Durianology, discovery, and saltation — the evolution of aroids

Abstract

If we become attentive to natural objects, particularly living ones, in such a manner as to desire to achieve an insight into the correlation of their nature and activity, we believe ourselves best able to come to such a comprehension through a division of the parts, and this method is suitable to take us very far. With but a word one may remind the friends of science of what chemistry and anatomy have contributed to an intensive and extensive view of Nature... But these analytic efforts, continued indefinitely, produce many disadvantages. The living may indeed be separated into its elements, but one cannot put these back together and revive them. This is true even of inorganic bodies, not to mention organic ones... For this reason, the urge to cognize living forms as such, to grasp their outwardly visible and tangible parts contextually, to take them as intimations of that which is inward, and so master, to some degree, the whole in an intuition, has always arisen in men of science."-J.W. von Goethe (1749-1832) in Brady, 2012: 272. ABSTRACT. It is argued that E.J.H. Corner's 'durianology' is an integrative, holistic approach to the evolution of angiosperm form which complements reductive, atomistic phylogenetic methods involving the reification of individuated high-level abstractions in the concept of morphological 'character evolution'. A case is made that the Durian Theory involved in part the advanced, holistic cognitive mode of insight, and, drawing on recent findings from cognitive science, it is proposed that insight problem-solving may overcome some of the limitations and distortions of dis-integrative character analysis, and lead to discovery of novel morphological relations and global pattern recognition. Evidence drawn from molecular phylogenetic analyses, developmental studies, and from gross morphology is presented that supports an insight-based hypothesis of direct, saltatory derivation of the Araceae from an ancestor with shoot apices not enclosed by sheathing leaf bases, acropetally developed, reticulate-veined compound leaves, and a terminal polymerous strobiloid flower. It is proposed that this saltation led to an array of morphologically hybrid and compound decanalised structures blurring conventional morphological categories such as rhachis, rhachilla, petiolule and venation; leaf base and stipule; leaf and leaflet; leaf and perianth; flower and inflorescence; flower and floral organ; fruit and infructescence; and fruit and seed. The associated perturbation of developmental routines led both to great diversification and to widespread parallel simplification series. It is argued that holistic evolutionary hypotheses cannot usefully be tested using current atomistic phylogenetic methodology applied to morphological characters. It is suggested that holarchical Gard. Bull. Singapore 71 (Suppl. 2) 2019 258 (nested-hierarchical) rather than matrix character sets may provide a more holistic framework for evolutionary hypothesis-testing involving the interplay between molecular phylogeny, evodevo data...

Plant parts: processes, structures, or functions?

“…In a volume honouring my undergraduate tutor, David Mabberley, it seems appropriate to use as a jumping-off point, . This paper, like other papers by these authors (Hay & Mabberley, 1991;Hay, 2019 in this volume), challenges the instinct to fragment a plant into parts. Instead, it argues for 'process morphology', an outlook that downplays the idea that organisms have discrete parts assignable to one of a few discrete flavours in favour of an emphasis on the dynamic nature of development.…”

Studies on Potheae (Araceae) of Borneo II: Pedicellarum M.Hotta subsumed into Pothos L., and recognition of three new species

“…Some floral terminology used in this paper differs intentionally from those of previous papers on Pothos and is intended to pave the way to interpreting the 'inflorescence' of Pothos, and indeed of all other aroids, as a unique array of structures that are neither flowers nor inflorescences as defined by current prevailing orthodoxy, but something of both. For the background to this conceptual change see Hay (2019), Hay and Mabberley (1991), Mabberley and Hay (1994). The 'pedicellarums' described in this paper are perhaps particularly germane as they present some of the inflorescences or blooms, and flowers or florets of Araceae that most resemble, at least to first glance, racemose inflorescences of more or less standard pedicellate trimerous monocotyledonous flowers of text books.…”

Taxonomic revision of the threatened African genus Pseudohydrosme Engl. (Araceae), with P. ebo, a new, critically endangered species from Ebo, Cameroon

“…They derive from complex splitting of a ‘simple’ and virtually entire blade as the leaf unfurls after emergence, which is why the leaflets at the margin are truncate with two ‘tips’. This is unique to Pseudohydrosme / Anchomanes ( Hay, 2019 : 285). Differences between Pseudohydrosme and Anchomanes are re-assessed in the discussion below.…”