Polar Biology

, Volume 38, Issue 11, pp 1881–1890 | Cite as

The abundance structure of Azorella selago Hook. f. on sub-Antarctic Marion Island: testing the peak and tail hypothesis

  • Ethel E. Phiri
  • Melodie A. McGeoch
  • Steven L. ChownEmail author
Original Paper


Understanding the spatial distribution of organisms and the factors underlying it are key questions in ecology. Two competing hypotheses exist about the form of spatial variation in abundance. The abundant centre hypothesis suggests that abundance is highest in the centre of a species’ range and declines towards the range margins. By contrast, the peak and tail spatial pattern in abundance posits that several high abundance areas exist across a species range. Here, we test these competing hypotheses by surveying the abundance of the keystone plant species Azorella selago Hook. f. (Apiaceae) across sub-Antarctic Marion Island on a regular spatial grid. We also examine several factors that might explain variation in abundance. Azorella selago occurs between ca. 30 and 850 m above sea level, with sharp discontinuities in abundance at ca. 30 m and at 667 m a.s.l. The survey and analyses revealed a complex abundance structure with patches of high abundance alternating with areas of low abundance or absence, providing support for the peak and tail hypothesis, but with some support for the abundant centre idea too. Variation in abundance was best explained by a model including the negative effects of elevation and of closed vegetation. Our work provides support for the peak and tail pattern of spatial variation in abundance, which has profound importance for understanding the mechanisms underlying the spatial distribution of abundance and other macroecological regularities.


Abundance Abundant centre hypothesis Cushion plant Range limits Spatial aggregation 



We thank Asanda Phiri for assistance in the field, the South African National Antarctic Programme for logistic support, and three anonymous reviewers for their comments. This work was funded by the United States Agency for International Development (USAID), DST-NRF Centre of Excellence for Invasion Biology and National Research Foundation (SNA2011110700005 and SNA14071475789).

Supplementary material

300_2015_1749_MOESM1_ESM.docx (22 kb)
Supplementary material 1 (DOCX 21 kb)
300_2015_1749_MOESM2_ESM.docx (36 kb)
Supplementary material 2 (DOCX 35 kb)
300_2015_1749_MOESM3_ESM.docx (25 kb)
Supplementary material 3 (DOCX 24 kb)


