RELATIONSHIPS IN THE ORDER MARCHANTIALES (HEPATICAE)

Abstract

  The order Marchantiales (Hepaticae) contains morphologically well delimited families and genera of which many are monotypic. Its range is world-wide. Present classifications and phylogenetic derivations are based mainly upon morphological and morphogenetic homologies that are partly questionable. Recent differentiation is presumed only in two large genera that correspond to two morphologically as well as ecologically divergent trends in the order. Many other genera are pioneers of xeric, cold, or disrupted, harsh habitats. Morphology and ecology appear linked. The role of ecological adaptation in evolutionary processes is discussed.