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

. Abstract Research on fragmented ecosystems has focused mostly on the biogeograpbic consequences of the creation of habitat “islands” of different sizes and has provided little of practical value to managers. However, ecosystem fragmentation causes large changes in the physical environment as well as biogeograpbic changes. Fragmentation generally results in a landscape that consists of remnant areas of native vegetation surrounded by a matrix of agricultural or other developed land. As a result fluxes of radiation, momentum (La, wind), water, and nutrients across the landscape are altered significantly. These in turn can have important influences on biota within remnant areas, especially at or near the edge between the remnant and the surrounding matrix. The isolation of remnant areas by clearing also has important consequences for the biota. These consequences vary with the time since isolation distance from other remnants, and degree of connectivity with other remnants. The influences of physical and biogeographic changes are modified by the size, shape, and position in the landscape of individual remnant, with larger remnants being less adversely affected by the fragmentation process. The Dynamics of remnant areas are predominantly driven by factors arising in the surrounding landscape. Management of, and research on, fragmented ecosystems should be directed at understanding and controlling these external influences as much as at the biota of the remnants themselves. There is a strong need to develop an integrated approach to landscape management that places conservation reserves in the context of the overall landscape

Biological consequences of ecosystem fragmentation: a review

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Biological Consequences of Ecosystem Fragmentation: A Review

Habitat fragmentation implies a loss of habitat, reduced patch size and an increasing distance between patches, but also an increase of new habitat. Simulations of patterns and geometry of landscapes with decreasing proportion of the suitable habitat give rise to the prediction that the effect of habitat fragmentation on e.g. population size of a species would be primarily through habitat loss in landscape with a high proportion of suitable habitat. However, ast the proportion of suitable habitat

Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: a review

Since the Age of Exploration began, there has been a drastic breaching of biogeographic barriers that previously had isolated the continental biotas for millions of years. We explore the nature of these recent biotic exchanges and their consequences on evolutionary processes. The direct evidence of evolutionary consequences of the biotic rearrangements is of variable quality, but the results of trajectories are becoming clear as the number of studies increases. There are examples of invasive species altering the evolutionary pathway of native species by competitive exclusion, niche displacement, hybridization, introgression, predation, and ultimately extinction. Invaders themselves evolve in response to their interactions with natives, as well as in response to the new abiotic environment. Flexibility in behavior, and mutualistic interactions, can aid in the success of invaders in their new environment.

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The evolutionary impact of invasive species.

The distribution of native, chaparral-requiring bird species was determined for 37 isolated fragments of canyon habitat ranging in size from 0.4 to 104 hectares in coasta4 urban San Diego County, California The area of chaparral habitat and canyon age (time since isolation of the habitat fragment) explains most of the variation in the number of chaparral-requiring bird species. In additiolz, the distribution of native predators may influence species num- ber. There is statistical evidence that coyotes control thepop- ulations of smallerpredators such as foxes and domestic cats. The absence of coyotes may lead to higher levels of predation by a process of mesopredator release. The distance of canyons from otherpatches of chaparral habitat does not add significantly to the explained variance in chaparral- requiring species number-probably because of the virtual inability of most chaparral-requiring species to disperse through developed areas and nonscrub habitats. These re- sults and other lines of evidence suggest that chaparral- requiring birds in isolated canyons have very high rates of extinction, in part because of their low vagility. The best predictors of vulnerability of the individual species are their abundances (densities) in undisturbed habitat and their

/pdf/reconstructed-dynamics-of-rapid-extinctions-of-chaparral-1bq40to8yv.pdf

Reconstructed Dynamics of Rapid Extinctions of Chaparral‐Requiring Birds in Urban Habitat Islands

Species interactions, as revealed by historical introductions of predators and competitors, affect population densities and sometimes result in extinctions of island reptiles. Mongoose introductions to Pacific islands have diminished the abundance of diurnal lizards and in some cases have led to extinctions. Through these population level effects, biogeographic patterns are produced, such as the reciprocal co-occurrence pattern seen with the tuatara and its predator, the Polynesian rat, and with the tropical gecko competitorsHemidactylus frenatus andLepidodactylus lugubris in urban habitats in the Pacific. Although competition has led to changes in abundance and has caused habitat displacement and reduced colonization success, extinctions of established reptile populations usually occur only as a result of predation.

The role of introduced species in shaping the distribution and abundance of island reptiles

The competitive displacement by a sexual gecko species of an asexual resident gecko has been documented over a wide geographic area. To test hypotheses concerning the detailed mechanism of this displacement, an experimental system was developed to follow populations of geckos in a duplicated, controlled environment that closely approximates the natural arena for the competitive interaction. Asymmetric competition occurred only in the presence of light, which attracts a dense concentration of insect food sources. The mechanism of competition was partly due to the behavioral dominance of the larger sexual species over the smaller asexual species in areas near the concentrated food. However, this behavior resulted from an avoidance response of subordinate asexuals rather than overt aggression by the sexual species.

https://science.sciencemag.org/content/sci/259/5093/354.full.pdf

Mechanisms in the Competitive Success of an Invading Sexual Gecko over an Asexual Native.

The fossil record of the earth shows that faunal and floral extinctions increased dramatically during certain periods. These “paleo” upheavals like those at the end of Permian and Cretaceous have long provided the punctuations that geologists and paleontologists use to divide the geological periods. A challenging question in conservation science is whether the processes affecting extinction rates today are helpful in interpreting extinction in the past and, conversely, whether prehistoric extinctions are useful for understanding recent extinctions.

Douglas T. Bolger

Papers

Reconstructed Dynamics of Rapid Extinctions of Chaparral‐Requiring Birds in Urban Habitat Islands

The role of introduced species in shaping the distribution and abundance of island reptiles

Mechanisms in the Competitive Success of an Invading Sexual Gecko over an Asexual Native.

Reptilian Extinctions Over the Last Ten Thousand Years

Intra- and interspecific interference behaviour among sexual and asexual geckos