scholarly journals The ecological genetics of growth in Drosophila 6. The genetic correlation between the duration of the larval period and body size in relation to larval diet.

1963 ◽  
Vol 4 (1) ◽  
pp. 74-92 ◽  
Author(s):  
Forbes W. Robertson
Keyword(s):  
Body Size ◽  
Development Time ◽  
Larval Growth ◽  
Large Body ◽  
Ecological Genetics ◽  
Larval Period ◽  
Limiting Factor ◽  
Adult Size ◽  
Critical Stage ◽  
Larval Size

1. The low but regular positive correlation between body-size and the duration of the larval period in populations of D. melanogaster has been studied by selecting for large size or shorter development time on aseptic defined diets deficient in RNA and comparing the results with parallel selection on unrestricted yeast diets or on media in which RNA is not a limiting factor.2. There is a striking contrast according to the nature of the diet during selection. On unrestricted diets and where RNA is adequate there is little or no evidence of correlation between the two characters, but on low RNA media there is a striking correlation whether selection is for large body size or shorter development time.3. This contrast is accounted for in terms of particular changes in larval growth which can be divided into a first stage of growth to a critical size in the early 3rd instar and a second stage thereafter. The duration of the first stage can be greatly prolonged by inadequate diet but the duration of the later stage appears to be virtually unaffected by such variation although the amount of growth and hence final body-size, may be drastically reduced. The different diets which lead to presence or absence of correlation have enabled selection either to extend the growing period, so that the critical stage is reached later at a larger larval size, or to accelerate the growth rate in the later stage.4. Variation in the final stage of growth predominates on unrestricted diets and is responsible for the greater part of the variation in body size in unselected populations. Stabilization of body-size about an intermediate optimum refers especially to growth in this later stage.5. Lines selected for fast development on low RNA media are especially sensitive to minor nutritional variation. Probably only under rather special conditions is it possible to shorten the duration of the larval period and this is compatible with the importance of development time in fitness generally.6. There is evidence that the restriction of early growth, in the 2nd instar, reduces the size of the 3rd instar mouth-parts. Such reduction is correlated with changes in adult size probably because smaller mouth-parts restrict food intake.7. The pattern of larval growth suggests a flexible system which can be adjusted to different ecological conditions since the same body-size can be attained by adjusting the amount of growth effected before or after the critical stage. Differ ences in this respect will involve characteristic differences in reaction to environ mental variation and particular nutritional conditions are likely to influence the way in which adaptive changes are realized.

Effect of larval body size on overwinter survival and emerging adult size in the burying beetle, Nicrophorus investigator

2002 ◽  
Vol 80 (9) ◽  
pp. 1588-1593 ◽  
Author(s):  
Rosemary J Smith
Keyword(s):  
Body Size ◽  
Parental Care ◽  
Emerging Adults ◽  
Survival Data ◽  
Life Stage ◽  
Large Body ◽  
Winter Period ◽  
Adult Size ◽  
Larval Size ◽  
Overwinter Survival

Body size may influence both adult fecundity and the probability of survival through each life stage. Previous studies of burying beetles (Nicrophorus, Coleoptera: Silphidae) have revealed reproductive advantages for larger adults and the role of parental care in determining larval size and number. In this study I measure the effect of size on survival over the winter period and the correlation between larval size and the size of emerging adults. I collected data from 24 groups of 20–25 larvae sorted by size and overwintered outside under natural conditions in Colorado, U.S.A. There was a significant positive correlation between larval size and adult size at emergence and a significant effect of size on overwinter survival. Data from 2 years yielded the following mean survival rates: small, 47.3 ± 1.0%; medium, 73.2 ± 0.7%; large, 85.7 ± 0.4%. These values were then used to accurately predict adult emergence from broods of larvae whose range of size was measured prior to the overwinter period. The results indicate that selection for large body size may result from an overwinter survival advantage and not just from reproductive success. This has implications for fitness models of parental care and models of population dynamics.

scholarly journals The ecological genetics of growth in Drosophila 7. The role of canalization in the stability of growth relations

1964 ◽  
Vol 5 (1) ◽  
pp. 107-126 ◽  
Author(s):  
Forbes W. Robertson
Keyword(s):  
Body Size ◽  
Phenotypic Variation ◽  
Larval Growth ◽  
Exponential Phase ◽  
Larval Period ◽  
Environment Interaction ◽  
Adult Size ◽  
Gene Environment Interaction ◽  
Gene Environment ◽  
The Difference

