World Library  
Flag as Inappropriate
Email this Article

Priority effect

Article Id: WHEBN0026956160
Reproduction Date:

Title: Priority effect  
Author: World Heritage Encyclopedia
Language: English
Subject: Landscape ecology, Relative abundance distribution, Ascendency, Gradient analysis, Functional ecology
Publisher: World Heritage Encyclopedia

Priority effect

In ecology, a priority effect is the impact that a particular species can have on community development due to prior arrival at a site.[1][2][3]

There are two basic types: inhibitory priority effects occur when a species that arrives first at a site negatively impacts a species that arrives later by reducing the availability of space or resources. Facilitative priority effects occur when a species that arrives first at a site alters abiotic or biotic conditions in ways that positively impact a species arriving later.[3][4] Priority effects are a central and pervasive element of ecological community development. These effects have important implications for natural systems as well as ecological restoration efforts.[3][5]

Theoretical foundation

Community succession theory

Early in the 20th century, [7]

Early ecological succession theory maintained that the directional shifts from one stage of succession to the next were induced by the plants themselves.[8] In this sense, succession theory implicitly recognized priority effects; the prior arrival of certain species had important impacts on future community composition. At the same time, the climax concept implied that species shifts were predetermined. A given species would always appear at the same point during the development of the climax community, and always have the same impact on community development.

This static view of priority effects remained essentially unchanged by the concept of patch dynamics, which was introduced by Alex Watt in 1947.[9] Watt conceived of plant communities as dynamic "mechanisms" that followed predetermined succession cycles. Although Watt questioned the idea of a stable endpoint to community development, he seemed to agree with Clements that each particular species had a predetermined role to play in community development. They viewed succession as a process driven by facilitation, in which each species made local conditions more suitable for another species.

Individualistic approach

In 1926, [10] Gleason suggested that the distribution of various species across the landscape reflected species-specific dispersal limitations and environmental requirements rather than predetermined associations among species. Gleason set the stage for future research on priority effects by explaining that initially identical ponds colonized by different species could develop through succession into very different communities. Thus, Gleason contested the idea of a predetermined climax community and recognized that different colonizing species could produce alternative trajectories of community development.

Frank Egler (1954) built on Gleason's hypothesis by developing the Initial Floristic Composition model to describe community development in abandoned agricultural fields.[11] According to this model, the set of species present in a field immediately after abandonment had strong influences on community development and final community composition. Although rooted in succession theory, this approach foreshadowed the development of alternative stable state and community assembly theory.[1]

Alternative stable states

In the 1970s, it was suggested that natural communities could be characterized by multiple or alternative stable states.[12][13][14] In accordance with the conclusions of Gleason and Egler, multiple stable state models indicated that the same environment could support several different combinations of species.[10][11] Theorists argued that historical context could play a central role in determining which stable state would be present at any given time. Robert May explained, "If there is a unique stable state, historical accidents are unimportant; if there are many alternative locally stable states, historical accidents can be of overriding significance."[14]

Community assembly theory

The development of assembly theory followed from the emergence of alternative stable state theory. Assembly theory explains community development processes in the context of multiple stable states. It asks why a particular type of community developed when other stable community types were possible. In contrast to succession theory, assembly theory was developed largely by animal ecologists and explicitly incorporated historical context.[1]

In one of the first models based on this theory, Jared Diamond (1975)[15] developed quantitative "assembly rules" to predict avian community composition on an archipelago. Although the idea of deterministic community assembly quickly drew criticism,[16] the assembly approach, which emphasized historical contingency and multiple stable states, continued to gain support.[14][17] Drake (1991) used an assembly model to demonstrate that different community types would result from different sequences of species invasions.[18] In Drake’s model, early invaders had major impacts on the invasion success of species that arrived later. Other modeling studies suggested that priority effects may be especially important when invasion frequency is low enough to allow species to become established before replacement,[19] or when other factors that could drive assembly (e.g., competition, abiotic stress) are relatively unimportant.[20] In a 1999 review, Belyea and Lancaster described three basic determinants of community assembly: dispersal constraints, environmental constraints, and internal dynamics.[21] They identified priority effects as a manifestation of the interaction between dispersal constraints and internal dynamics.

Empirical evidence

On January 25, 2007, a search of the ISI Web of Science citation index using the key word "priority effect*" returned 65 ecology-related studies. The first study to explicitly mention priority effects was published in 1983. Although early research focused on animals and aquatic systems, more recent studies have begun to examine terrestrial and plant-based priority effects. Inhibitory priority effects have been documented more frequently than facilitative priority effects. Priority effects among species within the same trophic level and functional group, or guild, have been documented more frequently than effects across trophic levels or guilds. Studies indicate that both abiotic (e.g. resource availability) and biotic (e.g. predation) factors can affect the strength of priority effects.


