Floristic Associations in Western North America

Abstract

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Vegetation of the Great Smoky Mountains

“…Vegetation forms a complex population pattern in relation to environment. In this pattern species (of green plants, at least) distribute themselves "individualistically"; they occur together wherever their distributions overlap, and associate and dissociate freely in space and in evolutionary time (Mason 1947). Neither in time nor in space does a species occur in terms of associations, but where it maywhere at a given time some combination of genetic and environmental possibility for that species is realized in one of its populations.…”

The individualistic and community-unit concepts as falsifiable hypotheses

“…The works of Cain (1947), Egler (1947), Mason (1947), Whittaker (1951Whittaker ( , 1956Whittaker ( , 1967 and others quickly converted the majority of angloamerican community ecologists (Mclntosh, 1967(Mclntosh, , 1975 to the 'individualistic concept' of community organization based primarily on the ideas of Gleason (1926Gleason ( , 1939. This transition to an individualistic viewpoint was due in part because, by using direct or indirect gradient analysis (Whittaker, 1967, the observed pattern of species replacements along a gradient was stated to be inconsistent with the patterns predicted by Clements. In the context of testing between the two concepts mentioned above, direct gradient analysis still suffers from the problem of using subjective methods of analysing the observed patterns by failing to use inferential statistics to compare empirical data to the proposed models.…”

"Towards establishing ecology as a science instead of an art": the work of John T. Curtis on the plant community continuum

“…A number of younger American ecologists expressed dissatisfaction with the state of ecological science and called for a cautious re-examination of the individualistic hypothesis (e.g. Cain 1947, Egler 1947, Mason 1947. In the 1950s, the nature of the plant community was investigated in a series of major field studies (Whittaker 1951, 1953, Curtis 1959a.…”

“…There were therefore, in his view, no integrative processes working above the level of the population: "The organic functions of the population, then, are solely the functions of population genetics and result from the reproductive and genetic activity within the population. … Furthermore, there are no organic functions that operate between genetically unrelated populations … A community made up of such populations has neither organic nor functional unity but is an aggregation of independently operating populations of interbreeding individuals (Mason 1947)". Therefore, Mason concluded: "Floristic evolution is activated by the interplay between environmental conditions and genetic and physiological phenomena that … select those genetic races within the species population are preadapted to the new conditions.…”

“…The production and selection of the genetic races must be construed as steps in the evolutionary process known as natural selection. (Mason 1947) Curtis's supervisor, Benjamin Duggar, was a plant physiologist of international renown (Walker 1958). For his doctorate, Curtis worked on the seed germination of native species of orchids, but, in essence, Duggar taught Curtis how to do good plant science.…”