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H. C. J. Godfray - One of the best experts on this subject based on the ideXlab platform.

  • SEX RATIO STRATEGIES AFTER PERTURBATION OF THE Stable Age Distribution
    Journal of Theoretical Biology, 1997
    Co-Authors: Stuart A. West, H. C. J. Godfray
    Abstract:

    Abstract Animals with overlapping generations may be selected to change their sex ratios after perturbation of the Stable Age Distribution. Specifically, Werren and Taylor have shown that in a tightly regulated population with normally constant recruitment, sex ratios are based at times of exceptional recruitment towards the sex with the most even Distribution of reproductive value over its adult life. It is shown that an episode of exceptional recruitment also affects the optimal sex ratios of cohorts born subsequently, although the sex ratio adjustment is typically in the opposite direction. It is also shown that the expected sex ratio depends critically on female mating behaviour: whether females mate throughout their reproductive life or, as in many insects, once after emergence. Perturbation of the Stable Age Distribution by an episode of exceptional mortality may also lead to selection for biased sex ratios, even if the mortality affects both sexes equally.

Stuart A. West - One of the best experts on this subject based on the ideXlab platform.

  • SEX RATIO STRATEGIES AFTER PERTURBATION OF THE Stable Age Distribution
    Journal of Theoretical Biology, 1997
    Co-Authors: Stuart A. West, H. C. J. Godfray
    Abstract:

    Abstract Animals with overlapping generations may be selected to change their sex ratios after perturbation of the Stable Age Distribution. Specifically, Werren and Taylor have shown that in a tightly regulated population with normally constant recruitment, sex ratios are based at times of exceptional recruitment towards the sex with the most even Distribution of reproductive value over its adult life. It is shown that an episode of exceptional recruitment also affects the optimal sex ratios of cohorts born subsequently, although the sex ratio adjustment is typically in the opposite direction. It is also shown that the expected sex ratio depends critically on female mating behaviour: whether females mate throughout their reproductive life or, as in many insects, once after emergence. Perturbation of the Stable Age Distribution by an episode of exceptional mortality may also lead to selection for biased sex ratios, even if the mortality affects both sexes equally.

T.k. Singh - One of the best experts on this subject based on the ideXlab platform.

  • Comparative life table studies of Aphis gossypii Glover (Homoptera: Aphididae) on two host plants.
    Indian journal of entomology, 2010
    Co-Authors: M.a. Sattar Shah, T.k. Singh, G.k.n. Chhetry
    Abstract:

    Life table studies of Aphis gossypii Glover revealed that the net reproductive rate was higher on brinjal (29.225 females/female/generation) than on okra (25.621 females/female/generation) and the intrinsic rate of increase (rm) was also higher on brinjal. Brinjal was found to be better host of A. gossypii when compared to okra as the pest revealed higher fecundity,higher net reproductive rate (Ro), higher intrinsic rate of increase (rm) and shorter doubling time (DT). On both the host plants, the maximum contribution towards the Stable Age Distribution was made by nymphs, and the life expectancy of A. gossypii declined gradually with the advancement of Age.

  • Life table, Stable Age, Distribution and life expectancy of Aphis gossypii glover on okra
    Annals of Plant Protection Sciences, 2007
    Co-Authors: M.a. Sattar Shah, T.k. Singh, G.k.n. Chhetry
    Abstract:

    Life table and Age specific fecundity of aphis gossypii was studied on Okra in the laboratory (26.05 ± 0.71°C temperature, 79.55 ± 1.28% R.H.). The net reproductive rate was evaluated as 26.62 females/female/generation. The intrinsic rate of increase (rm) and finite rate of increase (λ) were worked out as 0.312 and 1.379 females/female/day, respectively. On reaching the Stable Age Distribution, the population comprised mainly of nymphs and the life expectancy (ex) of A. gossypii declined gradually with the advancement of Age.

  • Life-table, Stable-Age Distribution and life expectancy of Plutella xylostella (Linnaeus) on Brassica juncea var. rugosa
    Annals of Plant Protection Sciences, 2005
    Co-Authors: O. Hemchandra, T.k. Singh
    Abstract:

    The number of Plutella xylostella that survived from egg to adult emergence was worked out. The net reproductive rate (R0) was 24.916 representing total female birth with a mean length of generation (T0) being 29.428. The population increase with intrinsic rate of increase (rm) was 0.1109 and finite rate of increase (λ) was 1.117 females/female/day. On reaching the Stable-Age Distribution, the population comprised mainly of immature stAges and further life at the time of adult emergence was reduced from 7.59 to 5.47 days.

