long-term study (1949-2005) of experimental introductions to an island; freshwater amphipods (Crustacea) in the Isle of Man (British Isles)

• Published in: Diversity & distributions Vol. 15; no. 2; pp. 232 - 241
• Main Authors: MacNeil, Calum, Dick, Jaimie T. A., Gell, Fiona R., Selman, Richard, Lenartowicz, Paul, Hynes, H. B. Noel
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.03.2009; Blackwell Publishing Ltd; Blackwell Publishing; Blackwell; John Wiley & Sons, Inc
• Subjects: Amphipoda; Amphipods; Animal, plant and microbial ecology; Applied ecology; Biodiversity Research; Biogeography; Biological and medical sciences; biological invasions; Crangonyx pseudogracilis; Crustacea; Crustaceans; Ecological invasion; Ecology; Ecotoxicology, biological effects of pollution; Experiments; Fresh water; Fresh water environment; Freshwater; Fundamental and applied biological sciences. Psychology; Gammarus; Gammarus duebeni celticus; introductions; Invertebrates; Islands; Isle of Man; Macroinvertebrates; Marine ecology; metal pollution; mining; Nonnative species; Organic pollution; Oxygen; propagule pressure; Species; Water pollution; Water quality; Isle of Man; Commonwealth; British Isles; ANE, Irish Sea, Isle of Man; North America; Biological invasion; Isle of Man; Fresh water; Metal; Biodiversity; Experimental study; Long term; biological invasions; Amphipoda; Crustacea; Mining; Gammarus; Arthropoda; propagule pressure; Water pollution; metal pollution; Invertebrata; Mining industry; Amphipods; introductions
• ISSN: 1366-9516; 1472-4642
• DOI: 10.1111/j.1472-4642.2008.00529.x

Using data from field introduction experiments with Gammarus spp. conducted in the rivers of a small island, commencing in 1949, with resampling in the 60s, 70s, 80s, 90s and finally in 2005, we aimed to examine the long-term interaction of the native freshwater amphipod Gammarus duebeni celticus with the introduced G. pulex. Using physico-chemical data from a 2005 island-wide survey, we also aimed to find what environmental factors could influence the distribution of the two species. The Isle of Man, British Isles. We used species distribution data from 10 river sites from a field introduction study in 1949-69, resampling of these sites in 1974/5, 1988, 1995 and 2005. We sampled a further 82 sites in 2005, where physico-chemical characteristics of each site were obtained. ANOVA was used to ascertain significant differences in environmental variables between native and introduced amphipod assemblages. Multiple discriminant analysis was used to relate Gammarus distribution to environmental gradients in rivers. Field introductions of G. pulex into previously G. d. celticus dominated sites failed, despite the large propagule pressure in terms of numbers of individuals released and repeated introductions. The island-wide survey revealed that G. d. celticus was found in areas of higher water quality than G. pulex. Sites where the two species co-occurred also tended to be of lower water quality than native only sites. Continuing metal pollution from past mining activity may be a major factor excluding all amphipods from many rivers. The North American amphipod Crangonyx pseudogracilis, which was first discovered on the Isle of Man in one river site in 1995, was found in a further five sites. This ecological experiment, through long-term monitoring, thus continues to elucidate factors influencing the distributions of introduced and native species. Under some physicochemical regimes, G. d. celticus is able to withstand its usual displacement by G. pulex, whereas increased river pollution could promote replacement of the native by the introduced species.