JOINT EFFECTS OF DENSITY AND A GROWTH INHIBITOR ON THE LIFE HISTORY AND POPULATION GROWTH RATE OF THE MIDGE CHIRONOMUS RIPARIUS

2005 ◽  
Vol 24 (5) ◽  
pp. 1140 ◽  
Author(s):  
Helen L. Hooper ◽  
Richard M. Sibly ◽  
Thomas H. Hutchinson ◽  
Stephen J. Maund
Keyword(s):  
Growth Rate ◽  
Life History ◽  
Population Growth ◽  
Population Growth Rate ◽  
Growth Inhibitor ◽  
Chironomus Riparius ◽  
Joint Effects ◽  
Effects Of Density

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.

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