scholarly journals Spatial and temporal variation in the generation time of a bird metapopulation: density regulation and the evolutionary potential of a pace-of-life measure

2020 ◽  
Author(s):  
Yimen Araya-Ajoy ◽  
Alina Niskanen ◽  
Peter Ranke ◽  
Hannah Froy ◽  
Thomas Kvalnes ◽  
...  
Keyword(s):  
Generation Time ◽  
Life History Strategies ◽  
Spatial And Temporal Variation ◽  
Lifetime Reproductive Success ◽  
Evolutionary Potential ◽  
Life Measure ◽  
Density Regulation ◽  
Pace Of Life ◽  
Generation Times ◽  
Classic Theory

Generation time determines the pace of key demographic and evolutionary processes. Quantified as the weighted mean age at reproduction, it can be studied as a trait that varies within and among populations and may evolve in response to ecological conditions. We combined quantitative genetic analyses with age- and density-dependent models to study generation time variation in a bird metapopulation. Generation time was heritable, and males had longer generation times compared with females. Individuals with longer generation times had a higher lifetime reproductive success but not a higher expected population growth rate. Density regulation acted on recruit production, suggesting that longer generation times should be favored when populations are closer to carrying capacity. Furthermore, generation times were shorter when populations were growing, and longer when populations were closer to equilibrium or declining. These results support classic theory predicting that density regulation is an important driver of the pace of life-history strategies.

scholarly journals Demographic drivers of generation time in a bird metapopulation: evolutionary potential and the ecological determinants of pace-of-life

2020 ◽  
Author(s):  
Yimen Araya Ajoy ◽  
Alina Niskanen ◽  
Peter Ranke ◽  
Hannah Froy ◽  
Thomas Kvalnes ◽  
...  
Keyword(s):  
Generation Time ◽  
Evolutionary Potential ◽  
Pace Of Life

scholarly journals Variation in generation time reveals density regulation as an important driver of pace of life in a bird metapopulation

2021 ◽  
Author(s):  
Yimen G. Araya‐Ajoy ◽  
Alina K. Niskanen ◽  
Hannah Froy ◽  
Peter Sjolte Ranke ◽  
Thomas Kvalnes ◽  
...  
Keyword(s):  
Generation Time ◽  
Density Regulation ◽  
Pace Of Life

Behaviour ofStreptococcus lactisin heat treated (80 °C for 30 min) or sterilized cow's and ewe's milk

1983 ◽  
Vol 50 (3) ◽  
pp. 357-363 ◽  
Author(s):  
Francisco J. Chavarri ◽  
Jose A. Nuñez ◽  
Manuel Nuñez
Keyword(s):  
Acid Production ◽  
Generation Time ◽  
Buffer Capacity ◽  
Cow’S Milk ◽  
Cow's Milk ◽  
Vitamin Content ◽  
Streptococcus Lactis ◽  
Generation Times ◽  
Heat Treated ◽  
Ewe's Milk

SummaryGeneration times and acid production after 6 and 24 h by 20 strains ofStreptococcus lactisof dairy origin were determined in heat treated (80 °C for 30 min) and sterilized cow's and ewe's milk. Ewe's milk enhanced growth of the streptococci, with significantly (P< 0·001) shorter generation times and higher acid production after 6 h incubation than cow's milk, probably due to its higher vitamin content. The stronger buffer capacity of ewe's milk allowed a higher (P< 0·001) acid production after 24 h than cow's milk. A stimulatory effect of sterilization on generation time and acid production after 24 h was observed in cow's milk. However, the heat treated ewe's milk was shown to be a better substrate than sterilized ewe's milk forStr. lactis.

scholarly journals A review of the life cycles and life-history adaptations of pelagic tunicates to environmental conditions

2011 ◽  
Vol 69 (3) ◽  
pp. 358-369 ◽  
Author(s):  
Don Deibel ◽  
Ben Lowen
Keyword(s):  
Life History ◽  
Environmental Conditions ◽  
Generation Time ◽  
Egg Production ◽  
Food Concentration ◽  
Life Cycles ◽  
Population Doubling ◽  
Event Scale ◽  
Generation Times ◽  
Doubling Times

Abstract Deibel, D., and Lowen, B. 2012. A review of the life cycles and life-history adaptations of pelagic tunicates to environmental conditions. – ICES Journal of Marine Science, 69: 358–369. Phylogeny, life cycles, and life-history adaptations of pelagic tunicates to temperature and food concentration are reviewed. Using literature data on lifetime egg production and generation time of appendicularians, salps, and doliolids, rmax, the maximum rate of lifetime reproductive fitness, is calculated as a common metric of adaptation to environmental conditions. The rmax values are high for all three groups, ranging from ∼0.1 to 1.9 d−1, so population doubling times range from ∼8 h to 1 week. These high values of rmax are attributable primarily to short generation times, ranging from 2 to 50 d. Clearly, pelagic tunicates are adapted to event-scale (i.e. days to weeks) rather than seasonal-scale changes in environmental conditions. Although they are not closely related phylogenetically, all three groups have a unique life-history adaptation promoting high lifetime fitness. Appendicularians have late oocyte selection, salps are viviparous, and doliolids possess a polymorphic asexual phase. There has been little research on hermaphroditic appendicularians, on large oceanic salps, and on doliolids generally. Research is needed on factors regulating generation time, on the heritability of life-history traits, and on age- and size-specific rates of mortality.