  1. Barendse J, Chown SL (2001) Abundance and seasonality of mid-altitude fellfield arthropods from Marion Island. Polar Biol 24:73–82CrossRefGoogle Scholar
  2. Boelhouwers JC, Meiklejohn KI, Holness SD, Hedding DW (2008) Geology, geomorphology and climate change. In: Chown SL, Froneman PW (eds) The Prince Edward Islands. Land-sea interactions in a changing ecosystem. Sun Press, Stellenbosch, pp 65–96Google Scholar
  3. Born C, le Roux PC, Spohr C, McGeoch MA, van Vuuren BJ (2012) Plant dispersal in the sub-Antarctic inferred from anisotropic genetic structure. Mol Ecol 21:184–194CrossRefPubMedGoogle Scholar
  4. Brown JH (1984) On the relationship between abundance and distribution of species. Am Nat 124:255–279CrossRefGoogle Scholar
  5. Case TJ, Taper ML (2000) Interspecific competition, environmental gradients, gene flow, and the coevolution of species’ borders. Am Nat 155:583–605CrossRefPubMedGoogle Scholar
  6. Caughley G, Grice D, Barker R, Brown B (1988) The edge of the range. J Anim Ecol 57:771–785CrossRefGoogle Scholar
  7. Chown SL, Froneman PW (eds) (2008) The Prince Edward Islands. Land-sea interactions in a changing ecosystem. Sun Press, StellenboschGoogle Scholar
  8. Coomes DA, Rees M, Turnbull L (1999) Identifying aggregation and association in fully mapped spatial data. Ecology 80:554–565CrossRefGoogle Scholar
  9. Crafford JE, Chown SL (1991) Comparative nutritional ecology of bryophyte and angiosperm feeders in a sub-Antarctic weevil species complex (Coleoptera: Curculionidae). Ecol Entomol 16:323–329CrossRefGoogle Scholar
  10. Crawley MJ (2013) The R book, 2nd edn. Wiley, ChichesterGoogle Scholar
  11. Frenot Y, Gloaguen JC, Picot G, Bougére J, Benjamin D (1993) Azorella selago Hook. used to estimate glacier fluctuations and climatic history in the Kerguelen Islands over the last two centuries. Oecologia 95:140–144CrossRefGoogle Scholar
  12. Gaston KJ (2003) The structure and dynamics of geographic ranges. Oxford University Press, OxfordGoogle Scholar
  13. Gaston KJ, Blackburn TM (2000) Pattern and process in macroecology. Blackwell Science, OxfordCrossRefGoogle Scholar
  14. Gremmen NJM (1981) The vegetation of the subantarcic islands Marion and Prince Edward. Junk Press, The HagueGoogle Scholar
  15. Gremmen NJM, Smith VR (2008) Terrestrial vegetation and dynamics. In: Chown SL, Froneman PW (eds) The Prince Edward Islands. Land-sea interactions in a changing ecosystem. Sun Press, Stellenbosch, pp 215–244Google Scholar
  16. Hall K (1980) Late glacial ice cover and paleotemperatures on sub-Antarctic Marion Island. Paleogeogr Paleoclimatol Paleoecol 29:243–254CrossRefGoogle Scholar
  17. Hamill DN, Wright SJ (1986) Testing the dispersion of juveniles relative to adults: a new analytic method. Ecology 67:952–957CrossRefGoogle Scholar
  18. Haussmann NS, Boelhouwers JC, McGeoch MA (2009a) Fine scale variability in soil frost dynamics surrounding cushions of the dominant vascular plant species (Azorella selago) on sub-Antarctic Marion Island. Geogr Ann 91:257–268CrossRefGoogle Scholar
  19. Haussmann NS, McGeoch MA, Boelhouwers JC (2009b) Interactions between a cushion plant (Azorella selago) and surface sediment transport on sub-Antarctic Marion Island. Geomorphology 107:139–148CrossRefGoogle Scholar
  20. Haussmann NS, McGeoch MA, Boelhouwers JC (2010) Contrasting nurse plants and nurse rocks: the spatial distribution of seedlings of two sub-Antarctic species. Acta Oecol 36:299–305CrossRefGoogle Scholar
  21. He F, Gaston KJ (2000) Occupancy-abundance relationships and sampling scales. Ecography 23:503–511CrossRefGoogle Scholar
  22. Hedding DW (2006) Geomorphology and geomorphological responses to climate change in the interior of sub-Antarctic Marion Island. MSc Thesis, University of PretoriaGoogle Scholar
  23. Hugo EA, McGeoch MA, Marshall DJ, Chown SL (2004) Fine scale variation in microarthropod communities inhabiting the keystone species Azorella selago on Marion Island. Polar Biol 27:466–473CrossRefGoogle Scholar
