History of an invasion: presence and representativity of Cortaderia selloana in the Iberian herbaria

Abstract

Herbaria are a useful source of information for the study of the geographic distribution and expansion dynamics of plants. In invasive alien species, variations in their geographic range and niche may occur in short periods of time, which can be observed in herbarium materials. Cortaderia selloana (Schult. & Schult.f.) Asch. & Graebn (Poaceae) is an invasive grass introduced as a garden plant, today widely naturalized along the north, west and east coast of the Iberian Peninsula. In this study, a complete review of the herbarium sheets of the species available in the Iberian public herbaria was carried out, in order to understand the history of its introduction and expansion in the Iberian Peninsula. A total of 155 sheets from 21 herbaria were received and reviewed, dating from the beginning of the 20th century to present day. The information collected in the sheets does not allow to describe the complete process of introduction and expansion in the studied territory, but it provides data on the distribution of specimens according to their invasiveness and sex over the decades, and the territorial representativeness of the sheets. In addition, larvae of the midge Spanolepis selloanae Gagné (Diptera, Cecidomyiidae) were found in inflorescences from Asturias and northern Portugal collected in 2018 and later dates, confirming that the introduction of S. selloanae into the Iberian Peninsula occurred later and independently from that of C. selloana.