Joseph E. Neigel

Bio: Joseph E. Neigel is an academic researcher from University of Louisiana at Lafayette. The author has contributed to research in topics: Population & Callinectes. The author has an hindex of 30, co-authored 53 publications receiving 8563 citations. Previous affiliations of Joseph E. Neigel include Sewanee: The University of the South & University of Georgia.

Intraspecific Phylogeography: The Mitochondrial DNA Bridge Between Population Genetics and Systematics

Abstract: 1Department of Genetics, University of Georgia, Athens, Georgia 30602; 2NMFS/ CZES, Genetics, 2725 Montlake Boulevard East, Seattle, Washington 98112; 3Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29801; ~Department of Microbiology and Immunology, School of Medicine, University of California, Los Angeles, California 90024; -SSchool f Veterinary Medicine, Virginia Tech University, Blacksburg, Virginia 24046

Hurricane Allen's Impact on Jamaican Coral Reefs

Abstract: Coral reefs of north Jamaica, normally sheltered, were severely damaged by Hurricane Allen, the strongest Caribbean hurricane of this century. Immediate studies were made at Discovery Bay, where reef populations were already known in some detail. Data are presented to show how damage varied with the position and orientation of the substraturn and with the shape, size, and mechanical properties of exposed organisms. Data collected over succeeding weeks showed striking differences in the ability of organisms to heal and survive.

Demographic influences on mitochondrial DNA lineage survivorship in animal populations

Abstract: Probability models of branching processes and computer simulations of these models are used to examine stochastic survivorship of female lineages under a variety of demographic scenarios. A parameter II, defined as the probability of survival of two or more independent lineages over G generations, is monitored as a function of founding size of a population, population size at carrying capacity, and the frequency distributions of surviving progeny. Stochastic lineage extinction can be very rapid under certain biologically plausible demographic conditions. For stable-sized populations initiated by n females and/or regulated about carrying capacity k = n, it is highly probable that within about 4n generations all descendants will trace their ancestries to a single founder female. For a given mean family size, increased variance decreases lineage survivorship. In expanding populations, however, lineage extinction is dramatically slowed, and the final k value is a far more important determinant of II than is the size of the population at founding. The results are discussed in the context of recent empirical observations of low mitochondrial DNA (mtDNA) sequence heterogeneity in humans and expected distributions of asexually transmitted traits among sexually reproducing species.

Genetic assessment of connectivity among marine populations

Abstract: Geographical surveys of genetic variation provide an indirect means of tracing movements made between marine populations by larvae and other propagules. Genetic markers can provide strong evidence that populations are closed (self-recruiting) because genetic differentiation is highly sensitive to migration. However, inferences based on genetic data must necessarily be based on models that make assumptions concerning inheritance, selective neutrality of markers, and equilibrium between genetic drift, migration, and mutation. We briefly introduce the types of genetic markers that can be used to infer demographic connections between populations and the forces causing evolutionary changes in these markers, and then we outline six patterns revealed by geographic surveys of genetic markers in marine species. Four of these patterns represent the possible combinations of high or low migration rates and large or small effective population sizes; two others are due to history and natural selection. Future genetic surveys should include more detailed spatial and temporal sampling and employ analyses of DNA sequence data that can reveal the signatures of natural selection and historical changes. Given the vast size of the ocean and the small size of most marine propagules, determining whether propagules settle away from their natal site or close to their parents can be a daunting task. Successful migrants should leave a genetic trail of their movements, offering an indirect means of estimating population connectivity. Genes are also recombined and passed through multiple generations, however, so the genotype of a larva cannot indicate its origin in the same direct way as a physical tag (Hedgecock, 1994a). Instead, the geographic distribution of genetic markers must be interpreted using population genetic models (Neigel, 1997; Waples, 1998). Clear interpretation of population genetic data, then, requires understanding and acknowledging the powers and pitfalls of these models. Here, we summarize how geographic patterns of genetic variation can be used to estimate the degree to which marine populations are closed or open. Our intended audience is the marine biologist who is new to genetic approaches to population biology; more detailed reviews can be found in Palumbi (1994) and Grosberg and Cunningham (2001). We begin by briefly categorizing the types of genetic markers that can be employed as population markers, the forces affecting their evolution, and the general models of population genetic structure that provide the framework for the interpretation of data. Next, we outline six patterns seen repeatedly in geographic surveys of genetic variation among marine populations, along with examples and possible underlying mechanisms for each. Finally, we discuss instances where patterns appear to conflict and point to future research that might both resolve these conflicts, and provide greater insights into the degree of connection between marine populations.

