Biol Invasions (2008) 10:435–454 DOI 10.1007/s10530-007-9142-9 ORIGINAL PAPER Animal xenodiversity in Italian inland waters: distribution, modes of arrival, and pathways Francesca Gherardi Æ Sandro Bertolino Æ Marco Bodon Æ Sandra Casellato Æ Simone Cianfanelli Æ Marco Ferraguti Æ Elisabetta Lori Æ Graziella Mura Æ Annamaria Nocita Æ Nicoletta Riccardi Æ Giampaolo Rossetti Æ Emilia Rota Æ Riccardo Scalera Æ Sergio Zerunian Æ Elena Tricarico Received: 2 July 2007 / Accepted: 4 August 2007 / Published online: 15 August 2007 Ó Springer Science+Business Media B.V. 2007 Abstract The paper provides a list of the non- invertebrates and intentional for vertebrates). Acci- indigenous animal species occurring today in Italian dental transport, in association with both fish (for inland waters. Xenodiversity was found to amount to aquaculture or stock enhancement) and crops, has 112 species (64 invertebrates and 48 vertebrates), been the main vector of invertebrate introductions, which contribute for about 2% to the inland-water whereas vertebrates were mostly released for stock- fauna in Italy. Northern and central regions are most ing purposes. Overall stock enhancement (47.92%) affected, and Asia, North America, and the rest of and culture (37.5%) prevailed over the other path- Europe are the main donor continents. The large ways. Seventeen and 7 species of our list are included majority of non-indigenous species entered Italy as a among the 100 worst invasive species of Europe direct or indirect effect of human intervention. A (DAISIE) and of the world (IUCN), respectively. For difference between invertebrates and vertebrates was some (but not all) non-indigenous species recorded in found for their mode of arrival (unintentional for Italy the multilevel impact exerted on the recipient F. Gherardi (&) Á E. Tricarico M. Ferraguti Dipartimento di Biologia Animale e Genetica, Universita` Dipartimento di Biologia, Universita` degli Studi di di Firenze, Via Romana 17, Firenze 50125, Italy Milano, Milano, Italy e-mail: francesca.gherardi@unifi.it G. Mura S. Bertolino Dipartimento di Biologia Animale e dell’Uomo, Dipartimento di Valorizzazione e Protezione delle Risorse Universita` di Roma 1, Roma, Italy Agroforestali, Universita` di Torino, Grugliasco, Italy N. Riccardi M. Bodon Á E. Rota Istituto per lo Studio degli Ecosistemi, CNR, Verbania, Dipartimento di Scienze Ambientali, Universita` di Siena, Pallanza, Italy Siena, Italy G. Rossetti S. Casellato Dipartimento di Scienze Ambientali, Universita` di Parma, Dipartimento di Biologia, Universita` di Padova, Padova, Parma, Italy Italy R. Scalera S. Cianfanelli Á E. Lori Á A. Nocita Via Torcegno, 49, Roma, Italy Museo di Storia Naturale, Sezione di Zoologia ‘‘La Specola’’, Universita` di Firenze, S. Zerunian Firenze, Italy Laboratorio di Ittiologia delle Acque Dolci, Maenza, Italy 123 436 F. Gherardi et al. communities and ecosystems is known, even if rarely polymorpha (MacIsaac et al. 2001). Other less cele- quantified, but knowledge on their chronic impact is brated dramas are ongoing in many freshwater still missing. Additional research is needed to provide systems of the world with the intervention of criteria for prioritizing intervention against well previously unsuspected actors, such as Lepomis established invaders and identify which new potential gibbosus among fish, Dikerogammarus villosus invader should be targeted as ‘‘unwanted’’. among crustaceans, or Rana catesbeiana among amphibians (Gherardi 2007a). Keywords Inland waters Á Italy Á These and other examples (cfr. Leppa¨koski et al. Mode of introduction Á Non-indigenous species Á 2002a; Gherardi 2007b) confirm that, compared to Pathway Á Vector Á Xenodiversity terrestrial systems, inland waters are highly vulner- able to either inadvertent or deliberate introductions of species and to their subsequent spread. This Introduction vulnerability is the effect of the intensive human uses (Ricciardi 2001), on the one hand, and of the There is a large consensus today that the human- natural linkages among streams and lakes, the effects mediated introduction of species outside their natural of water flow, and the dispersal capability of aquatic range is one of the main threats to biodiversity and organisms, on the other. the second leading cause of animal extinctions As a result, several NIS dominate some vast (Millennium Ecosystem Assessment 2005). Indeed, waterscapes of the world (e.g. the red swamp several non-indigenous species (NIS) have been crayfish, Procambarus clarkii, dominating many beneficial to humans (e.g. corn, wheat, rice, planta- waterbodies of southern Europe; Gherardi 2006b). tion forests, and others) (Ewel et al. 1999) and many Xenodiversity (sensu Leppa¨koski et al. 2002b) may cause minimal environmental impacts, as