1
|
History of Land Cover Change on Santa Cruz Island, Galapagos. LAND 2022. [DOI: 10.3390/land11071017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Islands are particularly vulnerable to the effects of land cover change due to their limited size and remoteness. This study analyzes vegetation cover change in the agricultural area of Santa Cruz (Galapagos Archipelago) between 1961 and 2018. To reconstruct multitemporal land cover change from existing land cover products, a multisource data integration procedure was followed to reduce imprecision and inconsistencies that may result from the comparison of heterogeneous datasets. The conversion of native forests and grasslands into agricultural land was the principal land cover change in the non-protected area. In 1961, about 94% of the non-protected area was still covered by native vegetation, whereas this had decreased to only 7% in 2018. Most of the agricultural expansion took place in the 1960s and 1970s, and it created an anthropogenic landscape where 67% of the area is covered by agricultural land and 26% by invasive species. Early clearance of native vegetation took place in the more accessible—less rugged—areas with deeper-than-average and well-drained soils. The first wave of settlement consisted of large and isolated farmsteads, with 19% of the farms being larger than 100 ha and specializing in diary and meat production. Over the period of 1961–1987, the number of farms doubled from less than 100 to more than 200, while the average farm size decreased from 90 to 60 ha/farmstead. Due to labor constraints in the agricultural sector, these farms opted for less labor-intensive activities such as livestock farming. New farms (popping up in the 1990s and 2000s) are generally small in size, with <5 ha per farmstead, and settled in areas with less favorable biophysical conditions and lower accessibility to markets. From the 1990s onwards, the surge of alternative income opportunities in the tourism and travel-related sector reduced pressure on the natural resources in the non-protected area.
Collapse
|
2
|
Miller AZ, Jiménez-Morillo NT, Coutinho ML, Gazquez F, Palma V, Sauro F, Pereira MF, Rull F, Toulkeridis T, Caldeira AT, Forti P, Calaforra JM. Organic geochemistry and mineralogy suggest anthropogenic impact in speleothem chemistry from volcanic show caves of the Galapagos. iScience 2022; 25:104556. [PMID: 35789844 PMCID: PMC9250005 DOI: 10.1016/j.isci.2022.104556] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 05/09/2022] [Accepted: 06/02/2022] [Indexed: 11/22/2022] Open
Abstract
The network of lava tubes is one of the most unexploited natural wonders of the Galapagos Islands. Here, we provide the first morphological, mineralogical, and biogeochemical assessment of speleothems from volcanic caves of the Galapagos to understand their structure, composition, and origin, as well as to identify organic molecules preserved in speleothems. Mineralogical analyses revealed that moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves were composed of calcite, opal-A, and minor amounts of clay minerals. Extracellular polymeric substances, fossilized bacteria, silica microspheres, and cell imprints on siliceous minerals evidenced microbe-mineral interactions and biologically-mediated silica precipitation. Alternating depositional layers between siliceous and carbonate minerals and the detection of biomarkers of surface vegetation and anthropogenic stressors indicated environmental and anthropogenic changes (agriculture, human waste, and cave visits) on these unique underground resources. Stable isotope analysis and Py-GC/MS were key to robustly identify biomarkers, allowing for implementation of future protection policies. Speleothems from lava tubes of Galapagos are archives of anthropogenic stressors Moonmilk and coralloids are composed of calcite, opal-A, and clay minerals Microbe-mineral interactions promote mineral dissolution and precipitation Biomarkers of surface vegetation and anthropogenic impacts detected by Py-GC/MS
Collapse
Affiliation(s)
- Ana Z. Miller
- Instituto de Recursos Naturales y Agrobiologia de Sevilla (IRNAS-CSIC), Seville, Spain
- HERCULES Laboratory, University of Évora, Évora, Portugal
- Corresponding author
| | - Nicasio T. Jiménez-Morillo
- MED—Mediterranean Institute for Agriculture, Environment and Development, University of Évora, Évora, Portugal
| | | | - Fernando Gazquez
- Department of Biology and Geology, University of Almería, Almería, Spain
- Andalusian Centre for the Monitoring and Assessment of Global Change (CAESCG), University of Almería, Almería, Spain
| | - Vera Palma
- HERCULES Laboratory, University of Évora, Évora, Portugal
| | - Francesco Sauro
- Department of Earth Sciences and Environmental Geology, University of Bologna, Bologna, Italy
| | | | - Fernando Rull
- CSIC-CAB Associated Unit ERICA, Department of Condensed Matter Physics, Mineralogy and Crystallography, University of Valladolid, Boecillo, Spain
| | | | | | - Paolo Forti
- Department of Earth Sciences and Environmental Geology, University of Bologna, Bologna, Italy
| | - José M. Calaforra
- Department of Biology and Geology, University of Almería, Almería, Spain
- Andalusian Centre for the Monitoring and Assessment of Global Change (CAESCG), University of Almería, Almería, Spain
| |
Collapse
|
3
|
High 3He/ 4He in central Panama reveals a distal connection to the Galápagos plume. Proc Natl Acad Sci U S A 2021; 118:2110997118. [PMID: 34799449 PMCID: PMC8617460 DOI: 10.1073/pnas.2110997118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2021] [Indexed: 11/18/2022] Open
Abstract
We report the discovery of anomalously high 3He/4He in “cold” geothermal fluids of central Panama, far from any active volcanoes. Combined with independent constraints from lava geochemistry, mantle source geochemical anomalies in Central America require a Galápagos plume contribution that is not derived from hotspot track recycling. Instead, these signals likely originate from large-scale transport of Galápagos plume material at sublithospheric depths. Mantle flow modeling and geophysical observations further indicate these geochemical anomalies could result from a Galápagos plume-influenced asthenospheric “mantle wind” that is actively “blowing” through a slab window beneath central Panama. The lateral transport of plume material represents a potentially widespread yet underappreciated mechanism that scatters enriched geochemical signatures in mantle domains far from plumes. It is well established that mantle plumes are the main conduits for upwelling geochemically enriched material from Earth's deep interior. The fashion and extent to which lateral flow processes at shallow depths may disperse enriched mantle material far (>1,000 km) from vertical plume conduits, however, remain poorly constrained. Here, we report He and C isotope data from 65 hydrothermal fluids from the southern Central America Margin (CAM) which reveal strikingly high 3He/4He (up to 8.9RA) in low-temperature (≤50 °C) geothermal springs of central Panama that are not associated with active volcanism. Following radiogenic correction, these data imply a mantle source 3He/4He >10.3RA (and potentially up to 26RA, similar to Galápagos hotspot lavas) markedly greater than the upper mantle range (8 ± 1RA). Lava geochemistry (Pb isotopes, Nb/U, and Ce/Pb) and geophysical constraints show that high 3He/4He values in central Panama are likely derived from the infiltration of a Galápagos plume–like mantle through a slab window that opened ∼8 Mya. Two potential transport mechanisms can explain the connection between the Galápagos plume and the slab window: 1) sublithospheric transport of Galápagos plume material channeled by lithosphere thinning along the Panama Fracture Zone or 2) active upwelling of Galápagos plume material blown by a “mantle wind” toward the CAM. We present a model of global mantle flow that supports the second mechanism, whereby most of the eastward transport of Galápagos plume material occurs in the shallow asthenosphere. These findings underscore the potential for lateral mantle flow to transport mantle geochemical heterogeneities thousands of kilometers away from plume conduits.
