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Amblyrhynchus Cristatus Ssp. Venustissimus, Española Marine Iguana

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Amblyrhynchus Cristatus Ssp. Venustissimus, Española Marine Iguana The IUCN Red List of Threatened Species™ ISSN 2307-8235 (online) IUCN 2020: T175537718A2993292 Scope(s): Global Language: English Amblyrhynchus cristatus ssp. venustissimus, Española Marine Iguana Assessment by: MacLeod, A., Nelson, K. & Grant, T.D. View on www.iucnredlist.org Citation: MacLeod, A., Nelson, K. & Grant, T.D. 2020. Amblyrhynchus cristatus ssp. venustissimus. The IUCN Red List of Threatened Species 2020: e.T175537718A2993292. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T175537718A2993292.en Copyright: © 2020 International Union for Conservation of Nature and Natural Resources Reproduction of this publication for educational or other non-commercial purposes is authorized without prior written permission from the copyright holder provided the source is fully acknowledged. Reproduction of this publication for resale, reposting or other commercial purposes is prohibited without prior written permission from the copyright holder. For further details see Terms of Use. The IUCN Red List of Threatened Species™ is produced and managed by the IUCN Global Species Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership. The IUCN Red List Partners are: Arizona State University; BirdLife International; Botanic Gardens Conservation International; Conservation International; NatureServe; Royal Botanic Gardens, Kew; Sapienza University of Rome; Texas A&M University; and Zoological Society of London. If you see any errors or have any questions or suggestions on what is shown in this document, please provide us with feedback so that we can correct or extend the information provided. THE IUCN RED LIST OF THREATENED SPECIES™ Taxonomy Kingdom Phylum Class Order Family Animalia Chordata Reptilia Squamata Iguanidae Scientific Name: Amblyrhynchus cristatus ssp. venustissimus Eibl-Eibesfeldt, 1962 Parent Species: See Amblyrhynchus cristatus Common Name(s): • English: Española Marine Iguana Taxonomic Source(s): Iguana Taxonomy Working Group (ITWG). 2019. A Checklist of the Iguanas of the World (Iguanidae; Iguaninae). Supplement to: 2016 Herpetological Conservation and Biology 11(Monograph 6): 4–46. Available at: http://www.iucn-isg.org/wp- content/uploads/2019/05/ITWG_Checklist_2019_Supplement.pdf. Miralles, A., Macleod, A., Rodríguez, A., Ibáñez, A., Jiménez-Uzcategui, G., Quezada, G., Vences, M. and Steinfartz, S. 2017. Shedding light on the Imps of Darkness: an integrative taxonomic revision of the Galápagos Marine Iguanas (genus Amblyrhynchus). Zoological Journal of the Linnean Society 181(3): 678–710. DOI: 10.1093/zoolinnean/zlx007. Taxonomic Notes: Amblyrhynchus cristatus venustissimus was previously described by Eibl-Eibesfeldt (1962) and included iguanas from Española and surrounding islets only. Iguanas from Floreana and surrounding islets are now included in this subspecies as a result of taxonomic revision by Miralles et al. (2017). Assessment Information Red List Category & Criteria: Endangered B1ab(iii)c(iv)+2ab(iii)c(iv) ver 3.1 Year Published: 2020 Date Assessed: December 1, 2019 Justification: The Española Marine Iguana is found on the islands of Española, Floreana, Gardner-by-Floreana, Champion, and very likely their satellite cays in the Galápagos Islands, Ecuador. The estimated extent of occurrence is 1,184 km2 by minimum convex polygon and the area of occupancy is estimated at 308 km 2. The population size is poorly known and crudely estimated at 3,700–37,000 total iguanas with fewer than 22,200 mature individuals. Genetic data indicate a small to moderate effective population size. Overall population trend is unknown, but is subject to extreme reductions and fluctuations during El Niño events, which are predicted to intensify in the future with ongoing climate change. This iguana is threatened by invasive alien Black Rats, feral cats, and free-roaming pigs and dogs. Española Marine Iguanas are threatened by a region-wide increase in human population and visitation that has multiplied the impacts from stress, marine pollution, habitat degradation, and chance of further invasive species introductions and emergent diseases. Land-based tourist presence and intensity has been shown to © The IUCN Red List of Threatened Species: Amblyrhynchus cristatus ssp. venustissimus – published in 2020. 