The Experts below are selected from a list of 46932 Experts worldwide ranked by ideXlab platform

Tim L. King - One of the best experts on this subject based on the ideXlab platform.

  • Spatiotemporal Analysis of gene flow in Chesapeake Bay Diamondback Terrapins (Malaclemys terrapin).
    Molecular ecology, 2015
    Co-Authors: Paul E. Converse, Willem M. Roosenburg, Shawn R. Kuchta, Paula F. P. Henry, G. Michael Haramis, Tim L. King
    Abstract:

    There is widespread concern regarding the impacts of anthropogenic activities on connectivity among populations of plants and animals, and understanding how contemporary and historical processes shape metapopulation dynamics is crucial for setting appropriate conservation targets. We used genetic data to identify population clusters and quantify gene flow over historical and contemporary time frames in the Diamondback Terrapin (Malaclemys terrapin). This species has a long and complicated history with humans, including commercial overharvesting and subsequent translocation events during the early twentieth century. Today, terrapins face threats from habitat loss and mortality in fisheries bycatch. To evaluate population structure and gene flow among Diamondback Terrapin populations in the Chesapeake Bay region, we sampled 617 individuals from 15 localities and screened individuals at 12 polymorphic microsatellite loci. Our goals were to demarcate metapopulation structure, quantify genetic diversity, estimate effective population sizes, and document temporal changes in gene flow. We found that terrapins in the Chesapeake Bay region harbour high levels of genetic diversity and form four populations. Effective population sizes were variable. Among most population comparisons, estimates of historical and contemporary terrapin gene flow were generally low (m ≈ 0.01). However, we detected a substantial increase in contemporary gene flow into Chesapeake Bay from populations outside the bay, as well as between two populations within Chesapeake Bay, possibly as a consequence of translocations during the early twentieth century. Our study shows that inferences across multiple time scales are needed to evaluate population connectivity, especially as recent changes may identify threats to population persistence.

Earl Taylor - One of the best experts on this subject based on the ideXlab platform.

  • geo referenced Spatiotemporal Analysis of the urban citrus canker epidemic in florida
    Phytopathology, 2002
    Co-Authors: T R Gottwald, Tim Riley, J H Graham, Frank Ferrandino, Earl Taylor
    Abstract:

    Gottwald, T. R., Sun, X., Riley, T., Graham, J. H., Ferrandino, F., and Taylor, E. L. 2002. Geo-referenced Spatiotemporal Analysis of the urban citrus canker epidemic in Florida. Phytopathology 92:361-377. Five areas in urban Miami were identified to study the spread of Xanthomonas axonopodis pv. citri to determine if the practice of removing exposed citrus trees within 38.1 m of trees affected by citrus canker was adequate to curtail further bacterial spread. To accomplish this, 18,769 trees in dooryards were surveyed, geo-referenced by differential global positioning systems (GPS), and assayed for disease severity, age of infection, citrus cultivar, location of infection in tree, and canopy size. For each tree, the date the tree became infected was estimated and used to separate trees into contiguous 30-day categories. For each area studied, distance measurements between focal trees and newly infected trees were calculated for various temporal periods of 30, 60, 90, and 120 days in duration, corresponding to intervals of inspection survey. A visual basic application was used to calculate the distances between each newly diseased tree and all prior focal trees. The nearest distance was used because it was considered the most conservative estimate possible. It is therefore likely to be an underestimate of spread but is a good estimate of the minimum possible distances of spread. For the first four 30-day periods among the five study areas, calculated maximum distances of spread ranged from 12 to 3,474 m, indicating a broad continuum of distance for bacterial spread was possible. Disease increased during the first two-thirds of the time studied and reached an asymptote due to dry conditions in the final one-third of the duration of the study. Cross correlation Analysis indicated that disease was best visualized 107 days following rainstorms with wind. Analysis of regional spatial point patterns was performed temporally for each 30-day period via a modified Ripley’s K-function. Spatiotemporal analyses between periods over areas larger than previously examined were accomplished via Spatiotemporal semivariogram Analysis. These methods in combination demonstrated rapid increases in range of spatial dependency and range of Spatiotemporal dependency for all study sites. This corresponded to rapid spread of disease across the regions studied in response to rainstorms with wind followed by a “filling in” of disease on remaining noninfected susceptible trees through time by less intense rain events. A stochastic quadratization technique demonstrated that disease incidence and disease severity were not greatly affected by urban host density but were positively correlated to host susceptibility within local 0.25-km 2

