Integrative Zoology 2016; 11: 207–213 doi: 10.1111/1749-4877.12187 1 SHORT COMMUNICATION 1 2 2 3 3 4 4 5 5 6 Galápagos land iguana (Conolophus subcristatus) as a seed 6 7 7 8 disperser 8 9 9 10 10 11 11 1 2 3 4 5 12 Anna TRAVESET, Manuel NOGALES, Pablo VARGAS, Beatriz RUMEU, Jens M. OLESEN, 12 13 Patricia JARAMILLO6 and Ruben HELENO4 13 14 14 15 1Institut Mediterrani d’Estudis Avançats (CSIC-UIB), C/ Miquel Marqués 21, Esporles, Mallorca 07190, Balearic Islands, Spain, 15 16 2Island Ecology and Evolution Research Group (CSIC-IPNA), Instituto de Productos Naturales y Agrobiología, 38206 Tenerife, 16 17 Canary Islands, Spain, 3Real Jardín Botánico (CSIC-RJB), Department of Biodiversity and Conservation, Plaza de Murillo 2, 28014 17 18 Madrid, Spain, 4Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 18 19 5 6 19 Coimbra 3000-456, Portugal, Institute of Bioscience, Aarhus University, Aarhus, Denmark and Charles Darwin Foundation, Puerto 20 20 Ayora, Santa Cruz, Galápagos, Quito, Ecuador 21 21 22 22 23 23 24 Abstract 24 25 25 26 The role of the most common land iguana (Conolophus subcristatus) in the Galápagos Islands as an effective 26 27 seed disperser is explored in this study. A total of 5705 seeds of 32 plant species were identified from 160 scats, 27 28 4545 of which (80%) appeared visually undamaged. Germination trials of 849 seeds from 29 species revealed 28 29 that at least 10 species remained viable after passing through the iguana’s gut, although only a small propor- 29 30 tion of those seeds (4%) germinated. In any case, we argue that C. subcristatus exerts an important role on the 30 31 7 Galapagos islands where it occurs because of its abundance and capacity to ingest and disperse seeds at long 31 32 distances. Our results strongly suggest that the Galápagos C. subcristatus plays an important role as a seed dis- 32 33 perser of not only of native species but also some introduced plants in the Galápagos Islands. 33 34 Key words: Conolophus subcristatus, Fernandina Island, Galápagos Islands Saurochory, seed dispersal 34 35 35 36 36 37 37 38 38 39 INTRODUCTION lizards often undertake an important ecological role as 39 40 seed dispersers (Olesen & Valido 2003). Furthermore, 40 41 Seed dispersal and pollination are 2 key services pro- the reported niche expansion or interaction release of is- 41 42 vided by animals to plants. On oceanic islands, where land vertebrates, which tend to occupy underexplored 42 43 strong isolation limits the arrival of medium and large ecological niches and adopt super-generalized diets, 43 44 sized mammals (Gorman 1979), tortoises, iguanas or magnifies the ecological importance of insular native 44 45 fauna (MacArthur et al. 1972; Cox & Ricklefs 1977; 45 46 Traveset et al. 2015). 46 47 The capacity to disperse seeds is largely limited by 47 Correspondence: Anna Traveset, Institut Mediterrani d’Estudis 48 animal body size and, consequently, by their gape width. 48 49 Avançats (CSIC-UIB), C/ Miquel Marqués 21, 07190-Esporles, Therefore, large animals are disproportionately import- 49 50 Mallorca, Balearic Islands, Spain. ant as seed dispersers in most ecosystems (Blake et al. 50 51 Email: [email protected] 51 © 2016 International Society of Zoological Sciences, Institute of Zoology/ 207 Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd A. Traveset et al. 1 2012; Galetti et al. 2015). For instance, the Galápagos ness in this arid zone can be found in Jaramillo et al. 1 2 giant tortoise is the largest terrestrial animal in the ar- (2014). Iguanas are usually concentrated in areas with 2 3 chipelago and was found to be pivotal for vegetation vegetation (Werner 1983). The predominant plant spe- 3 4 dynamics by dispersing the seeds of many plants over cies in our study area were, in order of abundance: Bur- 4 5 long distances (Heleno et al. 2011; Blake et al. 2012). sera graveolens, Lantana peduncularis Andersson, Bo- 5 6 The second largest terrestrial animals in the Galápagos erhaavia caribaea Darwiniothamnus lancifolius Hook. 6 7 are the endemic land iguanas (Conolophus spp.), rep- f., Cordia leucophlyctis Waltheria ovata Cav., Scutia 7 8 resented by 3 endemic species currently distributed in spicata and Cryptocarpus pyriformis Fernandina has 8 9 7 islands (Fernandina, Isabela, Santa Cruz, Santa Fé, never had human settlement despite its large size, and 9 10 Plazas, Baltra and Seymour) (Jiménez-Uzcátegui et al. partially for this reason is one of the world’s most pris- 10 11 2014). However, except for a few anedoctal records (re- tine tropical islands and harbors very few introduced 11 12 viewed in Heleno et al. 2011), the dispersal potential of species (Jaramillo et al. 2014), none of them vertebrates. 