Four characters in a trade-off: dissecting their phenotypic and genetic relations

Phenotypic characters may covary negatively because they are in a trade-off or positively because they contribute to a single function. Genetic correlations can be used to test the validity and generality of these functional relationships by indicating the level of genetic integration and checking the conditions under which they are expressed. Phenotypic correlations indicate that there is a widespread trade-off between flight capability and early fecundity in insects. Different wing morphs (long and short wing) are thought to have a suite of reproductive and flight capability traits. In a half-sib mating experiment, we estimated phenotypic relationships between two flight-capability-related characters (flight muscle condition, wing morph) and two components of early fecundity (number of eggs in the ovaries, number of eggs laid), as well as genetic correlations relating wing morph and both components of fecundity in the wing-dimorphic cricket, Gryllus firmus. The number of eggs in the ovaries and the number of eggs laid were negatively correlated phenotypically and genetically with wing length morph (i.e., long wings associated with low fecundity). Both fecundity characters differed between wing morphs, but only if flight muscle was present and not histolyzed. The phenotypic and genetic correlations between fecundity characters were not significant. This suggests that the phenotypic relationship between ovary development and eggs laid is complex, they are not genetically integrated, and they may evolve independently. However, both early fecundity characters are functionally and genetically integrated within the trade-off to a similar degree. Finally, the trade-off affects early fecundity of both wing morphs suggesting that the functional relationship depends on flight muscle size. Received: 1 December 1998 / Accepted: 20 May 1999     

Male sand crickets trade-off flight capability for reproductive potential

In this paper, we test the hypothesis that male sand crickets, Gryllus firmus, experience a trade-off between flight capability and reproductive potential expressed as reduced testis weight in flight-capable morphs. We used a half-sib design with 130 sires, three dams per sire and an average of 5.66 males per dam family, for a total of 2206 F1 offspring. Traits measured were head width, somatic dry weight, testis weight, wing morph (micropterous/macropterous), weight of the dorso-longitudinal flight muscles (DLM) and the functional status of these muscles. Heritabilities of all traits were significant and ranged from 0.14 to 0.43. All traits were positively correlated with body size, but removal of this covariance revealed a highly significant trade-off, both phenotypically and genetically, between testes size and flight capability as measured by wing morph, DLM size or DLM status. The possible implications of this for morph-specific reproductive tactics are discussed.     

Differential allocation of resources underlies the dispersal-reproduction trade-off in the wing-dimorphic cricket,Gryllus rubens

The cricket, Gryllus rubens (Orthoptera, Gryllidae), exists in natural populations as either a fully-winged (LW), flight-capable morph or as a short-winged (SW) morph that cannot fly. The SW morph is substantially more fecund than the LW morph. In this study we report on the physiological basis of this trade-off between flight capability and fecundity. Results from gravimetric feeding trials indicate that LW and SW morphs are equivalent in their consumption and digestion of food. However, during the adult stage, the LW morph is less efficient in converting assimilated nutrients into biomass. This may be a consequence of the respired loss of assimilated nutrients due to the maintenance of functional flight muscles in the LW morph. In both morphs the gross biomass devoted to flight muscles does not change significantly during the first 14 days of adult growth while there is a significant biomass gain in ovarian tissue mass during the same period. SW morphs have vestigial flight muscles and gain substantially more ovarian mass relative to the LW morphs. These data are consistent with a trade-off between flight muscle maintenance in the LW morph and ovarian growth in the SW form. This is the first evidence for a life-history trade-off that has a physiological basis which is limited to the allocation of acquired and assimilated nutrients within the organism.     

