POND CONSERVATION Monitoring the invasion of the aquatic bug Trichocorixa verticalis verticalis (Hemiptera: Corixidae) in the wetlands of Don ˜ ana National Park (SW Spain) He ´ctor Rodrı ´guez-Pe ´rez Æ Margarita Florencio Æ Carola Go ´mez-Rodrı ´guez Æ Andy J. Green Æ Carmen Dı ´az-Paniagua Æ Laura Serrano Published online: 29 July 2009 Ó Springer Science+Business Media B.V. 2009 Abstract We have detected the presence of the North American native corixid Trichocorixa verticalis ver- ticalis (Fieber, 1851) in Don ˜ ana wetlands (SW Spain). We have collected data from different research projects done in the area during the period of 2001–2007. We have sampled 134 different sites in Don ˜ana and we found the exotic corixid in 66 occasions. We have found two reproductive populations that might act as sources for the colonization of other waterbodies in the area. When reproduction occurred T. v. verticalis outcompeted native corixids. Its presence out of the waterbodies where we detected reproduction was in small numbers and probably due to vagrant individuals. Keywords Corixid Á Trichocorixa Á Exotic species Á Invasive Á Don ˜ana Introduction The spread of exotic species occurrence worldwide is one of the major causes of global change (Vitousek et al., 1996; Ricciardi, 2006). The establishment of exotic invasive species within an ecosystem usually has strong consequences, affect- ing ecological functions (Ricciardi et al., 1997; Maezono & Miyashita, 2003), and causing a loss of indigenous biodiversity (Witte et al., 2000). Several scenarios have been described once an exotic species arrives to an ecosystem before it becomes an invasive species, and it controls ecological processes (Carlton, 2003). In this article, we consider the status and possible impact of an exotic aquatic insect recently detected in the Don ˜ana wetlands in south-west Spain. Trich- ocorixa verticalis verticalis (Fieber, 1851) is a small Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Net work, Valencia, Spain, 14–16 May 2008 He ´ctor Rodrı ´guez-Pe ´rez and Margarita Florencio have contributed equally to this work. H. Rodrı ´guez-Pe ´rez (&) Á M. Florencio Á C. Go ´mez-Rodrı ´guez Á A. J. Green Á C. Dı ´az-Paniagua Department of Wetland Ecology, Estacio ´n Biolo ´gica de Don ˜ana-CSIC, C/Americo Vespucio, s/n, 41092 Sevilla, Spain e-mail: hectorrodriguez@vet.ucm.es Present Address: H. Rodrı ´guez-Pe ´rez Department of Animal Production. Veterinary Faculty, Complutense University of Madrid, Av. Puerta de Hierro, 28040 Madrid, Spain L. Serrano Department of Plant Biology and Ecology. Biology Faculty, Sevilla University, 41080 Sevilla, Spain 123 Hydrobiologia (2009) 634:209–217 DOI 10.1007/s10750-009-9901-y