1. Similar changes in the body-size of Drosophila melanogaster have been achieved by different developmental pathways, especially either by altering the duration of the early exponential phase of larval growth or by influencing the growth rate in the phase which is independent of time.2. Such changes have been effected by selecting in the same population for larger or smaller size or shorter development time on chemically defined media, deficient in alternative nutrients. Selection for larger size on media deficient in protein or choline does not involve correlated changes in the larval period, whereas selection on media deficient in RNA does. The evidence suggests that shortage of this nutrient may be uniquely favourable for promoting a correlated change between body-size and duration of the larval period.3. Strains which differ in presence or absence of such correlation are characteristically different with respect to gene-environment interaction. In the former, the differences due to selection are generally more fully or completely expressed when the diet is changed whereas in the latter this is not so, and different, especially competitive condition, leads to a drastic reduction of the difference.4. How far the expression of the differences due to selection are affected, when the diet is altered, is also influenced by how long selection has been carried out. In early generations, the difference is only or best expressed in the special conditions provided during selection, but later on the changes due to selection are either fully expressed or partly so, as noted above.5. Many of the differences in gene-environment interaction between selected strains can be accounted for in terms of variation in the duration of the exponential phase. Thus two lines selected for small body-size on low RNA or low protein diets responded in different ways to the same nutritional change—one became relatively larger and took porportionately longer to develop, the other became relatively smaller and developed in a shorter time.6. There is clear evidence from various tests in which the amino-acid composition of the diet has been altered, that the nutritional requirements in the two stages of growth are not identical and this is consistent with the evidence for considerable genetic independence as well.7. It is proposed that the first stage of larval growth, which principally determines the duration of the larval period and may also influence body-size, is canalized. Genetic variation which can influence this stage is present in the population but contributes little to the phenotypic variation of adult size, except under special nutritional conditions as when ribonucleic acid is the sole limiting nutrient. But, at the same time, such canalization is dynamic in the sense that the absolute amount of growth which is completed in the first stage may vary with respect to diet and thereby lead to correlated variation in the duration of larval life and adult size. But individuals of an adapted population behave alike in this respect so that gene-environment interaction which leads to correlated variation in the two characters is of a very low order.8. The canalized phase sets a limit to the potential growth in the later stage and thereby influences greatly the mean value about which such growth is equilibrated. This canalization plays a major role in the general stability of growth relations and body-size although this is normally concealed by the high level of phenotypic variation. This interpretation can account for a great variety of data and provides a rational guide to further analysis.

Effects of initial (larval) size and host body temperature on growth in trematodes

2003 ◽  
Vol 81 (4) ◽  
pp. 574-581 ◽  
Author(s):  
Robert Poulin ◽  
A David M. Latham
Keyword(s):  
Body Size ◽  
Body Temperature ◽  
Adult Stage ◽  
Species Variation ◽  
Adult Size ◽  
Model Group ◽  
Larval Size ◽  
Relative Growth ◽  
Host Body ◽  
Adult Body

For ectotherms, temperature is an important correlate of variation in body size within species. Variation in body size among related species could also be attributable in part to temperature if the different species grow under different thermal regimes. The roles of both initial (larval) size and host body temperature on final (adult) size of parasitic trematodes were investigated in a comparative analysis. Trematodes are a good model group for such a study, with almost half of known species growing at high and constant temperatures in endothermic vertebrates and the rest at lower and fluctuating temperatures in ectothermic vertebrates. The relative growth of trematodes, i.e., their growth relative to the size of their larvae, varied greatly among species. Increases in body size from the cercarial larval stage to the adult stage averaged almost 40-fold (maximum 1300-fold), whereas increases in size from the metacercarial stage to the adult stage averaged 6-fold (maximum 110-fold). There were no differences between trematodes in ectothermic hosts and trematodes in endothermic hosts with respect to these measures of relative growth, however, which suggests that host type and the thermal regime provided by the host have no effect on the growth of trematodes from larval to adult stages. In contrast, the final (adult) body size of trematodes appears to be determined to some extent by their initial (larval) size, independently of the type of host in which they developed.