predicted be extraordinarily high in, for example, large rivers of by the often cited ‘‘tens rule’’ (Williamson and Fitter developed countries (e.g. the Hudson; Strayer et al. 1996; but see Jerscke and Strayer 2005). So, the 2005) and largely affects many taxa (e.g. fish; fraction of NIS that may yield problems is small, but Lehtonen 2002). these although few species have had catastrophic Species originating from diverse bio-geographical impacts. Following their introduction into the wild, areas now coexist in several basins. In the Rhine, for they soon turned out to be ‘‘invasive’’ (for definitions example, indigenous crustaceans [Gammarus pulex of ‘‘invasiveness’’ see Gherardi 2006a), becoming (Linnaeus)] occur together with North American numerically and ecologically prominent, spreading species (e.g. Gammarus tigrinus Sexton), Mediterra- from the point of introduction and being often nean species (the freshwater shrimp Atyaephyra capable to dominate indigenous populations and desmaresti Millet), and Ponto-Caspian species (e.g. communities (Kolar and Lodge 2001); ultimately, D. villosus) (Beisel 2001). Biotic homogenization— they had a profound effect on indigenous species, i.e. the ecological process leading to an increased ecosystem processes, economic interests, and public similarity of formerly disparate biota over time health (e.g. Ricciardi et al. 1998). The economic (Olden and Rooney 2006)—is constantly accelerating costs produced by the various attempts to control NIS (Clavero and Garcı´a-Berthou 2006; Rahel 2007) and and to mitigate their impact may be high, although some freshwater systems, such as the Great Lakes, seldom assessed (for a short review see McNeely function as ‘‘hotspots’’ of xenodiversity (e.g. Mac- 2004). Isaac et al. 2001). Inland waters have been the theatre of spectacular Finally, many freshwater invaders are moved invasions. Well-known examples are the introduction within and among continents in association with of the Nile perch Lates niloticus (Linnaeus) into Lake economic activity and trade globalization that benefit Victoria followed by the elimination of about 200 millions worldwide (Lodge and Shrader-Frechette species of haplochromine cichlids (Craig 1992) and 2003). The inevitable tension between two often the alteration of the Laurentian Great Lakes commu- competing goals—increasing economic activity and nities and ecosystems by the sea lamprey Petromyzon protecting the environment from invasive species— marinus Linnaeus and the zebra mussel Dreissena makes it difficult to justify the need for decision 123 Animal xenodiversity in Italian inland waters 437 makers to contain the spread of these species and to that need freshwater systems to complete their life mitigate the environmental risks they pose (Gherardi cycle, and invertebrates (free-living and parasitic) 2006a). and fish inhabiting inland water systems. Inland All this implies the need to improve our under- waters are here defined as all standing or flowing standing of the dynamics of species introductions water on the surface of the land (Directive 2000/60/ with the purpose to prevent or control future EC of the European Parliament and of the Council invasions and to predict and reduce their effects establishing a framework for the Community action (Shea and Chesson 2002). When engaged in this in the field of water policy). The analyzed NIS are effort, the main steps to undertake are, first, to ‘‘foreign’’ (i.e. species non native to Italy; Copp et al. identify the NIS occurring in a given area and, 2005) and not ‘‘translocated’’ species (i.e. species second, to individuate the vectors of their introduc- introduced from other basins). tion and the pathways they followed to enter that NIS have been classified according to several area. Inventories of NIS have had the potential to lay categories, i.e. their native range, the date of their the basis for describing patterns of invasion at both (first) introduction into the wild, their current distri- global (e.g. Lonsdale 1999) and regional scales (e.g. bution in Italy, mode/s of their arrival in Italy Rabitsch and Essl 2006; Gollasch and Nehring 2006). (unintentional or intentional introduction), and vec- An accurate knowledge of xenodiversity is also tor/s and pathway/s of their first introduction. Dates needed to develop policies to cope with the problems of NIS first introduction refer to either the exact or associated with biological invasions. Ultimately, an the approximate year reported in scientific publica- understanding of the mechanisms of previous inva- tions or, when this was not available, to the year of sions may help protect aquatic ecosystems from the the first record. To reduce the bias due to both impacts of future invaders. approximation and the obvious