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Phylogeny, ontogeny and intraspecific variation in Balsamorhiza (Asteraceae:Heliantheae): A study of evolutionary phenomena
Abstract
A hierarchical approach to the study of phylogenetic, ontogenetic and environmental variation is demonstrated using a combination of cladistics and principal components analysis (PCA). Intraspecific variation within the genus Balsamorhiza (Asteraceae, Heliantheae) was explored in terms of a partial phylogenetic hypothesis, independently constructed for representative species, and based on a limited set of shared, novel characters. The genus and its presently recognized sections, Artorhiza and Balsamorhiza, appear to be monophyletic. Based upon this, intraspecific variation in the three species of section Artorhiza was further examined through the analysis of data describing the growth of flowering shoots at sequential stages of development. The morphological variation expressed during annual growth in these herbaceous perennials was examined; (1) for the species of Artorhiza; (2) among presumably allopatric sites within the single species B. careyana; (3) and between two successive years of growth repeated in a group of individual plants of this species. The variables examined were: lengths of shoot internodes; associated cauline leaves; and axillary flowering shoots (when present). Comparable data were collected for a single species in section Balsamorhiza and three outgroup species. These data were subjected to PCA by site and stage. Because the interest here was to describe changing structural organization, graphics consisted of plottings of eigenvector coefficients against the first two principal components. The changing relationships of variables to each other and to the overall variation summarized in the axes was assessed within the cladistic framework. While some variables change at random, two groups, describing lowermost cauline leaves and axillary flowering shoots, show patterns that appear to reflect phylogenetic history within Artorhiza alone, suggesting an independent origin. Among-site and between-year variation in B. careyana is reflected as the rotation of eigenvector coefficients about the major axes, but where patterns among and within these variables remain relatively constant. Applications to the partitioning of phylogenetic and environmental factors in evolutionary phenomena are suggested. The structure of scientific explanation is discussed; concepts and theories regarding biological change through time are examined within this framework.
Subject Area
Botany|Biology
Recommended Citation
Robson, Kathleen Anne, "Phylogeny, ontogeny and intraspecific variation in Balsamorhiza (Asteraceae:Heliantheae): A study of evolutionary phenomena" (1989). ETD collection for University of Nebraska-Lincoln. AAI8925255.
https://digitalcommons.unl.edu/dissertations/AAI8925255