New smallest specimen of the pterosaurPteranodonand ontogenetic niches in pterosaurs

2017 ◽  
Vol 92 (2) ◽  
pp. 254-271 ◽  
Author(s):  
S. Christopher Bennett
Keyword(s):  
Body Size ◽  
Parental Care ◽  
Large Body ◽  
Taxonomic Diversity ◽  
Ecological Niches ◽  
Adult Size ◽  
Niobrara Formation ◽  
Large Body Size ◽  
Juvenile Specimen

AbstractA new juvenile specimen ofPteranodonfrom the Smoky Hill Chalk Member of the Niobrara Formation of western Kansas had an estimated wingspan in life of 1.76 m, ~45% smaller than the smallest previously known specimens, but does not differ in morphology from larger specimens. Its presence indicates that juveniles were capable of flying long distances, so it falsifies the interpretation ofPteranodonas growing rapidly to adult size under parental care before flying. Instead juveniles were precocial, growing more slowly to adult size while flying and feeding independently for several years before going to sea. Because juveniles are otherwise unknown in the Smoky Hill Chalk Member, they must have occupied different environments and ecological niches than adults; thusPteranodonexhibited ontogenetic niches. Evidence is presented that most other pterosaurs (e.g.,Rhamphorhynchus,Pterodactylus,Anhanguera) also exhibited various ontogenetic niches, which, along with their large body size, suggests that pterosaur taxonomic diversity was rather low, like that of crocodilians.

scholarly journals The ecological genetics of growth in Drosophila 3. Growth and competitive ability of strains selected on different diets

1960 ◽  
Vol 1 (3) ◽  
pp. 333-350 ◽  
Author(s):  
Forbes W. Robertson
Keyword(s):  
Body Size ◽  
Development Time ◽  
Competitive Ability ◽  
Variable Degree ◽  
Adult Size ◽  
Adverse Conditions ◽  
Low Protein ◽  
Unselected Population ◽  
Selection For ◽  
Live Yeast

1. The growth of strains of Drosophila melanogaster selected for large size under different nutritional conditions has been recorded on a variety of different media and compared with that of the unselected population. The experiments were designed to test the inference from earlier work that selection for the same ‘character’, body size, on different diets leads to more or less different changes in growth and metabolism. The inference has been amply confirmed.2. When compared on a number of deficient synthetic diets, the strains which had been selected either on a low-protein diet or on one in which all the essential nutrients had been reduced, suffered a much smaller reduction in body size than either the unselected population or, especially, a large strain selected on the favourable live yeast medium. Some diets which drastically reduced the body size of the unselected population lead to no change in the size of strains selected on the synthetic media, although development time was prolonged. Hence selection had extended the capacity for maintaining a characteristic adult body size to diets which normally would lead to a decline. This is taken as evidence of improved adaptation to such conditions. There is also some evidence that selection on the synthetic diets had lowered the level of adaptation to the usual live yeast diet, since body size tended to be lower on this medium than on some of the normally sub-optimal diets.3. To provide comparisons in adverse conditions which are probably more closely related to those commonly encountered by populations in nature or the laboratory, the performance of the strains has been compared in a graded series of competitive conditions on the live yeast medium. By using genetically marked files of the foundation population, which were shown to react in the same way as unmarked flies—in terms of survival, body size and development time—the competitive ability of the different strains has been tested against that of unselected individuals. The latter are generally superior to the selected strains, which differ among themselves, however, in a way which can be related to the conditions in which they were selected.4. Under such competitive conditions, the strains selected on the synthetic diets suffer a much greater decline in body size than do the unselected individuals. For the strain selected on live yeast, the proportional reduction of body size is about the same for the unselected flies at lower levels of crowding, but is clearly greater under more severe conditions of competition.5. The low-protein strain has been backcrossed to the unselected stock. When reared on a variety of synthetic diets, the performance of the F1 was generally intermediate between that of the parents.6. Nutritional variation may be responsible for either a high environmental correlation between the two measures of growth, body size and duration of larval period, or no apparent correlation. Provided the diet is not too unfavourable, body size remains constant although development time may be lengthened to a variable degree. With more adverse conditions, body size is reduced and development time is lengthened more or less proportionately. Such differences in reaction probably depend on the particular stage of larval growth and development primarily affected by the treatment; this problem is being examined further. The inverse relations between body size and development time may represent the operation of a kind of safety mechanism which ensures that the adult reproductive state is attained sooner than would be so if the capacity for maintaining a characteristic body size were more effective in relation to deficient diets. Populations and species adapted to different conditions are likely to differ as to where the balance is struck between effective maintenance of a characteristic adult size, with maximum potential egg production, and the alternative response, according to their ecology. This possibility must be borne in mind when the response to selection for, say, body size is compared in different species.