Collapse
|
4
|
Incorporating Topological and Age Uncertainty into Event-Based Biogeography of Sand Spiders Supports Paleo-Islands in Galapagos and Ancient Connections among Neotropical Dry Forests. DIVERSITY 2021. [DOI: 10.3390/d13090418] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Event-based biogeographic methods, such as dispersal-extinction-cladogenesis, have become increasingly popular for attempting to reconstruct the biogeographic history of organisms. Such methods employ distributional data of sampled species and a dated phylogenetic tree to estimate ancestral distribution ranges. Because the input tree is often a single consensus tree, uncertainty in topology and age estimates are rarely accounted for, even when they may affect the outcome of biogeographic estimates. Even when such uncertainties are taken into account for estimates of ancestral ranges, they are usually ignored when researchers compare competing biogeographic hypotheses. We explore the effect of incorporating this uncertainty in a biogeographic analysis of the 21 species of sand spiders (Sicariidae: Sicarius) from Neotropical xeric biomes, based on a total-evidence phylogeny including a complete sampling of the genus. Using a custom R script, we account for uncertainty in ages and topology by estimating ancestral ranges over a sample of trees from the posterior distribution of a Bayesian analysis, and for uncertainty in biogeographic estimates by using stochastic maps. This approach allows for counting biogeographic events such as dispersal among areas, counting lineages through time per area, and testing biogeographic hypotheses, while not overestimating the confidence in a single topology. Including uncertainty in ages indicates that Sicarius dispersed to the Galapagos Islands when the archipelago was formed by paleo-islands that are now submerged; model comparison strongly favors a scenario where dispersal took place before the current islands emerged. We also investigated past connections among currently disjunct Neotropical dry forests; failing to account for topological uncertainty underestimates possible connections among the Caatinga and Andean dry forests in favor of connections among Caatinga and Caribbean + Mesoamerican dry forests. Additionally, we find that biogeographic models including a founder-event speciation parameter (“+J”) are more prone to suffer from the overconfidence effects of estimating ancestral ranges using a single topology. This effect is alleviated by incorporating topological and age uncertainty while estimating stochastic maps, increasing the similarity in the inference of biogeographic events between models with or without a founder-event speciation parameter. We argue that incorporating phylogenetic uncertainty in biogeographic hypothesis-testing is valuable and should be a commonplace approach in the presence of rogue taxa or wide confidence intervals in age estimates, and especially when using models including founder-event speciation.
Collapse
|
5
|
Comparative Phylogeography of Floreana's Lizards Supports Galápagos Pleistocene Paleogeographical Model and Informs Conservation Management Decisions. J HERPETOL 2021. [DOI: 10.1670/20-110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
6
|
Phillips JG, Linscott TM, Rankin AM, Kraemer AC, Shoobs NF, Parent CE. Archipelago-Wide Patterns of Colonization and Speciation Among an Endemic Radiation of Galápagos Land Snails. J Hered 2021; 111:92-102. [PMID: 31841140 DOI: 10.1093/jhered/esz068] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 11/08/2019] [Indexed: 01/18/2023] Open
Abstract
Newly arrived species on young or remote islands are likely to encounter less predation and competition than source populations on continental landmasses. The associated ecological release might facilitate divergence and speciation as colonizing lineages fill previously unoccupied niche space. Characterizing the sequence and timing of colonization on islands represents the first step in determining the relative contributions of geographical isolation and ecological factors in lineage diversification. Herein, we use genome-scale data to estimate timing of colonization in Naesiotus snails to the Galápagos islands from mainland South America. We test inter-island patterns of colonization and within-island radiations to understand their contribution to community assembly. Partly contradicting previously published topologies, phylogenetic reconstructions suggest that most Naesiotus species form island-specific clades, with within-island speciation dominating cladogenesis. Galápagos Naesiotus also adhere to the island progression rule, with colonization proceeding from old to young islands and within-island diversification occurring earlier on older islands. Our work provides a framework for evaluating the contribution of colonization and in situ speciation to the diversity of other Galápagos lineages.
Collapse
Affiliation(s)
- John G Phillips
- Department of Biological Sciences, University of Idaho, Moscow ID.,Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho, Moscow, ID.,BEACON Center for Evolution in Action, East Lansing, MI
| | - T Mason Linscott
- Department of Biological Sciences, University of Idaho, Moscow ID.,Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho, Moscow, ID.,BEACON Center for Evolution in Action, East Lansing, MI
| | - Andrew M Rankin
- Department of Biological Sciences, University of Idaho, Moscow ID.,Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho, Moscow, ID.,BEACON Center for Evolution in Action, East Lansing, MI
| | - Andrew C Kraemer
- Department of Biological Sciences, University of Idaho, Moscow ID.,Department of Biology, Creighton University, Omaha, NE
| | - Nathaniel F Shoobs
- Department of Malacology, Academy of Natural Sciences of Drexel University, Philadelphia, PA.,Department of Biodiversity, Earth, and Environmental Science, Drexel University, Philadelphia, PA
| | - Christine E Parent
- Department of Biological Sciences, University of Idaho, Moscow ID.,Institute for Bioinformatics and Evolutionary Studies (IBEST), University of Idaho, Moscow, ID.,BEACON Center for Evolution in Action, East Lansing, MI
| |
Collapse
|
7
|
Arnés-Urgellés C, Buglass S, Ahyong ST, Salinas-de-León P, Wicksten MK, Marsh L. Arthropoda; Crustacea; Decapoda of deep-sea volcanic habitats of the Galapagos Marine Reserve, Tropical Eastern Pacific. Biodivers Data J 2020; 8:e54482. [PMID: 32973394 PMCID: PMC7483338 DOI: 10.3897/bdj.8.e54482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/06/2020] [Indexed: 11/12/2022] Open
Abstract
Background The deep-sea biome (> 200 m depth) is the world's last great wilderness, covering more than 65% of the earth's surface. Due to rapid technological advances, deep-sea environments are becoming more accessible to scientific research and ocean exploration around the world and, in recent years, this is also true for the Galapagos Islands. Deep-sea habitats cover the largest proportion of Galapagos Marine Reserve (GMR), yet to date, no comprehensive baseline exists on the biodiversity of the benthic fauna associated with volcanic seafloor formations within this region. Closing this knowledge gap is essential to provide information for decision-making for the management of marine resources within the GMR and assessing any potential changes in biodiversity resulting from climate-driven alterations that deep-sea environments are expected to experience. In 2015, the Charles Darwin Foundation's Seamounts of the GMR Research Project, together with the Galapagos National Park Directorate (GNPD) and Ocean Exploration Trust (OET), conducted a joint expedition on board the EV Nautilus. Using Remotely operated vehicles (ROVs), the aim of the expedition was to characterise the geological formations and biological communities present on seamounts, lava flows and other deep-sea habitats (> 200 m) within the GMR. New information We provide the first comprehensive image inventory for the phylum Arthropoda from 260 to 3400 m of depth within the GMR. Past studies on deep-sea macroinvertebrates in the GMR have been limited to voucher samples collected from dredging (restricted to soft bottom environments) or by submersibles (only allowing limited biological sampling). The image inventory, presented here, is based on high-definition video transects conducted by the Hercules ROV on board the EV Nautilus. Images of macroinvertebrate morphospecies were captured, catalogued and identified, thus providing the first known image inventory of in-situ macroinvertebrate species from the deep-sea region of the GMR.We present 32 distinct morphospecies occurrences within the class Malacostraca and order Decapoda. We also report 17 different families, three species that are new records to the GMR, in-situ images of two new species to science recently described and one possible new squat lobster, as well as interesting behavioural observations.
Collapse
Affiliation(s)
- Camila Arnés-Urgellés
- Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora, Galapagos, Ecuador Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora Galapagos Ecuador
| | - Salome Buglass
- Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora, Galapagos, Ecuador Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora Galapagos Ecuador
| | - Shane T Ahyong
- Australian Museum Research Institute, 1 William St., Sydney, NSW 2010, Australia and School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, Sydney, Australia Australian Museum Research Institute, 1 William St., Sydney, NSW 2010, Australia and School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington Sydney Australia
| | - Pelayo Salinas-de-León
- Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora, Galapagos, Ecuador Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora Galapagos Ecuador.,Pristine Seas, National Geographic Society, Washington, D.C., United States of America Pristine Seas, National Geographic Society Washington, D.C. United States of America
| | - Mary K Wicksten
- Department of Biology, Texas A&M University, College Station, Texas, United States of America Department of Biology, Texas A&M University, College Station Texas United States of America
| | - Leigh Marsh
- Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora, Galapagos, Ecuador Charles Darwin Research Station, Charles Darwin Foundation, Av. Charles Darwin s/n, Puerto Ayora Galapagos Ecuador.,Ocean and Earth Science, University of Southampton, Waterfront Campus, Southampton, United Kingdom Ocean and Earth Science, University of Southampton, Waterfront Campus Southampton United Kingdom
| |
Collapse
|
8
|
Huppert KL, Perron JT, Royden LH. Hotspot swells and the lifespan of volcanic ocean islands. SCIENCE ADVANCES 2020; 6:eaaw6906. [PMID: 31911939 PMCID: PMC6938699 DOI: 10.1126/sciadv.aaw6906] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 10/24/2019] [Indexed: 06/10/2023]
Abstract
Volcanic ocean islands generally form on swells-seafloor that is shallower than expected for its age over areas hundreds to more than a thousand kilometers wide-and ultimately subside to form atolls and guyots (flat-topped seamounts). The mechanisms of island drowning remain enigmatic, however, and the subaerial lifespan of volcanic islands varies widely. We examine swell bathymetry and island drowning at 14 hotspots and find a correspondence between island lifespan and residence time atop swell bathymetry, implying that islands drown as tectonic plate motion transports them past mantle sources of swell uplift. This correspondence argues strongly for dynamic uplift of the lithosphere at ocean hotspots. Our results also explain global variations in island lifespan, which influence island topography, biodiversity, and climate.
