Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

This book is the second of two volumes in a series on terrestrial and marine comparisons, focusing on the temporal complement of the earlier spatial analysis of patchiness and pattern (Levin et al. 1993). The issue of the relationships among pattern, scale, and patchiness has been framed forcefully in John Steele’s writings of two decades (e.g., Steele 1978). There is no pattern without an observational frame. In the words of Nietzsche, “There are no facts… only interpretations.”

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1941447

The Problem of Pattern and Scale in Ecology: The Robert H. MacArthur Award Lecture

The metacommunity concept is an important way to think about linkages between different spatial scales in ecology. Here we review current understanding about this concept. We first investigate issues related to its definition as a set of local communities that are linked by dispersal of multiple potentially interacting species. We then identify four paradigms for metacommunities: the patch-dynamic view, the species-sorting view, the mass effects view and the neutral view, that each emphasizes different processes of potential importance in metacommunities. These have somewhat distinct intellectual histories and we discuss elements related to their potential future synthesis. We then use this framework to discuss why the concept is useful in modifying existing ecological thinking and illustrate this with a number of both theoretical and empirical examples. As ecologists strive to understand increasingly complex mechanisms and strive to work across multiple scales of spatio-temporal organization, concepts like the metacommunity can provide important insights that frequently contrast with those that would be obtained with more conventional approaches based on local communities alone.

/pdf/the-metacommunity-concept-a-framework-for-multi-scale-4dcjhfvx5w.pdf

The metacommunity concept: a framework for multi-scale community ecology

SUMMARY
1According 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.
2Most 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.
3Several 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.


4The 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.
5In 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.
6The 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.
7The 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.


8A 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.
9All 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.


10In 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.

The maintenance of species-richness in plant communities: the importance of the regeneration niche

The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate. About half of the current emissions are being absorbed by the ocean and by land ecosystems, but this absorption is sensitive to climate as well as to atmospheric carbon dioxide concentrations, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change. Here we present results from a fully coupled, three-dimensional carbon–climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a 'business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr-1 is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback.

/pdf/acceleration-of-global-warming-due-to-carbon-cycle-feedbacks-3788793i7v.pdf

Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model

Comparative studies on plant species have not distinguished between two inherently different applications of the idea of a trade-off. In the first case, the theoretical trade-off between two variables leads to a trend line, about which there is a degree of scatter. Any two species in the study are expected, in theory, to show a true trade-off, i.e. feature A must decrease for feature B to increase. This I call the ‘trend line’ type of plot. In the second case, the species are expected to fill a considerable part of the space defined by two axes and the theoretical trade-off leads to a boundary line which limits the extent of the cloud of points. In this case, many interspecific comparisons are not expected to show evidence of a trade-off, but those on the boundary line are expected to do so. This I call the ‘boundary line’ type of plot. In both types of plot, species within a given clade may show a true trade-off, while large numbers of unrelated species do not.First, I undertake to show, by means of exam...

https://www.tandfonline.com/doi/pdf/10.1080/17550874.2015.1048761

Trade-offs in interspecific comparisons in plant ecology and how plants overcome proposed constraints

Summary

1
Previous studies on tropical rainforest seedlings have demonstrated low physiological plasticity in shade-tolerant species in response to light, but little is known about the morphological plasticity of such species. We examined morphological traits in seedlings of 10 shade-tolerant tropical rainforest tree species grown in four combinations of high and low light (10 and 0·8% full daylight, respectively). Plasticity of each trait was quantified using coefficients of variation.

2
Plant traits varied in their plasticity, and could broadly be ranked as follows: stem form > crown traits > root form > leaf form > biomass allocation. Acclimation to an increase in light was generally greater than acclimation to a decrease in light, but crown traits showed significant changes in the high–low treatment.

3
The ranking of species according to plasticity varied depending on the trait examined. Mean plasticity across all light treatments showed no relationship with either dry mass or relative growth rate of dry mass (RGRM) across species. However, plasticity in stem mass fraction (fraction of stem to total dry mass) was negatively correlated with low-light RGRM across species.

4
Principal components analysis indicated clustering of species depending on trait plasticity. These results suggest different strategies of light response among shade-tolerant tropical tree seedlings.

https://www.jstor.org/stable/pdfplus/3599193.pdf

Morphological plasticity of shade-tolerant tropical rainforest tree seedlings exposed to light changes

A study was made in Bukit Timah Nature Reserve of niche differentiation among 11 woody species that have very small seeds (22–460 µg) and establish in deep shade, i.e., where the indirect site factor (isf) under cloudy conditions is ≤2%, and one taxonomically related light-demander (seed mass 33 µg). Comparative observations were made on changing light requirement with age. The species varied from shrubs and treelets (Urophyllum) via small to medium-height trees (Ficus, Pternandra) to tall trees (Gynotroches and Pellacalyx). In general, the shorter species fruited in deep shade while the taller needed direct irradiance. All produced ripe fruit at least once a year.

The ecology of very small-seeded shade-tolerant trees and shrubs in lowland rain forest in Singapore

Mean seed dry mass values were determined for 27 species of trees and shrubs in Amazonian caatinga (a forest-type especially short of nitrogen) and for 11 species in adjacent much taller forest on less poor soil. The tall trees (>15 m) of caatinga have smaller seeds than the tall trees in adjacent forest on less infertile soil (both overall and in six taxonomically controlled comparisons), and than the tall trees in lowland rainforests elsewhere. The smaller seed size is interpreted in terms of a major advantage of keeping up seed number outweighing the marginal advantages of larger seed size. For trees of caatinga and adjacent forest considered together, there is a significantly greater concentration of P and Mg, and almost significantly greater concentration of N, in the embryo-cum-endosperm fraction of smallerseeded species, but the content per seed of N, P and Mg is smaller in smaller seeds. The mean contribution of the seed coat (including endocarp for pyrenes) was 17% for dry mass, 3% for content of P, 10% for N and Mg, 15% for K, and 30% for Ca.

Seed mass and nutrient content in nutrient-starved tropical rainforest in Venezuela

Demography is central to both ecology and evolution, and characterizing the feedback between ecology and evolution is critical for understanding organisms' life histories and how these might evolve through time. Here, we show how, by combining a range of theoretical approaches with the statistical analysis of individually structured databases, accurate prediction of life history decisions is possible in natural density-regulated populations undergoing large fluctuations in demographic rates from year to year. Our predictions are remarkably accurate and statistically well defined. In addition, we show that the predicted trait values are evolutionarily and convergence stable and that protected polymorphisms are possible.

https://www.pnas.org/content/pnas/105/30/10466.full.pdf

Peter J. Grubb

Papers

Trade-offs in interspecific comparisons in plant ecology and how plants overcome proposed constraints

Morphological plasticity of shade-tolerant tropical rainforest tree seedlings exposed to light changes

The ecology of very small-seeded shade-tolerant trees and shrubs in lowland rain forest in Singapore

Seed mass and nutrient content in nutrient-starved tropical rainforest in Venezuela

Evolution of flowering decisions in a stochastic, density-dependent environment