First contribution to the knowledge of the urban flora of Modena

Apart from some sporadic observation, mainly performed during the floristic exploration of the entire provincial territory, the sole investigation published concerning the urban flora of Modena is a list of 69 species, mostly ruderal (1). In this study, carried out from February to December 2014, only the northern part of the historic town centre was considered. All the roads and public squares were sampled, excluding parks, gardens and private courtyards (2). Only vascular plants growing in sidewalks, bicycle paths, roads, pavements and their fissures, flowerbeds, house walls up to a height of 50 cm above the ground were recorded. Cultivated ornamental species were recorded only in case of ascertained propagation by seed. During the study period, 8 complete samplings of the whole study area were performed, in order to cover the entire vegetative period. Globally, 267 specific and subspecific taxa were recorded. Most of them were ruderal synanthropic species, typical of trampled areas (Polycarpon tetraphyllum L., Polygonum aviculare L., Portulaca oleracea L., etc.), others were species typical of grasslands or cultivated fields (Bellis perennis L., Cynodon dactylon L., Cynosurus cristatus L., Festuca rubra L., Setaria viridis L., Stellaria media L., Taraxacum F.H.Wigg. sect. Taraxacum, Trifolium, etc.), others were typical rupiculous species (Cymbalaria muralis G.Gaertn., B.Mey. & Scherb., Parietaria judaica L.). It is worth noting that 5 species resulted new for the provincial flora: Berberis aquifolium Pursh, Lobelia erinus L., Mollugo verticillata L., Solanum pseudocapsicum L., and Viburnum tinus L. All of them are alien species for the provincial flora and, in many cases, they are alien also for the flora of Italy (3, 4). Apart from M. verticillata, they are ornamental plants whose presence can be considered as casual, likely escaped from culture in parks and gardens. Further interesting species were Dianthus armeria L., protected at a regional level (Emilia-Romagna L.R. 2/77), Fumaria capreolata L., last found in 1883, and Sonchus arvensis subsp. uliginosus (M.Bieb.) Nyman, infrequent if compared to the nominal subspecies (4). Among all the recorded taxa, 19% of them are allochthonous neophytes, mainly coming from the New World (Galinsoga quadriradiata Ruiz & Pav., Gleditsia triacanthos L., Phytolacca americana L., Symphyotrichum squamatum (Spreng.) G.L.Nesom, etc.). The percentage of alien flora is not so elevated, if compared to other European cities where alien species can reach up to 50%. Probably, the reason for such a low percentage can be the climate of Modena, that shows some sub-Mediterranean features allowing Mediterranean species to establish and grow: this fact perhaps subtracts space to alien and invasive species. Among aliens, 6 are invasive (3): Ailanthus altissima (Mill.) Swingle, Ambrosia artemisiifolia L., Buddleja davidii Franch., Erigeron canadensis L., Panicum dichotomiflorum Michx., and Robinia pseudoacacia L. It is worth noting that species richness, due to the great variety of environments typical of the cities, can reach notable values (up to 145 species in the same road). Thanks to a comparison with herbarium samples preserved at MOD, we noticed that certain species (e.g., Amaranthus deflexus L., Broussonnetia papyrifera (L.) Vent., Diplotaxis tenuifolia (L.) DC.) are present in Modena since the late 1800: at that time, they were collected on the city walls. This study demonstrates the utility of such investigations, to increase the floristic knowledge of the territory and to discover and monitor the presence of new alien species that is becoming more and more common in a globalized world. The southern half of the historic centre of Modena will be analyzed in the next years, so to have a more complete picture of the urban flora.