Frugivory of Plocama pendula (Rubiaceae) by the rabbit (Oryctolagus cuniculus) in xerophytic zones of Tenerife (Canary Islands)

In this paper we present a new case of the scarcely known phenomenon of fruigivory by the Rabbit. A total of 1,843 seeds of Plocama pendula (Rubiaceae), an endemic species of the Canary Islands, were found in an analysis of 1.200 faeces collected in three different zones of a ravine located on Tenerife island (inverbed, hillside and slopiong zone). The external damage produced by rabbits upon the seeds was relatively low (16% of broken seeds) and significant differences in germination percentage were found when comparing with control seeds collected on the plants (plants: 66.5% vs rabbits: 34.5%). Furthermore, seeds from plants germinated significantly earlier than those from rabbit's droppings. This experiment was performed over two months. In terms of frecuency of seed occurrences, the highest value was found in the riverbed (77.5%), decreasing gradually away from this habitat (16.4% on hillside and 6.1% in the sloping zone). Furthermore it is in the riverbed where the species reaches the highest density of plants. This is a clear case where and introduced hervibore is interacting with the seed dispersal system together with the native frugivore species (lizards and warblers).
We are grateful to Luisa Hernández and Mercedes González for helping us to collect and to analyze the droppings, Pedro Jordano, José Guitián and an anonymous referee who made helpful comments that improved the manuscript, and Mr. Jesús Vega for permission to work on Teno Bajo. Part of this investigation was supported by Dirección General de Universidades e Investigación del Gobierno de Canarias, grant 93/150.