  24. Hui C, McGeoch MA (2007) Capturing the “droopy-tail” in the occupancy-abundance relationship. Ecoscience 14:103–108CrossRefGoogle Scholar
  25. Hui C, Veldtman R, McGeoch MA (2010) Measures, perceptions and scaling patterns of aggregated species distributions. Ecography 33:95–102CrossRefGoogle Scholar
  26. Huntley BJ (1970) Altitudinal distribution and phenology of Marion Island vascular plants. Tydskrif Natuurwet 10:225–262Google Scholar
  27. Huntley BJ (1972) Notes on the ecology of Azorella selago Hook. f. J S Afr Bot 38:103–113Google Scholar
  28. Jackman S (2012) pscl: classes and methods for R developed in the political science computational laboratory, Stanford University. Department of Political Science, Stanford University. Stanford, California, R package version 1.04.4.
  29. le Roux PC (2008) Climate and climate change. In: Chown SL, Froneman PW (eds) The Prince Edward Islands. Land-sea interactions in a changing ecosystem. Sun Press, Stellenbosch, pp 39–64Google Scholar
  30. le Roux PC, McGeoch MA (2004) The use of size as an estimator of age in the subantarctic cushion plant, Azorella selago (Apiaceae). Arct Antarct Alp Res 36:509–517CrossRefGoogle Scholar
  31. le Roux PC, McGeoch MA (2008a) Rapid range expansion and community reorganization in response to warming. Global Change Biol 14:2950–2962CrossRefGoogle Scholar
  32. le Roux PC, McGeoch MA (2008b) Spatial variation in plant interactions across a severity gradient in the sub-Antarctic. Oecologia 155:831–844CrossRefPubMedGoogle Scholar
  33. le Roux PC, McGeoch MA (2010) Interaction intensity and importance along two stress gradients: adding shape to the stress-gradient hypothesis. Oecologia 162:733–745CrossRefPubMedGoogle Scholar
  34. le Roux PC, McGeoch MA, Nyakatya MJ, Chown SL (2005) Effects of a short-term climate change experiment on a sub-Antarctic keystone plant species. Global Change Biol 11:1628–1639CrossRefGoogle Scholar
  35. le Roux PC, Shaw JD, Chown SL (2013a) Ontogenetic shifts in plant interactions vary with environmental severity and affect population structure. New Phytol 200:241–250CrossRefPubMedGoogle Scholar
  36. le Roux PC, Ramaswiela T, Kalwij JM, Shaw JD, Ryan PG, Treasure AM, McClelland GTW, McGeoch MA, Chown SL (2013b) Human activities, propagule pressure, and alien plants in the sub-Antarctic: tests of generalities and evidence in support of management. Biol Conserv 161:18–27CrossRefGoogle Scholar
  37. Lee JE, Janion C, Marais E, Van Vuuren BJ, Chown SL (2009) Physiological tolerances account for range limits and abundance structure in an invasive slug. Proc R Soc B 276:1459–1468PubMedCentralCrossRefPubMedGoogle Scholar
  38. Legendre L, Legendre P (1998) Numerical ecology. Elsevier, AmsterdamGoogle Scholar
  39. McGeoch MA, Gaston KJ (2002) Occupancy frequency distributions: patterns, artefacts and mechanisms. Biol Rev 77:311–331CrossRefPubMedGoogle Scholar
  40. McGeoch MA, Price PW (2004) Spatial abundance structures in an assemblage of gall-forming sawflies. J Anim Ecol 73:506–516CrossRefGoogle Scholar
  41. McGeoch MA, le Roux PC, Hugo EA, Chown SL (2006) Species and community responses to short-term climate manipulation: microarthropods in the sub-Antarctic. Austral Ecol 31:719–731CrossRefGoogle Scholar
  42. McGeoch MA, le Roux PC, Hugo EA, Nyakatya MJ (2008) Spatial variation in the terrestrial biotic system. In: Chown SL, Froneman PW (eds) The Prince Edward Islands. Land-sea interactions in a changing ecosystem. Sun Press, Stellenbosch, pp 245–276Google Scholar
  43. McGill BJ (2010) Towards a unification of unified theories of biodiversity. Ecol Lett 13:627–642CrossRefPubMedGoogle Scholar
  44. McGill BJ, Collins M (2003) A unified theory for macroecology based on spatial patterns of abundance. Evol Ecol Res 5:469–492Google Scholar
