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

So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Predation has long been implicated as a major selective force in the evolution of several morphological and behavioral characteristics of animals. The importance of predation during evolutionary ti...

Behavioral decisions made under the risk of predation: a review and prospectus

For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from...

/pdf/hormones-and-endocrine-disrupting-chemicals-low-dose-effects-2vn32zoqc8.pdf

Hormones and endocrine-disrupting chemicals: Low-dose effects and nonmonotonic dose responses

A tool changer is disclosed for automatically removing a working tool after having been used from the spindle of a machine tool such as a vertical milling machine, transferring the used working tool to a rack which stores a plurality of working tools, picking up from the rack another working tool for the next machining operation, transferring such new working tool to the spindle, and operatively mounting such new working tool on the spindle.

Temperature and Organism Size—A Biological Law for Ectotherms?

The relationships among timing of metamorphosis, size at metamorphosis, and traits related to adult fitness were studied for 8 yr in the salamander Ambystoma talpoideum at a temporary pond. Among years, the modal time of metamorphosis and mean body size at metamorphosis were positively correlated with the date the pond dried. In years that the pond dried late, one group of larvae metamorphosed well before the pond dried, whereas the other group metamorphosed just before pond drying. Mean body size of late—metamorphosing individuals was not greater than that of individuals metamorphosing early. Early—metamorphosing males and females were larger at first and second reproduction than were late—metamorphosing individuals. Independent of timing of metamorphosis, larger juveniles at metamorphosis were also larger adults at first reproduction. Age at first reproduction for males was not associated with timing of or size at metamorphosis but large early—metamorphosing females reproduced at a younger age than did small early—metamorphosing females. Neither time of metamorphosis nor size at metamorphosis was associated with survival to first reproduction. These results demonstrate a direct relationship between phenotypic variation generated in the larval stage and adult traits closely associated with an individual's fitness.

Time and size at metamorphosis related to adult fitness in Ambystoma talpoideum

Terrestrial habitats surrounding wetlands are critical to the management of natural resources. Al- though the protection of water resources from human activities such as agriculture, silviculture, and urban development is obvious, it is also apparent that terrestrial areas surrounding wetlands are core habitats for many semiaquatic species that depend on mesic ecotones to complete their life cycle. For purposes of conser- vation and management, it is important to define core habitats used by local breeding populations surround- ing wetlands. Our objective was to provide an estimate of the biologically relevant size of core habitats sur- rounding wetlands for amphibians and reptiles. We summarize data from the literature on the use of terrestrial habitats by amphibians and reptiles associated with wetlands (19 frog and 13 salamander species representing 1363 individuals; 5 snake and 28 turtle species representing more than 2245 individuals). Core terrestrial habitat ranged from 159 to 290 m for amphibians and from 127 to 289 m for reptiles from the edge of the aquatic site. Data from these studies also indicated the importance of terrestrial habitats for feed- ing, overwintering, and nesting, and, thus, the biological interdependence between aquatic and terrestrial habitats that is essential for the persistence of populations. The minimum and maximum values for core hab- itats, depending on the level of protection needed, can be used to set biologically meaningful buffers for wet- land and riparian habitats. These results indicate that large areas of terrestrial habitat surrounding wetlands are critical for maintaining biodiversity.

/pdf/biological-criteria-for-buffer-zones-around-wetlands-and-1of77ixc63.pdf

Biological Criteria for Buffer Zones around Wetlands and Riparian Habitats for Amphibians and Reptiles

Reports of declining amphibian populations in many parts of the world are numerous, but supporting long-term census data are generally unavailable. Census data from 1979 to 1990 for three salamander species and one frog species at a breeding pond in South Carolina showed fluctuations of substantial magnitude in both the size of breeding populations and in recruitment of juveniles. Breeding population sizes exhibited no overall trend in three species and increased in the fourth. Recent droughts account satisfactorily for an increase in recruitment failures. These data illustrate that to distinguish between natural population fluctuations and declines with anthropogenic causes may require long-term studies.