The evolution of adult body size in black-bellied salamanders (Desmognathus quadramaculatus complex)

2000 ◽  
Vol 78 (10) ◽  
pp. 1712-1722 ◽  
Author(s):  
Carlos D Camp ◽  
Jeremy L Marshall ◽  
Richard M Austin, Jr.
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Larval Growth ◽  
Larval Period ◽  
Moisture Level ◽  
Adult Body Size ◽  
Larval Growth Rate ◽  
Size At Metamorphosis ◽  
Adult Body ◽  
Desmognathus Quadramaculatus

We investigated the possible role of environmental variables in determining body size within a complex of salamander species (Desmognathus quadramaculatus). We analyzed data generated from life-history studies on populations from throughout the range of this species complex. We incorporated an alternative-hypothesis framework (sensu Platt) to determine the better predictor of adult body size, age at maturity, or size at metamorphosis. We found that almost 90% of the variation in adult body size was explained by size at metamorphosis, which was determined by a combination of rate of larval growth and length of the larval period. Environmental temperature and moisture level were positively correlated with larval growth rate and length of the larval period, respectively. We propose a simple model of body-size evolution that incorporates both adaptive and plastic components. We suggest that the length of the larval period may adaptively respond to moisture-level predictability. In addition, we suggest that the response of the larval growth rate to temperature may be plastic. Because the selection pressure due to drying-induced mortality is pervasive among species of amphibians, it may have played a role in shaping body-size radiation in desmognathines as well as the ecological structure of Appalachian streamside communities.

scholarly journals The ecological genetics of growth in Drosophila 2. Selection for large body size on different diets

1960 ◽  
Vol 1 (2) ◽  
pp. 305-318 ◽  
Author(s):  
Forbes W. Robertson
Keyword(s):  
Body Size ◽  
Egg Production ◽  
Large Body ◽  
Selection Response ◽  
Ecological Genetics ◽  
Response To Selection ◽  
Genetic Changes ◽  
Alternative Pathways ◽  
Selection For ◽  
Live Yeast

1. Strains from a cage population of Drosophila melanogaster were selected for increased body size on the live yeast medium and on two aseptic synthetic media, (1) deficient in protein and (2) with all nutrients reduced to one-third the normal concentration required for growth to normal size. Both these media reduce body size by about 25%.2. In two strains, mass selected on the live yeast medium, the response continued fairly steadily for at least sixteen generations, when the experiment was discontinued. By this time body size had been increased by some 30%.3. On the sub-optimal diets the number of selected parents per generation was twice as great as on the live yeast medium, for technical reasons, but the response ceased abruptly after seven or eight generations of selection at a level considerably below that attained by the strains selected on the more favourable diet. Also, when selection was continued on the live yeast diet, no further progress occurred.4. Flies selected on the different diets and also unselected flies have been grown on the alternative conditions to see how the deviation from unselected is affected. For both strains selected on sub-optimal diets, the deviation from unselected is appreciably greater on the medium used for selection than on the live yeast medium.5. The response to selection for larger body size on deficient diets can be attributed partly to better adaptation to these conditions. This inference is supported by several lines of evidence. The within-culture variance, which is clearly greater when selected flies are grown on deficient diets, declines with effective selection. Also in the low-protein strain, for which data are available, the duration of the larval period is shortened in the early stages of selection, while egg production considerably exceeds that of unselected flies grown on the same diet.6. Other effects, of the kind normally selected for on the live yeast medium, also contribute to the variation and selection response on the deficient diets. At first they appear to act more or less independently of the genetic changes which favour increased size via improved adaptation to the diet, but continued selection soon leads to mutual incompatibility between the alternative pathways in growth. Since no further progress occurred when selection was continued on the live yeast medium, the earlier selection had probably lowered the level of adaptation to the live yeast medium. A new genetic situation had been created in which it was impossible to gauge the amount of further progress by reference to the behaviour of strains selected on the live yeast medium from the beginning.7. Estimates of heritability, based on cumulated selection differentials, are rather similar in the different diets and range between 0·30 and 0·38. On the live yeast medium, the estimate provides a fair guide to future progress, whereas, on the deficient diets, the predictive value is nil since response ceases immediately after the generations which provide the data for the estimates.8. By comparing the deviation from unselected on the media used for selection and also the other media, alternative estimates of genetic correlation in performance in different conditions can be computed. The estimates were sufficiently divergent to cast doubt on the practical utility of the statistical procedure, which takes no account of the likelihood that individual variation in body size in different environment represents to greater or lesser degree the effects of segregation on different processes of growth and metabolism.9. Since the course of selection is influenced by nutritional conditions, comparisons of response to selection for the same ‘character’ such as body size, in populations or species adapted to different conditions, must allow for the likelihood that unequal differences between the conditions in which selection is carried out and those in which the animal normally lives may be an important cause of differences in response.

