THE MAINTENANCE OF SPECIES‐RICHNESS IN PLANT COMMUNITIES: THE IMPORTANCE OF THE REGENERATION NICHE

THE MAINTENANCE OF SPECIES‐RICHNESS IN PLANT COMMUNITIES: THE IMPORTANCE OF THE REGENERATION NICHE SUMMARY 1 According to ‘Gause's hypothesis’ a corollary of the process of evolution by natural selection is that in a community at equilibrium every species must occupy a different niche. Many botanists have found this idea improbable because they have ignored the processes of regeneration in plant communities. 2 Most plant communities are longer‐lived than their constituent individual plants. When an individual dies, it may or may not be replaced by an individual of the same species. It is this replacement stage which is all‐important to the argument presented. 3 Several mechanisms not involving regeneration also contribute to the maintenance of species‐richness: (a). differences in life‐form coupled with the inability of larger plants to exhaust or cut off all resources, also the development of dependence‐relationships, (b) differences in phenology coupled with tolerance of suppression, (c) fluctuations in the environment coupled with relatively small differences in competitive ability between many species, (d) the ability of certain species‐pairs to form stable mixtures because of a balance of intraspecific competition against interspecific competition, (e) the production of substances more toxic to the producer‐species than to the other species, (f) differences in the primary limiting mineral nutrients or pore‐sizes in the soil for neighbouring plants of different soecies, and (g) differences in the competitive abilities of species dependent on their physiological age coupled with the uneven‐age structure of many populations. 4 The mechanisms listed above do not go far to explain the indefinite persistence in mixture of the many species in the most species‐rich communities known. 5 In contrast there seem to be almost limitless possibilities for differences between species in their requirements for regeneration, i.e. the replacement of the individual plants of one generation by those of the next. This idea is illustrated for tree species and it is emphasized that foresters were the first by a wide margin to appreciate its importance. 6 The processes involved in the successful invasion of a gap by a given plant species and some characters of the gap that may be important are summarized in Table 2. 7 The definition of a plant's niche requires recognition of four components: (a) the habitat niche, (b) the life‐form niche, (c) the phenological niche, and (d) the regeneration niche. 8 A brief account is given of the patterns of regeneration in different kinds of plant community to provide a background for studies of differentiation in the regeneration niche. 9 All stages in the regeneration‐cycle are potentially important and examples of differentiation between species are given for each of the following stages: (a) Production of viable seed (including the sub‐stages of flowering, pollination and seed‐set), (b) dispersal, in space and time, (c) germination, (d) establishment, and (e) further development of the immature plant. 10 In the concluding discussion emphasis is placed on the following themes: (a) the kinds of work needed in future to prove or disprove that differentiation in the regeneration niche is the major explanation of the maintenance of species‐richness in plant communities, (b) the relation of the present thesis to published ideas on the origin of phenological spread, (c) the relevance of the present thesis to the discussion on the presence of continua in vegetation, (d) the co‐incidence of the present thesis and the emerging ideas of evolutionists about differentiation of angiosperm taxa, and (e) the importance of regeneration‐studies for conservation. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biological Reviews Wiley

THE MAINTENANCE OF SPECIES‐RICHNESS IN PLANT COMMUNITIES: THE IMPORTANCE OF THE REGENERATION NICHE

Biological Reviews, Volume 52 (1) – Feb 1, 1977

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Publisher
Wiley
Copyright
Copyright © 1977 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1464-7931
eISSN
1469-185X
DOI
10.1111/j.1469-185X.1977.tb01347.x
Publisher site
See Article on Publisher Site

Abstract

SUMMARY 1 According to ‘Gause's hypothesis’ a corollary of the process of evolution by natural selection is that in a community at equilibrium every species must occupy a different niche. Many botanists have found this idea improbable because they have ignored the processes of regeneration in plant communities. 2 Most plant communities are longer‐lived than their constituent individual plants. When an individual dies, it may or may not be replaced by an individual of the same species. It is this replacement stage which is all‐important to the argument presented. 3 Several mechanisms not involving regeneration also contribute to the maintenance of species‐richness: (a). differences in life‐form coupled with the inability of larger plants to exhaust or cut off all resources, also the development of dependence‐relationships, (b) differences in phenology coupled with tolerance of suppression, (c) fluctuations in the environment coupled with relatively small differences in competitive ability between many species, (d) the ability of certain species‐pairs to form stable mixtures because of a balance of intraspecific competition against interspecific competition, (e) the production of substances more toxic to the producer‐species than to the other species, (f) differences in the primary limiting mineral nutrients or pore‐sizes in the soil for neighbouring plants of different soecies, and (g) differences in the competitive abilities of species dependent on their physiological age coupled with the uneven‐age structure of many populations. 4 The mechanisms listed above do not go far to explain the indefinite persistence in mixture of the many species in the most species‐rich communities known. 5 In contrast there seem to be almost limitless possibilities for differences between species in their requirements for regeneration, i.e. the replacement of the individual plants of one generation by those of the next. This idea is illustrated for tree species and it is emphasized that foresters were the first by a wide margin to appreciate its importance. 6 The processes involved in the successful invasion of a gap by a given plant species and some characters of the gap that may be important are summarized in Table 2. 7 The definition of a plant's niche requires recognition of four components: (a) the habitat niche, (b) the life‐form niche, (c) the phenological niche, and (d) the regeneration niche. 8 A brief account is given of the patterns of regeneration in different kinds of plant community to provide a background for studies of differentiation in the regeneration niche. 9 All stages in the regeneration‐cycle are potentially important and examples of differentiation between species are given for each of the following stages: (a) Production of viable seed (including the sub‐stages of flowering, pollination and seed‐set), (b) dispersal, in space and time, (c) germination, (d) establishment, and (e) further development of the immature plant. 10 In the concluding discussion emphasis is placed on the following themes: (a) the kinds of work needed in future to prove or disprove that differentiation in the regeneration niche is the major explanation of the maintenance of species‐richness in plant communities, (b) the relation of the present thesis to published ideas on the origin of phenological spread, (c) the relevance of the present thesis to the discussion on the presence of continua in vegetation, (d) the co‐incidence of the present thesis and the emerging ideas of evolutionists about differentiation of angiosperm taxa, and (e) the importance of regeneration‐studies for conservation.

Journal

Biological ReviewsWiley

Published: Feb 1, 1977

References

  • Speciation among tropical forest trees: some deductions in the light of recent evidence
    Ashton, Ashton
  • An analysis of the competition between barley and white persicaria. I. The effects of growth
    Aspinall, Aspinall; Milthorpe, Milthorpe
  • Statistical plant ecology
    Goodall, Goodall
  • Observations on population structure and longevity of Festuca rubra L
    Harberd, Harberd
  • The shapes and sizes of seeds
    Harper, Harper; Lovell, Lovell; Moore, Moore
  • Forest succession
    Horn, Horn
  • Seed predation by animals
    Janzen, Janzen
  • Effects of high temperature on the yield of peas
    Lambert, Lambert; Linck, Linck
  • Phenology of a tropical rain forest in Malaya
    Medway, Medway
  • Speciation in the tropical rain forest and the concept of the niche
    Richards, Richards
  • Adaptive radiation of reproductive characteristics in angiosperms. I. Pollination mechanisms
    Stebbins, Stebbins
  • Adaptive radiation of reproductive characteristics of angiosperms. II. Seeds and seedlings
    Stebbins, Stebbins

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