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

The lipid concentration (LC) of the embryo–endosperm fraction was determined for the seeds of 60 species in 22 families from an Australian tropical lowland rainforest. It was negatively related to the mass of the embryo–endosperm across all species, but the relationship was not significant at P < 0.05. LC was significantly and positively correlated with N concentration when all species were considered, but not within the families represented by the most species (Lauraceae, 13; Sapindaceae, 9; Proteaceae, 6). LC was significantly and markedly higher in more heavily defended seeds (medians: 27 and 6.9%); there is evidence for the view that seeds rich in either lipid or nitrogen are markedly defended. Lipid concentration was also markedly higher, on average, in seeds taken by the scatter-hoarding Uromys caudimaculatus (white-tailed rat) than in seeds of comparable size not taken by Uromys, but not known to be protected by any toxin or irritant (medians: 35 and 3.7%, respectively). However, LC was not notably high in one major group of seeds taken by Uromys – the largest-seeded species of Beilschmiedia and Endiandra (Lauraceae). The comparisons mostly involved different phyletic lines, and were not consistently supported by contrasts within phyletic lines.

Lipid concentration in the embryo–endosperm fraction of seeds of Australian tropical lowland rainforest trees: relevance to defence and dispersal

Eleven European shrub and tree species have been grown for 13 years in a randomized array (with 2 or 3 provenances for 5 of 11 species) in an experimental garden in southern England. A plague of rabbits in the second year damaged a greater proportion of plants in species with faster height growth, including those that are the commonest colonizers of pastures; most plants recovered rapidly. Apparently, resilience rather than resistance enables these plants to be invaders of abandoned grasslands. Among the shrubs there was little evidence of a trade-off between initial rate of height growth and final height. The small tree Crataegus monogyna overtook the tallest shrub (Cornus sanguinea) in the 12th year. Among the shrubs, after 12 years, there was a trend for basal area to be greater in taller species; the trees had notably low basal area for their height. Most individuals of the shrub species reproduced before those of Crataegus and Sorbus aria (in 3–6 years rather than 5–13). Among the shrubs, the earliest to reproduce were fast-growing (Rosa canina, then Ligustrum vuigare, Prunus spinosa and Rhamnus catharticus), but then species with a wide range of growth rates all reproduced at the same time (Euony-mus europaeus, Juniperus communis and Viburnum opulus slow-growing, Cornus sanguinea and V. lantana fast-growing). The results are discussed in relation to theories of resource allocation, and the behaviour of the particular species in the field.

A Garden Experiment on Susceptibility to Rabbit‐Grazing, Sapling Growth Rates, and Age at First Reproduction for Eleven European Woody Species

Summary
1Previous studies on the combined effects of light and nutrient supply on the growth rates of plants have involved adding nutrients to soils to levels rarely (or never) met by the plants in nature. As a better test of the likely response of plants to root competition for nutrients, we grew for 1 year seedlings of six species of Australian rainforest tree on forest topsoil undiluted and on soil diluted 50/50, 25/75 and 5/95 with coarse sand. Seedlings were grown in tall tubes in 6 and 9% daylight, equivalent to gap-edge and gap-centre conditions.
2 The six species varied in their light requirements for establishment and onward growth.
3 One species grew significantly and markedly more quickly on soil diluted 50/50 with sand (Elaeocarpus grandis). Improved aeration is the most likely explanation.
4 The extent of inhibition by soil dilution correlated positively with the absolute amount of new dry mass accreted in one year, whether the larger accretion resulted from a combination of high relative growth rate (RGR) and small embryo size, or moderate RGR and larger embryo size.
5 Soil dilution generally reduced leaf mass fraction and leaf area ratio, but had no significant effect on specific leaf area.
6 In all species the overall concentration of nitrogen in the whole plant declined with soil dilution; in the four species tested, N concentration in leaves declined, and it is likely that the reduction in growth arose partly from a reduced unit leaf rate. Most species showed increases in the concentrations of P, K, Ca and Mg with soil dilution, or no change, but in Diploglottis bracteata the concentrations of Ca and Mg, especially in the older leaves, declined markedly with soil dilution, and one of these cations could have been limiting growth.
7 Extrapolation of the results to the field suggests that in single-treefall gaps the fastest growing species will the most inhibited by root competition.
8 The soil-dilution technique is likely to be more appropriate than nutrient addition as an indicator of sensitivity to root competition on a given soil.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2435.2002.00614.x

Soil dilution as a surrogate for root competition: effects on growth of seedlings of Australian tropical rainforest trees

Studies on whether or not species which need more light for establishment have smaller seeds should be made between plants of similar mature height living in the same soil and macroclimate. Salisbury's classic comparisons confused differences in light-requirement during establishment with differences in mature height and in the supply of soil resources.

Peter J. Grubb

Papers

Lipid concentration in the embryo–endosperm fraction of seeds of Australian tropical lowland rainforest trees: relevance to defence and dispersal

A Garden Experiment on Susceptibility to Rabbit‐Grazing, Sapling Growth Rates, and Age at First Reproduction for Eleven European Woody Species

Soil dilution as a surrogate for root competition: effects on growth of seedlings of Australian tropical rainforest trees

Seed mass and light‐demand: the need to control for soil–type and plant stature

Biological Flora of Central Europe: Cornus sanguinea L.