Genetic Data Support the Relict and Native Status of Styrax officinalis L. (Styracaceae) in Italy

Laura Parducci^1*Maria Margarida Ribeiro^2,3,4,5Kevin Nota⁶Alessandro Nobile¹SIMONE DE SANTIS⁷Tatiana Diamantino⁵Andreas Drouzas⁸Eirini Aplada⁹Shun K. Hirota^10,11Yoshihisa Suyama¹⁰Francesco Spada⁷

• ¹Department of Ecology and Genetics, Uppsala University, Uppsala, Uppsala, Sweden
• ²Higher Agricultural School of Castelo Branco, Polytechnic Institute of Castelo Branco, Castelo Branco, Castelo Branco, Portugal
• ³CERNAS, Research Center for Natural Resources, Environment and Society, Polytechnic Institute of Castelo Branco,, Castelo Branco, Portugal
• ⁴Forest Research Centre, Higher Institute of Agronomy, University of Lisbon, Lisboa, Lisboa, Portugal
• ⁵Biotech Plant Lab of Beira Interior, School of Agriculture, Castelo Branco, Portugal
• ⁶Department of Genetics and Ecology, University of Uppsala, Uppsala, Sweden
• ⁷Department of Environmental Biology, La Sapienza University of Rome, Rome, Sicily, Italy
• ⁸Laboratory of Systematic Botany and Phytogeography, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
• ⁹1st General Lyceum of Kamatero, GR-15451, Athens, Greece
• ¹⁰Field Science Center, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
• ¹¹Botanical Gardens, Osaka Metropolitan University, Katano, Osaka, Japan

The woody angiosperm Styrax officinalis L., primarily occurring in the Near East and South-eastern Europe, has been historically considered a human introduction in the Italian Peninsula. In this study, we challenge this assumption by conducting a genetic analysis on a comprehensive sample of individuals across its range utilizing chloroplast microsatellites and a genome-wide single-nucleotide polymorphism (MIG-seq) sequencing approach. The analysis of 351 individuals revealed clear genetic structure across the species' range. Most Italian populations form a distinct nuclear genetic cluster, suggesting long-term isolation, while three populations show signs of admixture with Cypriot individuals. Although one rare chloroplast haplotype was unique to Italy, widespread eastern haplotypes were entirely absent from the peninsula, which does not support the hypothesis of a recent human-mediated introduction. The results largely support the indigenous nature of the species in the Italian Peninsula, rejecting the notion of recent human introduction, and elevating S. officinalis to the status of a local relict, probably representing a component of the Late Neogene warm-temperate vegetation in Southern Paleo Europe.