Collapse
Affiliation(s)
- Kimberly L. Huppert
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- GFZ German Research Centre for Geosciences, Earth Surface Process Modelling, 14473 Potsdam, Germany
| | - J. Taylor Perron
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Leigh H. Royden
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| |
Collapse
|
9
|
The 2017 Noneruptive Unrest at the Caldera of Cerro Azul Volcano (Galápagos Islands) Revealed by InSAR Observations and Geodetic Modelling. REMOTE SENSING 2019. [DOI: 10.3390/rs11171992] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
An unrest event occurred at the Cerro Azul volcano, Galápagos Islands, South America, in March 2017, leading to significant surface deformation on the southern Isabela Island, without eruption or surface rupture. We collected single-look complex synthetic aperture radar (SAR) images sensed by the Sentinel-1A satellite, obtaining eight differential interferograms, of which four showed extensive surface displacement during the co-unrest period. Geodetic data indicated that the unrest continued from 18 March to 25 March, reaching a negative peak displacement of −32.9 cm in the caldera and a positive peak displacement of 41.8 cm on the south-east plain in the line-of-sight direction. A joint magma source deformation model, consisting of a Mogi source below the caldera and a sill source south-east of the caldera, was inverted by the Markov chain Monte Carlo method combined with the Metropolis–Hasting algorithm, acquiring the best fit with the four interferograms. The magma transport mechanism of the event was explained by magma overflowing from the compressive Mogi to the tensile sill source, resulting in the observed “∞”-shaped deformation fields. Additionally, we investigated previous events with eruption rifts and lava lakes in 1979, 1998, and 2008, and proposed a potential hazard of tectonic volcanic activity for further volcanic susceptibility research in the Cerro Azul area.
Collapse
|
10
|
Comparative phylogeography of oceanic archipelagos: Hotspots for inferences of evolutionary process. Proc Natl Acad Sci U S A 2017; 113:7986-93. [PMID: 27432948 DOI: 10.1073/pnas.1601078113] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Remote island archipelagos offer superb opportunities to study the evolution of community assembly because of their relatively young and simple communities where speciation contributes to the origin and evolution of community structure. There is great potential for common phylogeographic patterns among remote archipelagos that originate through hotspot volcanism, particularly when the islands formed are spatially isolated and linearly arranged. The progression rule is characterized by a phylogeographic concordance between island age and lineage age in a species radiation. Progression is most likely to arise when a species radiation begins on an older island before the emergence of younger islands of a hotspot archipelago. In the simplest form of progression, colonization of younger islands as they emerge and offer appropriate habitat, is coincident with cladogenesis. In this paper, we review recent discoveries of the progression rule on seven hotspot archipelagos. We then discuss advantages that progression offers to the study of community assembly, and insights that community dynamics may offer toward understanding the evolution of progression. We describe results from two compelling cases of progression where the mosaic genome may offer insights into contrasting demographic histories that shed light on mechanisms of speciation and progression on remote archipelagos.
Collapse
|
11
|
Genome-wide SNPs reveal low effective population size within confined management units of the highly vagile Galapagos shark (Carcharhinus galapagensis). CONSERV GENET 2017. [DOI: 10.1007/s10592-017-0967-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
12
|
Torres-Carvajal O, Rodríguez-Guerra A, Chaves JA. Present diversity of Galápagos leaf-toed geckos (Phyllodactylidae: Phyllodactylus) stems from three independent colonization events. Mol Phylogenet Evol 2016; 103:1-5. [PMID: 27400628 DOI: 10.1016/j.ympev.2016.07.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 05/23/2016] [Accepted: 07/07/2016] [Indexed: 10/21/2022]
Abstract
We re-examined the biogeography of the leaf-toed geckos (Phyllodactylus) endemic to the Galápagos Islands by analyzing for the first time samples of P. gilberti, a species endemic to Wolf island, in a phylogenetic framework. Our aim was to test the three-colonizations scenario previously proposed for these lizards and estimate the age of each colonization event. To achieve this we estimated simultaneously a species tree and divergence times with Bayesian methods. Our results supported the three-colonizations scenario. Similar to a previous hypothesis, the species tree obtained here showed that most species of Phyllodactylus are nested in a single clade with an age between 5.49 and 13.8Ma, whereas a second independent colonization corresponding to P. darwini from San Cristóbal island occurred 3.03Ma ago. The species from Wolf island, P. gilberti, stems from a more recent colonization event (0.69Ma). Thus, present diversity of Galápagos leaf-toed geckos stems from three independent, asynchronous colonization events. As with other Galápagos organisms, the Pacific coast of South America seems to be the source for the founders of P. gilberti.
Collapse
Affiliation(s)
- Omar Torres-Carvajal
- Museo de Zoología, Escuela de Biología, Pontificia Universidad Católica del Ecuador, Avenida 12 de Octubre y Roca, Apartado 17-01-2184, Quito, Ecuador.
| | - Andrea Rodríguez-Guerra
- Museo de Zoología, Escuela de Biología, Pontificia Universidad Católica del Ecuador, Avenida 12 de Octubre y Roca, Apartado 17-01-2184, Quito, Ecuador
| | - Jaime A Chaves
- Universidad San Francisco de Quito, Colegio de Ciencias Biológicas y Ambientales - Extensión Galápagos, Campus Cumbayá, Casilla Postal 17-1200-841, Quito, Ecuador
| |
Collapse
|
13
|
Taylor SJ, Katz AD, Soto-Adames FN, Addison A, Hoese GB, Sutton MR, Toulkeridis T. New records and new species of springtails (Collembola: Entomobryidae, Paronellidae) from lava tubes of the Galápagos Islands (Ecuador). SUBTERRANEAN BIOLOGY 2016. [DOI: 10.3897/subtbiol.17.7660] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
|
14
|
Wolf PG, Rowe CA, Der JP, Schilling MP, Visger CJ, Thomson JA. Origins and diversity of a cosmopolitan fern genus on an island archipelago. AOB PLANTS 2015; 7:plv118. [PMID: 26487677 PMCID: PMC4662730 DOI: 10.1093/aobpla/plv118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 10/09/2015] [Indexed: 05/12/2023]
Abstract
Isolated oceanic islands are characterized by patterns of biological diversity different from that on nearby continental mainlands. Isolation can provide the opportunity for evolutionary divergence, but also set the stage for hybridization between related taxa arriving from different sources. Ferns disperse by haploid spores, which are produced in large numbers and can travel long distances in air currents, enabling these plants to become established on most oceanic islands. Here, we examine the origins and patterns of diversity of the cosmopolitan fern genus Pteridium (Dennstaedtiaceae; bracken) on the Galapagos Islands. We use nucleotide sequences from two plastid genes, and two nuclear gene markers, to examine phylogeography of Pteridium on the Galapagos Islands. We incorporate data from a previous study to provide a worldwide context. We also sampled new specimens from South and Central America. We used flow cytometry to estimate genome size of some accessions. We found that both plastid and nuclear haplotypes fall into two distinct clades, consistent with a two-diploid-species taxonomy of P. aquilinum and P. esculentum. As predicted, the allotetraploid P. caudatum possesses nuclear haplotypes from both diploid species. Samples from the Galapagos include P. esculentum subsp. arachnoideum, P. caudatum and possible hybrids between them. Multiple Pteridium taxa were also observed growing together at some sites. We find evidence for multiple origins of Pteridium on the Galapagos Islands and multiple origins of tetraploid P. caudatum throughout its range in Central and South America. We also posit that P. caudatum may include recent diploid hybrids, backcrosses to P. esculentum, as well as allotetraploid plants. The Galapagos Islands are positioned close to the equator where they can receive dispersing propagules from both hemispheres. This may partly explain the high levels of diversity found for this cosmopolitan fern on these islands.