  • LIFE TABLE, RATE OF INCREASE AND Stable-Age Distribution OF PLUTELLA XYLOSTELLA (LINN.) ON KNOL KHOL
    Uttar Pradesh Journal of Zoology, 2004
    Co-Authors: O. Hemchandra, T.k. Singh
    Abstract:

    Studies on life table, rate of increase and Stable-Age Distribution for the Plutella xylostella were carried out in laboratory on knol khol during February and March 2000, At Department of Life Sciences, Manipur University, Canchipur. The numbers that survived from egg to adult emergence was worked out. The net reproductive rate (R) was 19.2303 representing total birth with a mean length of generation (T,) being 32.542. The population increase with intrinsic rate of increase (r) was 0.092.12 and finite rate of increase ().) was 1.09649 females per female per day. On reaching the Stable-Age Distribution the population comprised mainly of immature stAges and further life at the time of adult emergence was reduced from 9.51 to 5.27.

  • Life Table, Rate of Increase and Stable-Age Distribution of Plutella xylostella (Linnaeus) on Cauliflower
    Annals of Plant Protection Sciences, 2003
    Co-Authors: O. Hemchandra, T.k. Singh
    Abstract:

    The net reproductive rate (R0) was 27.19 representing total female birth with a mean length of generation (Tc) 26.54 was determined. The population increase with intrinsic rate of increase (rm) was 0.12 and finite rate of increase (λ) was 1.13 females/female/day. On reaching the Stable-Age distributin, the population comprised mainly of immature stAges and further life at the time of adult emergence, was reduced from 7.40 to 3.11 days.

Punit Vaibhav Patel - One of the best experts on this subject based on the ideXlab platform.

  • Life Table, Rate of increase and Stable Age Distribution of Spodoptera litura (Fabricius) on cotton
    Annals of Plant Protection Sciences, 2008
    Co-Authors: M.v. Gedia, H.j. Vyas, M.f. Acharya, Punit Vaibhav Patel
    Abstract:

    The studies on life fecundity tables of Spodoptera litura were carried out on cotton at 27±1°C under laboratory conditions. The next reproductive rate (Ro) was 316.14 females with the generation period (T) of 39.75 days. The innate capacity for increase (Rm) and finite rate of increase (λ) were found to be 0.1448 and 1.1558 females/day, respectively with a weekly multiplication rate of 2.7555 times. The per cent contribution of eggs, larvae, pupae and adults were 54.4, 42.4, 2.6 and 0.4, respectively at Stable Age Distribution of S. litura on cotton.

  • Studies on life fecundity tables of Spodoptera litura (Fabricius) on groundnut
    Annals of Plant Protection Sciences, 2008
    Co-Authors: M.v. Gedia, H.j. Vyas, M.f. Acharya, Punit Vaibhav Patel
    Abstract:

    Studies on life fecundity tables of Spodoptera litura, were carried out on groundnut cv. GG 20 at constant temperature of 271°C under laboratory. The net reproductive rate (Ro) was 510.79 females with the generation period (T) of 35.67 days. The innate capacity for increase (Rm) and finite rate of increase () were found to be 0.1748 and 1.1910 females/day, respectively with a weekly multiplication rate of 3.3994 times. The % contribution of eggs, larvae, pupae and and adults were 52.0, 46.4, 1.3 and 0.3%, respectivlely at Stable Age Distribution of S. litura on groundnut.

  • Life Table, Intrinsic Rate of Increase and Age-specific Distribution of Helicoverpa armigera (Hübner) on Cotton
    Annals of Plant Protection Sciences, 2007
    Co-Authors: M.f. Acharya, M.v. Gedia, H.j. Vyas, Punit Vaibhav Patel
    Abstract:

    The reproductive rate (Ro) of Helicoverpa armigera was 376.01 representing total female birth with a mean length of generation (Tc) 42.99 days was determined on cotton. The population increase with intrinsic rate of increase (rm) was 0.1379 and finite rate of increase (λ) was 1.1489 females/female/day. On reaching Stable Age Distribution, the population comprised mainly of immature stAges and further life at the time of adult emergence, was reduced from 16.38 to 1.75 days.

Leah Gerber - One of the best experts on this subject based on the ideXlab platform.

  • Short- and long-term population response to changes in vital rates: implications for population viability analysis
    Ecological Applications, 2010
    Co-Authors: Haridas Chirakkal, Leah Gerber
    Abstract:

    Conservation practitioners use demographic population viability analysis (PVA) to understand long-term effects of changing demographic rates on population growth rate. Sensitivities and elasticities of stAge-specific survival and fertility rates provide manAgers with guidelines on the relative contributions of various life-history stAges to long-term population growth. However, short-term patterns, especially single-year effects, of elasticity may be dramatically different from long-term effects, calling for caution in implementing manAgement policies focusing entirely on only long- or short-term elasticities. Here we illustrate the temporal and spatial variation in elasticity patterns for four populations of California sea lions. Short-term stochastic elasticities were significantly different from long- term elasticities, and spatial patterns of short- and long-term elasticities varied across sites. These differences may be explained by transient effects in Age structure and deviations from the Stable Age Distribution, as well as environmental variation. Our results suggest that conservation practitioners should consider calculations of both short-and long-term elasticity in viability analyses that are used to guide manAgement and should use caution in generalizing elasticity patterns across populations.