The evolution of threshold traits: effects of selection on fecundity and correlated response in wing dimorphism in the sand cricket

The quantitative genetic basis of traits can be determined using a pedigree analysis or a selection experiment. Each approach is valuable and the combined data can contribute more than either method alone. Analysis using both sib analysis and selection is particularly essential when there are likely to be nonlinearities in the functional relationships among traits. A class of traits for which this occurs is that of threshold traits, which are characterized by a dichotomous phenotype that is determined by a threshold of sensitivity and a continuously distributed underlying trait called the liability. In this case, traits that are correlated with the liability may show a nonlinear relationship due to the dichotomy of expression at the phenotypic level. For example, in wing dimorphic insects fecundity of the macropterous (long-winged) females appears in part to be determined by the allocation of resources to the flight muscles, which are almost invariably small or absent in the micropterous (short-winged, flightless) females. Pedigree analysis of the cricket Gryllus firmus has shown that wing morph, fecundity and the trade-off between the two have additive genetic (co)variance. It has also been shown that selection on proportion macroptery produced an asymmetric correlated response of fecundity. The present paper details the results of direct selection on fecundity and the correlated response in proportion macroptery. Selection for increased fecundity resulted in increased fecundity within both wing morphs and a correlated decrease in proportion macroptery. Similarly, selection for decreased fecundity resulted in a decrease within morphs and a correlated increase in the proportion of macropterous females. This provides additional evidence that the trade-off between fecundity and wing morphology has a genetic basis and will thus modulate the evolution of the two traits.     

The evolution of trade-offs: effects of inbreeding on fecundity relationships in the cricket Gryllus firmus

The evolution of traits is modulated by their interrelationships with each other, particularly when those relationships result in a fitness trade-off. In this paper we explore the consequences of genetic architecture on functional relationships between traits. Specifically, we address the consequences of inbreeding on these relationships. We show that the linear regression between two traits will not be affected if there is no dominance genetic variance in either trait, whereas the intercept but not the slope of the regression will change if there is dominance genetic variance in one trait only. We test the latter hypothesis using fecundity relationships in the cricket Gryllus firmus. Data from pedigree analysis and an inbreeding experiment show that there is significant dominance genetic variance in fecundity, but not head width (an index of body size) or dorsal longitudinal muscle (DLM) mass. Fecundity increases with head width, but decreases with DLM mass. As predicted, the intercepts of the regressions of fecundity on these two morphological traits decrease with inbreeding, but there is little or no change in slope. Gryllus firmus is wing dimorphic, with the macropterous (LW) morph having a lower fecundity than the micropterous (SW) morph. We hypothesize that the difference in fecundity arises primarily because of a competition for resources in the LW females between DLM maintenance (i.e., mass) and egg production. As a consequence, we predict that the fecundity within each morph should decline linearly with the inbreeding coefficient at the same rate in both morphs. The result of this will be a change in the relative fitness of the two morphs, that of the SW morph increasing with inbreeding. This prediction is supported. These results indicate that trade-offs will evolve and such changes will affect evolutionary trajectories by altering the pattern of relationships among fitness components.     

Laboratory evolution of the migratory polymorphism in the sand cricket: combining physiology with quantitative genetics

Predicting evolutionary change is the central goal of evolutionary biology because it is the primary means by which we can test evolutionary hypotheses. In this article, we analyze the pattern of evolutionary change in a laboratory population of the wing-dimorphic sand cricket Gryllus firmus resulting from relaxation of selection favoring the migratory (long-winged) morph. Based on a well-characterized trade-off between fecundity and flight capability, we predict that evolution in the laboratory environment should result in a reduction in the proportion of long-winged morphs. We also predict increased fecundity and reduced functionality and weight of the major flight muscles in long-winged females but little change in short-winged (flightless) females. Based on quantitative genetic theory, we predict that the regression equation describing the trade-off between ovary weight and weight of the major flight muscles will show a change in its intercept but not in its slope. Comparisons across generations verify all of these predictions. Further, using values of genetic parameters estimated from previous studies, we show that a quantitative genetic simulation model can account for not only the qualitative changes but also the evolutionary trajectory. These results demonstrate the power of combining quantitative genetic and physiological approaches for understanding the evolution of complex traits.     