Collapse
Affiliation(s)
- Paul G Wolf
- Department of Biology, Utah State University, Logan, UT 84322, USA Ecology Center, Utah State University, Logan, UT 84322, USA
| | - Carol A Rowe
- Department of Biology, Utah State University, Logan, UT 84322, USA
| | - Joshua P Der
- Department of Biological Science, California State University, Fullerton, CA 92834, USA
| | | | - Clayton J Visger
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - John A Thomson
- National Herbarium of NSW, Royal Botanic Gardens and Domain Trust, Mrs Macquaries Road, Sydney, NSW 2000, Australia
| |
Collapse
|
15
|
Husemann M, Habel JC, Namkung S, Hochkirch A, Otte D, Danley PD. Molecular evidence for an old world origin of Galapagos and Caribbean band-winged grasshoppers (Acrididae: Oedipodinae: Sphingonotus). PLoS One 2015; 10:e0118208. [PMID: 25692768 PMCID: PMC4334964 DOI: 10.1371/journal.pone.0118208] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 01/12/2015] [Indexed: 11/23/2022] Open
Abstract
Patterns of colonization and diversification on islands provide valuable insights into evolutionary processes. Due to their unique geographic position and well known history, the Galapagos Islands are an important model system for evolutionary studies. Here we investigate the evolutionary history of a winged grasshopper genus to infer its origin and pattern of colonization in the Galapagos archipelago. The grasshopper genus Sphingonotus has radiated extensively in the Palaearctic and many species are endemic to islands. In the New World, the genus is largely replaced by the genus Trimerotropis. Oddly, in the Caribbean and on the Galapagos archipelago, two species of Sphingonotus are found, which has led to the suggestion that these might be the result of anthropogenic translocations from Europe. Here, we test this hypothesis using mitochondrial and nuclear DNA sequences from a broad sample of Sphingonotini and Trimerotropini species from the Old World and New World. The genetic data show two distinct genetic clusters representing the New World Trimerotropini and the Old World Sphingonotini. However, the Sphingonotus species from Galapagos and the Caribbean split basally within the Old World Sphingonotini lineage. The Galapagos and Caribbean species appear to be related to Old World taxa, but are not the result of recent anthropogenic translocations as revealed by divergence time estimates. Distinct genetic lineages occur on the four investigated Galapagos Islands, with deep splits among them compared to their relatives from the Palaearctic. A scenario of a past wider distribution of Sphingonotus in the New World with subsequent extinction on the mainland and replacement by Trimerotropis might explain the disjunct distribution.
Collapse
Affiliation(s)
- Martin Husemann
- Department of Ecology and Ecosystem Management, Terrestrial Ecology Research Group, Technische Universität München, Freising-Weihenstephan, Bavaria, Germany
- Biology Department, Baylor University, Waco, Texas, United States of America
- General Zoology, Institute of Biology, Martin-Luther University Halle-Wittenberg, Halle (Saale), Saxony-Anhalt, Germany
| | - Jan Christian Habel
- Department of Ecology and Ecosystem Management, Terrestrial Ecology Research Group, Technische Universität München, Freising-Weihenstephan, Bavaria, Germany
| | - Suk Namkung
- Biology Department, Baylor University, Waco, Texas, United States of America
| | - Axel Hochkirch
- Department of Biogeography, Trier University, Trier, Rhineland-Palatinate, Germany
| | - Daniel Otte
- Department of Biodiversity, Earth & Environmental Science, Academy of Natural Sciences of Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Patrick D. Danley
- Biology Department, Baylor University, Waco, Texas, United States of America
| |
Collapse
|
16
|
Geist DJ, Snell H, Snell H, Goddard C, Kurz MD. A Paleogeographic Model of the Galápagos Islands and Biogeographical and Evolutionary Implications. THE GALÁPAGOS 2014. [DOI: 10.1002/9781118852538.ch8] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
|
17
|
Jefferson AJ, Ferrier KL, Perron JT, Ramalho R. Controls on the Hydrological and Topographic Evolution of Shield Volcanoes and Volcanic Ocean Islands. THE GALÁPAGOS 2014. [DOI: 10.1002/9781118852538.ch10] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
|
18
|
Mok HF, Stepien CC, Kaczmarek M, Albelo LR, Sequeira AS. Genetic status and timing of a weevil introduction to Santa Cruz Island, Galapagos. J Hered 2014; 105:365-80. [PMID: 24399746 DOI: 10.1093/jhered/est096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Successful invasive species can overcome or circumvent the potential genetic loss caused by an introduction bottleneck through a rapid population expansion and admixture from multiple introductions. We explore the genetic makeup and the timing of a species introduction to Santa Cruz Island in the Galápagos archipelago. We investigate the presence of processes that can maintain genetic diversity in populations of the broad-nosed weevil Galapaganus howdenae howdenae. Analyses of combined genotypes for 8 microsatellite loci showed evidence of past population size reductions through moment and likelihood-based estimators. No evidence of admixture through multiple introductions was found, but substantial current population sizes (N0 298, 95% credible limits 50-2300), genetic diversity comparable with long-established endemics (Mean number of alleles = 3.875), and lack of genetic structure across the introduced range (F ST = 0.01359) could suggest that foundations are in place for populations to rapidly recover any loss of genetic variability. The time estimates for the introduction into Santa Cruz support an accidental transfer during the colonization period (1832-1959) predating the spurt in human population growth. Our evaluation of the genetic status of G. h. howdenae suggests potential for population growth in addition to our field observations of a concurrent expansion in range and feeding preferences towards protected areas and endemic host plants.
Collapse
Affiliation(s)
- Hoi-Fei Mok
- the Department of Biological Sciences, Wellesley College, Wellesley
| | | | | | | | | |
Collapse
|
19
|
Heleno RH, Olesen JM, Nogales M, Vargas P, Traveset A. Seed dispersal networks in the Galápagos and the consequences of alien plant invasions. Proc Biol Sci 2013; 280:20122112. [PMID: 23173203 DOI: 10.1098/rspb.2012.2112] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Alien plants are a growing threat to the Galápagos unique biota. We evaluated the impact of alien plants on eight seed dispersal networks from two islands of the archipelago. Nearly 10 000 intact seeds from 58 species were recovered from the droppings of 18 bird and reptile dispersers. The most dispersed invaders were Lantana camara, Rubus niveus and Psidium guajava, the latter two likely benefiting from an asynchronous fruit production with most native plants, which facilitate their consumption and spread. Lava lizards dispersed the seeds of 27 species, being the most important dispersers, followed by small ground finch, two mockingbirds, the giant tortoise and two insectivorous birds. Most animals dispersed alien seeds, but these formed a relatively small proportion of the interactions. Nevertheless, the integration of aliens was higher in the island that has been invaded for longest, suggesting a time-lag between alien plant introductions and their impacts on seed dispersal networks. Alien plants become more specialized with advancing invasion, favouring more simplified plant and disperser communities. However, only habitat type significantly affected the overall network structure. Alien plants were dispersed via two pathways: dry-fruited plants were preferentially dispersed by finches, while fleshy fruited species were mostly dispersed by other birds and reptiles.
Collapse
Affiliation(s)
- Ruben H Heleno
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
| | | | | | | | | |
Collapse
|
20
|
White WM, Duncan RA. Geochemistry and Geochronology of the Society Islands: New Evidence for Deep Mantle Recycling. EARTH PROCESSES: READING THE ISOTOPIC CODE 2013. [DOI: 10.1029/gm095p0183] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
21
|
Chamorro S, Heleno R, Olesen JM, McMullen CK, Traveset A. Pollination patterns and plant breeding systems in the Galapagos: a review. ANNALS OF BOTANY 2012; 110:1489-501. [PMID: 22691541 PMCID: PMC3489146 DOI: 10.1093/aob/mcs132] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
BACKGROUND Despite the importance of the Galápagos Islands for the development of central concepts in ecology and evolution, the understanding of many ecological processes in this archipelago is still very basic. One such process is pollination, which provides an important service to both plants and their pollinators. The rather modest level of knowledge on this subject has so far limited our predictive power on the consequences of the increasing threat of introduced plants and pollinators to this unique archipelago. SCOPE As a first step toward building a unified view of the state of pollination in the Galápagos, a thorough literature search was conducted on the breeding systems of the archipelago's flora and compiled all documented flower-visitor interactions. Based on 38 studies from the last 100 years, we retrieved 329 unique interactions between 123 flowering plant species (50 endemics, 39 non-endemic natives, 26 introduced and eight of unknown origin) from 41 families and 120 animal species from 13 orders. We discuss the emergent patterns and identify promising research avenues in the field. CONCLUSIONS Although breeding systems are known for <20 % of the flora, most species in our database were self-compatible. Moreover, the incidence of autogamy among endemics, non-endemic natives and alien species did not differ significantly, being high in all groups, which suggests that a poor pollinator fauna does not represent a constraint to the integration of new plant species into the native communities. Most interactions detected (approx. 90 %) come from a single island (most of them from Santa Cruz). Hymenopterans (mainly the endemic carpenter bee Xylocopa darwinii and ants), followed by lepidopterans, were the most important flower visitors. Dipterans were much more important flower visitors in the humid zone than in the dry zone. Bird and lizard pollination has been occasionally reported in the dry zone. Strong biases were detected in the sampling effort dedicated to different islands, time of day, focal plants and functional groups of visitors. Thus, the existing patterns need to be confronted with new and less biased data. The implementation of a community-level approach could greatly increase our understanding of pollination on the islands and our ability to predict the consequences of plant invasions for the natural ecosystems of the Galápagos.
