Reproductive success of the Canarian Echium simplex (Boraginaceae) mediated by vertebrates and insects.

BACKGROUND AND AIMS: Oceanic island ecosystems favor the appearance of novel interactions as a consequence of their depauperate and disharmonic flora and fauna. Echium simplex, endemic to the Anaga Biosphere Reserve in NE Tenerife, Canary Islands, belongs to the Canarian bird-flower element.

METHODS: Along two flowering seasons, we studied its breeding system, identified the floral visitors, and compared the pollination effectiveness of different animal guilds (insects vs. vertebrates) by means of selective exclosures.

KEY RESULTS: The plant showed to be self-compatible but selfing significantly reduced fruit set. The flowers were visited by five bird species (mostly Phylloscopus canariensis and Serinus canarius, but also Cyanistes teneriffae, Sylvia atricapilla and Sylvia melanocephala), a lizard species (Gallotia galloti), and over a hundred insect species (mainly hymenopterans and coleopterans). Flying insects increased fruit set whereas small flower dwellers (mostly beetles) decreased both fruit and seed set; by contrast, vertebrates had a negligible effect on reproductive success.

CONCLUSIONS: We conclude that despite the floral resources provided by E. simplex may be important to some vertebrate species, these do not appear to notably contribute to increase the fitness of the plant, which show to be more dependent upon flying insects to set fruits and seeds. We additionally found that plant reproductive structures are heavily damaged by feral goats, which threaten the maintenance of this Canarian endemic species. This article is protected by copyright. All rights reserved.