Most of the earliest empirical evidence for priority effects came from studies on aquatic animals. Sutherland (1974) found that final community composition varied depending on the initial order of larval recruitment in a community of small aquatic organisms (sponges, tunicates, hydroids, and other species).[22] Shulman (1983) and Almany (2003) found strong priority effects among coral reef fish.[23][24] The former study found that prior establishment by a territorial damselfish reduced establishment rates of other fish. The authors also identified cross-trophic priority effects; prior establishment by a predator fish reduced establishment rates of prey fishes.

In the late 1980s, several studies examined priority effects in aquatic microcosms. Robinson and Dickerson (1987) found that priority effects were important in some cases, but suggested, "Being the first to invade a habitat does not guarantee success; there must be sufficient time for the early colonist to increase its population size for it to pre-empt further colonization."[25] Robinson and Edgemon (1988) later developed 54 communities of phytoplankton species by varying invasion order, rate, and timing. They found that although invasion order (priority effects) could explain a small fraction of the resulting variation in community composition, most of the variation was explained by changes in invasion rate and invasion timing.[26] These studies indicate that priority effects may not be the only or the most important historical factor affecting the trajectory of community development.

In a striking example of cross-trophic priority effects, Hart (1992) found that priority effects explain the maintenance of two alternate stable states in stream ecosystems. While a macroalga is dominant in some patches, sessile grazers maintain a "lawn" of small microalgae in others. If the sessile grazers colonize a patch first, they exclude the macroalga, and vice versa.[27]


In two of the most commonly cited empirical studies on priority effects, Alford and Wilbur documented inhibitory and facilitative priority effects among and toad larvae in experimental ponds.[28][29] They found that hatchlings of a toad species (Bufo americanus) exhibited higher growth and survivorship when introduced to a pond before those of a frog species (Rana sphenocephala). The frog larvae, however, did best when introduced after the toad larvae. Thus, prior establishment by the toad species facilitated the frog species, while prior establishment by the frog species inhibited the toad species. Studies on tree frogs have also documented both types of priority effect.[30][31] Morin (1987) also observed that priority effects became less important in the presence of a predatory salamander. He hypothesized that predation mediated priority effects by reducing competition between frog species.[30] Studies on larval insects and frogs in water-filled tree holes and stumps found that abiotic factors such as space, resource availability, and toxin levels can also be important in mediating priority effects.[32][33]


Terrestrial studies on priority effects are rare. The aforementioned ISI Web of Science search retrieved only 19 studies on fully terrestrial organisms, and all of these studies were published during or after 1993. Most studies have focused on arthropods or grassland plant species. In a lab experiment, Shorrocks and Bingley (1994) showed that prior arrival increased survivorship for two species of fruit flies; each fly species had inhibitory impacts on the other.[34] A 1996 field study on desert spiders by Ehmann and MacMahon showed that the presence of species from one spider guild reduced establishment of spiders from a different guild.[35] More recently, Palmer (2003) demonstrated that priority effects allowed a competitively subordinate ant species to avoid exclusion by a competitively dominant species.[36] If the competitively subordinate ants were able to colonize first, they altered their host tree’s morphology in ways that made it less suitable for other ant species. This study was especially important because it was able to identify a mechanism driving observed priority effects.

With the exception of an early study exploring the facilitative effects of litter deposition,[37] studies that explicitly addressed terrestrial plant priority effects began to appear in the literature around the year 2000. A study on two species of introduced grasses in Hawaiian woodlands found that the species with inferior competitive abilities may be able to persist through priority effects.[38] At least three studies have come to similar conclusions about the coexistence of native and exotic grasses in California grassland ecosystems.[39][40][41] If given time to establish, native species can successfully inhibit the establishment of exotics. Authors of the various studies attributed the prevalence of exotic grasses in California to the low seed production and relatively poor dispersal ability of native species.

