Reproduction, croissance et morphologie comparées des Grands Corégones (Coregonus clupeaformis) nains et normaux du réservoir Outardes-2 (Québec)

1990 ◽  
Vol 68 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Réjean Fortin ◽  
Marc Gendron
Keyword(s):  
Growth Rate ◽  
Reproductive Isolation ◽  
Time Lag ◽  
Coregonus Clupeaformis ◽  
Sympatric Populations ◽  
Caudal Peduncle ◽  
Spawning Site ◽  
Egg Deposition ◽  
Younger Age ◽  
Egg Diameter

Fall experimental fishing for spawners and drift net samples of eggs revealed the presence of sympatric populations of dwarf and normal lake whitefish in Outardes-2 Reservoir. Dwarfs mature at a younger age (1 + vs. 4 + ) than normal spawners. They also show a much slower growth rate, a lower absolute fecundity (1009 vs. 9787 eggs), a higher relative fecundity (32.2 vs. 11.8 eggs/g), and a smaller ovarian egg diameter (1.60 vs. 2.63 mm). Four morphometric variables out of the 13 measured differed significantly between the two forms, including the length and depth of the caudal peduncle and the diameter of the orbit; six out of the seven meristic variables that were enumerated also differed between the two forms, including the number of gillrakers on the first gill arch (dwarfs, 24.7; normal whitefish, 25.9). Reproductive isolation is virtually nonexistent, the two forms using the same spawning site, with a minimal time lag between their mean dates of egg deposition (1983: normal whitefish, November 15 and dwarfs, November 22; 1984: normals, November 9 and dwarfs, November 12). The characteristics associated with dwarfism in the various sympatric populations of Coregonus clupeaformis are discussed.

Validation and Analysis of Modeled Predictions of Growth of Bacillus cereus Spores in Boiled Rice

2000 ◽  
Vol 63 (2) ◽  
pp. 268-272 ◽  
Author(s):  
DANA M. McELROY ◽  
LEE-ANN JAYKUS ◽  
PEGGY M. FOEGEDING
Keyword(s):  
Growth Rate ◽  
Bacillus Cereus ◽  
Exponential Growth ◽  
Generation Time ◽  
Time Lag ◽  
Lag Phase ◽  
Exponential Growth Rate ◽  
Phase Duration ◽  
Margin Of Safety ◽  
Fail Safe

The growth of psychrotrophic Bacillus cereus 404 from spores in boiled rice was examined experimentally at 15, 20, and 30°C. Using the Gompertz function, observed growth was modeled, and these kinetic values were compared with kinetic values for the growth of mesophilic vegetative cells as predicted by the U.S. Department of Agriculture's Pathogen Modeling Program, version 5.1. An analysis of variance indicated no statistically significant difference between observed and predicted values. A graphical comparison of kinetic values demonstrated that modeled predictions were “fail safe” for generation time and exponential growth rate at all temperatures. The model also was fail safe for lag-phase duration at 20 and 30°C but not at l5°C. Bias factors of 0.55, 0.82, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, indicated that the model generally was fail safe and hence provided a margin of safety in its growth predictions. Accuracy factors of 1.82, 1.60, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, quantitatively demonstrated the degree of difference between predicted and observed values. Although the Pathogen Modeling Program produced reasonably accurate predictions of the growth of psychrotrophic B. cereus from spores in boiled rice, the margin of safety provided by the model may be more conservative than desired for some applications. It is recommended that if microbial growth modeling is to be applied to any food safety or processing situation, it is best to validate the model before use. Once experimental data are gathered, graphical and quantitative methods of analysis can be useful tools for evaluating specific trends in model prediction and identifying important deviations between predicted and observed data.

scholarly journals A Spatio-Temporal Investigation of the Growth Rate of COVID-19 Incidents in Ohio, USA, Early in the Pandemic

