Showing papers by "John C. Avise published in 1996"

Conservation Genetics: Case Histories from Nature

Abstract: Contributors. Prologue. 1. Introduction: The Scope of Conservation Genetics Part I: Case Histories with a Focus on Particular Taxonomic Groups. 2. Population Structure, Molecular Systematics and Forensic Identification of Whales and Dolphins C.S. Baker, S.R. Palumbi 3. Conservation Genetics of the Felidae S.J. O'Brien, et al. 4. Conservation Genetics in the Canidae R.K. Wayne 5. Socioecology, Population Fragmentation and Patterns of Genetic Loss in Endangered Primates T.R. Pope 6. Avian Conservation Genetics S.M. Haig, J.C. Avise 7. Conservation Genetics of Marine Turtles B.W. Bowen, J.C. Avise 8. Conservation and Genetics of Salmonid Fishes F.W. Allendorf, R.S. Waples Part II: Case Histories that Involve a Regional or Ecosystem Perspective, or a Pattern and Process Orientation. 9. Conservation Genetics of Endemic Plant Species J.L. Hamrick, Mary J.W. Godt 10. Conservation Genetics of Endangered Island Plants L.H. Rieseberg, S.M. Swensen 11. Conservation Genetics of Fishes in the Pelagic Marine Realm J.E. Graves 12. Conservation Genetics of North American Desert Fishes: R.C. Vrijenhoek 13. A Landscape Approach to Conservation Genetics: Conserving Evolutionary Processes in the African Bovidae A.R. Templeton, N.J. Georgiadis 14. Toward a Regional Conservation Genetics Perspective: Phylogeography of Faunas in the Southeastern United States J.C. Avise 15. A Quantitative-Genetic Perspective on Conservation Issues M.Lynch Epilogue. Index.

Molecular genetic analysis of a stepped multilocus cline in the american oyster (crassostrea virginica).

Abstract: Gulf of Mexico versus Atlantic populations of several coastal species in the southeastern United States are known to differ sharply in genetic composition, but most transitional zones have not previously been examined in detail. Here we employ molecular markers from mitochondrial and nuclear loci to characterize cytonuclear genetic associations at meso- and microgeographic scales along an eastern Florida transitional zone between genetically distinct Atlantic and Gulf populations of the American oyster, Crassostrea virginica. The single- and multilocus cytonuclear patterns display: (1) a cline extending along 340 km of the east Florida coastline; (2) a pronounced step in the cline centered at Cape Canaveral (shifts in allelic frequencies by 50-75% over a 20 km distance); (3) a close agreement of observed genotypic frequencies with Hardy-Weinberg expectations within locales; and (4) mild or nonexistent nuclear and cytonuclear disequilibria in most local population samples. These results imply: (1) considerable restrictions to interpopulational gene flow along the eastern Florida coastline; (2) within locales, free interbreeding (as opposed to mere population admixture) between Gulf and Atlantic forms of oysters; and (3) localized population recruitment in the transition zone localities. These findings demonstrate that marine organisms with high dispersal potential via long-lived pelagic larvae can nonetheless display pronounced spatial population genetic structure, and more generally they exemplify the utility of pronounced genetic transition zones for the study of population level processes.

Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves.

Abstract: A puzzling population-genetic phenomenon widely reported in allozyme surveys of marine bivalves is the occurrence of heterozygote deficits relative to Hardy-Weinberg expectations. Possible explanations for this pattern are categorized with respect to whether the effects should be confined to protein-level assays or are genomically pervasive and expected to be registered in both protein- and DNA-level assays. Anonymous nuclear DNA markers from the American oyster were employed to reexamine the phenomenon. In assays based on the polymerase chain reaction (PCR), two DNA-level processes were encountered that can lead to artifactual genotypic scorings: (a) differential amplification of alleles at a target locus and (b) amplification from multiple paralogous loci. We describe symptoms of these complications and prescribe methods that should generally help to ameliorate them. When artifactual scorings at two anonymous DNA loci in the American oyster were corrected, Hardy-Weinberg deviations registered in preliminary population assays decreased to nonsignificant values. Implications of these findings for the heterozygote-deficit phenomenon in marine bivalves, and for the general development and use of PCR-based assays, are discussed.

