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

The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. 
The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. 
The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. 
The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on

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Landscape moderation of biodiversity patterns and processes - eight hypotheses

The degree of genetic diversity differs greatly among species and across genomic loci within genomes. The wide ranges in genetic diversity have important implications, including for evolution, conservation and management of wild and domesticated species. In this Review, the authors discuss how genome-scale sequencing strategies are providing insight into the varied determinants of genetic variation both among species and across genomic regions.

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Determinants of genetic diversity

Ecology of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae in temperate agroecosystems: Potential for conservation biological control

The large number of animals that coexist in soil without any clear niche differentiation has puzzled biologists for a long time. We investigated stable isotope ratios ( 15 N/ 14 N) in a diverse group of soil microarthropods, oribatid mites, to evaluate trophic niche differentiation. The natural variation of the stable isotopes 15 N/ 14 N was measured in 36 species/taxa from four beech and beech-oak forests. Signatures of d 15 N formed a gradient spanning over 12 d units suggesting that (a) different species occupy different trophic niches and (b) oribatid mites span three to four trophic levels. This study for the first time documented strong trophic niche differentiation in decomposer microarthropods. The results suggest that trophic niche differentiation within taxonomic groups significantly contributes to the high diversity of soil animal taxa. q 2004 Elsevier Ltd. All rights reserved.

Trophic niche differentiation in soil microarthropods (Oribatida, Acari): evidence from stable isotope ratios ( 15 N/ 14 N)

The large number of animals that coexist in soil without any clear niche differentiation has puzzled biologists for a long time. We investigated stable isotope ratios (15N/14N) in a diverse group of soil microarthropods, oribatid mites, to evaluate trophic niche differentiation. The natural variation of the stable isotopes 15N/14N was measured in 36 species/taxa from four beech and beech-oak forests. Signatures of δ15N formed a gradient spanning over 12 δ units suggesting that (a) different species occupy different trophic niches and (b) oribatid mites span three to four trophic levels. This study for the first time documented strong trophic niche differentiation in decomposer microarthropods. The results suggest that trophic niche differentiation within taxonomic groups significantly contributes to the high diversity of soil animal taxa.

Trophic niche differentiation in soil microarthropods (Oribatida, Acari): evidence from stable isotope ratios (15N/14N)

In this review we summarize our knowledge of using stable isotopes ( 15 N/ 14 N, 13 C/ 12 C) to better understand the trophic ecology of oribatid mites. Our aims are (a) to recapitulate the history of stable isotope research in soil animals with a focus on oribatid mites, (b) to present new stable isotope data for oribatid mites and overview the current state of knowledge of oribatid mite trophic niche differentiation, (c) to compile problems and limitations of stable isotope based analyses of trophic relationships and (d) to suggest future challenges, questions and problems that may be solved using stable isotope analyses and other novel techniques for improving our understanding on the trophic ecology of soil invertebrates. We conclude that (1) in addition to 15 N/ 14 N ratios, 13 C/ 12 C ratios contribute to our understanding of the trophic ecology of oribatid mites, allowing, e.g. separation of lichen- and moss-feeding species, (2) there likely are many lichen but few moss feeding oribatid mite species, (3) oribatid mite species that are endophagous as juveniles are separated by their stable isotope signatures from all other oribatid mite species, (4) fungivorous oribatid mite species cannot be separated further, e.g. the fungal taxa they feed on cannot be delineated. A particular problem in using stable isotope data is the difficulty in determining signatures for basal food resources, since decomposing material, fungi and lichens comprise various components differing in stable isotope signatures; 13 C/ 12 C ratios and potentially other isotopes may help in identifying the role of these resources for decomposer animal nutrition.

Stable isotopes revisited: Their use and limits for oribatid mite trophic ecology

The effects of mechanical perturbations on two soil microarthropod communities (oribatid mites and collembolans) were investigated in a moder beech forest on sandstone. We disturbed the soil matrix by sieving and mixing the litter and soil of the moder profile. The top litter layer (L material) and the deep mineral soil (Bv) remained intact. Three amounts of disturbance were established: a single perturbation, perturbations once every 2 months (60 d) and once every 2 weeks (14 d). Densities of most groups of oribatid mites and all groups of collembolans declined in the disturbance treatments. In most cases, densities were lowest in the strong perturbation treatment (14 d). Desmonomata were the only group of oribatid mites that benefited from intermediate amounts of disturbance but not from the strongest disturbance. Also, disturbances reduced diversity of oribatid mites and collembolans. According to their sensitivity to disturbances oribatid mites ranked Poronota=Enarthronota=Suctobelbidae (the most sensitive)>Oppiidae> Tectocepheus >Desmonomata. The ranking of collembolans was Folsomia (the most sensitive)>Hypogastruridae/Neanuridae>Onychiuridae=Isotomidae>Entomobryidae. Generally, tolerance of disturbance was wider for oribatid mites than for collembolans. The results indicate that disturbances such as mixing of litter and soil and comminution of litter material strongly affect the density and diversity of soil microarthropods. However, they also indicate that the soil microarthropod community is resistant to weaker disturbances. In the field, mechanical disturbances are often caused by burrowing of earthworms. Our results suggest that the high density of microarthropods in moder soils may be due to the low intensities of mechanical disturbances by earthworms.

Oribatid mite and collembolan diversity, density and community structure in a moder beech forest (Fagus sylvatica): effects of mechanical perturbations

The coexistence of a large number of soil animals without extensive niche differentiation is one of the great riddles in soil biology. The main aim of this study was to explore the importance of partitioning of food resources for the high diversity of micro-arthropods in soil. In addition, we investigated if ectomycorrhizal fungi are preferentially consumed compared to saprotrophic fungi. Until today, ectomycorrhizal fungi have never been tested as potential food resource for oribatid mites. We offered six ectomycorrhizal fungi [Amanita muscaria (L.) Hook., Boletus badius (Fr.) Fr., Cenococcum geophilum Fr., Laccaria laccata (Scop.) Fr., Paxillus involutus (Batsch) Fr. and Piloderma croceum J. Erikss. & Hjortstam], one ericoid mycorrhizal fungus [Hymenoscyphus ericae (D.J. Read) Korf & Kernan] and three saprotrophic fungi [Agrocybe gibberosa (Fr.) Fayod, Alternaria alternata (Fr.) Keissl. and Mortierella ramanniana (A. Moller) Linnem.] simultaneously to each of the mainly mycophagous oribatid mite species Carabodes femoralis (Nicolet), Nothrus silvestris Nicolet and Oribatula tibialis Nicolet. The ericoid mycorrhizal fungus H. ericae and the ectomycorrhizal fungus B. badius were preferentially consumed by each oribatid mite species. However, feeding preferences differed significantly between the three species, with O. tibialis being most selective. This study for the first time documented that oribatid mites feed on certain ectomycorrhizal fungi.

Katja Schneider

Papers

Trophic niche differentiation in soil microarthropods (Oribatida, Acari): evidence from stable isotope ratios ( 15 N/ 14 N)

Trophic niche differentiation in soil microarthropods (Oribatida, Acari): evidence from stable isotope ratios (15N/14N)

Stable isotopes revisited: Their use and limits for oribatid mite trophic ecology

Oribatid mite and collembolan diversity, density and community structure in a moder beech forest (Fagus sylvatica): effects of mechanical perturbations

Oribatid mite (Acari, Oribatida) feeding on ectomycorrhizal fungi.