Intraspecific density dependence in the dynamics of zooplankton under hypertrophic conditions

2003 ◽  
Vol 60 (8) ◽  
pp. 919-928 ◽  
Author(s):  
Steven Declerck ◽  
Vanessa Geenens ◽  
Nicole Podoor ◽  
José Maria Conde Porcuna ◽  
Luc De Meester
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Population Growth ◽  
Population Growth Rate ◽  
Interference Competition ◽  
The Body ◽  
Crustacean Zooplankton ◽  
Intraspecific Interactions ◽  
Zooplankton Dynamics ◽  
Intraspecific Density Dependence

Intraspecific interactions may limit population growth of small cladoceran taxa under food-rich, hypertrophic conditions. Multiple-regression models significantly explained a large proportion of the variation in the body size adjusted fecundity and population growth rate of crustacean zooplankton taxa in a shallow, hypertrophic lake. The results of partial correlation analyses suggested exploitative competition to have only limited significance in determining the zooplankton dynamics. The analyses also revealed strong negative relationships between biomass and both body size adjusted fecundity and population growth rate within most taxa. Most of these relationships cannot be explained by food shortage or predation and suggest alternative mechanisms such as chemically mediated, intraspecific interference competition or life history shifts.

scholarly journals Population growth rate and its determinants: an overview

2002 ◽  
Vol 357 (1425) ◽  
pp. 1153-1170 ◽  
Author(s):  
Richard M. Sibly ◽  
Jim Hone
Keyword(s):  
Growth Rate ◽  
Population Density ◽  
Population Growth ◽  
Population Ecology ◽  
Ecological Niche ◽  
Population Growth Rate ◽  
Population Regulation ◽  
Interference Competition ◽  
Environmental Stressors ◽  
Future Population

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 t +1 / 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.

Relationship between body size and population growth rate in two opportunistic polychaetes

2002 ◽  
Vol 82 (3) ◽  
pp. 403-408 ◽  
Author(s):  
D. Prevedelli ◽  
R. Simonini
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Sex Ratio ◽  
Population Growth ◽  
Growth Rates ◽  
Life Histories ◽  
Population Growth Rate ◽  
Population Growth Rates ◽  
The Relationship ◽  
Dinophilus Gyrociliatus

The relationship between body size and population growth rate λ has been studied in two species of opportunistic polychaetes, Dinophilus gyrociliatus and Ophryotrocha labronica, which colonize harbour environments. These species exhibit a semi-continuous iteroparous reproductive strategy, are phylogenetically closely-related but differ in body size and in some aspects of their sexuality. Ophryotrocha labronica is about 4 mm in body length, displays only slight sexual dimorphism and its sex ratio is biased towards the female sex in the ratio 2:1. Dinophilus gyrociliatus is about 1 mm in length, the males are extremely small and the sex ratio is strongly biased (3:1) in favour of the females. In spite of the considerable differences in all traits of their life histories and in many demographic parameters, the growth rates of the two populations are very similar. The analyses carried out have shown that the rapid attainment of sexual maturity of D. gyrociliatus gives it an advantage that offsets the greater fecundity of O. labronica. It is very likely that the reproductive peculiarities of D. gyrociliatus help to raise the population growth rates. The ‘saving’ on the male sex achieved both by the shift of the sex ratio in favour of the females and by the reduction in the males' body size would appear to enable D. gyrociliatus to grow at the same rate as O. labronica, a larger and more fecund species.

scholarly journals Contrasting size-dependent life history strategies of an insular lizard

2020 ◽  
Vol 66 (6) ◽  
pp. 625-633
Author(s):  
Andreu Rotger ◽  
José Manuel Igual ◽  
Giacomo Tavecchia
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Body Size ◽  
Population Growth ◽  
Population Growth Rate ◽  
Body Growth ◽  
Demographic Model ◽  
Continuous Growth ◽  
Size Dependent ◽  
Selective Pressures

Abstract In many species with continuous growth, body size is an important driver of life-history tactics and its relative importance is thought to reflect the spatio-temporal variability of selective pressures. We developed a deterministic size-dependent integral projection model for 3 insular neighboring lizard populations with contrasting adult body sizes to investigate how size-related selective pressures can influence lizard life-history tactics. For each population, we broke down differences in population growth rates into contributions from size-dependent body growth, survival, and fecundity. A life table response experiment (LTRE) was used to compare the population dynamics of the 3 populations and quantify the contributions of intrinsic demographic coefficients of each population to the population growth rate (λ). Perturbation analyses revealed that the largest adults contributed the most to the population growth rate, but this was not true in the population with the smallest adults and size-independent fertility. Although we were not able to identify a single factor responsible for this difference, the combination of the demographic model on a continuous trait coupled with an LTRE analysis revealed how individuals from sister populations of the same species follow different life strategies and showed different compensatory mechanisms among survival, individual body growth, and fertility. Our results indicate that body size can play a contrasting role even in closely-related and closely-spaced populations.

scholarly journals Delayed maturity does not offset negative impact afflicted by ectoparasitism in salmon