2021 ◽  
Vol 121 (2) ◽  
pp. 33-47
Author(s):  
Alessandro M. Selvitella ◽  
Liam Carolan ◽  
Justin Smethers ◽  
Christopher Hernandez ◽  
Kathleen L. Foster
Keyword(s):  
Growth Rate ◽  
Transmission Rate ◽  
Time Lag ◽  
Early Period ◽  
Mitigation Strategies ◽  
Initial Growth ◽  
School Closures ◽  
Policy Makers ◽  
Susceptible Population ◽  
Spatio Temporal

Understanding the initial growth rate of an epidemic is important for epidemiologists and policy makers as it can impact their mitigation strategies such as school closures, quarantines, or social distancing. Because the transmission rate depends on the contact rate of the susceptible population with infected individuals, similar growth rates might be experienced in nearby geographical areas. This research determined the growth rate of cases and deaths associated with COVID-19 in the early period of the 2020 pandemic in Ohio, United States. The evolution of cases and deaths was modeled through a Besag-York-Molliè model with linear- and power-type deterministic time dependence. The analysis showed that the growth rate of the time component of the model was subexponential in both cases and deaths once the time-lag across counties of the appearance of the first COVID-19 case was considered. Moreover, deaths in the northeast counties in Ohio were strongly related to the deaths in nearby counties.

scholarly journals Large males have a mating advantage in a species of darter with smaller, allopaternal males Etheostoma olmstedi

2010 ◽  
Vol 56 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Kelly A. Stiver ◽  
Suzanne H. Alonzo
Keyword(s):  
Mating Success ◽  
Breeding Population ◽  
Male Mating ◽  
Breeding Sites ◽  
Spawning Site ◽  
Egg Deposition ◽  
Artificial Breeding ◽  
Mean Size ◽  
Natural Breeding ◽  
To Receive

Abstract Theory suggests that males that are larger than their competitors may have increased mating success, due to both greater competitive ability and increased attractiveness to females. We examined how male mating success varies with male size in the tessellated darter Etheostoma olmstedi. Previous work has shown that large males tend to move around and breed in vacant breeding sites, and consequently provide less care for their eggs, while smaller individuals can be allopaternal, caring for the eggs of other males as well as for their own. We studied female egg deposition in a natural breeding population using artificial breeding sites and in the laboratory, where female choice of spawning site was restricted to two breeding sites tended by two males of different sizes. In both the field and the laboratory, nests tended by larger males were more likely to receive new eggs. Additionally, the mean size of males associated with a nest was positively correlated with both the maximum coverage of eggs at the nest and the number of times new eggs were deposited. We discuss how the increased mating success of larger males, despite their decreased parental care, may help explain allopaternal care in this species.

scholarly journals Host races in plant–feeding insects and their importance in sympatric speciation

2002 ◽  
Vol 357 (1420) ◽  
pp. 471-492 ◽  
Author(s):  
Michele Drès ◽  
James Mallet
Keyword(s):  
Linkage Disequilibrium ◽  
Gene Flow ◽  
Natural Selection ◽  
Reproductive Isolation ◽  
Sympatric Speciation ◽  
Accurate Information ◽  
Sympatric Populations ◽  
New Host ◽  
Host Races ◽  
Plant Feeding