Emerging concepts

Long-term implications: convergence and divergence

Although many studies have documented priority effects, the persistence of these effects over time often remains unclear. Young(2001) indicated that both convergence (in which "communities proceed towards a predisturbance state regardless of historical conditions") and divergence (in which historical factors continue to affect the long-term trajectory of community development) are present in nature.[1] Among studies of priority effects, both trends seem to have been observed.[2][27] Fukami (2005) argued that a community could be both convergent and divergent at different levels of community organization. The authors studied experimentally-assembled plant communities and found that while the identities of individual species remained unique across different community replicates, species traits generally became more similar.[3]

Trophic ecology

Some studies indicate that priority effects can occur across guilds[35] or trophic levels.[27] Such priority effects could have dramatic impacts on community composition and food web structure. Even intra-guild priority effects could have important consequences at multiple trophic levels if the affected species are associated with unique predator or prey species. Consider, for example, a plant species that is eaten by a host-specific herbivore. Priority effects that influence the ability of the plant species to establish would indirectly affect the establishment success of the associated herbivore. Theoretical models have described cyclical assembly dynamics in which species associated with different suites of predators are able to repeatedly replace one another.[42][43]

Intraspecific aggregation

In situations where two species are introduced at the same time, spatial aggregation of a species' propagules could cause priority effects by initially reducing interspecific competition.[44] Aggregation during recruitment and establishment could allow inferior competitors to coexist with or even displace competitive dominants over the long-term. Several modeling efforts have begun to examine the implications of spatial priority effects for species coexistence.[34][45][46][47] Rejmanek (2002) suggested that only 10 empirical studies examining intraspecific aggregation had been published by 2002.[48]

Mechanisms and new organisms

The literature on priority effects is currently growing in both depth and breadth. A few studies have begun to explore the mechanisms driving observed priority effects.[36] Moreover, although past studies focused on a small subset of species, recent papers indicate that priority effects may be important for a wide range of organisms, including fungi,[49][50] birds,[51] lizards,[52] and salamanders.[53]

Ecological restoration

Priority effects have important implications for ecological restoration. In many systems, information about priority effects can help practitioners identify cost-effective strategies for improving the survival and persistence of certain species, especially species of inferior competitive ability.[2][5][54] For example, in a study on the restoration of native Californian grasses and forbs, Lulow (2004) found that forbs could not establish in plots where she had previously planted bunchgrasses. When bunchgrasses were added to plots where forbs had already been growing for a year, forbs were able to coexist with grasses for at least 3–4 years. Lulow’s results suggested that planting forbs before grasses might improve forb persistence in this system.[2]