1 https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T175537718A2993292.en have a significant overall negative effect on iguana health. This subspecies qualifies for listing as Endangered. Geographic Range Range Description: The Española Marine Iguana is restricted to Española, Floreana, Gardner-by-Floreana, Champion and very likely their satellite cays (Miralles et al. 2017), Galápagos Archipelago, Ecuador. This iguana has an estimated extent of occurrence of 1,184 km2 by minimum convex polygon enclosing all subpopulations. The area of occupancy is estimated at 308 km2 by excluding land mass beyond 2 km from the shoreline of the larger islands and using a 2x2 km grid overlay. They are found near and below sea level at depths up to 30 m (large adult males). Maximum elevation for Floreana is 640 m, although it is unlikely they are found at high elevation. Country Occurrence: Native, Extant (resident): Ecuador (Galápagos) FAO Marine Fishing Areas: Native: Pacific - southeast © The IUCN Red List of Threatened Species: Amblyrhynchus cristatus ssp. venustissimus – published in 2020. 2 https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T175537718A2993292.en Distribution Map © The IUCN Red List of Threatened Species: Amblyrhynchus cristatus ssp. venustissimus – published in 2020. 3 https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T175537718A2993292.en Population Only very rough estimates of population size are available for the Española Marine Iguana. They are noted to be as low as 3,700 total individuals after a strong El Niño famine and as many as 37,000 after several years of La Niña abundant food conditions (Wikelski and Nelson 2004). Recent genetic analysis indicates that the population shows a small to moderate effective population size (209, range: 160–265; MacLeod and Steinfartz 2016), which may have serious consequences for the fitness of the population and could reduce the ability to adapt to rapidly changing environmental conditions (Frankham et al. 2014). Little is known regarding current adult numbers, but it is estimated to be under 22,200 based on calculations indicating that 60% of the maximum total population are adults (Laurie 1983, Laurie and Brown 1990a, MacLeod et al. 2016). Average generation length is five years for females and 12 years for males. Populations undergo extreme fluctuations by cyclic, but unpredictably recurring, famine (El Niño) and feast (La Niña) events. El Niño events dramatically reduce the abundance, diversity, and nutritional value of available marine algae, as the iguanas are unable to digest the algae that grows during these periods (Trillmich and Trillmich 1986). Population declines are strongly density-dependent: the higher the population density, the higher the mortalities during El Niños (from 10–90%). Population recovery after El Niños can be rapid, as individuals grow faster, reproduce more frequently and lay more eggs (Laurie and Brown 1990a). Current Population Trend: Unknown Habitat and Ecology (see Appendix for additional information) Marine Iguanas are the only lizard species that forage in the ocean. Adults and juveniles occur on rocky coasts and intertidal zones. Adult females can be found nesting up to 2 km inland and adult males can be found foraging in marine waters, up to depths of 30 m. Española Marine Iguanas feed almost exclusively on marine algae, primarily three red genera (Centroceras, Gelidium, Pterocladia; Rubenstein and Wikelski 2003) and the green algal genus Ulva when exposed during low tides (Shepherd and Hawkes 2005). The majority of iguanas graze intertidally, though the largest iguanas of each colony also dive beneath the sea surface to forage on offshore algal beds (30 m offshore, 2–30 m depth; Buttemer and Dawson 1993, Wikelski and Trillmich 1994). Some iguana populations have been known to supplement their algal diet with highly salty land plants, primarily Saltwort (Batis maritima), but also other coastal succulents such as Sesuvium portulacastrum (Wikelski and Wrege 2000). Marine Iguanas exhibit high morphological diversity, including substantial body size and shape variation among populations and sexes (Chiari et al. 2016). On Española and Floreana, males are larger, with different head morphology than females and more pronounced spines on the head and along the back. These iguanas are the most colorful of the subspecies, with turquoise, red, and pink accents. Average body size (snout-to-vent length) is 264 mm (range 200–325 mm; Miralles et al. 2017). Adult males weigh approximately 70% more than adult females (Laurie and Brown 1990a). Differences in maximum body size across islands is likely due to variability in algal productivity and sea surface temperature between islands (Wikelski and Trillmich 1997, Wikelski and Romero 2003, Wikelski 2005). © The IUCN Red List of Threatened Species: Amblyrhynchus cristatus ssp. venustissimus – published in 2020. 4 https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T175537718A2993292.en Reproduction occurs once a year during a month-long mating season, coinciding with the highest abundance and best nutritional quality of food (Rubenstein and Wikelski 2003). Nutrient-rich upwellings from the Humboldt and Cromwell currents affect all islands differently, so mating occurs at different times across
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