Rapid juvenile development in old forest lichens

Botany ◽  
2011 ◽  
Vol 89 (1) ◽  
pp. 65-72 ◽  
Author(s):  
Per Larsson ◽  
Yngvar Gauslaa
Keyword(s):  
Growth Rates ◽  
Generation Time ◽  
Population Biology ◽  
Limiting Factors ◽  
Noninvasive Method ◽  
Relative Growth ◽  
Relative Growth Rates ◽  
Generation Times ◽  
Young Forests ◽  
Juvenile Development

Generation time and juvenile growth rates are important but poorly known parameters in lichen population biology. By using a noninvasive method, we aimed to quantify these variables in juvenile thalli of Lobaria pulmonaria (L.) Hoffm., L. scrobiculata (Scop.) D.C., and Pseudocyphellaria crocata (L.) Vain., in situ, on twigs of Picea abies (L.) H. Karst in boreal rainforests. Growth was monitored during the summer months (May–August, 106 d), as well as in the remaining part of the year (259 d), for each of two sequential years, by means of repeated photography and imaging analysis. The mean relative thallus-area growth rates were 0.53 ± 0.02, 0.41 ± 0.02, and 0.57 ± 0.04 mm2·mm–2·year–1 (mean ±SE), respectively, in the three species, equivalent to a yearly growth of 101 ± 5%, 70 ± 6%, and 121 ± 12%. Growth was much slower during the winter (0.09–0.12 mm2·cm–2·d–1) than in summer (0.19–0.27 mm2·cm–2·d–1). Relative growth rates significantly declined with increasing thallus size. Estimated generation times in L. scrobiculata and P. crocata, based upon the first observed formation of reproductive structures, were 15–22 and 9–13 years, respectively. Studied L. pulmonaria thalli produced no diaspores during the experiment, consistent with a generation time >17 years. The relative growth rates we measured and our estimated generation times are faster than those earlier recorded. Thus, our noninvasive method can estimate parameters needed to model population growth within a reasonable period of time. The rapid juvenile development implies that the growth rates and generation times are unlikely to be the limiting factors that exclude these lichens from young forests.

scholarly journals Beyond lifetime reproductive success: the posthumous reproductive dynamics of male Trinidadian guppies

2013 ◽  
Vol 280 (1763) ◽  
pp. 20131116 ◽  
Author(s):  
Andrés López-Sepulcre ◽  
Swanne P. Gordon ◽  
Ian G. Paterson ◽  
Paul Bentzen ◽  
David N. Reznick
Keyword(s):  
Generation Time ◽  
Significant Proportion ◽  
Sperm Storage ◽  
Lifetime Reproductive Success ◽  
Demographic Analysis ◽  
Genotype Diversity ◽  
Fluctuating Environments ◽  
In The Wild ◽  
Posthumous Reproduction

In semelparous populations, dormant germ banks (e.g. seeds) have been proposed as important in maintaining genotypes that are adaptive at different times in fluctuating environments. Such hidden storage of genetic diversity need not be exclusive to dormant banks. Genotype diversity may be preserved in many iteroparous animals through sperm-storage mechanisms in females. This allows males to reproduce posthumously and increase the effective sizes of seemingly female-biased populations. Although long-term sperm storage has been demonstrated in many organisms, the understanding of its importance in the wild is very poor. We here show the prevalence of male posthumous reproduction in wild Trinidadian guppies, through the combination of mark–recapture and pedigree analyses of a multigenerational individual-based dataset. A significant proportion of the reproductive population consisted of dead males, who could conceive up to 10 months after death (the maximum allowed by the length of the dataset), which is more than twice the estimated generation time. Demographic analysis shows that the fecundity of dead males can play an important role in population growth and selection.

scholarly journals On the relationship between serial interval, infectiousness profile and generation time

2021 ◽  
Vol 18 (174) ◽  
pp. 20200756
Author(s):  
Sonja Lehtinen ◽  
Peter Ashcroft ◽  
Sebastian Bonhoeffer
Keyword(s):  
Symptom Onset ◽  
Generation Time ◽  
Time Distribution ◽  
Contact Tracing ◽  
Time Interval ◽  
Single Individual ◽  
Generation Times ◽  
Serial Interval ◽  
The Impact ◽  
The Relationship