Collapse
Affiliation(s)
- Susana Chamorro
- Mediterranean Institute of Advanced Studies (CSIC-UIB), Terrestrial Ecology Group, Mallorca, Balearic Islands, Spain
- Charles Darwin Foundation, Puerto Ayora, Santa Cruz, Galápagos, Ecuador
| | - Ruben Heleno
- Mediterranean Institute of Advanced Studies (CSIC-UIB), Terrestrial Ecology Group, Mallorca, Balearic Islands, Spain
- Charles Darwin Foundation, Puerto Ayora, Santa Cruz, Galápagos, Ecuador
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - Jens M. Olesen
- Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Conley K. McMullen
- Department of Biology, 820 Madison Drive, MSC 7801, James Madison University, Harrisonburg, VA 22807, USA
| | - Anna Traveset
- Mediterranean Institute of Advanced Studies (CSIC-UIB), Terrestrial Ecology Group, Mallorca, Balearic Islands, Spain
- For correspondence. E-mail
| |
Collapse
|
22
|
Shen Y, Forsyth DW. Geochemical constraints on initial and final depths of melting beneath mid-ocean ridges. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/94jb02768] [Citation(s) in RCA: 187] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
23
|
Ito GT, Lin J. Mantle temperature anomalies along the past and paleoaxes of the Galápagos spreading center as inferred from gravity analyses. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/94jb02594] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
24
|
Reynolds RW, Geist DJ. Petrology of lavas from Sierra Negra volcano, Isabela Island, Galápagos archipelago. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/95jb02809] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
25
|
Bramow C, Hartvig I, Larsen SB, Philipp M. How a heterostylous plant species responds to life on remote islands: a comparative study of the morphology and reproductive biology of Waltheria ovata on the coasts of Ecuador and the Galápagos Islands. Evol Ecol 2012. [DOI: 10.1007/s10682-012-9588-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
26
|
Caetano S, Currat M, Pennington RT, Prado D, Excoffier L, Naciri Y. Recent colonization of the Galápagos by the tree Geoffroea spinosa Jacq. (Leguminosae). Mol Ecol 2012; 21:2743-60. [PMID: 22509817 DOI: 10.1111/j.1365-294x.2012.05562.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This study puts together genetic data and an approximate bayesian computation (ABC) approach to infer the time at which the tree Geoffroea spinosa colonized the Galápagos Islands. The genetic diversity and differentiation between Peru and Galápagos population samples, estimated using three chloroplast spacers and six microsatellite loci, reveal significant differences between two mainland regions separated by the Andes mountains (Inter Andean vs. Pacific Coast) as well as a significant genetic differentiation of island populations. Microsatellites identify two distinct geographical clusters, the Galápagos and the mainland, and chloroplast markers show a private haplotype in the Galápagos. The nuclear distinctiveness of the Inter Andean populations suggests current restricted pollen flow, but chloroplast points to cross-Andean dispersals via seeds, indicating that the Andes might not be an effective biogeographical barrier. The ABC analyses clearly point to the colonization of the Galápagos within the last 160,000 years and possibly as recently as 4750 years ago (475 generations). Founder events associated with colonization of the two islands where the species occurs are detected, with Española having been colonized after Floreana. We discuss two nonmutually exclusive possibilities for the colonization of the Galápagos, recent natural dispersal vs. human introduction.
Collapse
Affiliation(s)
- S Caetano
- Plant Systematics and Biodiversity Laboratory, Molecular Phylogeny and Genetics Unit, Conservatoire et Jardin botaniques, 1 Chemin de l'Impératrice, CP 60, CH-1292 Chambésy, Genève, Switzerland
| | | | | | | | | | | |
Collapse
|
27
|
Sequeira AS, Stepien CC, Sijapati M, Roque Albelo L. Comparative genetic structure and demographic history in endemic galapagos weevils. J Hered 2012; 103:206-20. [PMID: 22174444 PMCID: PMC3283505 DOI: 10.1093/jhered/esr124] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 10/12/2011] [Accepted: 10/12/2011] [Indexed: 11/12/2022] Open
Abstract
The challenge of maintaining genetic diversity within populations can be exacerbated for island endemics if they display population dynamics and behavioral attributes that expose them to genetic drift without the benefits of gene flow. We assess patterns of the genetic structure and demographic history in 27 populations of 9 species of flightless endemic Galápagos weevils from 9 of the islands and 1 winged introduced close relative. Analysis of mitochondrial DNA reveals a significant population structure and moderately variable, though demographically stable, populations for lowland endemics (F(ST) = 0.094-0.541; π: 0.014-0.042; Mismatch P = 0.003-0.026; and D((Tajima)) = -0.601 to 1.203), in contrast to signals of past contractions and expansions in highland specialists on 2 islands (Mismatch P = 0.003-0.026 and D((Tajima)) = -0.601 to 1.203). We interpret this series of variable and highly structured population groups as a system of long-established, independently founded island units, where structuring could be a signal of microallopatric differentiation due to patchy host plant distribution and poor dispersal abilities. We suggest that the severe reduction and subsequent increase of a suitably moist habitat that accompanied past climatic variation could have contributed to the observed population fluctuations in highland specialists. We propose the future exploration of hybridization between the introduced and highland endemic species on Santa Cruz, especially given the expansion of the introduced species into the highlands, the sensitivity to past climatic variation detected in highland populations, and the potentially threatened state of single-island endemics.
Collapse
Affiliation(s)
- Andrea S Sequeira
- Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA.
| | | | | | | |
Collapse
|
28
|
Sari EHR, Parker PG. Understanding the colonization history of the Galápagos flycatcher (Myiarchus magnirostris). Mol Phylogenet Evol 2012; 63:244-54. [PMID: 22348940 DOI: 10.1016/j.ympev.2011.10.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 10/15/2011] [Accepted: 10/30/2011] [Indexed: 11/15/2022]
Abstract
The Galápagos archipelago has never been connected to any continental land masses, so it is of interest to know the colonization and diversification history of its endemic species. We analyzed the phylogenetic placement of the endemic Galápagos flycatcher, M. magnirostris, within Myiarchus by using the genes ND2 and cytb (1970 bp) to compare 16 of the 22 species that comprise this genus. We also analyzed variability in cytb sequences from 154 M. magnirostris individuals captured on seven Galápagos islands. Our phylogenetic analyses recovered the two main Myiarchus clades that had been described by previous genetic, morphological, and vocal analyses. M. magnirostris is monophyletic and its closest living relative is M. tyrannulus from Mexico and Central America. The average age for the split node between these two groups was approximately 850,000 years (95% C.I. 630,735-1,087,557). M. tyrannulus, M. nugator, M. nuttingi, M. sagrae, and M. stolidus are not monophyletic species. Within M. magnirostris itself, we found low nucleotide and haplotype diversities (π=0.0009 and h=0.4913, respectively) and a high genetic structure among populations. We also detected a star-shaped haplotype network and significantly negative values for Tajima's D and Fu's Fs for this species. Our results suggest that M. magnirostris originated from a single colonization event and had a recent population expansion in the Galápagos archipelago.
