Re‐established mutualism in a seed‐dispersal system consisting of native and introduced birds and plants on the Bonin Islands, Japan

Abstract

The disruption of plant-animal interactions such as seed dispersal is one of the most critical effects of biological invasions. To understand the role of introduced species in current seed-dispersal systems, we conducted fecal analyses of the most common resident land birds on the Bonin Islands, Japan, and estimated their relative importance as seed-dispersal agents. Two native birds, the brown-eared bulbul and the Bonin Islands white-eye, and the introduced Japanese white-eye were the primary seed dispersers in secondary forest sites. Because the seed species composition in the feces of native and introduced white-eyes was similar, the latter may be replacing the former as a seed-dispersal agent. Introduced plants did not decrease the number of seeddispersal opportunities for native species through competition for seed dispersers. Because some bird species have already become extinct on the Bonin Islands, their ecological functions may also have been permanently lost; however, the introduced white-eye may be compensating for this loss of function. In addition, new mutualistic relationships involving native and introduced birds and plants have already been established. In order to control introduced species while having the least impact on the native biota, interspecific interactions must be thoroughly understood before initiating control efforts.

Seed dispersal networks in the Galápagos and the consequences of alien plant invasions

“…In recent years, this growing realization has lifted the focus of conservation efforts from species to ecosystems [1,19]. While there is an increasing number of studies documenting different aspects of the dispersal of native and invasive plants by frugivores [10,20], the consequences of the integration of alien plants into seed dispersal networks has been poorly explored [21]. By contrast, several studies have evaluated the impact of alien plants upon pollination networks.…”

Mutualisms: Key Drivers of Invasions … Key Casualties of Invasions

“…In New Zealand, the contribution of alien birds to seed dispersal of native plants is unexpectedly small (Kelly et al 2006 ). In the Bonin Islands, Kawakami et al (2009) found that introduced whiteeyes appear to compensate for extinct native seed dispersers.…”

Quantifying seed dispersal by birds and possums in a lowland New Zealand forest

“…Staddon et al 2010). The negative effect of species extinctions on seed dispersal processes could be lessened if other species are able to compensate for those that have been lost (Kawakami et al 2009). New Zealand lacks native land mammals (apart from three bat species), but now hosts 32 species of introduced mammals, most of which are considered pests (King 2005).…”