The timing of transmission plays a key role in the dynamics and controllability of an epidemic. However, observing generation times—the time interval between the infection of an infector and an infectee in a transmission pair—requires data on infection times, which are generally unknown. The timing of symptom onset is more easily observed; generation times are therefore often estimated based on serial intervals—the time interval between symptom onset of an infector and an infectee. This estimation follows one of two approaches: (i) approximating the generation time distribution by the serial interval distribution or (ii) deriving the generation time distribution from the serial interval and incubation period—the time interval between infection and symptom onset in a single individual—distributions. These two approaches make different—and not always explicitly stated—assumptions about the relationship between infectiousness and symptoms, resulting in different generation time distributions with the same mean but unequal variances. Here, we clarify the assumptions that each approach makes and show that neither set of assumptions is plausible for most pathogens. However, the variances of the generation time distribution derived under each assumption can reasonably be considered as upper (approximation with serial interval) and lower (derivation from serial interval) bounds. Thus, we suggest a pragmatic solution is to use both approaches and treat these as edge cases in downstream analysis. We discuss the impact of the variance of the generation time distribution on the controllability of an epidemic through strategies based on contact tracing, and we show that underestimating this variance is likely to overestimate controllability.

scholarly journals Causes and consequences of life-history variation in North American stocks of Pacific cod

2008 ◽  
Vol 66 (2) ◽  
pp. 349-357 ◽  
Author(s):  
Olav A. Ormseth ◽  
Brenda L. Norcross
Keyword(s):  
Life History ◽  
North American ◽  
Egg Production ◽  
Atlantic Cod ◽  
North Pacific Ocean ◽  
Life History Strategies ◽  
Lifetime Reproductive Success ◽  
Life History Variation ◽  
Pacific Cod ◽  
Trade Offs

Abstract Ormseth, O. A., and Norcross, B. L. 2009. Causes and consequences of life-history variation in North American stocks of Pacific cod. – ICES Journal of Marine Science, 66: 349–357. Life-history strategies of four Pacific cod (Gadus macrocephalus) stocks in the eastern North Pacific Ocean are outlined. Southern stocks grew and matured quicker, but reached smaller maximum size and had shorter lifespans than northern stocks. The trade-offs resulted in similar lifetime reproductive success among all stocks. Growth was highly dependent on latitude, but not on temperature, possibly because of differences in the duration of the growing season. Comparisons with Atlantic cod (Gadus morhua) revealed similar latitude/growth relationships among Atlantic cod stocks grouped by geographic region. In Pacific cod, greater size and longevity in the north appeared to be adaptations to overcome environmental constraints on growth and to maintain fitness. An egg production-per-recruit model suggested that the life-history strategy of northern Pacific cod stocks made them less resilient to fishing activity and age truncation than southern stocks.

scholarly journals Life history variation is maintained by fitness trade-offs and negative frequency-dependent selection

2018 ◽  
Vol 115 (17) ◽  
pp. 4441-4446 ◽  
Author(s):  
Mark R. Christie ◽  
Gordon G. McNickle ◽  
Rod A. French ◽  
Michael S. Blouin
Keyword(s):  
Life History ◽  
Reproductive Success ◽  
Life History Strategies ◽  
Lifetime Reproductive Success ◽  
Life History Variation ◽  
Additional Energy ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Trade Offs ◽  
Negative Frequency Dependent Selection

The maintenance of diverse life history strategies within and among species remains a fundamental question in ecology and evolutionary biology. By using a near-complete 16-year pedigree of 12,579 winter-run steelhead (Oncorhynchus mykiss) from the Hood River, Oregon, we examined the continued maintenance of two life history traits: the number of lifetime spawning events (semelparous vs. iteroparous) and age at first spawning (2–5 years). We found that repeat-spawning fish had more than 2.5 times the lifetime reproductive success of single-spawning fish. However, first-time repeat-spawning fish had significantly lower reproductive success than single-spawning fish of the same age, suggesting that repeat-spawning fish forego early reproduction to devote additional energy to continued survival. For single-spawning fish, we also found evidence for a fitness trade-off for age at spawning: older, larger males had higher reproductive success than younger, smaller males. For females, in contrast, we found that 3-year-old fish had the highest mean lifetime reproductive success despite the observation that 4- and 5-year-old fish were both longer and heavier. This phenomenon was explained by negative frequency-dependent selection: as 4- and 5-year-old fish decreased in frequency on the spawning grounds, their lifetime reproductive success became greater than that of the 3-year-old fish. Using a combination of mathematical and individual-based models parameterized with our empirical estimates, we demonstrate that both fitness trade-offs and negative frequency-dependent selection observed in the empirical data can theoretically maintain the diverse life history strategies found in this population.

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