scholarly journals Caterpillars selected for large body size and short development time are more susceptible to oxygen-related stress

2013 ◽  
Vol 3 (5) ◽  
pp. 1305-1316 ◽  
Author(s):  
Jon F. Harrison ◽  
Arianne J. Cease ◽  
John M. VandenBrooks ◽  
Todd Albert ◽  
Goggy Davidowitz
Keyword(s):  
Body Size ◽  
Development Time ◽  
Large Body ◽  
Large Body Size ◽  
Short Development Time ◽  
Related Stress

scholarly journals The ecological genetics of growth in Drosophila 8. Adaptation to a New Diet

1966 ◽  
Vol 8 (2) ◽  
pp. 165-179 ◽  
Author(s):  
Forbes W. Robertson
Keyword(s):  
Body Size ◽  
Egg Production ◽  
Development Time ◽  
Chelating Agent ◽  
Mean Value ◽  
Ecological Genetics ◽  
Original Population ◽  
Fast Development ◽  
Selection For ◽  
Food Medium

1. Populations of Drosophila melanogaster have been adapted to a new, initially unfavourable diet by adding to the food medium the chelating agent, EDTA, which lowers survival, lengthens development and reduces body size, according to the concentration.2. Six populations were allowed to adapt to the new diet without intervention and compared with two additional populations in which there was either artificial selection for fast development time or in which the effects of variation in development time were minimized and higher egg production was favoured instead.3. All populations adapted successfully and some were able to grow on medium with EDTA concentrations which were lethal for the original population.4. Under uncrowded conditions on EDTA-free medium, in seven out of the eight populations, body size was reduced by about 7% below the level of the original population and the larval period was shorter in several instances. But in the population in which higher egg production was favoured, body size was 7% greater than in the original population and 16% greater than the average of the other EDTA-adapted populations. This contrast was attributed either to intense natural selection for shorter development time or to selection for a higher rate of egg production, which is positively correlated with body size when larvae are grown on sub-optimal conditions.5. Under crowded, competitive conditions, the fitness of the EDTA-adapted and the original populations was reversed according to the presence or absence of EDTA.6. Genetic differences between one of the EDTA-adapted populations and the original population were studied by using marked inversions to interchange chromosome pairs. Larvae of the alternative genotypes were grown on different diets and adaptation was shown to have involved changes in all major chromosomes and also substantial, complementary interaction between non-homologous pairs. Substitution of the third pair of chromosomes from the original Pacific stock in the background of the adapted strain led to complete sterility of females, on all diets tested, and lethality of both sexes at higher levels of EDTA.7. The creation of new equilibria, by manipulating the relative importance of components of fitness, in the course of adaptation to a new environment, offers a valuable technique for studying the selective forces which influence the mean value of quantitative characters generally.

scholarly journals Larval Size and Recruitment Mechanisms in Fishes: Toward a Conceptual Framework

1988 ◽  
Vol 45 (9) ◽  
pp. 1657-1670 ◽  
Author(s):  
Thomas J. Miller ◽  
Larry B. Crowder ◽  
James A. Rice ◽  
Elizabeth A. Marschall
Keyword(s):  
Body Size ◽  
Conceptual Framework ◽  
Larval Fish ◽  
Larval Growth ◽  
Larval Survival ◽  
Freshwater Species ◽  
Larval Size ◽  
Growth And Survival ◽  
Fisheries Science ◽  
Risk Of Predation

Understanding the mechanisms controlling recruitment in fishes is a major problem in fisheries science. Although the literature on recruitment mechanisms is large and growing rapidly, it is primarily species specific. There is no conceptual framework to integrate the existing information on larval fish ecology and its relationship to survival and recruitment. In this paper, we propose an integrating framework based on body size. Although all larval fish are small relative to adult fish, total length at hatching differs among species by an order of magnitude. As many of the factors critical to larval survival and growth are size dependent, substantially different expectations arise about which mechanisms might be most important to recruitment success. We examined the evidence for the importance of size to feeding and starvation, to activity and searching ability, and to risk of predation. Regressions based on data from 72 species of marine and freshwater species suggest that body size is an important factor that unifies many of the published observations. A conceptual framework based on body size has the potential to provide a useful integration of the available data on larval growth and survival and a focus for future studies of recruitment dynamics.

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