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H. Allen Orr

Bio: H. Allen Orr is an academic researcher from University of Rochester. The author has contributed to research in topics: Population & Reproductive isolation. The author has an hindex of 47, co-authored 70 publications receiving 11479 citations. Previous affiliations of H. Allen Orr include University of Chicago & University of California, Davis.


Papers
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Journal ArticleDOI
TL;DR: To investigate the time course of speciation, literature data is gathered on 119 pairs of closely related Drosophila species with known genetic distances, mating discrimination, strength of hybrid sterility and inviability, and geographic ranges to provide a cross‐section of taxa at different stages ofSpeciation.
Abstract: To investigate the time course of speciation, we gathered literature data on 119 pairs of closely related Drosophila species with known genetic distances, mating discrimination, strength of hybrid sterility and inviability, and geographic ranges. Because genetic distance is correlated with divergence time, these data provide a cross-section of taxa at different stages of speciation. Mating discrimination and the sterility or inviability of hybrids increase gradually with time. Hybrid sterility and inviability evolve at similar rates. Among allopatric species, mating discrim- ination and postzygotic isolation evolve at comparable rates, but among sympatric species strong mating discrimination appears well before severe sterility or inviability. This suggests that pre- zygotic reproductive isolation may be reinforced when allopatric taxa become sympatric. Analysis of the evolution of postzygotic isolation shows that recently diverged taxa usually produce sterile or inviable male but not female hybrids. Moreover, there is a large temporal gap between the evolution of male-limited and female hybrid sterility or inviability. This gap, which is predicted by recent theories about the genetics of speciation, explains the overwhelming pre- ponderance of hybridizations yielding male-limited hybrid sterility or inviability (Haldane's rule).

1,411 citations

Journal ArticleDOI
TL;DR: The history of adaptation theory is surveyed, focusing on the rise and fall of various views over the past century and the reasons for the slow development of a mature theory of adaptation.
Abstract: Theoretical studies of adaptation have exploded over the past decade. This work has been inspired by recent, surprising findings in the experimental study of adaptation. For example, morphological evolution sometimes involves a modest number of genetic changes, with some individual changes having a large effect on the phenotype or fitness. Here I survey the history of adaptation theory, focusing on the rise and fall of various views over the past century and the reasons for the slow development of a mature theory of adaptation. I also discuss the challenges that face contemporary theories of adaptation.

1,120 citations

Journal ArticleDOI
TL;DR: Using Fisher's geometric model of adaptation, this work derives an approximate solution to the size distribution of factors fixed during adaptation, which is remarkably insensitive to changes in the fitness function and in the distribution of mutational effects.
Abstract: We know very little about the genetic basis of adaptation. Indeed, we can make no theoretical predictions, however heuristic, about the distribution of phenotypic effects among factors fixed during adaptation nor about the expected "size" of the largest factor fixed. Study of this problem requires taking into account that populations gradually approach a phenotypic optimum during adaptation via the stepwise substitution of favorable mutations. Using Fisher's geometric model of adaptation, I analyze this approach to the optimum, and derive an approximate solution to the size distribution of factors fixed during adaptation. I further generalize these results to allow the input of any distribution of mutational effects. The distribution of factors fixed during adaptation assumes a pleasingly simple, exponential form. This result is remarkably insensitive to changes in the fitness function and in the distribution of mutational effects. An exponential trend among factors fixed appears to be a general property of adaptation toward a fixed optimum.

836 citations

Journal ArticleDOI
TL;DR: The data from Drosophila are unique-and are likely to remain so-because of the large number of crossable species and the ease of estimating sexual and postzygotic isolation in the laboratory, and some estimates of reproductive isolation and phylogenetic relatedness when better data became available are revised.
Abstract: In a paper published seven years ago in this journal (Coyne and Orr 1989a), we analyzed the time course of speciation in Drosophila by correlating electrophoretic genetic distance between pairs of species (a number roughly proportional to their divergence time) with the strength of reproductive isolation between them. That analysis yielded five conclusions. First, both prezygotic and postzygotic reproductive isolation increase with divergence time between taxa. Second, prezygotic (sexual) isolation evolves more rapidly than postzygotic isolation (sterility and inviability of hybrids). This difference is, however, due entirely to much stronger prezygotic isolation between sympatric than between allopatric pairs of species. We suggested that this difference was due to "reinforcement," or direct selection for sexual isolation that occurs among sympatric taxa that produce unfit hybrids (Dobzhansky 1937). Third, hybrid sterility and inviability evolve at similar rates. This conclusion now appears to be incorrect because average divergence time between taxa is not a sensitive way to measure evolutionary rates of reproductive isolation, and more sensitive analyses show that hybrid sterility may in fact evolve more rapidly than inviability (Wu 1992). Fourth, the usual pathway for the production of postzygotic isolation is the initial appearance of sterility or inviability in hybrid males, followed by its appearance in females. This explains the frequent observation of Haldane's rule: the pattern that if only one gender of hybrids is sterile or inviable in species crosses, it is nearly always the heterogametic (XY or XO) sex (Haldane 1922; Coyne and Orr 1989b). Finally, there is a large increase in genetic distance between those species pairs producing sterile or inviable males only and those producing sterile or inviable hybrids of both sexes. This implies that there is a long time lag between the evolution of postzygotic isolation in males and in females. While a similar (but much smaller) analysis has since been conducted in salamanders (Tilley et al. 1990), the data from Drosophila are unique-and are likely to remain so-because of the large number of crossable species and the ease of estimating sexual and postzygotic isolation in the laboratory. These Drosophila data have hence attracted some interest. Because of this, we have continued to accumulate new data as they have appeared. We have also found a few errors in our original data set, and have revised some estimates of reproductive isolation and phylogenetic relatedness when better data became available. We now have data for 171 interspecific hybridizations in Drosophila, an increase of 43% over the 119 hybridizations described in our previous paper. Because DNA sequencing has largely supplanted gel electrophoresis as a way of measuring divergence between species, it is unlikely that this data set will grow much larger; and it will be many years before we possess DNA-based estimates of divergence between many pairs of Drosophila species. We therefore thought it timely to check our earlier conclusions using the new and larger data set.

811 citations

Journal ArticleDOI
TL;DR: Defining speciation as 'the origin of reproductive isolation between two taxa' is defined, and some important and tractable questions about speciation that have been neglected are pointed out.
Abstract: The last decade has brought renewed interest in the genetics of speciation, yielding a number of new models and empirical results. Defining speciation as 'the origin of reproductive isolation between two taxa', we review recent theoretical studies and relevant data, emphasizing the regular patterns seen among genetic analyses. Finally, we point out some important and tractable questions about speciation that have been neglected.

625 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
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

14,171 citations

Journal Article
Fumio Tajima1
30 Oct 1989-Genomics
TL;DR: It is suggested that the natural selection against large insertion/deletion is so weak that a large amount of variation is maintained in a population.

11,521 citations

Journal Article
TL;DR: For the next few weeks the course is going to be exploring a field that’s actually older than classical population genetics, although the approach it’ll be taking to it involves the use of population genetic machinery.
Abstract: 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

9,847 citations

01 Aug 2000
TL;DR: Assessment of medical technology in the context of commercialization with Bioentrepreneur course, which addresses many issues unique to biomedical products.
Abstract: BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

4,833 citations