Frugivore loss limits recruitment of large-seeded trees.

Although global declines in frugivores may disrupt seed dispersal mutualisms and inhibit plant recruitment, quantifying the likely reduction in plant regeneration has been difficult and rarely attempted. We use a manipulative factorial experiment to quantify dependence of recruitment on dispersal (i.e. fruit pulp removal and movement of seed away from parental area) in two large-seeded New Zealand tree species. Complete dispersal failure would cause a 66 to 81 per cent reduction in recruitment to the 2-year-old seedling stage, and synergistic interactions with introduced mammalian seed and seedling predators increase the reduction to 92 to 94 per cent. Dispersal failure reduced regeneration through effects on seed predation, germination and (especially) seedling survival, including distance- and density-dependent (Janzen-Connell) effects. Dispersal of both species is currently largely dependent on a single frugivore, and many fruits today remain uneaten. Present-day levels of frugivore loss and mammal seed and seedling predators result in 57 to 84 per cent fewer seedlings after 2 years. Our study demonstrates the importance of seed dispersal for local plant population persistence, and validates concerns about the community consequences of frugivore declines.

Eradication success down under: heat treatment of a sunken trawler to kill the invasive seaweed Undaria pinnatifida.

Eradication of invasive species is difficult in the marine environment, and there have only been a few successes. We report the successful eradication of the invasive seaweed Undaria pinnatifida from a sunken trawler in the Chatham Islands, New Zealand. New heat-treatment methods were developed as the most cost effective and environmentally acceptable option to kill Undaria. Monitoring of the trawler for three years after it sank found no Undaria after the vessel was treated. Key factors in the success of the eradication programme included: early detection, a rapid response, pre-existing knowledge of Undaria, an adaptive management approach, targeting of multiple life history stages, and the cooperation of the vessel's insurer.