The island syndrome and population dynamics of introduced rats

• Published in: Oecologia Vol. 167; no. 3; pp. 667 - 676
• Main Authors: Russell, James C., Ringler, David, Trombini, Aurélien, Le Corre, Matthieu
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer 01-11-2011; Springer-Verlag; Springer Nature B.V; Springer Verlag
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Anthropogenic factors; Atolls; Behavior, Animal - physiology; Biodiversity and Ecology; Biological and medical sciences; Biological Evolution; Biomedical and Life Sciences; Body Size; Corals; Demecology; Demography; Discriminant Analysis; Ecology; Ecosystem; Environmental Sciences; Forest habitats; Fundamental and applied biological sciences. Psychology; General aspects; Geography; Hydrology/Water Resources; Introduced species; Invasions; Invasive species; Islands; Life Sciences; Linear Models; Mice; Migration; Mozambique; Plant Sciences; Population density; Population Dynamics; Population ecology; Population ecology - Original Paper; Predators; Rats; Rattus rattus; Reproduction; Reproduction - physiology; Rodentia - growth & development; Rodentia - physiology; Rodents; Summer; Trophic relationships; Winter; Mozambique; Spatially explicit capture–recapture; Demography; Body-size; Density; Introduced species; Rat; Rodentia; Corporal biometry; Island; Syndrome; Vertebrata; Mammalia; Capture recapture method; Spatially explicit capture-recapture; Body size; Population dynamics; Rattus rattus; Geography; Body Size; Rats; Linear Models; Discriminant Analysis; Biological Evolution; Animals; Mozambique; Animal; Ecosystem; Behavior; Population Dynamics; reproduction
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-011-2031-z

The island syndrome predicts directional changes in the morphology and demography of insular vertebrates, due to changes in trophic complexity and migration rates caused by island size and isolation. However, the high rate of human-mediated species introductions to some islands also increases trophic complexity, and this will reduce the perceived insularity on any such island. We test four hypotheses on the role of increased trophic complexity on the island syndrome, using introduced black rats (Rattus rattus) on two isolated coral atolls in the Mozambique Channel. Europa Island has remained relatively pristine and insular, with few species introductions, whereas Juan de Nova Island has had many species introductions, including predators and competitors of rats, anthropogenically increasing its trophic complexity. In the most insular environments, the island syndrome is expected to generate increases in body size and densities of rodents but decreases in the rates of reproduction and population cycling. Morphology and reproduction were compared using linear regression and canonical discriminant analysis, while density and population cycling were compared using spatially explicit capture–recapture analysis. Results were compared to other insular black rat populations in the Mozambique Channel and were consistent with predictions from the island syndrome. The manifestation of an island syndrome in rodents depends upon the trophic composition of a community, and may not relate to island size alone when many species additions, such as invasions, have occurred. The differing patterns of rodent population dynamics on each island provide information for future rodent eradication operations.