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The Galápagos land iguana (Conolophus subcristatus) as a seed disperser.

By: Traveset, A.
Contributor(s): Nogales, M | Vargas, P | Rumeu, B | Olesen, J | Jaramillo, P | Heleno, R.
Material type: materialTypeLabelArticlePublisher: 2016Subject(s): Galápagos land | Tierra de Galápagos | Conolophus subcristatu | IguanaDDC classification: 597.9542 Online resources: Click here to access online In: Integrative Zoology (Apr 2016), p. 1-16Subject: Seed dispersal, together with pollination, are two key services provided by animals to plants. On oceanic islands, where strong isolation limits the arrival of medium and large sized mammals (Gorman 1979), tortoises, iguanas or lizards often undertake an important ecological role as dispersers (Olesen & Valido 2003). Furthermore, the reported niche expansion or interaction release of island vertebrates, which tend to occupy underexplored ecological niches and adopt super-generalized diets, magnifies the ecological importance of insular native fauna (MacArthur et al. 1972; Cox & Ricklefs 1977; Traveset et al. 2015). The capacity to disperse seeds is largely limited by animal body size and consequently by their gape width. Therefore, large animals are disproportionately important as seed dispersers in most ecosystems (Blake et al. 2012; Galetti et al. 2015). For instance, the Galápagos giant tortoise is the largest terrestrial animal in the archipelago and was found to be pivotal for vegetation dynamics by dispersing the seeds of many plants over long distances (Blake et al. 2012; Heleno et al. 2011). The second largest terrestrial animals in the Galápagos are the endemic land iguanas (Conolophus spp.), represented by three endemic species currently distributed in seven islands (Fernandina, Isabela, Santa Cruz, Santa Fé, Plazas, Baltra, and Seymour) (Jiménez-Uzcátegui et al. 2014). However, except for a few anedoctal records (reviewed in Heleno et al. 2011), the dispersal potential of the Galápagos land iguanas has never been explored. The three Galápagos land iguanas are vegetarian and highly generalized (Jackson 1994), e.g. consuming fruits of Opuntia spp., Psidium galapageium and Scutia spicata (Carpenter 1969; McMullen 1999). They feed mostly on low-growing vegetation as iguanas do not climb/creep, although they can stand on their hind This article is protected by copyright. All rights reserved. legs. It is known that in Fernandina, female iguanas migrate long distances (c.10 km) and ascend up to 1500 m, from the sea shore to the central crater of this volcanic island where they lay their eggs (Werner 1983). The population of Conolophus subcristatus (Gray 1831) reaches high densities in Fernandina, with thousands of reproductive females (Werner 1983). In order to disclose the potential role of Galápagos land iguanas as seed dispersers, we looked for intact seeds in the scats of C. subcristatus of the island of Fernandina and interpreted legitimate seed dispersal based on seed germinability tests.
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Seed dispersal, together with pollination, are two key services provided by animals to plants. On oceanic islands, where strong isolation limits the arrival of medium and large sized mammals (Gorman 1979), tortoises, iguanas or lizards often undertake an important
ecological role as dispersers (Olesen & Valido 2003). Furthermore, the reported niche expansion or interaction release of island vertebrates, which tend to occupy underexplored ecological niches and adopt super-generalized diets, magnifies the ecological importance of insular native fauna (MacArthur et al. 1972; Cox & Ricklefs 1977; Traveset et al. 2015). The capacity to disperse seeds is largely limited by animal body size and consequently by their gape width. Therefore, large animals are disproportionately important as seed dispersers in most ecosystems (Blake et al. 2012; Galetti et al. 2015). For instance, the Galápagos giant tortoise is the largest terrestrial animal in the archipelago and was found to be pivotal for vegetation dynamics by dispersing the seeds of many plants over long distances (Blake et al. 2012; Heleno et al. 2011). The second largest terrestrial animals in the Galápagos are the endemic land iguanas (Conolophus spp.), represented by three endemic species currently distributed in seven islands (Fernandina, Isabela, Santa Cruz, Santa Fé, Plazas, Baltra, and Seymour) (Jiménez-Uzcátegui et al. 2014). However, except for a few anedoctal records (reviewed in Heleno et al. 2011), the dispersal potential of the Galápagos land iguanas has never been explored. The three Galápagos land iguanas are vegetarian and highly generalized (Jackson 1994), e.g. consuming fruits of Opuntia spp., Psidium galapageium and Scutia spicata (Carpenter 1969; McMullen 1999). They feed mostly on low-growing vegetation as iguanas do not climb/creep, although they can stand on their hind This article is protected by copyright. All rights reserved. legs. It is known that in Fernandina, female iguanas migrate long distances (c.10 km) and ascend up to 1500 m, from the sea shore to the central crater of this volcanic island where they lay their eggs (Werner 1983). The population of Conolophus subcristatus (Gray 1831) reaches high densities in Fernandina, with thousands of reproductive females (Werner 1983). In order to disclose the potential role of Galápagos land iguanas as seed dispersers, we looked for intact seeds in the scats of C. subcristatus of the island of Fernandina and interpreted legitimate seed dispersal based on seed germinability tests.

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