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

Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

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Molecular Evolutionary Genetics Analysis

The principles of classification and a classification of mammals. Bulletin of the AMNH ; v. 85

Habitat loss has pervasive and disruptive impacts on biodiversity in habitat remnants. The magnitude of the ecological impacts of habitat loss can be exacerbated by the spatial arrangement -- or fragmentation -- of remaining habitat. Fragmentation per se is a landscape-level phenomenon in which species that survive in habitat remnants are confronted with a modified environment of reduced area, increased isolation and novel ecological boundaries. The implications of this for individual organisms are many and varied, because species with differing life history strategies are differentially affected by habitat fragmentation. Here, we review the extensive literature on species responses to habitat fragmentation, and detail the numerous ways in which confounding factors have either masked the detection, or prevented the manifestation, of predicted fragmentation effects. Large numbers of empirical studies continue to document changes in species richness with decreasing habitat area, with positive, negative and no relationships regularly reported. The debate surrounding such widely contrasting results is beginning to be resolved by findings that the expected positive species-area relationship can be masked by matrix-derived spatial subsidies of resources to fragment-dwelling species and by the invasion of matrix-dwelling species into habitat edges. Significant advances have been made recently in our understanding of how species interactions are altered at habitat edges as a result of these changes. Interestingly, changes in biotic and abiotic parameters at edges also make ecological processes more variable than in habitat interiors. Individuals are more likely to encounter habitat edges in fragments with convoluted shapes, leading to increased turnover and variability in population size than in fragments that are compact in shape. Habitat isolation in both space and time disrupts species distribution patterns, with consequent effects on metapopulation dynamics and the genetic structure of fragment-dwelling populations. Again, the matrix habitat is a strong determinant of fragmentation effects within remnants because of its role in regulating dispersal and dispersal-related mortality, the provision of spatial subsidies and the potential mediation of edge-related microclimatic gradients. We show that confounding factors can mask many fragmentation effects. For instance, there are multiple ways in which species traits like trophic level, dispersal ability and degree of habitat specialisation influence species-level responses. The temporal scale of investigation may have a strong influence on the results of a study, with short-term crowding effects eventually giving way to long-term extinction debts. Moreover, many fragmentation effects like changes in genetic, morphological or behavioural traits of species require time to appear. By contrast, synergistic interactions of fragmentation with climate change, human-altered disturbance regimes, species interactions and other drivers of population decline may magnify the impacts of fragmentation. To conclude, we emphasise that anthropogenic fragmentation is a recent phenomenon in evolutionary time and suggest that the final, long-term impacts of habitat fragmentation may not yet have shown themselves.

Confounding factors in the detection of species responses to habitat fragmentation

The predominantly selfing slug species Arion (Carinarion) fasciatus, A. (C.) silvaticus and A. (C.) circumscriptus are native in Europe and have been introduced into North America, where each species consists of a single, homozygous multilocus genotype (strain), as defined by starch gel electrophoresis (SGE) of allozymes. In Europe, the "one strain per species" hypothesis does not hold since polyacrylamide gel electrophoresis (PAGE) of allozymes uncovered 46 strains divided over the three species. However, electrophoretic techniques may differ in their ability to detect allozyme variation. Therefore, several Carinarion populations from both continents were screened by applying the two techniques simultaneously on the same individual slugs and enzyme loci. SGE and PAGE yielded exactly the same results, so that the different degree of variation in North American and European populations cannot be attributed to differences in resolving power between SGE and PAGE. We found four A. (C.) silvaticus strains in North America indicating that in this region the "one strain per species" hypothesis also cannot be maintained. Hence, the discrepancies between previous electrophoretic studies on Carinarion are most likely due to sampling artefacts and possible founder effects.

Congruence between starch gel and polyacrylamide gel electrophoresis in detecting allozyme variation in pulmonate land slugs.

A new genus and species of pseudosigmurethrous orthurethran pulmonate of the family Cerastidae, Darwininitium shiwalikianum gen. n. and sp. n. is described from the Lesser Himalaya of Nepal. It represents the first record of an orthurethran with a fully developed pseudosigmurethrous pallial system, having a completely closed secondary ureteric system. Biogeographically this new taxon provides a significant range extension for the family north of the previously known distribution range.

Darwininitium - a new fully pseudosigmurethrous orthurethran genus from Nepal (Gastropoda, Pulmonata, Cerastidae).

Allozyme variation in two forest populations of Platynothrus peltifer (Acari, Oribatida)

Application of isoelectric focusing in molluscan studies

Using isoelectric focusing of esterases (EST), general proteins (GP) and myoglobin (Mb), we surveyed intra- and interspecific differentiation in flat periwinkles along a vertical intertidal transect in the Ensenada do Bano at Ria Ferrol, NW Spain In this region, L obtusata occurs in four algal belts, although it is rare in the lowest zone defined by Fucus serratus L fabalis is common in the F serratus and F vesiculosus belt, but is absent higher up on Ascophyllum nodosum and F spiralis Our data show that (1) EST and GP consistently differentiate between L obtusata and L fabalis, without however providing useful diagnostic markers, (2) L fabolis is the less variable (heterozygous), but more heterogeneous species, (3) Mb patterns show significant heterogeneity in L obtusata between the F serratus zone and the other algal belts, but not in L fabalis, and (4) the data on littorinid Mb appear inconsistent with a dimeric protein controlled by a single locus Yet, assuming two loci coding for a monomeric (or dissociated dimeric) protein produces for the flat periwinkles a data set in which no significant deviations from Hardy-Weinberg expectations were detected Nevertheless, this speculative interpretation fails to explain all littorinid Mb data Hence the genetics and structure of littorinid Mb need further study

Thierry Backeljau

Papers

Congruence between starch gel and polyacrylamide gel electrophoresis in detecting allozyme variation in pulmonate land slugs.

Darwininitium - a new fully pseudosigmurethrous orthurethran genus from Nepal (Gastropoda, Pulmonata, Cerastidae).

Allozyme variation in two forest populations of Platynothrus peltifer (Acari, Oribatida)

Application of isoelectric focusing in molluscan studies

Electrophoretic heterogeneity within and between flat periwinkles (Mollusca: Gastropoda) along an intertidal transect at Ria Ferrol, northwest Spain