PRIMARY RESEARCH PAPER Waterbird-mediated passive dispersal of river shrimp Athyaephyra desmaresti Filipe Banha • Pedro Manuel Anasta ´cio Received: 9 September 2011 / Revised: 29 April 2012 / Accepted: 6 May 2012 / Published online: 19 May 2012 Ó Springer Science+Business Media B.V. 2012 Abstract The river shrimp Athyaephyra desmaresti is a Mediterranean species which in recent years expanded its distribution, colonizing rivers of central Europe. The purpose of this study was to investigate the possibility of passive external dispersal of the river shrimp Athyaephyra desmaresti by waterfowl. We performed experiments testing shrimp desiccation survival, probability of attachment to waterfowl, and probability of successful transport. We found that in the laboratory 10% of the river shrimps can survive out of water for up to 90.1 min, but this period was reduced to 18.5 min under simulated bird flight conditions. Two different outdoor experiments simulating bird flight conditions indicated a 50% probability of successful transport on flight distances over 15 km. Our results using dead ducks show evidence that small, large or ovigerous river shrimps can attach to and be transported by ducks and that this capacity is affected by water depth. This study demonstrated that water- bird-mediated passive dispersal of river shrimps can occur and may be important for genetic flows between populations and for the colonization of new sites. Keywords Athyaephyra desmaresti Á Passive dispersal Á Waterfowl Á Desiccation Introduction Dispersal is the movement of organisms or propagules between spatially (or temporally) discrete localities or populations (Bilton et al., 2001). It is the main process influencing the dynamics and evolution of populations and species (Mayr, 1963). Dispersal defines the spatial limits for colonization of new sites (Ca ´ceres & Soluk, 2002) and influences the probability of extinction (Vos et al., 2001). Therefore, understanding dispersal mechanisms will help to understand the patterns of colonization and will improve our capacity to control alien species (Bohonak & Jenkins, 2003; Colautti et al., 2005). The mechanisms of dispersal can be divided into active and passive. The former entails self-generated movements of individual organisms, while the latter involves movements achieved using an external agent. For freshwater invertebrates, the relevance of passive dispersal is mostly associated with overland movement, since this way they can cross inhospitable terrestrial landscape. It is generally recognized that the main passive dispersal vectors of freshwater inverte- brates are water flow, wind and animal vectors (Bilton et al., 2001). Passive transport by animal vectors can occur in two different ways, the first via external dispersal or ectozoochory (hitchhiking or phoresy). In Handling editor: Nuria Bonada F. Banha (&) Á P. M. Anasta ´cio IMAR – Centro de Mar e Ambiente, c/o. Departamento de Paisagem, Ambiente e Ordenamento, Universidade de E ´ vora, Rua Roma ˜o Ramalho, no. 59, 7000-671 E ´ vora, Portugal e-mail: filipebanha@hotmail.com 123 Hydrobiologia (2012) 694:197–204 DOI 10.1007/s10750-012-1160-7