Predation on Seeds of Invasive Lantana camara by Darwin's Finches in the Galapagos Islands

Abstract

Observations on birds feeding on fruits of the invasive shrub Lantana camara (Supirrosa) were conducted on Santa Cruz Island, Galapagos (Ecuador) in the Dry Zone during the 2009 dry season. The endemic ground finches Geospiza magnirostris (Large Ground Finch) and G. fortis (Medium Ground Finch) were recorded eating Lantana seeds with G. fortis the main consumer (>90% of records). Both finch species crushed the seeds and ate the embryos, discarding the exocarp and empty seed coats. They also dropped entire fruits to the ground, which could contribute to short-distance dispersal, but both finches also consumed fruits of L. camara on the ground. Density of L. camara seedlings under adult plants was higher in rockier areas than in bare soil since seeds were less accessible to predators and/or found more suitable microsites for germination and establishment. Both species of finches serve as short-distance dispersers, but mainly as seed predators of L. camara fruits.