Impacts of climate variability and human colonization on the vegetation of the Galápagos Islands.

A high-resolution (2-9 year sampling interval) fossil pollen record from the Galápagos Islands, which spans the last 2690 years, reveals considerable ecosystem stability. Vegetation changes associated with independently derived histories of El Niño Southern Oscillation variability provided evidence of shifts in the relative abundance of individual species rather than immigration or extinction. Droughts associated with the Medieval Climate Anomaly induced rapid ecological change that was followed by a reversion to the previous state. The paleoecological data suggested nonneutral responses to climatic forcing in this ecosystem prior to the period of human influence. Human impacts on the islands are evident in the record. A marked decline in long-term codominants of the pollen record, Alternanthera and Acalypha, produced a flora without modern analogue before 1930. Intensified animal husbandry after ca. 1930 may have induced the local extinction of Acalypha and Alternanthera. Reductions in populations of grazing animals in the 1970s and 1980s did not result in the return of the native flora, but in invasions by exotic species. After ca. 1970 the trajectory of habitat change accelerated, continuously moving the ecosystem away from the observed range of variability in the previous 2690 years toward a novel ecosystem. The last 40 years of the record also suggest unprecedented transport of lowland pollen to the uplands, consistent with intensified convection and warmer wet seasons.

[1]  M. Leng,et al.  Ecosystem Resilience and Threshold Response in the Galápagos Coastal Zone , 2011, PloS one.

[2]  S. Hubbell,et al.  The unified neutral theory of biodiversity and biogeography at age ten. , 2011, Trends in ecology & evolution.

[3]  N. Stansell,et al.  A 2,300-year-long annually resolved record of the South American summer monsoon from the Peruvian Andes , 2011, Proceedings of the National Academy of Sciences.

[4]  M. Bush,et al.  An analysis of modern pollen representation and climatic conditions on the Galápagos Islands , 2011 .

[5]  N. d’Ozouville,et al.  Characterizing the Galapagos terrestrial climate in the face of global climate change , 2010 .

[6]  G. Faluvegi,et al.  Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly , 2009, Science.

[7]  S. Golubić,et al.  Southward movement of the Pacific intertropical convergence zone AD 1400-1850 , 2009 .

[8]  R. Ricklefs,et al.  Adaptation and diversification on islands , 2009, Nature.

[9]  J. Overpeck,et al.  Unprecedented recent warming of surface temperatures in the eastern tropical Pacific Ocean , 2009 .

[10]  A. Caccone,et al.  Colonization and diversification of Galápagos terrestrial fauna: a phylogenetic and biogeographical synthesis , 2008, Philosophical Transactions of the Royal Society B: Biological Sciences.

[11]  B. Grant,et al.  Fission and fusion of Darwin's finches populations , 2008, Philosophical Transactions of the Royal Society B: Biological Sciences.

[12]  J. Overpeck,et al.  Holocene changes in eastern tropical Pacific climate inferred from a Galápagos lake sediment record , 2008 .

[13]  Peter R. Grant,et al.  Evolution of Character Displacement in Darwin's Finches , 2006, Science.

[14]  L. Orlóci,et al.  Multiscale analysis of palynological records: new possibilities , 2006 .

[15]  D. Richardson,et al.  Novel ecosystems: theoretical and management aspects of the new ecological world order , 2006 .

[16]  F. Sirocko,et al.  El Niño variability off Peru during the last 20,000 years , 2005 .

[17]  N. P. Smith,et al.  Flowering plants of the neotropics. , 2004 .

[18]  F. Sirocko,et al.  A major Holocene ENSO anomaly during the Medieval period , 2004 .

[19]  Donlan,et al.  Eradication of feral goats Capra hircus from Pinta Island, Galápagos, Ecuador , 2004, Oryx.

[20]  O. Hamann Demographic studies of three indigenous stand-forming plant taxa (Scalesia, Opuntia, and Bursera) in the Galápagos Islands, Ecuador , 2001, Biodiversity & Conservation.

[21]  O. Hamann On vegetation recovery, goats and giant tortoises on Pinta Island, Galápagos, Ecuador , 1993, Biodiversity & Conservation.

[22]  P. Reimer,et al.  Discussion: Reporting and Calibration of Post-Bomb 14C Data , 2004, Radiocarbon.

[23]  B. Grant,et al.  What Darwin's Finches Can Teach Us about the Evolutionary Origin and Regulation of Biodiversity , 2003 .

