A new species of Festuca L. (Poaceae) endemic to the Sila plateau in Italy.

Mattia Pallanza ¹, Nicola Maria Giuseppe Ardenghi ², Liliana Bernardo ³, Petr Šmarda ⁴, Petra Šarhanová ⁴, Orsenigo Simone ¹, Graziano Rossi ⁵, Bruno Foggi ⁶

Dipartimento di Scienze della Terra e dell’Ambiente, Università degli Studi di Pavia, Via Sant’Epifanio 14, 27100 Pavia; National Biodiversity Future centre, 90133 Palermo. ¹, Orto Botanico, Sistema Museale di Ateneo, Università degli Studi di Pavia, Via Sant’Epifanio 14, 27100 Pavia. ², Dipartimento di Biologia, Ecologia e Scienze della Terra, Università della Calabria, Via Pietro Bucci, 87030 Arcavacata di Rende (Cosenza). ³, Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic. ⁴, Dipartimento di Scienze della Terra e dell’Ambiente, Università degli Studi di Pavia, Via Sant’Epifanio 14, 27100 Pavia. ⁵, Dipartimento di Biologia, Università degli Studi di Firenze, Via G. La Pira 4, 50121 Firenze. ⁶

During a sampling campaign aimed at revising the Festuca marginata (Hack.) K.Richt. (= F. circummediterranea Patzke) group in the Mediterranean, a curious taxon belonging to the genus Festuca was found on the Sila plateau. Historically, specimens with similar morphology had been collected in the area by Sarfatti and identified as Festuca ovina L. subsp. laevis Hack. var. gallica (Hack.) St.-Yves subvar. costei St.-Yves (≡ Festuca costei (St.-Yves) Markgr.-Dann.) by Markgraf-Dannenberg. However, the specimens displayed quite an unique morphology resembling other members of the F. marginata group (to which F. costei belongs) but occasionally showed a complete sclerenchymatic ring with irregular thickness, a trait typically associated with the Festuca stricta Host group. Preliminary chromosome counts revealed that this taxon is hexaploid (2n=6×=42), differing from the consistently diploid F. marginata (2n=2×=14) and tetraploid F. costei (2n=4×=28), confirming the inconsistencies that emerged from a preliminar morphological study. This distinctive combination of morphological traits and unusual ploidy level lead to further investigations using an integrated taxonomic approach. To clarify the identity of this taxon, four additional comparative taxa were selected based on shared morphological and karyological characteristics: Festuca stricta Host, Festuca rupicola Heuff., Festuca trachyphylla (Hack.) R.P.Murray, and Festuca marginata (Hack.) K. Richt. A total of 158 individuals from 25 populations across the Alps and Apennines were sampled. Of these, 47 were analyzed via flow cytometry to estimate genome size and infer ploidy levels. Additionally, morphometric analyses included 19 herbarium specimens housed at FI. Flow cytometry results confirmed that the Sila taxon is consistently hexaploid, as are other species within the F. stricta complex, while all F. marginata samples were diploid, as expected in accordance with literature. Morphometric analysis involved 35 diagnostic traits (17 continuous numerical, 15 ordinal categorical, and 3 binary) selected based on prior studies of the genus Festuca. An exploratory Principal Coordinate Analysis (PCoA) revealed three primary morphological groups: one comprising F. stricta, F. rupicola, and F. trachyphylla; another of F. marginata individuals; and a distinct cluster of hexaploid Sila individuals positioned between the other two groups. The groups identified via PCoA were subsequently tested using Linear Discriminant Analysis (LDA) with jackknife resampling. Additionally, ddRADseq analyses were carried out to better clarify the genetic relationships within the different taxa, revealing that despite the mixed morphological characters the new taxon from the Sila is more closely related to the F. marginata group rather than the F. stricta group. Overall, all performed analyses suggest that the hexaploid populations from Sila represent a distinct taxon separate from other similar fescues present in the italian flora. It is likely that it originated through auto- or allopolyploidization events of other F. marginata group members present in the area, as suggested by the preliminary genomic analyses.

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