Format: ORAL

Manuel Tiburtini1, Salvatore Tomasello2, Giovanni Astuti1, Luca Sandroni1, Thomas Abeli3, Lorenzo Peruzzi1

1 University of Pisa, Pisa, Italy 2 Georg-August-University, Göttingen, Germany 3 Roma Tre University, Rome, Italy

Ultramafic substrates can play a role in fostering ecological adaptation and microevolutionary dynamics. The Italian endemic Armeria denticulata complex includes two species (A. denticulata and A. saviana): the former is a serpentinophyte endemic to Tuscany and western Liguria, the latter grows on limestone/jasper in a small area of southern Tuscany. Intriguingly, also northern Apennine populations of A. arenaria subsp. praecox, a subspecies otherwise endemic to western Alps, grow on ophiolites. Finally, the central-southern Italian endemic A. gracilis is strictly linked to limestone. We aimed at understanding whether substrate specificity and/or hybridization-introgression promoted speciation in the A. denticulata complex, despite similar ecological conditions failed to cause speciation in the nearby A. arenaria. We extracted DNA from two populations of A. arenaria subsp. praecox, three of A. denticulata, one of Armeria saviana, and one of A. gracilis. Sequencing was conducted using genome skimming on a NovaSeq sequencer, gathering about four Gb of sequence information per sample. After quality trimming of the reads, we performed reference-based assembly of plastomes (152kb) and nrDNA (ETS+ITS+rRNA regions, 12kb altogether) to infer phylogenies. The genomic data were complemented by a morphometric study using a Principal Component Analysis (134 individuals 27 characters). Phylogenomic results suggest that A. saviana may have a homoploid hybrid origin involving A. denticulatas.str. (pollen donor) and A. gracilis (ovule donor), whereas a population of A. denticulata from inner Tuscany (Monte Ferrato) could have originated from an introgression/hybridization event between Armeria denticulata s.str. (pollen donor) and one of the haplotypes found in A. arenaria subsp. praecox (ovule donor). This is supported also by morphometric results, which highlight positions of the putative hybridogenic populations somehow intermediate between the putative parents in the morphospace. In summary, our results suggest that substrate specificity and hybridization/introgression prompted microevolutionary processes.