12 13 the Galápagos land iguanas has never been explored. Moreover, the population of land iguana of Fernandina 13 14 The 3 Galápagos land iguanas are vegetarian and high- is the only one in Galápagos that remain mostly undis- 14 15 ly generalized (Jackson 1994): for example, consum- turbed, as all other populations have been under anthro- 15 16 ing fruits of Opuntia spp., Psidium galapageium and pogenic stressors such as direct disturbance and the in- 16 17 Scutia spicata (Carpenter 1969; McMullen 1999). They troduction of feral dogs, pigs, goats, cats and rats (Snell 17 18 feed mostly on low-growing vegetation as iguanas do et al. 1984). 18 19 not climb/creep, although they can stand on their hind In February 2010 and 2011, we collected scats of C. 19 20 legs. It is known that in Fernandina, female iguanas mi- subcristatus in the remote Cabo Douglas (northwest of 20 21 grate long distances (approximately 10 km) and ascend Fernandina). The scats were collected in an area of ap- 21 22 up to 1500 m, from the sea shore to the central crater of proximately 1 km2 of the arid zone, which holds most 22 23 this volcanic island where they lay their eggs (Werner plant diversity and endemic species and is the most 23 24 1983). The population of Conolophus subcristatus (Gray, abundant habitat type in the Galápagos (Guézou et al. 24 25 1831) reaches high densities in Fernandina, with thou- 2010). This area was scanned by 5 observers and all 25 26 sands of reproductive females (Werner 1983). iguana scats, either fresh or old, were collected as long 26 27 To disclose the potential role of Galápagos land igua- as they kept their intact structure. This allowed us to 27 28 nas as seed dispersers, we looked for intact seeds in the study its diet over a relatively long period of time, given 28 29 scats of C. subcristatus of the island of Fernandina and that scats remain intact for many months (pers. observ.) 29 30 interpreted legitimate seed dispersal based on seed ger- mainly due to the large quantity of plant fiber ingested 30 31 minability tests. and to the dry climate. Our direct observations of igua- 31 32 nas in the study area lead us to think that the scats might 32 33 33 MATERIAL AND METHODS belong to a few dozens individuals. All collected scats 34 were taken to the Charles Darwin Foundation’s labo- 34 35 Fernandina is the youngest (0.3 Myr, Ali & Aitchi- ratory in Santa Cruz, where seeds were extracted and 35 36 son 2014) and westernmost Galápagos island, consist- identified by comparison with a reference collection of 36 37 ing of a single active shield volcano (last eruption in seeds from the archipelago. All seeds were counted and 37 2 38 2009), with a 5-km wide crater. The island is 642 km visually inspected under a stereomicroscope and classi- 38 39 and the maximum elevation is approximately 1500-m fied as either damaged or undamaged. 39 40 40 a.s.l. It is very heterogeneous in ecological conditions, As a second step, to evaluate the capacity of seed ger- 41 41 bearing habitats rich in resources for iguanas as well as mination, we carried out an experiment by sowing 849 42 42 much bare soil that is used for their burrow construc- seeds from 29 plant species found in the scats. Seeds, 43 43 tion (Werner 1983). The vegetation patterns are largely previously extracted from the surrounding fecal materi- 44 44 determined by volcanic activity and deposition, and the al, were sown on 1 April 2011, on trays of 104 units pre- 45 45 slopes of the volcano are mostly barren lava (Hendrix & viously filled with a substrate composed of agricultural 46 46 Smith 1986). In the lowlands, most vegetation is found soil, volcanic lapilli and turf (2:1:1 ratio). In a shad- 47 47 in small crevices within the recent lava fields. There is ed greenhouse, soil in trays was kept moist throughout 48 48 low water availability in this zone, and the black lava the experiment. Seedling emergence was recorded for 49 49 can reach over 60 °C on sunny days during the hot sea- 2 years: every other day during the first year and once a 50 50 son (Christian et al. 1983). Information on plant rich- week during the second year. In addition, we performed 51 51 208 © 2016 International Society of Zoological Sciences, Institute of Zoology/ Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd Galápagos land iguana as a seed disperser 1 a seed viability analysis, by applying the bioindicator 1 2 2,3,5 triphenyl-2H-tetrazolium chloride diluted to 0.1% 2 3 for 24 h in the dark and at room temperature (Porter et 3 4 al.