Predispersal seed predation in shrubs of Grevillea (Proteaceae) from south-eastern Australia

Abstract

The agents responsible for predispersal seed losses and the magnitude of these losses in five shrubby Grevillea species from the Sydney region of south-eastern Australia were examined by scoring seed fates in ripe fruits. Predispersal seed predation was evident in all study species, with losses varying from 5 to 46%. Seed losses of from <1 to 27% were attributed to the weevils Cydmaea dorsalis (Coleoptera: Curculionidae) (occurring in all study species), and Cydmaeasp. (occurring in Grevillea buxifolia only), with greatest losses in the two largest-seeded species (G. buxifolia and the endangered G. caleyi). Seed losses to the wasp Eurytoma sp. (Hymenoptera: Eurytomidae) were also found in all species except G. buxifolia. In G. caleyi such losses were confined to only one of three sampled sites and one of two sampled years. Highest seed losses to Eurytoma sp. occurred in the threatened plant G. shiressii (46% of developing seeds). Levels of predispersal seed predation varied across different sampling years and species occupying the same site.