  45. Mortimer E, McGeoch MA, Daniels SR, Jansen van Vuuren B (2008) Growth form and population genetic structure of Azorella selago on sub-Antarctic Marion Island. Antarct Sci 20:381–390CrossRefGoogle Scholar
  46. Murphy HT, van der Wal J, Lovett-Doust J (2006) Distribution of abundance across the range in eastern North American trees. Global Ecol Biogeogr 15:63–71CrossRefGoogle Scholar
  47. Nicolas AN, Plunkett GM (2012) Untangling generic limits in Azorella, Laretia, and Mulinum (Apiaceae: Azorelloideae): insights from phylogenetics and biogeography. Taxon 61:826–840Google Scholar
  48. Nyakatya MJ, McGeoch MA (2008) Temperature variation across Marion Island associated with a keystone plant species (Azorella selago Hook. (Apiaceae)). Polar Biol 31:139–151CrossRefGoogle Scholar
  49. Phiri EE, McGeoch MA, Chown SL (2009) Spatial variation in structural damage to a keystone plant species in the sub-Antarctic: interactions between Azorella selago and invasive house mice. Antarct Sci 21:189–196CrossRefGoogle Scholar
  50. Raunkiær C (1934) The life forms of plants and statistical plant geography. Oxford University Press, OxfordGoogle Scholar
  51. R Core Team (2012) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0,
  52. Rossi RE, Mulla DJ, Journel AG, Franz EH (1992) Geostatistical tools for modeling and interpreting ecological spatial dependence. Ecol Monogr 62:277–314CrossRefGoogle Scholar
  53. Sagarin RD, Gaines SD (2002a) Geographical abundance distributions of coastal invertebrates: using one-dimensional ranges to test biogeographic hypotheses. J Biogeogr 29:985–997CrossRefGoogle Scholar
  54. Sagarin RD, Gaines SD (2002b) The ‘abundant centre’ distribution: to what extent is it a biogeographical rule? Ecol Lett 5:137–147CrossRefGoogle Scholar
  55. Sagarin RD, Gaines SD, Gaylord B (2006) Moving beyond assumptions to understand abundance distributions across the ranges of species. Trends Ecol Evol 21:524–530CrossRefPubMedGoogle Scholar
  56. Samaniego H, Marquet PA (2013) Range structure analysis: unveiling the internal structure of species ranges. Theor Ecol 6:419–426CrossRefGoogle Scholar
  57. Samis KE, Eckert CG (2007) Testing the abundant centre model using range-wide demographic surveys of two coastal dune plants. Ecology 88:1747–1758CrossRefPubMedGoogle Scholar
  58. Smith VR, Steenkamp M, Gremmen NJM (2001) Terrestrial habitats on sub-Antarctic Marion Island: their vegetation, edaphic attributes, distribution and response to climate change. S Afr J Bot 67:641–654CrossRefGoogle Scholar
  59. Sumner PD, Meiklejohn KI, Boelhouwers JC, Hedding DW (2004) Climate change melts Marion Island’s snow and ice. S Afr J Sci 100:395–398Google Scholar
  60. Treasure AM, Chown SL (2014) Antagonistic effects of biological invasion and temperature change on body size of island ectotherms. Divers Distrib 20:202–213CrossRefGoogle Scholar
  61. Yeloff D, Mauquoy D, Barber K, Way S, van Geel B, Turney CSM (2007) Volcanic ash deposition and long-term vegetation change on Subantarctic Marion Island. Arct Antarct Alp Res 39:500–511CrossRefGoogle Scholar
  62. Zeileis A, Hothorn A (2002) Diagnostic checking in regression relationships. R News 2:7–10Google Scholar
  63. Zimmermann DL, Zimmermann MB (1991) A comparison of spatial semivariogram estimators and corresponding ordinary kriging predictors. Technometrics 33:77–91CrossRefGoogle Scholar
  64. Zuur AF, Ieno EN, Walker NJ, Saveliev AA, Smith GM (2009) Mixed effects models and extensions in ecology with R. Springer, New YorkCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Ethel E. Phiri
    • 1
  • Melodie A. McGeoch
    • 1
    • 2
  • Steven L. Chown
    • 1
    • 2
    Email author
  1. 1.Centre for Invasion Biology, Department of Botany and ZoologyStellenbosch UniversityMatielandSouth Africa
  2. 2.School of Biological SciencesMonash UniversityVictoriaAustralia

Personalised recommendations