Researchers solve nearly century-long riddle about Amazon flower

In an age where people increasingly want quick, almost instant, solutions and answers, it is necessary to understand that producing scientifically rigorous knowledge about a subject is a job that can take many decades and the effort of different specialists. Something that may seem simple to the public - the correct determination of the group to which a plant belongs - sometimes requires a lot of study. This is the case with Dialypetalanthus fuscescens Kuhlm., first described by the botanist João Geraldo Kuhlmann in 1925, and which has challenged researchers for almost a century. An article published 97 years later in the journal Plant Ecology and Evolution, with the participation of the Botanical Garden of Rio de Janeiro, finally solved the question.

D. fuscescens was collected in the Amazon by Adolpho Ducke (1876-1959) and planted in the Arboretum of the Botanical Garden of Rio de Janeiro, where it is cultivated until today, having flowered for the first time in 1942. This individual is the only specimen cultivated in a Botanical Garden in the world, highlighting one of its missions, the ex situ conservation of plants. Kuhlmann had classified Dialypetalanthus as a genus of a single species (D. fuscescens) belonging to the Rubiaceae family (the coffee family). However, its flower had some characteristics so different that the researchers Rizzini and Occhioni postulated in 1949 that it was a new plant family, which they called Dialypetalanthaceae.

This doubt remained until 2000, when molecular phylogenetic studies showed that Kuhlmann was right, but the morphological characteristics of the flower continued to puzzle scientists. Even then, the disparity of its flower characteristics from others in the same family was still an enigma.

Researcher Karen L. G. De Toni (JBRJ) explains that a new discussion on the carpel morphology of Dialypetalanthus was started in Rogério Figueiredo's master's degree, mentored by her at the National Museum, which was published in Acta Botanica Brasilica in 2017. Now, in October 2022, the relationship of the flower morphology of D. fuscescens with that of other Rubiaceae species has finally been clarified, through the publication of the article "Floral ontogeny links Dialypetalanthus (Condamineeae) with the floral developmental morphology of other Rubiaceae," of which Karen is a coauthor, in the journal Plant Ecology and Evolution.