Is the aquatic Dikerogammarus villosus a ‘killer shrimp’ in the field? – a case study on one of the most invasive species in Europe Dr. Meike Koester1,2, Bastian Bayer1 & Dr. René Gergs3 1Institute for Environmental Sciences, University of Koblenz-Landau, Campus Landau, Germany 2Institute of Natural Sciences, University of Koblenz-Landau, Campus Koblenz, Germany 3Federal Environment Agency, Berlin, Germany Introduction 143 animal 58 invasive 2 Introduction Bij de Vaate et al. (2002) 3 Introduction 1994/95 first record from the River Rhine Colonised most major European rivers within 2 decades www.aquatic-aliens.de 4 Introduction Larger than native amphipods High reproductive potential & growth rate Colonises different substrates Highly tolerant towards various environmental conditions (e.g. T, O2, salinity) Feeding behaviour 5 Introduction River Rhine species of number Mean Schöll, BfG-report Nr. 172 other gamarids Dikerogammarus villosus Gammarus roeselii Gammarus pulex/fossarum after Rey et al. 2005 6 Introduction 7 Hypothesis D. villosus is also strongly predacious in the field 8 Stable Isotope Analyses (SIA) 12 13 Carbon C C 13C/12C 98,89 % 1,11 % 14 15 Nitrogen N N 15N/14N 99,64 % 0,36 % δ15N: strong accumulation Predator 1 Trophic Level ca. 3.4 ‰ Secondary consumer N 13 15 δ C: less accumulated δ Primary consumer C-source of the food Producer δ13C 9 Sampling areas of the River Rhine and its tributaries B Bulk analyses δ13C and δ15N SIBER-Analyses comparing amphipod species Genetic gut content analyses with group-specific C B rDNA primers (Koester Aet al. 2013) A C 10 A. Feeding river vs. Lake Constance 14 Feeding river Lake Constance n = 21 8 n = 21 12 1 × Ephemera sp. 1 × Ephemeroptera 5 × Caenis sp. 7 N 10 15 1 × Heptageniidae 3 × Heptageniidae δ 6 8 2 × Asellus aquaticus 3 × Gammarus sp. 6 5 -32 -31 -30 -29 -28 -27 -26 -25 -30 -25 -20 -15 δ13C Dikerogammarus villosus Caenis sp. Limnomysis benedeni Echinogammarus berelloni Chironominae Potamopyrgus antipodarum + Gammarus roeselii Dreissena polymorpha Simuliidae Asellus aquaticus Hydropsyche sp. Characea sp. Bithynia tentaculata Hirudinae Periphyton Seston 11 B. Upper Rhine vs. Lower Rhine 12 Upper Rhine 16 Lower Rhine n = 20 15 n = 20 10 14 N 15 8 13 δ 3 × Ephemera sp. 1 × Chelicorophium sp. 12 6 11 4 10 -28 -26 -24 -22 -20 -18 -32 -30 -28 -26 -24 δ13C Dikerogammarus villosus Potamopyrgus antipodarum Echinogammarus ischnus Periphyton Corbicula fluminea Seston Jaera sarsi 12 C. Invasion front vs. Established 9 Invasion front Established 10 8 n = 32 from two sites n = 20 9 7 8 N 6 15 δ 7 5 1 × Ephemeroptera 1 × Jaera sarsi 6 1 × Ephemeroptera 4 5 3 -34 -32 -30 -28 -26 -32 -30 -28 -26 -24 -22 -20 δ13C Dikerogammarus villosus Diamesinae Echinogammarus ischnus + Gammarus fossarum Simuliidae Dreissena rostriformis × Gammarus pulex Orthocladiinae Jaera sarsi G. pulex/G. fossarum Rhyacophila sp. Potamopyrgus antipodarum Ancylus fluviatilis Periphyton Seston 13 Isotopic niche width D. villosus 5 A B C * 4 3 Area (‰²) Area 2 1 0 - Feeding river Lake Constance Upper Rhine Lower Rhine Invasion front Estab lished 14 Conclusion Hypothesis D. villosus is also strongly predacious in the field ‘killer shrimp’? less predatory in the River Rhine system supported by SIA and genetic analyses – apparently not more opportunistic at an invasion front 15 Thanks… … for your attention … to Andreas Hirsch … to Peter Rey, Uta Mürle and Johannes Ortlepp … and numerous other people Need more details? [email protected] 16 .