  • geo referenced Spatiotemporal Analysis of the urban citrus canker epidemic in florida
    Phytopathology, 2002
    Co-Authors: T R Gottwald, Tim Riley, J H Graham, Frank Ferrandino, Xiaoan Sun, Earl Taylor
    Abstract:

    Gottwald, T. R., Sun, X., Riley, T., Graham, J. H., Ferrandino, F., and Taylor, E. L. 2002. Geo-referenced Spatiotemporal Analysis of the urban citrus canker epidemic in Florida. Phytopathology 92:361-377. Five areas in urban Miami were identified to study the spread of Xanthomonas axonopodis pv. citri to determine if the practice of removing exposed citrus trees within 38.1 m of trees affected by citrus canker was adequate to curtail further bacterial spread. To accomplish this, 18,769 trees in dooryards were surveyed, geo-referenced by differential global positioning systems (GPS), and assayed for disease severity, age of infection, citrus cultivar, location of infection in tree, and canopy size. For each tree, the date the tree became infected was estimated and used to separate trees into contiguous 30-day categories. For each area studied, distance measurements between focal trees and newly infected trees were calculated for various temporal periods of 30, 60, 90, and 120 days in duration, corresponding to intervals of inspection survey. A visual basic application was used to calculate the distances between each newly diseased tree and all prior focal trees. The nearest distance was used because it was considered the most conservative estimate possible. It is therefore likely to be an underestimate of spread but is a good estimate of the minimum possible distances of spread. For the first four 30-day periods among the five study areas, calculated maximum distances of spread ranged from 12 to 3,474 m, indicating a broad continuum of distance for bacterial spread was possible. Disease increased during the first two-thirds of the time studied and reached an asymptote due to dry conditions in the final one-third of the duration of the study. Cross correlation Analysis indicated that disease was best visualized 107 days following rainstorms with wind. Analysis of regional spatial point patterns was performed temporally for each 30-day period via a modified Ripley’s K-function. Spatiotemporal analyses between periods over areas larger than previously examined were accomplished via Spatiotemporal semivariogram Analysis. These methods in combination demonstrated rapid increases in range of spatial dependency and range of Spatiotemporal dependency for all study sites. This corresponded to rapid spread of disease across the regions studied in response to rainstorms with wind followed by a “filling in” of disease on remaining noninfected susceptible trees through time by less intense rain events. A stochastic quadratization technique demonstrated that disease incidence and disease severity were not greatly affected by urban host density but were positively correlated to host susceptibility within local 0.25-km 2

Emanuel Donchin - One of the best experts on this subject based on the ideXlab platform.

  • Spatiotemporal Analysis of the late erp responses to deviant stimuli
    Psychophysiology, 2001
    Co-Authors: Kevin M Spencer, Joseph Dien, Emanuel Donchin
    Abstract:

    We used a novel application of principal components Analysis ~Spatiotemporal PCA! to decompose the event-related brain potentials ~ERPs! obtained with a dense electrode array, with the purpose of elucidating the late ERP components elicited by deviant stimuli under “attend” and “ignore” conditions. First, a “spatial” PCA was performed to identify a set of scalp distributions ~spatial factors or “virtual electrodes” ! that accounted for the spatial variance in the data set. The data were expressed as spatial factor scores or “virtual ERPs” measured at each of the virtual electrodes. These virtual ERPs were submitted to a “temporal” PCA, yielding a set of temporal factors or “virtual epochs.” Statistical analyses of the temporal factor scores found that ~1! attended deviant stimuli elicited the P300 and Novelty P3 components, the latter being largest for highly salient nontargets; ~2! “ignored” deviants elicited a small Novelty P3, and depending on the primary task, a small P300; and ~3! the classical Slow Wave consisted of separate frontal-negative and posterior-positive components. Descriptors: P300, Novelty P3, P3a, Slow Wave, Dense electrode array, Principal components Analysis In this report we examine in some detail the relationships between late components of the event-related brain potential ~ERP! that are elicited by deviant events, under different conditions or in response to different stimuli. Our data are consistent with the assertion that the P300 and Novelty P3 are indeed distinct components of the ERP, characterized by different scalp distributions and different responses to experimental manipulations ~see Donchin, Ritter, & McCallum, 1978, for an examination of the concept of the ERP component!. The P3a, on the other hand, appears to be a sum of the Novelty P3 and P300 components, the precise combination of which depends on experimental conditions. If these data are deemed persuasive, we suggest that investigators would do well to cease formulating their results in terms of a “late positive complex” whose elements are indistinguishably conflated, but would instead focus on the specific components elicited in their study. In their report on Publication Criteria for studies of ERPs,

