Dispersal: The case of the missing ant and the introduced mouse

Regeneration of Phylica arborea, a myrmecochorous species occurring on Gough Island, is failing on plateau areas on the Island. Regeneration only occurs on slip faces on steep slopes. Some data are presented to show that this could be attributed to the presence of an introduced rodent, Mus musculus. This rodent occurs on the island in comparatively high densities. It is an omnivore and feeds extensively on grain. Experiments showed that it can find seed of P. arborea and that seeds are consumed during field trials. Tests were also conducted to show that elaiosomes of P. arborea are still attractive to ants and that they will bury the seeds. It is speculated that regeneration fails since there are no ants on the island, seeds are not buried, and the introduced small mammal consumes all available seed. Verjonging van Phylica arborea, ’n plantsoort met sade wat deur miere versprei word, kom nie meer op die plato-gedeeltes van Gough Eiland voor nie. Jong plante word slegs op grondverskuiwings aangetref. Data wat daarop dui dat hierdie verskynsel toegeskryf kan word aan die teenwoordigheid van ’n uitheemse soogdier, Mus musculus word aangebied. Hierdie muis kom in redelike hoë digthede op die eiland voor. M. musculus is ’n omnivoor en vreet baie saad. Eksperimente is gedoen wat daarop dui dat die muis in staat is om sade van P. arborea in die veld op te spoor en te vreet. Toetse is ook gedoen om te wys dat miere wel die elaiosome van P. arborea kan opsoor en dat hulle die sade begrawe. Dit word gespekuleer dat verjonging faal omdat daar nie miere op die eiland is om die saad te begrawe nie, en die muis, M. musculus, al die beskikbare saad opvreet.

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