The connective potential of vertebrate vectors responsible for the dispersal of the Canary Island date palm (Phoenix canariensis)

Abstract

Accelerating human intervention has seen the creation of novel ecosystems through intentional planting and adventitious establishment of exotic species. One hundred and fifty years after its commercialisation by the horticultural industry, the Canary Island date palm (Phoenix canariensis) has become one of the most ubiquitous ornamental palm species throughout all temperate zones. Even though it has become naturalised in many parts of the world, colonising natural as well as managed landscapes, little is known about the vectors responsible for dispersal.This paper reviews the state of knowledge of vertebrate species utilising P. canariensis as habitat and those that feed on the palm’s drupes and disperse their seeds. Globally, P. canariensis forms a major urban habitat for invasive species. The significant dispersers are canids and three families of larger volant birds (Artamidae, Columbidae, and Corvidae). The review demonstrates that the majority of vectors consume the fruit on the tree or on a close-by perch, thereby contributing little to medium or long range dispersal. A few avian and terrestrial species facilitate long-distance dispersal, even though they too deposit the majority of seed close to the source.The paper postulates a conceptual model where effective dispersal success of a horticultural plant is governed not only by the established factors of distance of dispersal quantity of seeds dispersed and seed viability, but significantly also by the ability of a vector species to span several habitat boundaries (e.g. from urban to production landscapes or remnant vegetation) and to deposit multiple seeds at tightly defined locations.