Molecular Documentation of Polyembryony and the Micro-Spatial Dispersion of Clonal Sibships in the Nine-Banded Armadillo, Dasypus novemcinctus

Abstract: A battery of allelic markers at highly polymorphic microsatellite loci was developed and employed to confirm genetically, the clonal nature of sibships in nine-banded armadillos. This phenomenon of consistent polyembryony, otherwise nearly unknown among the vertebrates, was capitalized upon to describe the micro-spatial distributions of numerous clonal sibships in a natural population of armadillos. Adult clone mates were significantly more dispersed than were juvenile sibs, suggesting limited opportunities for altruistic behavioural interactions among mature individuals. These results, and considerations of armadillo natural history, suggest that evolutionary explanations for polyembryony in this species may not reside in the kinds of ecological and kin selection theories relevant to some of the polyembryonic invertebrates. Rather, polyembryony in armadillos may be associated evolutionarily with other reproductive peculiarities of the species, including delayed uterine implantation of a single egg.

Recognizing the forest for the trees: testing temporal patterns of cladogenesis using a null model of stochastic diversification.

Abstract: Computer simulations are developed and employed to examine the expected temporal distributions of nodes under a null model of stochastic lineage bifurcation and extinction. These Markovian models of phylogenetic process were constructed so as to permit direct comparisons against empirical phylogenetic trees generated from molecular or other information available solely from extant species. For replicate simulated phylads with n extant species, cumulative distribution functions (cdf's) of branching times were calculated, and compared (using the Kolmogorov-Smirnov test statistic D) to those from three published empirical trees. Molecular phylogenies for columbine plants and avian cranes showed statistically significant departures from the null expectations, in directions indicating recent and ancient species' radiations, respectively, whereas a molecular phylogeny for the Drosophila virilis species group showed no apparent historical clustering of branching events. Effects of outgroup choice and phylogenetic frame of reference were investigated for the columbines and found to have a predictable influence on the types of conclusions to be drawn from such analyses. To enable other investigators to statistically test for nonrandomness in temporal cladogenetic pattern in empirical trees generated from data on extant species, we present tables of mean cdf's and associated probabilities under the null model for expected branching times in phylads of varying size. The approaches developed in this report complement and extend those of other recent methods for employing null models to assess the statistical significance of pattern in evolutionary trees.

Development and application of long-PCR for the assay of full-length animal mitochondrial DNA.

Abstract: Keywords: polymerase chain reaction; molecular evolution; DNA amplification; restriction fragment length polymorphisms

Molecular genetic analysis of a stepped multilocus cline in the

Abstract: Gulf of Mexico versus Atlantic populations of several coastal species in the southeastern United States are known to differ sharply in genetic composition, but most transitional zones have not previously been examined in detail. Here we employ molecular markers from mitochondrial and nuclear loci to characterize cytonuclear genetic associations at meso- and microgeographic scales along an eastern Florida transitional zone between genetically distinct Atlantic and Gulf populations of the American oyster, Crassostrea virginica. The single- and multilocus cytonuclear patterns display: (1) a cline extending along 340 km of the east Florida coastline; (2) a pronounced step in the cline centered at Cape Canaveral (shifts in allelic frequencies by 50-75% over a 20 km distance); (3) a close agreement of observed genotypic frequencies with Hardy-Weinberg expectations within locales; and (4) mild or nonexistent nuclear and cytonuclear disequilibria in most local population samples. These results imply: (1) considerable restrictions to interpopulational gene flow along the eastern Florida coastline; (2) within locales, free interbreeding (as opposed to mere population admixture) between Gulf and Atlantic forms of oysters; and (3) localized population recruitment in the transition zone localities. These findings demonstrate that marine organisms with high dispersal potential via long-lived pelagic larvae can nonetheless display pronounced spatial population genetic structure, and more generally they exemplify the utility of pronounced genetic transition zones for the study of population level processes.