Seeing the Wood for the Trees: Detecting Density Dependence from Existing Life-Table Studies

Hassell, M. P.; Latto, John; May, Robert M.

doi:10.2307/5130

Cited by 134 publications

(76 citation statements)

References 70 publications

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“…A number of meta-analyses have been performed applying these methods to data from different taxa, including birds and insects (Hassell et al 1989;Greenwood & Baillie 1991;Woiwod & Hanski 1992). The largest such study is that of Woiwod & Hanski (1992), which analysed 5715 time-series of 447 species of moths and aphids in the UK, and found good agreement between three analytical methods which differ in their assumptions about the form of density dependence, namely those of Bulmer (1975); Pollard et al (1987) and simple regression of log e (N tϩ1 /N t ) against N t .…”

Section: The Form Of the Relationship Between Population Growth Rate mentioning

confidence: 99%

Population growth rate and its determinants: an overview

Sibly¹,

Hone²

2003

Wildlife Population Growth Rates

188

212

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We argue that population growth rate is the key unifying variable linking the various facets of population ecology. The importance of population growth rate lies partly in its central role in forecasting future population trends; indeed if the form of density dependence were constant and known, then the future population dynamics could to some degree be predicted. We argue that population growth rate is also central to our understanding of environmental stress: environmental stressors should be defined as factors which when first applied to a population reduce population growth rate. The joint action of such stressors determines an organism's ecological niche, which should be defined as the set of environmental conditions where population growth rate is greater than zero (where population growth rate = r = log e (N tϩ1 /N t )). While environmental stressors have negative effects on population growth rate, the same is true of population density, the case of negative linear effects corresponding to the well-known logistic equation. Following Sinclair, we recognize population regulation as occurring when population growth rate is negatively density dependent. Surprisingly, given its fundamental importance in population ecology, only 25 studies were discovered in the literature in which population growth rate has been plotted against population density. In 12 of these the effects of density were linear; in all but two of the remainder the relationship was concave viewed from above.Alternative approaches to establishing the determinants of population growth rate are reviewed, paying special attention to the demographic and mechanistic approaches. The effects of population density on population growth rate may act through their effects on food availability and associated effects on somatic growth, fecundity and survival, according to a 'numerical response', the evidence for which is briefly reviewed. Alternatively, there may be effects on population growth rate of population density in addition to those that arise through the partitioning of food between competitors; this is 'interference competition'. The distinction is illustrated using a replicated laboratory experiment on a marine copepod, Tisbe battagliae. Application of these approaches in conservation biology, ecotoxicology and human demography is briefly considered. We conclude that population regulation, density dependence, resource and interference competition, the effects of environmental stress and the form of the ecological niche, are all best defined and analysed in terms of population growth rate.

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Section: The Form Of the Relationship Between Population Growth Rate mentioning

confidence: 99%

Population growth rate and its determinants: an overview

Sibly¹,

Hone²

2003

Wildlife Population Growth Rates

188

212

View full text Add to dashboard Cite

show abstract

“…Research on other groups has shown that long-term population studies are required to detect and measure density dependence (Hassell et al 1989). The practical problems of sampling large, highly aggregated (sub) populations in difficult terrain may explain the paucity of long-term studies of benthic marine species (Hancock 1973, Vahl1982, Bowman 1985, Barnett & Watson 1986, Beukema & Essink 1986.…”

Section: Introductionmentioning

confidence: 99%

Population dynamics of the mussel Mytilus edulis: density changes and regulation of the population in the Exe estuary, Devon

McGrorty¹,

Clarke²,

Reading³

et al. 1990

Mar. Ecol. Prog. Ser.

