Impact of seed and seedling predators on recruitment of Newfoundland red maple

Abstract

Island ecosystems evolve in geographic isolation, making them particularly vulnerable to synergistic, sometimes irreversible, effects of non-native invasive species. The recent introduction of the southern red-backed vole (Clethrionomys gapperi) to Newfoundland adds another species to the growing list of understudied introduced herbivores. This study focused on the effects of red-backed voles on the early life history stages of red maple (Acer rubrum). The recruitment capacity of red maple on the east coast of Newfoundland, where red-backed voles have not yet invaded, and the maples on the west coast, where red-backed voles are abundant were compared. Seeds were marked and monitored to determine the effects of post-dispersal seed predation on seed survival. Predator activities were monitored using tracking stations baited with dormant and fresh red maple seeds. Semi-permeable cages were used to determine the effect of the various herbivores on seedling survival. Insects caused the greatest seed loss, followed by non-native slugs and lastly small mammals. Seedling mortality was highest in dry microsites, probably do to desiccation. The cumulative effects of pre- and post-dispersal insect seed predation, as well as shrew, slug, and red-backed vole seed predation are resulting in 100% red maple seed loss in western Newfoundland. Because red maple regeneration in disturbed areas is dependent on recruitment from seed, as opposed to vegetative growth, the presence of red backed voles increases the potential for recruitment failure in red maple, especially in combination with the effects of other non-native seed herbivores.