Population Ecology: A Unified Study of Animals and Plants.

Blower, J. Gordon; Begon, Mike; Mortimer, M.

doi:10.2307/2260115

Cited by 12 publications

(14 citation statements)

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“…It is surprising that there have been few attempts to assess the effects of plant density on dose–response relationships, given the well‐known effects that density has on the outcome of competition (Begon & Mortimer 1986; Firbank & Watkinson 1990; Goldberg & Barton 1992) and the general acceptance of its importance in commercial plant growing. The limited information that is available comes from a study on flame weeding showing that plant density was not as important as the size of plant in determining a plant’s response to flame weeding (Ascard 1994).…”

Section: Discussionmentioning

confidence: 99%

The effect of plant density on the response of Agrostemma githago to herbicide

Humphry

Mortimer

Marrs

2001

Journal of Applied Ecology

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Summary1. The estimation of dose-response relationships is an integral and legally necessary part of the routine regulatory process for herbicides. For each herbicide, plants of both target and non-target species are exposed to different levels of the chemical, and effects on mortality and performance expressed as LD 50 and ED 50 values (respectively, the dose at which 50% of plants die and the dose at which plants show a 50% response to herbicide). Thereafter, LD 50 and ED 50 values may provide comparative information between herbicides and species. There is little published on the effects of plant density on dose-response relationships. 2. We used the herbicide 2,4-D amine and Agrostemma githago as a model system to investigate the effects of plant density on the dose-response relationship (ED 50 ) between 2,4-D and A. githago biomass measured as fresh weight. 3. Plants were grown in a controlled environment room at both low and high densities (two and 64 plants per pot) for 2 weeks, sprayed with 2,4-D using a precision sprayer, and then harvested after a further 2 weeks. The ED 50 values were significantly greater when the plants were grown at high density (616 g active ingredient ha -1 ) than those grown at low density (42 g active ingredient ha -1 ); a 15-fold difference. 4. Mathematically, it was shown that a simple multiplicative relationship exists between ED 50 and dose received when plants are grown at different densities, all other conditions being equal. 5. To explore the underlying effects of competitive processes arising from different densities, we experimentally investigated three phases where competition could be influencing the response of plants: (i) before spraying, (ii) at the time of spraying and (iii) after spraying. We used a sequential series of experiments to determine which phase was contributing most to the observed difference between ED 50 values obtained from plants grown at low and high density. 6. It was shown that the competition between plants after spraying was the most likely phase to have contributed to the observed difference in ED 50 values between the two densities.7. These results demonstrate that trials used in the pesticide regulatory process ought to test not only different doses of pesticide but also different densities of plants (both crop and weed).

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Section: Discussionmentioning

confidence: 99%

The effect of plant density on the response of Agrostemma githago to herbicide

Humphry

Mortimer

Marrs

2001

Journal of Applied Ecology

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“…Still, many ecologists insist that populations can be regulated by social behaviour (e.g. Watson & Moss 1970, Klomp 1972, Patterson 1980, Begon & Mortimer 1981, Hassel & May 1985, Moss & Watson 1985. Others are less precise, only suggesting that social behaviour affects population dynamics (e.g.…”

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confidence: 99%

Territory economics and population stability—can populations be socially regulated?

Schantz

1991

Ornis Svec

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Although Wynne-Edwards' group selectionist theory of population regulation was soon rejected, the concept of social regulation still remains in the literature. Here I examine the importance of social behaviour (e.g. territoriality) in population regulation from an individual selectionist point of view. One of Watson and Moss' criteria for population regulation through social behaviour is that the individuals should defend resources that exceed their need for survival and reproduction. This is an analogy to Verner's super territory model which is not compatible with optimality theory. Moreover, the observations that per capita reproductive rate decreases with increased group size has often been taken as a sign of social regulation at the group level. However, it can be demonstrated, both theoretically and empirically, that population rate of increase as well as the population's efficiency of converting resources into reproduction can increase with increased population density in spite of a decrease in per capita reproductive rate. These correlations reduce population stability in variable environments. To be effectively regulative social behaviour must induce a negative correlation between efficiency of converting resources into reproduction and population density. With this background I conclude that the importance of social regulation is highly exaggerated. It is only in a special case that social behaviour can induce population stability in variable environments, viz. in permanently territorial species whose life expectancy exceeds the average time period of the environmental fluctuations.

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“…Una población es un conjunto de organismos de la misma especie que habitan en la misma área e interactúan entre sí (Krebs, 1985;Silvertown y Lovett Doust, 1995;Gotelli, 2008). La demografía es una ciencia que ayuda a describir numéricamente a las poblaciones mediante las descripción del tamaño, la densidad, la distribución espacial, la estructura poblacional, la proporción de sexos y los parámetros demográficos básicos (tasa de natalidad, de mortalidad, de inmigración y de emigración), en un intervalo de tiempo determinado (Harper y White, 1974;Caswell, 1989;Franco, 1990;Silvertown y Lovett Doust, 1995;Begon et al, 1996). Estos parámetros están relacionados con la historia de vida de las especies (Caswell, 1989;Silvertown y Lovett Doust, 1995;Krebs, 1999;Gotelli, 2008).…”

Section: Ecología De Poblacionesunclassified

“…donde Nt+1 es el número de individuos en el tiempo t+1, Nt es el número de individuos que compone la población en el tiempo t, B y D son el número de nacimientos y de muertes, respectivamente, que hubo entre el tiempo t y el t+1, I y E son la cantidad de organismos que inmigraron y emigraron en dicho periodo, respectivamente (Krebs, 1985;Silvertown y Lovett Doust, 1995;Begon et al, 1996;Gurevitch et al, 2006).…”

Section: Ecología De Poblacionesunclassified

“…La estructura estable de tamaños o edades corresponde al eigen-vector derecho de la matriz. Éste se obtiene iterando la matriz A (multiplicándola por un vector) y posteriormente multiplicándola por los vectores que vayan resultando de cada multiplicación, hasta obtener vectores cuyas proporciones internas se mantienen constantes (Caswell, 1989;Silvertown y Lovett Doust, 1995;Begon et al, 1996). Si se repite el mismo procedimiento, pero con la matriz transpuesta, entonces el vector estable que se alcanza corresponde al vector de los valores reproductivos específicos por categoría (v), que matemáticamente corresponde al eigen-vector izquierdo de la matriz (Caswell, 1989;Silvertown y Lovett Doust, 1995;Gurevitch et al, 2006).…”

Section: Ecología De Poblacionesunclassified

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Aspectos demográficos y biología reproductiva de Stenocactus obvallatus (DC) Hill

Venegas

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Population Ecology: A Unified Study of Animals and Plants.

Cited by 12 publications

References 0 publications

The effect of plant density on the response of Agrostemma githago to herbicide

The effect of plant density on the response of Agrostemma githago to herbicide

Territory economics and population stability—can populations be socially regulated?

Aspectos demográficos y biología reproductiva de Stenocactus obvallatus (DC) Hill

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