The Theory of Island Biogeography

Abstract: 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 genetic legacy of the Quaternary ice ages

Abstract: Global climate has fluctuated greatly during the past three million years, leading to the recent major ice ages. An inescapable consequence for most living organisms is great changes in their distribution, which are expressed differently in boreal, temperate and tropical zones. Such range changes can be expected to have genetic consequences, and the advent of DNA technology provides most suitable markers to examine these. Several good data sets are now available, which provide tests of expectations, insights into species colonization and unexpected genetic subdivision and mixture of species. The genetic structure of human populations may be viewed in the same context. The present genetic structure of populations, species and communities has been mainly formed by Quaternary ice ages, and genetic, fossil and physical data combined can greatly help our understanding of how organisms were so affected.

Population growth makes waves in the distribution of pairwise genetic differences.

Abstract: Episodes of population growth and decline leave characteristic signatures in the distribution of nucleotide (or restriction) site differences between pairs of individuals. These signatures appear in histograms showing the relative frequencies of pairs of individuals who differ by i sites, where i = 0, 1, .... In this distribution an episode of growth generates a wave that travels to the right, traversing 1 unit of the horizontal axis in each 1/2u generations, where u is the mutation rate. The smaller the initial population, the steeper will be the leading face of the wave. The larger the increase in population size, the smaller will be the distribution's vertical intercept. The implications of continued exponential growth are indistinguishable from those of a sudden burst of population growth Bottlenecks in population size also generate waves similar to those produced by a sudden expansion, but with elevated uppertail probabilities. Reductions in population size initially generate L-shaped distributions with high probability of identity, but these converge rapidly to a new equilibrium. In equilibrium populations the theoretical curves are free of waves. However, computer simulations of such populations generate empirical distributions with many peaks and little resemblance to the theory. On the other hand, agreement is better in the transient (nonequilibrium) case, where simulated empirical distributions typically exhibit waves very similar to those predicted by theory. Thus, waves in empirical distributions may be rich in information about the history of population dynamics.

Some genetic consequences of ice ages, and their role in divergence and speciation

Abstract: The genetic effects of pleistocene ice ages are approached by deduction from paleoenvironmental information, by induction from the genetic structure of populations and species, and by their combination to infer likely consequences. (1) Recent palaeoclimatic information indicate rapid global reversals and changes in ranges of species which would involve elimination with spreading from the edge. Leading edge colonization during a rapid expansion would be leptokurtic and lead to homozygosity and spatial assortment of genomes. In Europe and North America, ice age contractions were into southern refugia, which would promote genome reorganization. (2) The present day genetic structure of species shows frequent geographic subdivision, with parapatric genomes, hybrid zones and suture zones. A survey of recent DNA phylogeographic information supports and extends earlier work. (3) The grasshopperChorthippus parallelusis used to illustrate such data and processes. Its range in Europe is divided on DNA sequences into five parapatric races, with southern genomes showing greater haplotype diversity — probably due to southern mountain blocks acting as refugia and northern expansion reducing diversity. (4) Comparison with other recent studies shows a concordance of such phylogeographic data over pleistocene time scales. (5) The role that ice age range changes may have played in changing adaptations is explored, including the limits of range, rapid change in new invasions and refugial differentiation in a variety of organisms. (6) The effects of these events in causing divergence and speciation are explored usingChorthippusas a paradigm. Repeated contraction and expansion would accumulate genome differences and adaptations, protected from mixing by hybrid zones, and such a composite mode of speciation could apply to many organisms.