Collapse
Affiliation(s)
- Eloisa H R Sari
- Department of Biology and Whitney R. Harris World Ecology Center, University of Missouri-St. Louis, One University Boulevard, 223 Research Building, Saint Louis, MO 63121, USA.
| | | |
Collapse
|
29
|
HELENO R, BLAKE S, JARAMILLO P, TRAVESET A, VARGAS P, NOGALES M. Frugivory and seed dispersal in the Galápagos: what is the state of the art? Integr Zool 2011; 6:110-129. [DOI: 10.1111/j.1749-4877.2011.00236.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
30
|
The influence of historical geneflow, bathymetry and distribution patterns on the population genetics of morphologically diverse Galápagos' Opuntia echios. J Mol Evol 2011; 72:315-25. [PMID: 21336620 DOI: 10.1007/s00239-011-9434-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 01/28/2011] [Indexed: 10/18/2022]
Abstract
Throughout history, remote archipelagos have repeatedly been designated natural laboratories to study evolutionary processes. The extensive, geographically structured, morphological variation within Galápagos' Opuntia cacti has been presumed to be another example of how such processes shape diversity. However, recent genetic studies on speciation and potential effects of plasticity within this system failed to confirm earlier classification and hypothesized radiation on both global and single island levels. Detailed population genetic information, however, is crucial in conserving these semi-arid ecosystem keystone species. In this article, we re-evaluate the genetics of Opuntia echios inhabiting one of the most taxon rich places on the archipelago: Santa Cruz and its surrounding satellite islands, using microsatellite data. Our analysis revealed high genetic variability within all sampled locations, providing little support for the hypothesis of clonal reproduction. Inter-island gene flow patterns appear to be largely influenced by bathymetry and sea levels during last ice ages. Although O. echios from Seymour Norte are morphologically recognized as being a separate taxon, Daphné Major's cacti are the most differentiated. In addition, we found a potential barrier for gene flow along the ring-like distribution of Opuntias at the western side of Santa Cruz, suggesting potential links with geology.
Collapse
|
31
|
do Amaral FR, Sheldon FH, Gamauf A, Haring E, Riesing M, Silveira LF, Wajntal A. Patterns and processes of diversification in a widespread and ecologically diverse avian group, the buteonine hawks (Aves, Accipitridae). Mol Phylogenet Evol 2009; 53:703-15. [DOI: 10.1016/j.ympev.2009.07.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 07/18/2009] [Accepted: 07/22/2009] [Indexed: 10/20/2022]
|
32
|
Benavides E, Baum R, Snell HM, Snell HL, Sites JW. Island biogeography of Galápagos lava lizards (Tropiduridae: Microlophus): species diversity and colonization of the archipelago. Evolution 2009; 63:1606-26. [PMID: 19154379 DOI: 10.1111/j.1558-5646.2009.00617.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The "lava lizards" (Microlophus) are distributed throughout the Galápagos Archipelago, and consist of radiations derived from two independent colonizations. The "Eastern Radiation" includes M. bivittatus and M. habeli endemic to San Cristobal and Marchena Islands. The "Western Radiation" includes five to seven historically recognized species distributed across almost the entire Archipelago. We combine dense geographic sampling and multilocus sequence data to estimate a phylogenetic hypothesis for the Western Radiation, to delimit species boundaries in this radiation, and to estimate a time frame for colonization events. Our phylogenetic hypothesis rejects two earlier topologies for the Western Radiation and paraphyly of M. albemarlensis, while providing strong support for single colonizations on each island. The colonization history implied by our phylogeny is consistent with general expectations of an east-to-west route predicted by the putative age of island groups, and prevailing ocean currents in the Archipelago. Additionally, combined evidence suggests that M. indefatigabilis from Santa Fe should be recognized as a full species. Finally, molecular divergence estimates suggest that the two colonization events likely occurred on the oldest existing islands, and the Western Radiation represents a recent radiation that, in most cases, has produced species that are considerably younger than the islands they inhabit.
Collapse
Affiliation(s)
- Edgar Benavides
- Department of Biology, Brigham Young University, Provo, Utah 84602, USA.
| | | | | | | | | |
Collapse
|
33
|
Abstract
Despite the attention given to them, the Galápagos have not yet finished offering evolutionary novelties. When Darwin visited the Galápagos, he observed both marine (Amblyrhynchus) and land (Conolophus) iguanas but did not encounter a rare pink black-striped land iguana (herein referred to as "rosada," meaning "pink" in Spanish), which, surprisingly, remained unseen until 1986. Here, we show that substantial genetic isolation exists between the rosada and syntopic yellow forms and that the rosada is basal to extant taxonomically recognized Galápagos land iguanas. The rosada, whose present distribution is a conundrum, is a relict lineage whose origin dates back to a period when at least some of the present-day islands had not yet formed. So far, this species is the only evidence of ancient diversification along the Galápagos land iguana lineage and documents one of the oldest events of divergence ever recorded in the Galápagos. Conservation efforts are needed to prevent this form, identified by us as a good species, from extinction.
Collapse
|
34
|
Schmitz P, Cibois A, Landry B. Cryptic differentiation in the endemic micromoth Galagete darwini (Lepidoptera, Autostichidae) on Galápagos volcanoes. Philos Trans R Soc Lond B Biol Sci 2008; 363:3453-8. [PMID: 18765358 DOI: 10.1098/rstb.2008.0117] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To gain insight into the early stages of speciation, we reconstructed a DNA-based phylogeny, using combined mitochondrial (cytochrome c oxidase subunits I and II: 1008 bp) and nuclear (elongation factor 1-alpha and wingless: 1062 bp) markers of populations of the moth Galagete darwini endemic to the Galápagos, which belongs to an insular radiation similar in size to that of Darwin's finches. Adults of G. darwini were collected in the arid lowlands of 11 of the Galápagos Islands (Baltra, Española, Fernandina, Floreana, Isabela, Pinta, Pinzón, San Cristobal, Santa Cruz, Santiago and Seymour) and the humid highlands of a subset of 5 of them (Fernandina, Floreana, Isabela, Santa Cruz and Santiago). The combined phylogeographic analysis surprisingly revealed that G. darwini populations at higher elevation on the western islands (Fernandina, Isabela and Santiago) represent a distinct lineage from the one in the low arid zones of these same islands. This is the first reported case in the archipelago of genetic cryptic differentiation correlated with elevation on the western Galápagos volcanoes.
Collapse
Affiliation(s)
- Patrick Schmitz
- Department of Plant and Environmental Protection Sciences, University of Hawaii, 3050 Maile Way, Gilmore 310, Honolulu, HI 96822, USA.
| | | | | |
Collapse
|
35
|
Parent CE, Caccone A, Petren K. Colonization and diversification of Galápagos terrestrial fauna: a phylogenetic and biogeographical synthesis. Philos Trans R Soc Lond B Biol Sci 2008; 363:3347-61. [PMID: 18782729 PMCID: PMC2607378 DOI: 10.1098/rstb.2008.0118] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Remote oceanic islands have long been recognized as natural models for the study of evolutionary processes involved in diversification. Their remoteness provides opportunities for isolation and divergence of populations, which make islands remarkable settings for the study of diversification. Groups of islands may share a relatively similar geological history and comparable climate, but their inhabitants experience subtly different environments and have distinct evolutionary histories, offering the potential for comparative studies. A range of organisms have colonized the Galápagos Islands, and various lineages have radiated throughout the archipelago to form unique assemblages. This review pays particular attention to molecular phylogenetic studies of Galápagos terrestrial fauna. We find that most of the Galápagos terrestrial fauna have diversified in parallel to the geological formation of the islands. Lineages have occasionally diversified within islands, and the clearest cases occur in taxa with very low vagility and on large islands with diverse habitats. Ecology and habitat specialization appear to be critical in speciation both within and between islands. Although the number of phylogenetic studies is continuously increasing, studies of natural history, ecology, evolution and behaviour are essential to completely reveal how diversification proceeded on these islands.
Collapse
Affiliation(s)
- Christine E Parent
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, Canada.
| | | | | |
Collapse
|
36
|
Sequeira AS, Lanteri AA, Albelo LR, Bhattacharya S, Sijapati M. Colonization history, ecological shifts and diversification in the evolution of endemic Galápagos weevils. Mol Ecol 2008; 17:1089-107. [PMID: 18261050 DOI: 10.1111/j.1365-294x.2007.03642.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Mitochondrial DNA sequence data were obtained for eight species of flightless Galapaganus endemic weevils and one winged close relative in order to study their colonization history and modes of diversification in the Galápagos Archipelago. Contrary to most other insular radiations, the phylogeny estimates we recovered for Galapaganus do not follow the progression rule of island biogeography. The penalized likelihood age estimates of colonization of the archipelago exceed the age of the emerged islands and underscore the potential role of now sunken seamounts for the early evolution of Galapaganus. The phylogeny proposes one intra-island origin for Galapaganus endemics, but monophyly tests suggest a larger contribution of in-situ speciation on older islands. Generalist habitat preferences were reconstructed as ancestral while shifts to highland habitats were reconstructed as having evolved independently on different islands. Magnitudes and patterns of diversification rate were found to differ between older and younger islands. Our analyses reveal that the colonization sequence of islands and timing of colonization of Galapaganus could be linked with the geological and volcanic history of the islands in a rather complex scenario. Even though most islands appear to have been colonized soon after their emergence, there are notable deviations from the pattern of sequential colonization expected under the progression rule when considering only the extant emerged islands. Patterns of diversification rate variation on older and younger islands correspond to the volcanic activity or remnants of such activity, while the pattern of independent evolution of restricted habitat preferences in different islands suggests that habitat shifts could also have contributed to species diversity in Galapaganus.