  • Spatiotemporal Analysis of the late erp responses to deviant stimuli
    Psychophysiology, 2001
    Co-Authors: Kevin M Spencer, Joseph Dien, Emanuel Donchin
    Abstract:

    We used a novel application of principal components Analysis (Spatiotemporal PCA) to decompose the event-related brain potentials (ERPs) obtained with a dense electrode array, with the purpose of elucidating the late ERP components elicited by deviant stimuli under “attend” and “ignore” conditions. First, a “spatial” PCA was performed to identify a set of scalp distributions (spatial factors or “virtual electrodes”) that accounted for the spatial variance in the data set. The data were expressed as spatial factor scores or “virtual ERPs” measured at each of the virtual electrodes. These virtual ERPs were submitted to a “temporal” PCA, yielding a set of temporal factors or “virtual epochs.” Statistical analyses of the temporal factor scores found that (1) attended deviant stimuli elicited the P300 and Novelty P3 components, the latter being largest for highly salient nontargets; (2) “ignored” deviants elicited a small Novelty P3, and depending on the primary task, a small P300; and (3) the classical Slow Wave consisted of separate frontal-negative and posterior-positive components.

Paul E. Converse - One of the best experts on this subject based on the ideXlab platform.

  • Spatiotemporal Analysis of gene flow in Chesapeake Bay Diamondback Terrapins (Malaclemys terrapin).
    Molecular ecology, 2015
    Co-Authors: Paul E. Converse, Willem M. Roosenburg, Shawn R. Kuchta, Paula F. P. Henry, G. Michael Haramis, Tim L. King
    Abstract:

    There is widespread concern regarding the impacts of anthropogenic activities on connectivity among populations of plants and animals, and understanding how contemporary and historical processes shape metapopulation dynamics is crucial for setting appropriate conservation targets. We used genetic data to identify population clusters and quantify gene flow over historical and contemporary time frames in the Diamondback Terrapin (Malaclemys terrapin). This species has a long and complicated history with humans, including commercial overharvesting and subsequent translocation events during the early twentieth century. Today, terrapins face threats from habitat loss and mortality in fisheries bycatch. To evaluate population structure and gene flow among Diamondback Terrapin populations in the Chesapeake Bay region, we sampled 617 individuals from 15 localities and screened individuals at 12 polymorphic microsatellite loci. Our goals were to demarcate metapopulation structure, quantify genetic diversity, estimate effective population sizes, and document temporal changes in gene flow. We found that terrapins in the Chesapeake Bay region harbour high levels of genetic diversity and form four populations. Effective population sizes were variable. Among most population comparisons, estimates of historical and contemporary terrapin gene flow were generally low (m ≈ 0.01). However, we detected a substantial increase in contemporary gene flow into Chesapeake Bay from populations outside the bay, as well as between two populations within Chesapeake Bay, possibly as a consequence of translocations during the early twentieth century. Our study shows that inferences across multiple time scales are needed to evaluate population connectivity, especially as recent changes may identify threats to population persistence.

T R Gottwald - One of the best experts on this subject based on the ideXlab platform.

  • geo referenced Spatiotemporal Analysis of the urban citrus canker epidemic in florida
    Phytopathology, 2002
    Co-Authors: T R Gottwald, Tim Riley, J H Graham, Frank Ferrandino, Earl Taylor
    Abstract:

    Gottwald, T. R., Sun, X., Riley, T., Graham, J. H., Ferrandino, F., and Taylor, E. L. 2002. Geo-referenced Spatiotemporal Analysis of the urban citrus canker epidemic in Florida. Phytopathology 92:361-377. Five areas in urban Miami were identified to study the spread of Xanthomonas axonopodis pv. citri to determine if the practice of removing exposed citrus trees within 38.1 m of trees affected by citrus canker was adequate to curtail further bacterial spread. To accomplish this, 18,769 trees in dooryards were surveyed, geo-referenced by differential global positioning systems (GPS), and assayed for disease severity, age of infection, citrus cultivar, location of infection in tree, and canopy size. For each tree, the date the tree became infected was estimated and used to separate trees into contiguous 30-day categories. For each area studied, distance measurements between focal trees and newly infected trees were calculated for various temporal periods of 30, 60, 90, and 120 days in duration, corresponding to intervals of inspection survey. A visual basic application was used to calculate the distances between each newly diseased tree and all prior focal trees. The nearest distance was used because it was considered the most conservative estimate possible. It is therefore likely to be an underestimate of spread but is a good estimate of the minimum possible distances of spread. For the first four 30-day periods among the five study areas, calculated maximum distances of spread ranged from 12 to 3,474 m, indicating a broad continuum of distance for bacterial spread was possible. Disease increased during the first two-thirds of the time studied and reached an asymptote due to dry conditions in the final one-third of the duration of the study. Cross correlation Analysis indicated that disease was best visualized 107 days following rainstorms with wind. Analysis of regional spatial point patterns was performed temporally for each 30-day period via a modified Ripley’s K-function. Spatiotemporal analyses between periods over areas larger than previously examined were accomplished via Spatiotemporal semivariogram Analysis. These methods in combination demonstrated rapid increases in range of spatial dependency and range of Spatiotemporal dependency for all study sites. This corresponded to rapid spread of disease across the regions studied in response to rainstorms with wind followed by a “filling in” of disease on remaining noninfected susceptible trees through time by less intense rain events. A stochastic quadratization technique demonstrated that disease incidence and disease severity were not greatly affected by urban host density but were positively correlated to host susceptibility within local 0.25-km 2

  • geo referenced Spatiotemporal Analysis of the urban citrus canker epidemic in florida
    Phytopathology, 2002
    Co-Authors: T R Gottwald, Tim Riley, J H Graham, Frank Ferrandino, Xiaoan Sun, Earl Taylor
    Abstract:

    Gottwald, T. R., Sun, X., Riley, T., Graham, J. H., Ferrandino, F., and Taylor, E. L. 2002. Geo-referenced Spatiotemporal Analysis of the urban citrus canker epidemic in Florida. Phytopathology 92:361-377. Five areas in urban Miami were identified to study the spread of Xanthomonas axonopodis pv. citri to determine if the practice of removing exposed citrus trees within 38.1 m of trees affected by citrus canker was adequate to curtail further bacterial spread. To accomplish this, 18,769 trees in dooryards were surveyed, geo-referenced by differential global positioning systems (GPS), and assayed for disease severity, age of infection, citrus cultivar, location of infection in tree, and canopy size. For each tree, the date the tree became infected was estimated and used to separate trees into contiguous 30-day categories. For each area studied, distance measurements between focal trees and newly infected trees were calculated for various temporal periods of 30, 60, 90, and 120 days in duration, corresponding to intervals of inspection survey. A visual basic application was used to calculate the distances between each newly diseased tree and all prior focal trees. The nearest distance was used because it was considered the most conservative estimate possible. It is therefore likely to be an underestimate of spread but is a good estimate of the minimum possible distances of spread. For the first four 30-day periods among the five study areas, calculated maximum distances of spread ranged from 12 to 3,474 m, indicating a broad continuum of distance for bacterial spread was possible. Disease increased during the first two-thirds of the time studied and reached an asymptote due to dry conditions in the final one-third of the duration of the study. Cross correlation Analysis indicated that disease was best visualized 107 days following rainstorms with wind. Analysis of regional spatial point patterns was performed temporally for each 30-day period via a modified Ripley’s K-function. Spatiotemporal analyses between periods over areas larger than previously examined were accomplished via Spatiotemporal semivariogram Analysis. These methods in combination demonstrated rapid increases in range of spatial dependency and range of Spatiotemporal dependency for all study sites. This corresponded to rapid spread of disease across the regions studied in response to rainstorms with wind followed by a “filling in” of disease on remaining noninfected susceptible trees through time by less intense rain events. A stochastic quadratization technique demonstrated that disease incidence and disease severity were not greatly affected by urban host density but were positively correlated to host susceptibility within local 0.25-km 2