The existence of a continuous array of sympatric biotypes—from polymorphisms, through ecological or host races with increasing reproductive isolation, to good species—can provide strong evidence for a continuous route to sympatric speciation via natural selection. Host races in plant–feeding insects, in particular, have often been used as evidence for the probability of sympatric speciation. Here, we provide verifiable criteria to distinguish host races from other biotypes: in brief, host races are genetically differentiated, sympatric populations of parasites that use different hosts and between which there is appreciable gene flow. We recognize host races as kinds of species that regularly exchange genes with other species at a rate of more than ca . 1% per generation, rather than as fundamentally distinct taxa. Host races provide a convenient, although admittedly somewhat arbitrary intermediate stage along the speciation continuum. They are a heuristic device to aid in evaluating the probability of speciation by natural selection, particularly in sympatry. Speciation is thereby envisaged as having two phases: (i) the evolution of host races from within polymorphic, panmictic populations; and (ii) further reduction of gene flow between host races until the diverging populations can become generally accepted as species. We apply this criterion to 21 putative host race systems. Of these, only three are unambiguously classified as host races, but a further eight are strong candidates that merely lack accurate information on rates of hybridization or gene flow. Thus, over one–half of the cases that we review are probably or certainly host races, under our definition. Our review of the data favours the idea of sympatric speciation via host shift for three major reasons: (i) the evolution of assortative mating as a pleiotropic by–product of adaptation to a new host seems likely, even in cases where mating occurs away from the host; (ii) stable genetic differences in half of the cases attest to the power of natural selection to maintain multilocus polymorphisms with substantial linkage disequilibrium, in spite of probable gene flow; and (iii) this linkage disequilibrium should permit additional host adaptation, leading to further reproductive isolation via pleiotropy, and also provides conditions suitable for adaptive evolution of mate choice (reinforcement) to cause still further reductions in gene flow. Current data are too sparse to rule out a cryptic discontinuity in the apparently stable sympatric route from host–associated polymorphism to host–associated species, but such a hiatus seems unlikely on present evidence. Finally, we discuss applications of an understanding of host races in conservation and in managing adaptation by pests to control strategies, including those involving biological control or transgenic parasite–resistant plants.

No character displacement for reproductive isolation between Drosophila bipectinata and Drosophila malerkotliana

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 849-852 ◽  
Author(s):  
B. N. Singh ◽  
Sujata Chatterjee
Keyword(s):  
Reproductive Isolation ◽  
Sexual Isolation ◽  
Character Displacement ◽  
Sympatric Populations ◽  
Allopatric Populations ◽  
Drosophila Bipectinata ◽  
Isolation Index ◽  
Drosophila Malerkotliana

To test whether character displacement for reproductive isolation between Drosophila bipectinata and Drosophila malerkotliana exists, the degree of sexual isolation was measured between their sympatric and allopatric populations. Although the isolation indices vary in different crosses, the average isolation index for sympatric populations is very close to that for allopatric populations. This shows no difference in the degree of sexual isolation between sympatric and allopatric populations of D. bipectinata and D. malerkotliana. Thus there is no evidence for the existence of character displacement for sexual isolation between these two closely related sympatric species.Key words: Drosophila bipectinata, Drosophila malerkotliana, sexual isolation, sympatric and allopatric populations.

Trophic Structure, Reproductive Success, and Growth Rate of Fishes in a Natural and Modified Headwater Stream

1982 ◽  
Vol 39 (7) ◽  
pp. 968-978 ◽  
Author(s):  
Isaac J. Schlosser
Keyword(s):  
Growth Rate ◽  
Reproductive Success ◽  
Flow Regime ◽  
Age Structure ◽  
Trophic Structure ◽  
Headwater Stream ◽  
Organic Substrates ◽  
Age Classes ◽  
Younger Age ◽  
The Impact

