Developmental Genetics and Morphological Evolution of Flowering Plants, Especially Bladderworts (Utricularia): Fuzzy Arberian Morphology Complements Classical Morphology, , , , , , , , , <lk refid="m4.10"

Abstract

This review compares new developmental models on flowering and other vascular plants with evolutionary hypotheses formulated by Agnes Arber and like-minded botanists. Special emphasis is laid on philosophical basics such as perspectivism, pluralism about evolutionary modelling, continuum way of thinking, and fuzzy logic. Arber's perspective is best labelled as F uzzy A rberian M orphology (FAM Approach). Its proponents ('FAMmers') treat structural categories (e.g. 'roots', 'shoots', 'stems', 'leaves', 'stipules') in vascular plants as concepts with fuzzy borderlines allowing intermediates (including transitional forms, developmental mosaics). The FAM Approach complements Cla ssical Plant M orphology (ClaM Approach), which is the traditional approach in botany. ClaM proponents ('ClaMmers') postulate that the structural categories of vascular plants are regarded as concepts with clear-cut borderlines and without intermediates. However, during the evolution of vascular plants, the root-shoot distinction and the stem-leaf distinction have become blurred several times due to developmental changes, resulting in organs with unique combinations of features. This happened, for example, in the bladderworts (Utricularia, Lentibulariaceae). When focusing on the 'leaf', the FAM Approach is identical to Arber's 'partial-shoot theory of the leaf' and Sinha's 'leaf shoot continuum model'. A compound leaf can repeat the developmental pathway of the whole shoot, at least to some degree. For example, compound leaves of Chisocheton(Meliaceae) with indeterminate apical growth and three-dimensional branching may be seen as developmental mosaics sharing some growth processes with whole shoots! We focus here on the FAM Approach because this perspective is especially promising for developmental geneticists studying flowering and other vascular plants.

Expression patterns of class I KNOX and YABBY genes in Ruscus aculeatus (Asparagaceae) with implications for phylloclade homology

“…Such functional co-option of a gene would cause expressional commonality (homocracy) among non-homologous organs (Nielsen and Martinez, 2003). Thus, a homocracy among organs does not necessarily ensure their homology, but it could be a tool to assess their organ identity (Rutishauser and Isler, 2001;Nielsen and Martinez, 2003).…”

“…Traditional plant morphological studies emphasize the positional criterion (homotopy) to assess organ homology and do not permit coexistence of multiple identities in a single organ (Rutishauser and Isler, 2001). Such an approach is called Classical Morphology (ClaM) (Rutishauser and Isler, 2001), and the ClaM approach has been applied to homology assessments of the phylloclade, interpreting it as either a compressed stem (Turpin, 1820 cited in Hirsch, 1977;Zweigelt, 1913;Hirsch, 1977) or Hirayama, a leaf borne on an aborted shoot (de Candolle, 1827cited in Hirsch, 1977Schlittler, 1960;Cusset and Tran, 1966).…”

Recommendations and Goals for Evo-Devo Research

“…Perhaps homology as a concept is too simplistic to reflect the burgeoning knowledge from evo-devo, and has outlived its usefulness. At a minimum, partial homology seems to be real (Sattler and Rutishauser 1997;Rutishauser and Isler 2001;Vergara-Silva 2003). Perhaps one might say the structure has double homology, with one homology overlain upon the other, if one can infer the order in which the different gene cascades came to be expressed in that structure.…”

Nuevos registros de Gentianaceae y Lentibulariaceae para Honduras

“…Los miembros acuáticos del género presentan vejigas grandes y conspicuas (Salmon 2001), mientras que las especies epífitas pueden crecer en musgos húmedos y en cortezas esponjosas de árboles en selvas húmedas o lluviosas (Lloyd 1942). Todas sus especies son consideradas carnívoras, debido a que capturan pequeños organismos por medio de trampas con vejigas de succión (Rutishauser & Isler 2001).…”