Collapse
Affiliation(s)
- A S Sequeira
- Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA.
| | | | | | | | | |
Collapse
|
37
|
The relationship between hydrodynamic properties and weathering of soils derived from volcanic rocks, Galapagos Islands (Ecuador). ACTA ACUST UNITED AC 2007. [DOI: 10.1007/s00254-007-1138-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
38
|
Schmitz P, Cibois A, Landry B. Molecular phylogeny and dating of an insular endemic moth radiation inferred from mitochondrial and nuclear genes: The genus Galagete (Lepidoptera: Autostichidae) of the Galapagos Islands. Mol Phylogenet Evol 2007; 45:180-92. [PMID: 17604184 DOI: 10.1016/j.ympev.2007.05.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Accepted: 05/09/2007] [Indexed: 11/18/2022]
Abstract
Galagete is a genus of microlepidoptera including 12 nominate species endemic to the Galapagos Islands. In order to better understand the diversification of this endemic insular radiation, to unravel relationships among species and populations, and to get insight into the early stages of speciation, we developed a phylogenetic reconstruction based on the combined mitochondrial cytochrome oxidase I (555bp) and II (453bp), and the nuclear elongation factor-1alpha (711bp) and wingless (351bp) genes. Monophyly of the genus is strongly supported in the Bayesian and maximum likelihood analyses suggesting a single colonization event by a common ancestor. Two cases of paraphyly observed between species are hypothesized to represent imperfect species limits for G. espanolaensis nested within the G. turritella clade, and introgressive hybridization or lineage sorting in the case of the population of G. protozona from Santa Fe nested within the G. gnathodoxa clade. A geologically calibrated, relaxed molecular clock model was used for the first time to unravel the chronological sequence of an insular radiation. The first split occurring within the Galagete lineage on the archipelago is estimated at 3.3+/-0.4million years ago. The genus radiated relatively quickly in about 1.8million years, and gives an estimated speciation rate of 0.8 species per million years. Although the colonization scenario shows a stochastic dispersal pattern, the arrival of the ancestor and the diversification of the radiation coincide with the chronological emergence of the major islands.
Collapse
Affiliation(s)
- Patrick Schmitz
- Department of Entomology, Muséum d'histoire naturelle, C.P. 6434, CH-1211 Geneva 6, Switzerland.
| | | | | |
Collapse
|
39
|
Russello MA, Glaberman S, Gibbs JP, Marquez C, Powell JR, Caccone A. A cryptic taxon of Galápagos tortoise in conservation peril. Biol Lett 2007; 1:287-90. [PMID: 17148189 PMCID: PMC1617146 DOI: 10.1098/rsbl.2005.0317] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
As once boldly stated, 'bad taxonomy can kill', highlighting the critical importance of accurate taxonomy for the conservation of endangered taxa. The concept continues to evolve almost 15 years later largely because most legal protections aimed at preserving biological diversity are based on formal taxonomic designations. In this paper we report unrecognized genetic divisions within the giant tortoises of the Galápagos. We found three distinct lineages among populations formerly considered a single taxon on the most populous and accessible island of Santa Cruz; their diagnosability, degree of genetic divergence and phylogenetic placement merit the recognition of at least one new taxon. These results demonstrate the fundamental importance of continuing taxonomic investigations to recognize biological diversity and designate units of conservation, even within long-studied organisms such as Galápagos tortoises, whose evolutionary heritage and contribution to human intellectual history warrant them special attention.
Collapse
Affiliation(s)
- Michael A Russello
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA.
| | | | | | | | | | | |
Collapse
|
40
|
Parent CE, Crespi BJ. SEQUENTIAL COLONIZATION AND DIVERSIFICATION OF GALAPAGOS ENDEMIC LAND SNAIL GENUS BULIMULUS (GASTROPODA, STYLOMMATOPHORA). Evolution 2006. [DOI: 10.1111/j.0014-3820.2006.tb01867.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
41
|
Parker PG, Whiteman NK, Miller RE. Conservation Medicine on the Galápagos Islands: Partnerships Among Behavioral, Population, and Veterinary Scientists. THE AUK 2006; 123:625-638. [PMID: 32287336 PMCID: PMC7109894 DOI: 10.1093/auk/123.3.625] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Affiliation(s)
- Patricia G Parker
- Department of Biology and International Center for Tropical Ecology, University of Missouri at St. Louis, 8001 Natural Bridge Road, St. Louis, Missouri 63121, USA
- Saint Louis Zoo, 1 Government Drive, St. Louis, Missouri 63110, USA
| | - Noah Kerness Whiteman
- Department of Biology and International Center for Tropical Ecology, University of Missouri at St. Louis, 8001 Natural Bridge Road, St. Louis, Missouri 63121, USA
| | - R Eric Miller
- Saint Louis Zoo, 1 Government Drive, St. Louis, Missouri 63110, USA
| |
Collapse
|
42
|
Bollmer JL, Kimball RT, Whiteman NK, Sarasola JH, Parker PG. Phylogeography of the Galápagos hawk (Buteo galapagoensis): A recent arrival to the Galápagos Islands. Mol Phylogenet Evol 2006; 39:237-47. [PMID: 16376110 DOI: 10.1016/j.ympev.2005.11.014] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 10/05/2005] [Accepted: 11/09/2005] [Indexed: 11/25/2022]
Abstract
Galápagos hawks (Buteo galapagoensis) are one of the most inbred bird species in the world, living in small, isolated island populations. We used mitochondrial sequence and nuclear minisatellite data to describe relationships among Galápagos hawk populations and their colonization history. We sampled 10 populations (encompassing the entire current species range of nine islands and one extirpated population), as well as the Galápagos hawk's closest mainland relative, the Swainson's hawk (B. swainsoni). There was little sequence divergence between Galápagos and Swainson's hawks (only 0.42% over almost 3kb of data), indicating that the hawks colonized Galápagos very recently, likely less than 300,000 years ago, making them the most recent arrivals of the studied taxa. There were only seven, closely related Galápagos hawk haplotypes, with most populations being monomorphic. The mitochondrial and minisatellite data together indicated a general pattern of rapid population expansion followed by genetic isolation of hawk breeding populations. The recent arrival, genetic isolation, and phenotypic differentiation among populations suggest that the Galápagos hawk, a rather new species itself, is in the earliest stages of further divergence.
Collapse
Affiliation(s)
- Jennifer L Bollmer
- Department of Biology, University of Missouri-St. Louis, St. Louis, MO 63121, USA.
| | | | | | | | | |
Collapse
|
43
|
Ciofi C, Wilson GA, Beheregaray LB, Marquez C, Gibbs JP, Tapia W, Snell HL, Caccone A, Powell JR. Phylogeographic history and gene flow among giant Galápagos tortoises on southern Isabela Island. Genetics 2006; 172:1727-44. [PMID: 16387883 PMCID: PMC1456292 DOI: 10.1534/genetics.105.047860] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Accepted: 12/13/2005] [Indexed: 11/18/2022] Open
Abstract
Volcanic islands represent excellent models with which to study the effect of vicariance on colonization and dispersal, particularly when the evolution of genetic diversity mirrors the sequence of geological events that led to island formation. Phylogeographic inference, however, can be particularly challenging for recent dispersal events within islands, where the antagonistic effects of land bridge formation and vicariance can affect movements of organisms with limited dispersal ability. We investigated levels of genetic divergence and recovered signatures of dispersal events for 631 Galápagos giant tortoises across the volcanoes of Sierra Negra and Cerro Azul on the island of Isabela. These volcanoes are among the most recent formations in the Galápagos (<0.7 million years), and previous studies based on genetic and morphological data could not recover a consistent pattern of lineage sorting. We integrated nested clade analysis of mitochondrial DNA control region sequences, to infer historical patterns of colonization, and a novel Bayesian multilocus genotyping method for recovering evidence of recent migration across volcanoes using eleven microsatellite loci. These genetic studies illuminate taxonomic distinctions as well as provide guidance to possible repatriation programs aimed at countering the rapid population declines of these spectacular animals.