The impact of removing riparian vegetation, channel straightening, and fluctuations in flow regime on trophic structure, reproductive success, and growth rate of fishes was assessed in a natural (Jordan Creek (JC)) and modified (Big Ditch (BD)) headwater stream in east-central Illinois. Shallow habitats and organic substrates increased more in BD than JC during low flow periods in summer. Insect densities in JC were highest in late spring, declining to low levels by late summer. Insect densities in BD were high throughout summer. Fish in JC were predominantly benthic insectivores and insectivore–piscivores; trophic structure, age structure, and biomass were stable between years and seasons; recruits made up a small and stable portion of community biomass and were primarily insectivore–piscivores and generalized insectivores; younger age-classes were in shallow riffle habitats. Adult fish and recruits in BD were predominantly generalized insectivores, omnivores, and herbivore–detritivores; the last two were primarily mid-river species (Carpoides cyprinus and Dorosoma cepedianum). Considerable seasonal and annual variation in trophic structure, total biomass, and age structure occurred in BD associated with annual fluctuations in flow regime, abundance of organic substrates, and reproductive success of mid-river species. Younger age-classes had higher summer growth rates in BD than JC. The temporally variable physical environment and unstable autotrophic energy base created in modified headwater streams are probably major factors responsible for recent shifts in large river fish communities in the midwestern United States from insectivore and insectivore–piscivore species to omnivores and herbivore–detritivores.Key words: community organization, fishes, Illinois, stream continuum, stream alteration, trophic ecology, warmwater stream

Why are dwarf fish so small? An energetic analysis of polymorphism in lake whitefish (Coregonus clupeaformis)

2001 ◽  
Vol 58 (2) ◽  
pp. 394-405 ◽  
Author(s):  
Marc Trudel ◽  
Alain Tremblay ◽  
Roger Schetagne ◽  
Joseph B Rasmussen
Keyword(s):  
Life Span ◽  
Energy Budget ◽  
Coregonus Clupeaformis ◽  
Lake Whitefish ◽  
Sympatric Populations ◽  
Subarctic Lakes ◽  
Lower Growth ◽  
Chemical Tracers ◽  
Mass Balance Models ◽  
Consumption Rates

Sympatric populations of dwarf lake whitefish (Coregonus clupeaformis) (DLW) and normal lake whitefish (NLW) commonly occur in north temperate and subarctic lakes. DLW have a much lower growth, mature earlier, and have a shorter life span than NLW. Furthermore, they are usually not found when cisco (Coregonus artedi) are present, possibly due to competitive exclusion. In this study, we compared the energy budget of DLW, NLW, and cisco using food consumption rates estimated with mass balance models of chemical tracers (i.e., mercury and radiocesium). These chemicals are globally distributed and can be readily detected in fish and their prey. Our analysis showed that the energy budget of DLW and cisco was similar. DLW and cisco consumed on average 40–50% more food than NLW. The conversion efficiency of DLW and cisco was two to three times lower than that of NLW. These results suggest that DLW and cisco allocated a larger fraction of their energy budget to metabolism than NLW. Our analysis also suggests that the earlier maturation and shorter life span of DLW and cisco may be due to their higher metabolic rates.

The Systematics of Salmonid Fishes of Recently Glaciated Lakes

1972 ◽  
Vol 29 (6) ◽  
pp. 639-671 ◽  
Author(s):  
Robert J. Behnke
Keyword(s):  
Genetic Diversity ◽  
Reproductive Isolation ◽  
Fisheries Management ◽  
Common Ancestor ◽  
Morphological Divergence ◽  
Salmonid Fishes ◽  
Sympatric Populations ◽  
Homing Behavior ◽  
Taxonomic Problem ◽  
Fisheries Biology

The systematics of the subfamilies Salmoninae and Coregoninae of recently glaciated regions are reviewed. Interrelation between systematics and fisheries biology are stressed, pointing out the abundance of intraspecific genetic diversity of some salmonid fishes manifested in ecological and behavioral specializations, but not necessarily by morphological divergence. Innate, reproductive homing behavior of salmonid fishes may allow closely related populations to exist in sympatry and maintain reproductive isolation. Examples are cited to support the contention that many sympatric "sibling species" have evolved from a common ancestor in postglacial times. Closely related, sympatric populations are a major taxonomic problem, but this phenomenon which allows a species to consist of genetically discrete units with reproductive isolation between the stocks is of great significance for fisheries management. Postglacial salmonid communities are typically fragile and highly susceptible to disruption or destruction by introductions, eutrophication, and exploitation. Every effort should be made to protect the genetic diversity of a species.

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