https://science.sciencemag.org/content/sci/253/5022/892.full.pdf

Declining Amphibian Populations: The Problem of Separating Human Impacts from Natural Fluctuations

What is most evident in the recent debate concerning new wetland regulations drafted by the U.S. Army Corps of Engineers is that small, isolated wetlands will likely continue to be lost. The critical biological question is whether small wetlands are expendable, and the fundamental issue is the lack of biologically rele- vant data on the value of wetlands, especially so-called "isolated" wetlands of small size. We used data from a geographic information system for natural-depression wetlands on the southeastern Atlantic coastal plain (U.S.A.) to examine the frequency distribution of wetland sizes and their nearest-wetland distances. Our re- sults indicate that the majority of natural wetlands are small and that these small wetlands are rich in am- phibian species and serve as an important source of juvenile recruits. Analyses simulating the loss of small wetlands indicate a large increase in the nearest-wetland distance that could impede "rescue" effects at the metapopulation level. We argue that small wetlands are extremely valuable for maintaining biodiversity, that the loss of small wetlands will cause a direct reduction in the connectance among remaining species pop- ulations, and that both existing and recently proposed legislation are inadequate for maintaining the biodi- versity of wetland flora and fauna. Small wetlands are not expendable if our goal is to maintain present lev- els of species biodiversity. At the very least, based on these data, regulations should protect wetlands as small as 0.2 ha until additional data are available to compare diversity directly across a range of wetland sizes. Furthermore, we strongly advocate that wetland legislation focus not only on size but also on local and re- gional wetland distribution in order to protect ecological connectance and the source-sink dynamics of spe- cies populations.

Are Small, Isolated Wetlands Expendable?

Coordinated efforts by ecologists and natural resource managers are necessary to balance the conservation of biological diversity with the potential for sustained economic development. Because some amphibians have suffered world-wide declines during the last 20 years, it is important to consider biologically based management strategies that will preserve local and regional populations. This paper provides a brief overview of potential threats to local and regional populations, the state of knowledge on population and landscape processes, and the critical elements needed for an effective management plan for amphibians. Local population dynamics and ecological connectivity of amphibian metapopulations must be considered in effective management plans. There are 3 critical factors to consider in a management plan (1) the number or density of individuals dispersing from individual wetlands, (2) the diversity of wetlands with regard to hydroperiod, and (3) the probability of dispersal among adjacent wetlands or the rescue and recolonization of local populations. Wetland losses reduce the total number of sites where pond-breeding amphibians can reproduce and recruit juveniles into the breeding population. Loss of small, temporary wetlands (<4.0 ha) may be especially harmful to amphibians because of their abundance and high species diversity. Alteration of wetlands, particularly hydrologic cycles, can severely impair completion of larval metamorphosis through either early pond drying (if hydroperiod is shortened) or through increased predation (if hydroperiod is lengthened or connections made with fish-infested lakes, rivers, or canals). Wetland loss also increases the distance between neigh-boring wetlands that is critical to metapopulation source-sink processes. Reduction in wetland density reduces the probablity that populations will be rescued from extinction by nearby source populations. Local populations cannot be considered independent of source-sink processes that connect wetlands at the landscape or regional level. Further, the fragmentation of natural habitats from timber harvesting, agriculture, roads, drainage canals, or urban development impedes or prevents dispersal and decreases the probability of wetland recolonization. If our goal is to maintain or enhance present levels of amphibian diversity, then resource managers must incorporate critical elements into plans that protect population and landscape processes thereby maintaining viable populations and communities of amphibians.

Raymond D. Semlitsch

Papers

Time and size at metamorphosis related to adult fitness in Ambystoma talpoideum

Biological Criteria for Buffer Zones around Wetlands and Riparian Habitats for Amphibians and Reptiles

Declining Amphibian Populations: The Problem of Separating Human Impacts from Natural Fluctuations

Are Small, Isolated Wetlands Expendable?

Principles for Management of Aquatic-Breeding Amphibians