Collapse
Affiliation(s)
- Claudio Ciofi
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut 06520, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Parent CE, Crespi BJ. SEQUENTIAL COLONIZATION AND DIVERSIFICATION OF GALÁPAGOS ENDEMIC LAND SNAIL GENUS BULIMULUS (GASTROPODA, STYLOMMATOPHORA). Evolution 2006. [DOI: 10.1554/06-366.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
45
|
Beheregaray LB, Gibbs JP, Havill N, Fritts TH, Powell JR, Caccone A. Giant tortoises are not so slow: rapid diversification and biogeographic consensus in the Galápagos. Proc Natl Acad Sci U S A 2004; 101:6514-9. [PMID: 15084743 PMCID: PMC404076 DOI: 10.1073/pnas.0400393101] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2004] [Accepted: 03/05/2004] [Indexed: 11/18/2022] Open
Abstract
Isolated oceanic archipelagos have played a major role in the development of evolutionary theory by offering a unique setting for studying spatial and temporal patterns of biological diversification. However, the evolutionary events that cause associations between genetic variation and geography in archipelago radiations are largely unknown. This finding is especially true in the Galápagos Islands, where molecular studies have revealed conflicting biogeographic patterns. Here, we elucidate the history of diversification of giant Galápagos tortoises by using mtDNA sequences from 802 individuals representing all known extant populations. We test biogeographic predictions based on geological history and assess the roles of volcano emergence and island formation in driving evolutionary diversification. Patterns of colonization and lineage sorting appear highly consistent with the chronological formation of the archipelago. Populations from older islands are composed exclusively of endemic haplotypes that define divergent monophyletic clades. Younger populations, although currently differentiated, exhibit patterns of colonization, demographic variation and genetic interchange shaped by recent volcanism. Colonization probably occurs shortly after a volcano emerges through range expansion from older volcanoes. Volcanism can also create temporal shifts from historical to recurrent events, such as promoting gene flow by creating land bridges between isolated volcanoes. The association of spatial and temporal patterns of genetic variation with geophysical aspects of the environment can best be attributed to the limited dispersal and migration of tortoises following an oceanographic current. The endangered giant Galápagos tortoises represent a rapid allopatric radiation and further exemplify evolutionary processes in one of the world's greatest natural laboratories of evolution.
Collapse
Affiliation(s)
- Luciano B Beheregaray
- Department of Ecology and Evolutionary Biology, Yale Institute of Biospheric Studies, Yale University, New Haven, CT 06520-8106, USA.
| | | | | | | | | | | |
Collapse
|
46
|
Schaefer BF, Turner S, Parkinson I, Rogers N, Hawkesworth C. Evidence for recycled Archaean oceanic mantle lithosphere in the Azores plume. Nature 2002; 420:304-7. [PMID: 12447437 DOI: 10.1038/nature01172] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2002] [Accepted: 10/01/2002] [Indexed: 11/09/2022]
Abstract
The compositional differences between mid-ocean-ridge and ocean-island basalts place important constraints on the form of mantle convection. Also, it is thought that the scale and nature of heterogeneities within plumes and the degree to which heterogeneous material endures within the mantle might be reflected in spatial variations of basalt composition observed at the Earth's surface. Here we report osmium isotope data on lavas from a transect across the Azores archipelago which vary in a symmetrical pattern across what is thought to be a mantle plume. Many of the lavas from the centre of the plume have lower 187Os/188Os ratios than most ocean-island basalts and some extend to subchondritic 187Os/188Os ratios-lower than any yet reported from ocean-island basalts. These low ratios require derivation from a depleted, harzburgitic mantle, consistent with the low-iron signature of the Azores plume. Rhenium-depletion model ages extend to 2.5 Gyr, and we infer that the osmium isotope signature is unlikely to be derived from Iberian subcontinental lithospheric mantle. Instead, we interpret the osmium isotope signature as having a deep origin and infer that it may be recycled, Archaean oceanic mantle lithosphere that has delaminated from its overlying oceanic crust. If correct, our data provide evidence for deep mantle subduction and storage of oceanic mantle lithosphere during the Archaean era.
Collapse
Affiliation(s)
- Bruce F Schaefer
- Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
| | | | | | | | | |
Collapse
|
47
|
Ciofi C, Milinkovitch MC, Gibbs JP, Caccone A, Powell JR. Microsatellite analysis of genetic divergence among populations of giant Galápagos tortoises. Mol Ecol 2002; 11:2265-83. [PMID: 12406238 DOI: 10.1046/j.1365-294x.2002.01617.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Giant Galápagos tortoises represent an interesting model for the study of patterns of genetic divergence and adaptive differentiation related to island colonization events. Recent mitochondrial DNA work elucidated the evolutionary history of the species and helped to clarify aspects of nomenclature. We used 10 microsatellite loci to assess levels of genetic divergence among and within island populations. In particular, we described the genetic structure of tortoises on the island of Isabela, where discrimination of different taxa is still subject of debate. Individual island populations were all genetically distinct. The island of Santa Cruz harboured two distinct populations. On Isabela, populations of Volcan Wolf, Darwin and Alcedo were significantly different from each other. On the other hand, Volcan Wolf showed allelic similarity with the island of Santiago. On Southern Isabela, lower genetic divergence was found between Northeast Sierra Negra and Volcan Alcedo, while patterns of gene flow were recorded among tortoises of Cerro Azul and Southeast Sierra Negra. These tortoises have endured heavy exploitation during the last three centuries and recently attracted much concern due to the current number of stochastic and deterministic threats to extant populations. Our study complements previous investigation based on mtDNA diversity and provides further information that may help devising tortoise management plans.
Collapse
Affiliation(s)
- Claudio Ciofi
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520-8106, USA.
| | | | | | | | | |
Collapse
|
48
|
Caccone A, Gentile G, Gibbs JP, Frirts TH, Snell HL, Betts J, Powell JR. Phylogeography and history of giant Galápagos tortoises. Evolution 2002; 56:2052-66. [PMID: 12449492 DOI: 10.1111/j.0014-3820.2002.tb00131.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We examined the phylogeography and history of giant Galápagos tortoise populations based on mitochondrial DNA sequence data from 161 individuals from 21 sampling sites representing the 11 currently recognized extant taxa. Molecular clock and geological considerations indicate a founding of the monophyletic Galápagos lineage around 2-3 million years ago, which would allow for all the diversification to have occurred on extant islands. Founding events generally occurred from geologically older to younger islands with some islands colonized more than once. Six of the 11 named taxa can be associated with monophyletic maternal lineages. One, Geochelone porteri on Santa Cruz Island, consists of two distinct populations connected by the deepest node in the archipelago-wide phylogeny, whereas tortoises in northwest Santa Cruz are closely related to those on adjacent Pinzón Island. Volcan Wolf, the northernmost volcano of Isabela Island, consists of both a unique set of maternal lineages and recent migrants from other islands, indicating multiple colonizations possibly due to human transport or multiple colonization and partial elimination through competition. These genetic findings are consistent with the mixed morphology of tortoises on this volcano. No clear genetic differentiation between two taxa on the two southernmost volcanoes of Isabela was evident. Extinction of crucial populations by human activities confounds whether domed versus saddleback carapaces of different populations are mono- or polyphyletic. Our findings revealed a complex phylogeography and history for this tortoise radiation within an insular environment and have implications for efforts to conserve these endangered biological treasures.
Collapse
Affiliation(s)
- Adalgisa Caccone
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut 06520-8106, USA.
| | | | | | | | | | | | | |
Collapse
|
49
|
Kerr AC, Tarney J, Kempton PD, Spadea P, Nivia A, Marriner GF, Duncan RA. Pervasive mantle plume head heterogeneity: Evidence from the late Cretaceous Caribbean-Colombian oceanic plateau. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/2001jb000790] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Andrew C. Kerr
- Department of Earth Sciences; Cardiff University; Cardiff UK
| | - John Tarney
- Department of Geology; University of Leicester; Leicester UK
| | | | - Piera Spadea
- Dipartimento di Georisorse E Territorio; Università Degli Studi di Udine; Udine Italy
| | | | | | - Robert A. Duncan
- College of Oceanography; Oregon State University; Corvallis Oregon USA
| |
Collapse
|
50
|
Caccone A, Gentile G, Gibbs JP, Fritts TH, Snell HL, Betts J, Powell JR. PHYLOGEOGRAPHY AND HISTORY OF GIANT GALÁPAGOS TORTOISES. Evolution 2002. [DOI: 10.1554/0014-3820(2002)056[2052:pahogg]2.0.co;2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|