Developmental Foundations for Morphological Diversity Among Endomycorrhizal Fungi in Glomales (Zygomycetes)

Abstract

Diversity occurs at all levels of organization within a living organism, from nucleotide sequences in DNA to characters of the morphological phenotype. Other diversity is manifested in various interactions between the organism and its environment in local communities or following dispersal to new sites (Morton 1993; Morton and Bentivenga 1994). We will focus in this chapter on morphological diversity for several important reasons. First, morphology represents the phenotype of the “individual” organism and thus brings together structural properties and functional interactions in an ecological setting. Second, it is the fundamental reference system to identify experimental units in studying biological processes. Third, it provides an important starting point in hypothesizing phylogenetic relationships that establish some measure of a natural classification (Morton and Benny 1990; Morton and Bentivenga 1994). Last, it is the only measure of diversity which provides developmental characters for empirical determination of homology and evolutionary polarity (Hillis 1987), the two most important operations in phylogeny reconstruction (Wiley 1981).