John A. Jackman

Texas A&M University, College Station, TX, United States

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Publications (5)10.41 Total impact

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    ABSTRACT: This paper extends the application of the cumulative size based mechanistic model, which has previously been shown to describe diverse aphid population size data well. The mechanistic model is reviewed with a focus on the explanatory role of the birth and death rate formulation. An analysis of two data sets, one on the mustard aphid and the other on the pecan aphid, indicates that multiple linear regression equations based on the estimated birth and death rate parameters alone account for nearly all (R2 > 0.95) of the variability in two key population attributes, namely the peak count and the cumulative density. This indicates that population size variables may be projected directly from the growth rate parameters using linear equations. Such linear relationships based on the birth and death rate parameters are shown to hold also for certain generalized mechanistic models for which the analytical solution is not available. The birth and death rate coefficients, therefore, constitute a new succinct set of variables that could be included in the predictive modeling of aphid populations, as well as other insect and animal populations with local collapse which follow similar growth dynamics.
    Ecological Modelling 01/2008; 213(1):133-142. · 2.07 Impact Factor
  • John A. Jackman, Allen Dean, Mike Quinn
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    ABSTRACT: The occurrence of a large spider web at Lake Tawakoni State Park has received considerable attention by the media and the public. This study reports the identifications of a sample of the spiders found at that site. Various explanations of this case are discussed.
    Southwestern Entomologist 11/2007; · 0.50 Impact Factor
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    ABSTRACT: This paper investigates the use of a mechanistic model for describing the size of local aphid populations, specifically of the pecan aphid (Monellia caryella) and of the mustard aphid (Lipaphis erysimi). The mechanistic equation, like the logistic growth model, has parameters for a birth rate and a death rate, however the present mechanistic model generalizes the logistic growth model by incorporating the cumulative size of past generations into growth rate assumptions. A new non-linear regression model is derived, which solves the mechanistic model analytically and which may be fitted to data. The parameters of the regression model are the predicted peak size, Nmax⁡, the predicted time of peak, tmax⁡, and an approximate per capita birth rate, b, all of which are of interest in practical applications. The regression model is shown to fit diverse abundance curves adequately. The model also explains the population growth curves through the underlying rates. Simple approximations, based on these parameters, for the peak count and for the final cumulative aphid density are derived, and shown to be accurate. In general, this paper demonstrates the utility of analyzing local aphid population data using mechanistic models and their underlying rate parameters.
    Ecological Modelling 01/2007; 205:81-92. · 2.07 Impact Factor
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    Christopher G. Majka, John A. Jackman
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    ABSTRACT: Abstract—The Mordellidae of the Maritime provinces of Canada is surveyed. Thirty species have now been recorded from the region. Of these, 17 are newly recorded for Nova Scotia, 11 are newly recorded for Prince Edward Island, and 7 are newly recorded for New Brunswick, for a to- tal of 35 new provincial records. Three species, Mordellistena indistincta Smith, Mordellistena rubrifascia Liljeblad, and Mordellistena rubrilabris Helmuth, are newly recorded for Canada, while a further 11 species, Mordella melaena Germar, Mordellistena aspersa (Melsheimer), Mordellistena errans Fall, Mordellistena morula LeConte, Mordellistena picilabris Helmuth, Mordellistena sericans Fall, Mordellistena vilis (LeConte), Mordellina ancilla (LeConte), Mordellina nigricans (Melsheimer), Mordellina pustulata (Melsheimer), and Glipostenoda ambusta (LeConte), are newly recorded for Atlantic Canada. One subspecies, Mordella atrata lecontei Csiki, is removed from the region’s faunal listing. The composition of the region’s fauna as a whole, and related biogeographic questions, are briefly discussed. The Mordellidae are also discussed in the context of forest beetle communities,in the region and the impact of historical forest management,practices on old-growth specialist species. Résumé—Cet article examine le Mordellidae des provinces maritimes du Canada. À date, on a
    The Canadian Entomologist 01/2006; 138(3):292-304. · 0.90 Impact Factor
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    ABSTRACT: Host-race formation remains controversial as a source of herbivorous insect diversity, and examples of host races are still fairly scarce. In this study, analysis of five enzyme loci in the ostensibly generalist tumbling flower beetle Mordellistena convicta (Coleoptera: Mordellidae) revealed hidden host-plant and plant-organ related genetic differentiation. Mordellistena convicta turned out to be a complex of cryptomorphic species, each with fewer hosts than the nominal species. These cryptic species, in turn, were divided into taxa that showed host-race characteristics: samples from different host plants and organs exhibited (1) genetic indications of partial reproductive isolation, (2) differences in size and emergence timing that suggested divergent host-related selection, and (3) among-host selective differences in mortality from parasitoids. Host-race formation in M. convicta, which has a somewhat different life history from the well-studied host races, enlarges the group of insects considered likely to undergo this process. The widespread sympatry of the M. convicta species complex, along with its spectrum of host-correlated genetic differentiation, suggests that these host specialist taxa developed in sympatry.
    Evolution 03/2005; 59(2):304-16. · 4.86 Impact Factor