INVASION NOTE Replacement of estuarine communities by an exotic shrub: distribution and invasion history of Baccharis halimifolia in Europe L. Can ˜o • J. A. Campos • D. Garcı ´a-Magro • M. Herrera Received: 7 March 2012 / Accepted: 19 November 2012 / Published online: 27 November 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract Baccharis halimifolia L. (Asteraceae) is a shrub native to North America which is invading estuarine communities in Europe. We report the inva- sion history and the distribution limits of B. halimifolia in Europe, with particular emphasis on the frequency of its presence in estuarine communities in Spain. B. ha- limifolia has been cultivated in Europe since the 17th century to present. It was first recorded as naturalized in the Bay of Biscay in 1906, where it forms currently stable and locally abundant populations in almost all the estuaries of Northern Spain and Western France. The ongoing invasion to the west could reach well conserved estuarine communities in Galicia (Spain). B. halimifolia also forms scattered populations in Northern and Southern France, Belgium, Netherlands, United King- dom and Italy. In these countries it has experienced a rapid expansion during the last years. In Northern Spain, subhalophilous communities dominated by rush (Jun- cus maritimus) and/or sea couch (Elytrigia atherica), common reed stands (Phragmites australis) and un- grazed wet meadows are the most vulnerable to invasion. The subhalophilous communities are part of natural habitats of community interest according to the habitats directive 92/43/EEC. In some areas of Northern Spain these communities have been totally replaced by monospecific stands of B. halimifolia. In contrast, halophilous communities of the low marsh are resistant to invasion, suggesting that the survival of B. halimifolia may be limited by threshold values of salinity and waterlogging. With this study we want to raise aware- ness about the risk of replacement of estuarine subhal- ophilous communities by the ongoing invasion of B. halimifolia in Europe. Keywords Baccharis halimifolia Á Europe Á Naturalization chronology Á Northern Spain Á Estuarine communities Á Habitats of Community Interest Á Habitat vulnerability to invasion Introduction Baccharis halimifolia L. (Asteraceae) is a shrub native to the Atlantic Coast of North America, where it is present from Massachussets to Texas (USDA data- base). It is believed to have been introduced in continental Europe as an ornamental plant in the 17th century. On the Atlantic Coast of Southern Europe it is a harmful invasive species which is invading well conserved native coastal communities (Campos et al. 2004), most of which are habitats of community interest, according to the habitats directive 92/43/ EEC. B. halimifolia was also introduced at the end of the 19th century as an ornamental plant on the Eastern Coast of Australia, where it currently occupies L. Can ˜o (&) Á J. A. Campos Á D. Garcı ´a-Magro Á M. Herrera Departamento de Biologı ´a Vegetal y Ecologı ´a, Fac. de Ciencia y Tecnologı ´a, Universidad del Paı ´s Vasco, UPV/EHU, Apdo 644, 48080 Bilbao, Spain e-mail: lidia.cano.perez@gmail.com 123 Biol Invasions (2013) 15:1183–1188 DOI 10.1007/s10530-012-0360-4 Author's personal copy