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WITHIN‐SPECIES ORGANIZATION IN WYETHIA AND BALSAMORHIZA AND AN ASSESSMENT OF EVOLUTIONARY EXPLANATIONS
Author(s) -
Robson K. A.,
Scagel R. K.,
Maze J.
Publication year - 1988
Publication title -
taxon
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 81
eISSN - 1996-8175
pISSN - 0040-0262
DOI - 10.2307/1222137
Subject(s) - biology , variation (astronomy) , ontogeny , evolutionary biology , monophyly , genetic algorithm , evolutionary developmental biology , sympatric speciation , heterochrony , phylogenetics , zoology , clade , biochemistry , physics , astrophysics , gene , genetics
Summary The assertion that ontogeny and phylogeny are closely related phenomena seems to be valid, but the nature of this relationship has not been explored in sufficient depth. The present study details some quantitative methods through which the nature of speciation and development can be simultaneously addressed. Within‐species variation was assessed for species of the related genera Wyethia, Balsamorhiza , and Helianthella (Asteraceae, Heliantheae) for three data sets consisting of shoot, terminal head, and cauline leaf variables. Although the changes in organization that occur through development could not be directly measured here, variation among mature plants permits inferences to be made regarding the product of ontogeny. Within‐species variation appears to be unique and unpredictable, even among species that are sympatric or share membership in small monophyletic groups. Such unique and unpredictable variation can be interpreted as changes in organization that occur as the partial manifestation of phylogenesis. Studies on other plants indicate similar changes in variation occur during ontogeny. These results imply that studies concerned with changing organization will provide clarification of the relationship between development and speciation. A necessary prerequisite to a systematic study is an understanding of the development and integration of characters used in the study. A discussion of explanations claiming to address biological change and their applicability to these results is provided. Neo‐Darwinian theory appears incapable of providing an adequate explanation of the results presented here, as changing organization and increasing complexity would not be predicted from it. On the other hand, Brooks and Wiley's theory of evolution, based on non‐equilibrium thermodynamics, does predict an irreversible increase in complexity in biological systems as they change with time. Explication of the relationships between ontogeny and phylogeny may be forthcoming from studies stressing the description of ontogenetic variation among individuals set within an independently derived phylogenetic framework.