  1. ^ a b c d Young, Truman P.; Chase, Jonathan M.; Huddleston, Russell T. (2001-03-20). "Community Succession and Assembly Comparing, Contrasting and Combining Paradigms in the Context of". Ecological Restoration 19 (1): 5–18.  
  2. ^ a b c d Lulow, Megan Elizabeth (2004). Restoration of California's Inland Grasslands: The Role of Priority Effects and Management Strategies in Establishing Native Communities and the Ability of Native Grasses to Resist Invasion by Non-native Grasses (Ph.D.). University of California, Davis. 
  3. ^ a b c d Fukami, Tadashi; Martijn Bezemer, T.; Mortimer, Simon R.; van der Putten, Wim H. (2005-12-01). "Species divergence and trait convergence in experimental plant community assembly". Ecology Letters 8 (12): 1283–1290.  
  4. ^ Connell, Joseph H; Slatyer, Ralph O (1977). "Mechanisms of succession in natural communities and their role in community stability and organization". American naturalist: 1119–1144.  
  5. ^ a b Young, T. P.; Petersen, D. A.; Clary, J. J. (2005-06-01). "The ecology of restoration: historical links, emerging issues and unexplored realms". Ecology Letters 8 (6): 662–673.  
  6. ^ Clements, Frederic E. (1936-02). "Nature and Structure of the Climax". The Journal of Ecology 24 (1): 252.  
  7. ^ Clements, Frederic Edward (1916). Plant Succession: An Analysis of the Development of Vegetation. Carnegie Institution of Washington. 
  8. ^ Tansley, A. G. (1935-07). "The Use and Abuse of Vegetational Concepts and Terms". Ecology 16 (3): 284–307.  
  9. ^ Watt, Alex S. (1947-12). "Pattern and Process in the Plant Community". The Journal of Ecology 35 (1/2): 1–22.  
  10. ^ a b Gleason, H. A. (1926-01). "The Individualistic Concept of the Plant Association". Bulletin of the Torrey Botanical Club 53 (1): 7.  
  11. ^ a b Egler, Frank E. (1954-11-01). "Vegetation science concepts I. Initial floristic composition, a factor in old-field vegetation development with 2 figs.". Vegetatio 4 (6): 412–417.  
  12. ^ Lewontin, R C (1969). "The meaning of stability". Brookhaven symposia in biology 22: 13–24.  
  13. ^ Holling, Crawford S (1973). "Resilience and stability of ecological systems". Annual review of ecology and systematics: 1–23.  
  14. ^ a b c May, Robert M (1977). "Thresholds and breakpoints in ecosystems with a multiplicity of stable states". Nature 269 (5628): 471–477.  
  15. ^ Diamond, Jared M. (1975-01-01). "Assembly of speceis communities". In Cody, Martin L.; Diamond, Jared M. Ecology and Evolution of Communities. Harvard University Press. pp. 342–444.  
  16. ^ Connor, Edward F.; Simberloff, Daniel (1979-12). "The Assembly of Species Communities: Chance or Competition?". Ecology 60 (6): 1132.  
  17. ^ Hughes, Terence P. (1989-02). "Community Structure and Diversity of Coral Reefs: The Role of History". Ecology 70 (1): 275.  
  18. ^ Drake, James A (1991). "Community-assembly mechanics and the structure of an experimental species ensemble". American Naturalist: 1–26.  
  19. ^ Lockwood, Julie L.; Powell, Robert D.; Nott, M. Philip; Pimm, Stuart L. (1997-12). "Assembling Ecological Communities in Time and Space". Oikos 80 (3): 549.  
  20. ^ Weiher, E.; Keddy, P. A. (1995). "Assembly rules, null models, and trait dispersion: new questions front old patterns". Oikos 74: 159–164.  
  21. ^ Belyea, Lisa R.; Lancaster, Jill (1999-09). "Assembly Rules within a Contingent Ecology". Oikos 86 (3): 402.  
  22. ^ Sutherland, John P (1974). "Multiple stable points in natural communities". American Naturalist 108 (964): 859–873.  
  23. ^ Shulman, Myra J.; Ogden, John C.; Ebersole, John P.; McFarland, William N.; Miller, Steven L.; Wolf, Nancy G. (1983-12-01). "Priority Effects in the Recruitment of Juvenile Coral Reef Fishes". Ecology 64 (6): 1508–1513.  
  24. ^ Almany, Glenn R. (2003-07-01). "Priority Effects in Coral Reef Fish Communities". Ecology 84 (7): 1920–1935.  
  25. ^ Robinson, James F.; Dickerson, Jaime E. (1987-06-01). "Does Invasion Sequence Affect Community Structure?". Ecology 68 (3): 587–595.  
  26. ^ Robinson, James V.; Edgemon, Michael A. (1988-10). "An Experimental Evaluation of the Effect of Invasion History on Community Structure". Ecology 69 (5): 1410–1417.  
  27. ^ a b c Hart, David D. (1992-08-01). "Community organization in streams: the importance of species interactions, physical factors, and chance". Oecologia 91 (2): 220–228.  
  28. ^ Alford, Ross A.; Wilbur, Henry M. (1985-08-01). "Priority Effects in Experimental Pond Communities: Competition between Bufo and Rana". Ecology 66 (4): 1097–1105.  
  29. ^ Wilbur, Henry M.; Alford, Ross A. (1985-08). "Priority Effects in Experimental Pond Communities: Responses of Hyla to Bufo and Rana". Ecology 66 (4): 1106–1114.  
  30. ^ a b Morin, Peter Jay (1987-06-01). "Predation, Breeding Asynchrony, and the Outcome of Competition Among Treefrog Tadpoles". Ecology 68 (3): 675–683.  
