Taxonomic investigations on Polygonum gussonei Tod., a neglected species of the Italian Flora

Manuela Porrovecchio ¹, Salvatore Cambria ¹, Giuseppe Diego Puglia ², Saverio Sciandrello ¹

Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Catania, 95128 Catania, Italia ¹, Consiglio Nazionale di Ricerca d'Italia, Istituto per i Sistemi Agricoli e Forestali nel Mediterraneo, Via Empedocle, 58, 95128, Catania, Italia ²

In the frame of studies on the taxonomy of the Italian endemic flora, the first results of a study on the real consistency of Polygonum gussonei, a taxon described by Todaro in 1874 for Campania and Sicily, are presented. The species has often been synonymized with Polygonum arenastrum Boreau, in recent Italian Flora checklists (Pignatti 2016-2019, Bartolucci 2024). This treatment follows the study by Raffaelli (1982) on the genus Polygonum in Italy, where the author considered P. gussonei as a simple morphotype of P. arenastrum linked to particularly xeric climatic conditions. Conversely, P. gussonei is reported as a distinct species in Flora Europaea (1993) and POWO database (2024+). The aim of this study is to definitively clarify the status of this species through an integrated approach including in-depth morphological studies of the main diagnostic characters (including SEM study of pollen and seed microstructure), molecular and ecological investigations. As regards the morphological study, numerous characters were taken into consideration, such as basal stem diameter, length of the ocreas and internodes, shape and size of the leaves, of the perigonium and the tepals. These traits were measured on 10 specimens of 2 different populations both for P. gussonei and P. arenastrum. The results obtained show a certain morphological divergence between the two taxa that could support the treatment of P. gussonei as a different taxon from P. arenastrum. One-way ANOVA shows a significant difference for the following features: leaf length, basal ocreas length, basal internode length, apical ocreas length, ratio ocreas/apical internodes, tepal limb and tube size. Furthermore, P. gussonei always shows a perennial habit, with a highly branched root, very short apical internodes, succulent leaves, inflorescences particularly rich in flowers, perigonium always consisting of 5 tepals and the apex of the achene slightly protruding from the perigonium. SEM images revealed that P. gussonei has achenes that are narrower at the base, ovate in shape, and with a fruit surface featuring less pronounced ornamentation compared to P. arenastrum, which has pear-shaped and larger achenes. However, further studies are planned to demonstrate the maintenance of these morphological characteristics under the same cultivation conditions and above all molecular investigations will be able to confirm or deny the data obtained. Finally, further field and herbarium investigations will be able to better clarify the distribution of P. gussonei in Italy.

Main author career stage: PhD student

Contribution type: Talk

First choice session: 1. Systematics, phylogenetics, biogeography and evolution

Second choice session: 1. Systematics, phylogenetics, biogeography and evolution