Seed dispersal networks in the Galapagos and the functional consequences of plant invasions

• Main Authors: Heleno, Rubén H., Olesen, Jens M., Nogales, Manuel, Vargas, Pablo, Traveset, Anna
• Format: Conference Object
• Language: unknown
• Published: European Ecological Federation 2011
• Subjects: Finch; Galapagos; Rattus rattus
• Online Access: http://hdl.handle.net/10261/110955

Comunicación presentada en el: 12th EEF (European Ecological Federation) Congress, celebrado del 25 al 29 de septiembre de 2011 en Ávila (España). Congreso en el que se celebraron conjuntamente: 10th Annual Conference of the Spanish Association for Terrestrial Ecology; 13th Annual Meeting of the Portuguese Ecological Society; 3rd Iberian Congress of Ecology Despite the dramatic threat posed by introduced plants to the Galapagos unique biotas, our knowledge on the main ecosystem processes in the archipelago is still very basic. Here we analyze for the first time seed dispersal patterns in these islands and evaluate the impact of plant invasions on eight, quantitative seed dispersal networks from the two most populated islands. In total, 9124 seeds from 58 plant species were dispersed by 18 animal species. The global resulting network was composed by eight modules, the four main ones respectively dominated by: 1) Darwin finches; 2) Lava lizards and non-finch birds; 3) Giant tortoise; and 4) Land iguana and Lava lizards. Modules were connected through ubiquitous species such as the native Tournefortia psilostachya and several herbs. There were five network hubs: Chelonoidis nigra, Microlophus albemarlensis, Conolophus subcristatus, Rattus rattus and Geospiza fuliginosa. These results highlight, for the first time, the importance of Lava lizards and Land iguanas as key seed-dispersers in the Galapagos. The integration of introduced plants into the seed dispersal networks reduced network size and the number of seeds dispersed while increasing network compartmentalization, link density, interaction evenness and nestedness. Networks from the humid zone, were smaller, with lower interaction diversity and link density, lower interaction evenness and reduced robustness when compared to dry lowlands. Several dispersers are assisting the spread of invasive plants (e.g. Rubus niveus, Lantana camara). Although the dispersal of invasive alien seeds is still incipient in our study sites, it already has marked consequences for ...