2021 ◽  
Author(s):  
Knut Wiik Vollset ◽  
Martin Krkosek
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Body Size ◽  
Population Growth ◽  
Population Growth Rate ◽  
Negative Impact ◽  
Host Population ◽  
Sea Lice ◽  
Fish Farms ◽  
The Impact

AbstractThe negative effects of parasitism on host population dynamics may be mediated by plastic compensatory life-history changes in hosts. Theory predicts that hosts should shift their life-history towards early reproduction in response to virulent pathogens to maximize reproduction before death. However, for sublethal infections that affect growth, hosts whose fecundity is correlated with body size are predicted to shift towards delayed reproduction associated with larger body size and higher fecundity. This has been observed in Atlantic salmon and parasitic sea lice, via mark-recapture studies that recover mature fish from paired groups of control and parasiticide-treated smolts. We investigated whether such louse-induced changes to age at maturity can offset some of the negative effect of mortality on population growth rate in salmon using a structured population matrix model. Model results show that delayed maturity can partially compensate for reduced survival. However, this only occurs when marine survival is moderate to poor and growth conditions at sea are good. Also, the impact of delayed maturity on population growth when parameterizing the model with empirical data is negligible compared with effects of direct mortality. Our model thus suggests that management that works on minimizing the effect of sea lice from fish farms on wild salmon should focus mainly on correctly quantifying the effect of parasite-induced mortality during the smolt stage if the goal is to maximize population growth rate.

scholarly journals Clonal thermal preferences affect the strength of the temperature-size rule

2020 ◽  
Author(s):  
Anna Stuczyńska ◽  
Mateusz Sobczyk ◽  
Edyta Fiałkowska ◽  
Wioleta Kocerba-Soroka ◽  
Agnieszka Pajdak-Stós ◽  
...  
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Population Growth ◽  
Life Histories ◽  
Population Growth Rate ◽  
Temperature Response ◽  
Thermal Conditions ◽  
Thermal Acclimation ◽  
Life Strategy ◽  
Trade Offs

AbstractGenetically similar organisms act as a powerful study system for the subtle differences in various aspects of life histories. The issue of trade-offs among traits is of special interest. We used six parthenogenetic rotifer clones previously exposed to different thermal laboratory conditions. Interclonal differences in female body size were examined in common garden conditions. We estimated the population growth rate and strength of the size-to-temperature response across four thermal regimes. We tested hypotheses on the existence of the relationships between (i) thermal acclimation and species body size, (ii) thermal specialization and fitness and (iii) thermal specialization and strength of the temperature-size rule. Positive verification of (i) would make it justifiable to refer the other investigated traits to thermal preference and, further, to thermal specialization. Addressing the issues (ii) and (iii) is our pioneering contribution to the question on the strength of size-to-temperature response as differing across life strategies. We hypothesized that this plastic response may be affected by the level of thermal specialization and that this pattern may be traded off with the temperature-dependent potential for population growth rate. Additionally, we investigated the differences in reproductive strategy (number of eggs laid by a female and female lifetime duration) in one temperature assumed optimal, which acts as an important supplement to the general clonal life strategy. We confirmed that the thermal acclimation of a clone is related to body size, with clones acclimated to higher temperatures being smaller. We also found that warm-acclimated clones have a narrower thermal range (= are more specialized), and that the temperature-size rule is stronger in rotifers acclimated to intermediate thermal conditions than in specialists. Our results contribute into the issue of trade-offs between generalist and specialist strategies, in the context of plastic body size respone to different temperatures.

scholarly journals Biological scaling in green algae: the role of cell size and geometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Helena Bestová ◽  
Jules Segrestin ◽  
Klaus von Schwartzenberg ◽  
Pavel Škaloud ◽  
Thomas Lenormand ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Internal Diffusion ◽  
Scaling Exponent ◽  
Power Scaling ◽  
Nutrient Distribution ◽  
Metabolic Scaling ◽  
Key Factor ◽  
Size And Morphology

AbstractThe Metabolic Scaling Theory (MST), hypothesizes limitations of resource-transport networks in organisms and predicts their optimization into fractal-like structures. As a result, the relationship between population growth rate and body size should follow a cross-species universal quarter-power scaling. However, the universality of metabolic scaling has been challenged, particularly across transitions from bacteria to protists to multicellulars. The population growth rate of unicellulars should be constrained by external diffusion, ruling nutrient uptake, and internal diffusion, operating nutrient distribution. Both constraints intensify with increasing size possibly leading to shifting in the scaling exponent. We focused on unicellular algae Micrasterias. Large size and fractal-like morphology make this species a transitional group between unicellular and multicellular organisms in the evolution of allometry. We tested MST predictions using measurements of growth rate, size, and morphology-related traits. We showed that growth scaling of Micrasterias follows MST predictions, reflecting constraints by internal diffusion transport. Cell fractality and density decrease led to a proportional increase in surface area with body mass relaxing external constraints. Complex allometric optimization enables to maintain quarter-power scaling of population growth rate even with a large unicellular plan. Overall, our findings support fractality as a key factor in the evolution of biological scaling.

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