NEUTRAL MODELS FAIL TO REPRODUCE OBSERVED SPECIES–AREA AND SPECIES–TIME RELATIONSHIPS IN KANSAS GRASSLANDS

In contrast to competing explanations of species-area relationships (SARs), neutral theory is dynamic, meaning that it should explain patterns in both space and time. However, most empirical tests of neutral theory have relied on snapshots, such as com- parisons of observed and simulated SARs observed at one point in time. I used 35 years of data from permanent plots in Kansas grasslands to test the ability of strict and modified neutral models to reproduce observed species-area and species-time relationships (STRs). Holding species density to observed values, the models could generate realistic SARs or STRs, but not both simultaneously. Parameter combinations that simulated realistic STRs led to SARs with extremely steep slopes. To examine the consequences of relaxing neu- trality, I incorporated plant functional types into the model. More realistic dominance produced only limited improvement in the simulated results, and indicates that the models' primary flaw is their failure to reproduce rapid but spatially correlated changes in species composition. In these grasslands, characterized by large interannual variation in resources and many short-lived species, functional differences among species play a strong role in driving macroscopic patterns. The results emphasize the need to test neutral models, and other dynamic community models, with spatiotemporal data.

[1]  S. Pimm,et al.  Forest losses predict bird extinctions in eastern North America. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[2]  O. Arrhenius,et al.  Species and Area , 1921 .

[3]  Stephen P. Hubbell,et al.  Tree Dispersion, Abundance, and Diversity in a Tropical Dry Forest , 1979, Science.

[4]  P. Chesson,et al.  Environmental Variability Promotes Coexistence in Lottery Competitive Systems , 1981, The American Naturalist.

[5]  Brian J. McGill,et al.  Strong and weak tests of macroecological theory , 2003 .

[6]  G. Bell.  Neutral macroecology. , 2001, Science.

[7]  B. McGill.  A test of the unified neutral theory of biodiversity , 2003, Nature.

[8]  R. Ricklefs,et al.  A comment on Hubbell's zero‐sum ecological drift model , 2003 .

[9]  P. Adler,et al.  The power of time: spatiotemporal scaling of species diversity , 2003 .

[10]  Charting Quadrats with a Pantograph , 1920 .

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

[12]  B. A. Maurer,et al.  Spatial and temporal patterns of species diversity in montane mammal communities of western North America , 2001 .

[13]  Kinzig,et al.  Self-similarity in the distribution and abundance of species , 1999, Science.

[14]  R. May.  Patterns of species abundance and diversity , 1975 .

[15]  S. Hubbell,et al.  Neutral theory and relative species abundance in ecology , 2003, Nature.

[16]  Michael L. Rosenzweig.  14. Preston’s Ergodic Conjecture: The Accumulation of Species in Space and Time , 2001 .

[17]  G. E. Hutchinson,et al.  The Balance of Nature and Human Impact: The paradox of the plankton , 2013 .

[18]  Kalle Ruokolainen,et al.  Dispersal, Environment, and Floristic Variation of Western Amazonian Forests , 2003, Science.

[19]  F. W. Preston.  The Commonness, And Rarity, of Species , 1948 .

[20]  S. Hubbell.  Modes of speciation and the lifespans of species under neutrality: a response to the comment of robe , 2003 .

[21]  R. Mittermeier,et al.  Biodiversity hotspots for conservation priorities , 2000, Nature.

[22]  Richard F. Harner,et al.  The Role of Area, Heterogeneity, and Favorability in Plant Species Diversity of Pinyon‐Juniper Ecosystems , 1976 .

[23]  F. W. Albertson,et al.  Vegation Changes During a 30‐Year Period in Grassland Communities Near Hays, Kansas , 1965 .

[24]  F. W. Preston.  Time and Space and the Variation of Species , 1960 .

[25]  J. Lawton.  Are there general laws in ecology , 1999 .

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

[27]  T. Stohlgren,et al.  Comparison of rangeland vegetation sampling techniques in the Central Grasslands , 1998 .

[28]  H. Gleason.  Species and Area , 1925 .

[29]  C. E. Pake,et al.  Is Coexistence of Sonoran Desert Annuals Mediated by Temporal Variability Reproductive Success , 1995 .

[30]  Michael L. Rosenzweig,et al.  Species Diversity in Space and Time , 1997 .

[31]  Graham Bell,et al.  The Distribution of Abundance in Neutral Communities , 2000, The American Naturalist.

[32]  A. Shmida,et al.  Biological determinants of species diversity , 1985 .

[33]  N I , 2008 .

[34]  Hal Caswell,et al.  Community Structure: A Neutral Model Analysis , 1976 .