[24]  R. Lawrence Edwards,et al.  El Niño/Southern Oscillation and tropical Pacific climate during the last millennium , 2003, Nature.

[25]  James S. Clark,et al.  Stability of forest biodiversity , 2003, Nature.

[26]  O. Hamann Vietation changes over three decades on Santa Fe Island, Galhpagos, Ecuador , 2003 .

[27]  S. Renner,et al.  A new Miconia (Melastomatacaeae) from Bolivia, with remarks on angular-branched species in the Andes , 2003 .

[28]  David M. Anderson,et al.  Variability of El Niño/Southern Oscillation activity at millennial timescales during the Holocene epoch , 2002, Nature.

[29]  M. Steinitz‐Kannan,et al.  A ∼6100 14C yr record of El Niño activity from the Galápagos Islands , 2002 .

[30]  J. Grehan Biogeography and evolution of the Galapagos: integration of the biological and geological evidence , 2001 .

[31]  J. Terborgh,et al.  DOMINANCE AND DISTRIBUTION OF TREE SPECIES IN UPPER AMAZONIAN TERRA FIRME FORESTS , 2001 .

[32]  M. Bush,et al.  Reproductive ecology and pollen representation among neotropical trees , 2001 .

[33]  N. Arens Variation in performance of the tree fern Cyathea caracasana (Cyatheaceae) across a successional mosaic in an Andean cloud forest. , 2001 .

[34]  B. Grant,et al.  Effects of El Niño events on Darwin's finch productivity , 2000 .

[35]  M. Wikelski,et al.  Marine iguanas shrink to survive El Niño , 2000, Nature.

[36]  N. Arens,et al.  Distribution of Tree Ferns (Cyatheaceae) across the Successional Mosaic in an Andean Cloud Forest, Narino, Colombia , 1998 .

[37]  M. Steinitz-Kannan,et al.  Un registro de 6000 años de manifestaciones intensas del fenómeno de El Niño en sedimentos de lagunas de las islas Galápagos , 1998, Bulletin de l’Institut français d’études andines.

[38]  D. Pauly Anecdotes and the shifting baseline syndrome of fisheries. , 1995, Trends in ecology & evolution.

[39]  S. Itow Phytogeography and Ecology of Scalesia (Compositae) Endemic to the Galapagos Islands , 1995 .

[40]  Peter W. Glynn,et al.  Eastern Pacific sea surface temperature since 1600 A , 1994 .

[41]  W. G. Waateringe The effects of grazing on the pollen production of grasses , 1993 .

[42]  O. Sala,et al.  Effects of grazing on seedling establishment: the role of seed and safe-site availability , 1990 .

[43]  O. Latorre The curse of the giant tortoise : tragedies, mysteries and crimes in the galapagos islands , 1990 .

[44]  B. Grant,et al.  The Extraordinary El Niño Event of 1982-83: Effects on Darwin's Finches on Isla Genovesa, Galápagos@@@The Extraordinary El Nino Event of 1982-83: Effects on Darwin's Finches on Isla Genovesa, Galapagos , 1987 .

[45]  Hugh G. Gauch,et al.  Multivariate analysis in community ecology , 1984 .

[46]  James H. Brown,et al.  Turnover Rates in Insular Biogeography: Effect of Immigration on Extinction , 1977 .

[47]  P. Colinvaux,et al.  Historical Ecology in the Galapagos Islands: I. A Holocene Pollen Record from El Junco Lake, Isla San Cristobal , 1976 .

[48]  C. S. Holling Resilience and Stability of Ecological Systems , 1973 .

[49]  P. Colinvaux Climate and the Galapagos Islands , 1972, Nature.

[50]  W. Steere,et al.  Flora of the Galapagos Islands , 1971 .

[51]  J. Stockmarr Tablets with spores used in absolute pollen analysis , 1971 .

[52]  K. Faegri,et al.  Textbook of Pollen Analysis , 1965 .

[53]  H. K. Svenson VEGETATION OF THE COAST OF ECUADOR AND PERU AND ITS RELATION TO THAT OF THE GALAPAGOS ISLANDS. II. CATALOGUE OF PLANTS , 1946 .

[54]  C. H. Townsend The Galapagos tortoises : in their relation to the whaling industry , 1925 .

[55]  B. Robinson Flora of the Galapagos Islands , 2013, Contributions from the Gray Herbarium of Harvard University.

[56]  R. Fitzroy Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle between the years 1826 and 1836, describing their examination of the southern shores of South America, and the Beagle's circumnavigation of the globe. , 1839 .