  31. ^ Warner, Susan C.; Dunson, William A.; Travis, Joseph (1991-11-01). "Interaction of pH, density, and priority effects on the survivorship and growth of two species of hylid tadpoles". Oecologia 88 (3): 331–339.  
  32. ^ Fincke, OlA. M. (1999-02-01). "Organization of predator assemblages in Neotropical tree holes: effects of abiotic factors and priority". Ecological Entomology 24 (1): 13–23.  
  33. ^ Sunahara, Toshihiko; Mogi, Motoyoshi (2002-06-01). "Priority effects of bamboo-stump mosquito larvae: influences of water exchange and leaf litter input". Ecological Entomology 27 (3): 346–354.  
  34. ^ a b Shorrocks, B.; Bingley, M. (1994). "Priority effects and species coexistence: experiments with fungal-breeding Drosophila". Journal of animal ecology 63 (4): 799–806.  
  35. ^ a b Ehmann, William J; MacMahon, James A (1996). "Initial tests for priority effects among spiders that co-occur on sagebrush shrubs". Journal of Arachnology 24 (3): 173–185.  
  36. ^ a b Palmer, Todd M.; Stanton, Maureen L.; Young, Truman P. (2003-10). "Competition and Coexistence: Exploring Mechanisms That Restrict and Maintain Diversity within Mutualist Guilds". The American Naturalist 162 (s4): S63–S79.  
  37. ^ Facelli, J. M.; Facelli, E. (1993-08-01). "Interactions after death: plant litter controls priority effects in a successional plant community". Oecologia 95 (2): 277–282.  
  38. ^ D'Antonio, Carla M.; Hughes, R. Flint; Vitousek, Peter M. (2001-01-01). "Factors Influencing Dynamics of two Invasive C4 Grasses in Seasonally Dry Hawaiian Woodlands". Ecology 82 (1): 89–104.  
  39. ^ Seabloom, Eric W.; Harpole, W. Stanley; Reichman, O. J.; Tilman, David (2003-11-11). "Invasion, competitive dominance, and resource use by exotic and native California grassland species". Proceedings of the National Academy of Sciences 100 (23): 13384–13389.  
  40. ^ Corbin, Jeffrey D.; D'Antonio, Carla M. (2004-05-01). "Competition Between Native Perennial and Exotic Annual Grasses: Implications for a Historical Invasion". Ecology 85 (5): 1273–1283.  
  41. ^ Lulow, Megan E. (2006-12-01). "Invasion by Non-Native Annual Grasses: The Importance of Species Biomass, Composition, and Time Among California Native Grasses of the Central Valley". Restoration Ecology 14 (4): 616–626.  
  42. ^ Leibold, M. A.; Holyoak, M.; Mouquet, N.; Amarasekare, P.; Chase, J. M.; Hoopes, M. F.; Holt, R. D.; Shurin, J. B.; Law, R.; Tilman, D.; Loreau, M.; Gonzalez, A. (2004-07-01). "The metacommunity concept: a framework for multi-scale community ecology". Ecology Letters 7 (7): 601–613.  
  43. ^ Steiner, Christopher F.; Leibold, Mathew A. (2004-01-01). "Cyclic assembly trajectories and scale-dependent productivity–diversity relationships". Ecology 85 (1): 107–113.  
  44. ^ Inouye, Brian D. (1999-01-01). "Integrating nested spatial scales: implications for the coexistence of competitors on a patchy resource". Journal of Animal Ecology 68 (1): 150–162.  
  45. ^ Chesson, Peter (2000). "Mechanisms of Maintenance of Species Diversity". Annual Review of Ecology and Systematics 31 (1): 343–366.  
  46. ^ Hartley, Stephen; Shorrocks, Bryan (2002-07-01). "A general framework for the aggregation model of coexistence". Journal of Animal Ecology 71 (4): 651–662.  
  47. ^ Molofsky, Jane; Bever, James D. (2002-12-07). "A novel theory to explain species diversity in landscapes: positive frequency dependence and habitat suitability". Proceedings of the Royal Society of London. Series B: Biological Sciences 269 (1508): 2389–2393.  
  48. ^ Rejmanek, M. (2002). "Intraspecific aggregation and species coexistence". Trends in Ecology & Evolution 17: 209–210.  
  49. ^ Kennedy, Peter G.; Bruns, Thomas D. (2005-05-01). "Priority effects determine the outcome of ectomycorrhizal competition between two Rhizopogon species colonizing Pinus muricata seedlings". New Phytologist 166 (2): 631–638.  
  50. ^ Rohlfs, Marko (2005-09-01). "Density-dependent insect-mold interactions: effects on fungal growth and spore production". Mycologia 97 (5): 996–1001.  
  51. ^ Gamarra, Javier G. P.; Montoya, José M.; Alonso, David; Solé, Ricard V. (2005-03-01). "Competition and introduction regime shape exotic bird communities in Hawaii". Biological Invasions 7 (2): 297–307.  
  52. ^ M'Closkey, Robert T.; Hecnar, Stephen J.; Chalcraft, David R.; Cotter, Jill E. (1998-10-01). "Size distributions and sex ratios of colonizing lizards". Oecologia 116 (4): 501–509.  
  53. ^ Eitam, Avi; Blaustein, Leon; Mangel, Marc (2005-11-01). "Density and intercohort priority effects on larval Salamandra salamandra in temporary pools". Oecologia 146 (1): 36–42.  
  54. ^ Suding, Katharine N.; Gross, Katherine L.; Houseman, Gregory R. (2004-01-01). "Alternative states and positive feedbacks in restoration ecology". Trends in Ecology & Evolution 19 (1): 46–53.  
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.