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Population dynamics of the intertidal mussel population in the River Exe estuary, Devon (UK) over 7 yr (1976 to 1983) are described. There was no significant trend in adult numbers, and annual variations were small (1.5-fold, minimum to maximum). In contrast, the density of 'spat' mussels (0-year) varied uldely ( l ?~) , suggesting that a strong damping process acted during the first year. Considering just first-year mortality, failure to settle on the beds (k3) had the greatest influence on annual variations in total mortality (K). But losses in the first winter after settlement (k5) were strongly and positively denslty dependent. k3 was inversely density dependent, but only in 6 out of 7 yr. Other first-year losses were independent of density. After the large first-winter mortality (mean 68 %), there were only small gains in summer and small losses in winter for the next 4 yr. Thereafter, increasingly large losses occurred (mean 39 % ) each summer after spawning and each winter (mean 24 ?h), due mainly to bud predation. Some of the over-summer and over-winter changes in adult densities were density dependent, but their effect was small and only served as a 'fine tuning' mechanism keeping densities within very narrow limits. Though mortalities at various stages were correlated with the weather, the main feature of the population was its pronounced stability, due mainly to the powerful regulation acting during the first year on the mussel beds.

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“…Density-dependent processes may be relatively uncommon in insect populations (Stiling, 1988), although they are more likely to be detected when field studies are conducted across numerous generations of herbivores (Hassell et al, 1989;Woiwod and Hanski, 1992) or at an appropriate spatial scale (Walde and Murdoch, 1988;Ray and Hastings, 1996). Overall, natural enemies may have a relatively minor impact on the regulation of herbivore populations, because: 1) density-dependence is more frequently induced by bottom-up (host plant attributes) than top-down forces (biological control agents) (Stiling, 1988;Harrison and Cappuccino, 1995); 2) direct and inverse density-dependence are equally prevalent in host-parasitoid systems (Stiling, 1987;Walde and Murdoch, 1988); and 3) spatial density dependence of biological control agents may (Hassell et al, 1987) or may not (Thórarinsson, 1990;Ferguson et al, 1994) influence the population dynamics of herbivores over time.…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal density dependence in a population of melon aphid, Aphis gossypii Glover (Homoptera: Aphididae), on established and sentinel taro plants

Rhainds

Messing

2005

Appl. Entomol. Zool.

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A study carried out across 33 weeks in a patch of taro, Colocasia esculenta L., quantified demographic parameters and density-dependent processes for a population of melon aphid, Aphis gossypii Glover. Variation in relative density of aphids per cm 2 of leaf tissue between consecutive weeks declined with the initial density of aphids, indicating that density dependent processes regulate populations of A. gossypii on taro. High abundance of aphids on large leaves suggest that host attributes affect the rates of colonization or reproduction of adults. Even though the incidence of winged aphids was consistently low throughout the experiment, between plant dispersal by aphids still homogenizes their spatial distribution within an array of plants, as indicated by similar relative densities of aphids on established plants and on sentinel (initially uninfested) plants 60 days following their introduction in the patch. The proportion of aphids parasitised by Aphidius colemanii Viereck and Aphelinus spp. was low (Ͻ3%), which may be attributed to a high level (Ͼ95%) of hyperparasitism. Mortality caused by two entomopathogens, Neozygites fresenii Nowakowski and Verticillium lecanii Zimmerman, averaged 12%. The proportion of fungal infection increased with the density of aphids, both on a spatial and temporal scale. However, the population of A. gossypii on taro was most likely not regulated by entomopathogens, because the proportion of diseased aphids did not influence variations of population density between consecutive weeks. The lower proportion of fungal infection on sentinel plants than on established plants suggests a limited impact of entomopathogens on taro plants recently colonized by aphids.

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Seeing the Wood for the Trees: Detecting Density Dependence from Existing Life-Table Studies

Cited by 134 publications

References 70 publications

Population growth rate and its determinants: an overview

Population growth rate and its determinants: an overview

Population dynamics of the mussel Mytilus edulis: density changes and regulation of the population in the Exe estuary, Devon

Spatial and temporal density dependence in a population of melon aphid, Aphis gossypii Glover (Homoptera: Aphididae), on established and sentinel taro plants

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