Path analysis of the genetic integration of traits in the sand cricket: a novel use of BLUPs

This study combines path analysis with quantitative genetics to analyse a key life history trade-off in the cricket, Gryllus firmus. We develop a path model connecting five traits associated with the trade-off between flight capability and reproduction and test this model using phenotypic data and estimates of breeding values (best linear unbiased predictors) from a half-sibling experiment. Strong support by both types of data validates our causal model and indicates concordance between the phenotypic and genetic expression of the trade-off. Comparisons of the trade-off between sexes and wing morphs reveal that these discrete phenotypes are not genetically independent and that the evolutionary trajectories of the two wing morphs are more tightly constrained to covary than those of the two sexes. Our results illustrate the benefits of combining a quantitative genetic analysis, which examines statistical correlations between traits, with a path model that focuses upon the causal components of variation.     

Biogeographical survey identifies consistent alternative physiological optima and a minor role for environmental drivers in maintaining a polymorphism

The contribution of adaptive mechanisms in maintaining genetic polymorphisms is still debated in many systems. To understand the contribution of selective factors in maintaining polymorphism, we investigated large-scale (>1000 km) geographic variation in morph frequencies and fitness-related physiological traits in the damselfly Nehalennia irene. As fitness-related physiological traits, we investigated investment in immune function (phenoloxidase activity), energy storage and fecundity (abdomen protein and lipid content), and flight muscles (thorax protein content). In the first part of the study, our aim was to identify selective agents maintaining the large-scale spatial variation in morph frequencies. Morph frequencies varied considerably among populations, but, in contrast to expectation, in a geographically unstructured way. Furthermore, frequencies co-varied only weakly with the numerous investigated ecological parameters. This suggests that spatial frequency patterns are driven by stochastic processes, or alternatively, are consequence of highly variable and currently unidentified ecological conditions. In line with this, the investigated ecological parameters did not affect the fitness-related physiological traits differently in both morphs. In the second part of the study, we aimed at identifying trade-offs between fitness-related physiological traits that may contribute to the local maintenance of both colour morphs by defining alternative phenotypic optima, and test the spatial consistency of such trade-off patterns. The female morph with higher levels of phenoloxidase activity had a lower thorax protein content, and vice versa, suggesting a trade-off between investments in immune function and in flight muscles. This physiological trade-off was consistent across the geographical scale studied and supports widespread correlational selection, possibly driven by male harassment, favouring alternative trait combinations in both female morphs.     

Antagonistic and reinforcing pleiotropy: a study of differences in development time in wing dimorphic insects

Morphological dimorphisms are found in many different taxa. Wing dimorphism in insects, in which some individuals possess wings and associated flight muscles and are thus volant while others lack a functional flight apparatus and are thus flightless, is a typical example of such types of dimorphisms. It has been extensively studied and such studies have demonstrated that the volant form, although possessing the advantage of flight capability, suffers a fitness cost in a delay in the onset of reproduction after emergence into the adult form and a reduced fecundity. Previous comparative analyses have suggested that there is no consistent trend for development time (hatching to adult) to differ between the two morphs. The present study analyses the phenotypic and genetic correlations between development time and wing morph in the cricket Gryllus firmus. It is shown that the macropterous (volant) morph develops faster than the micropterous (flightless morph). This trade-off is manifested at both thephenotypic and genetic level. Further, a comparative analysis shows that the same phenotypic trade-off is generally found in other Orthopteran species so far studied, but in other orders the micropterous morph develops faster. Provided that the phenotypic trade-off is genetically based, in the Orthoptera the fitness advantage of the earlier onset of reproduction in micropterous females is offset by the extended development time (antagonistic pleiotropy). However, in other orders there is reinforcing pleiotropy in that the micropterous females develop faster and reproduce sooner than the macropterous morph. These results highlight the complexity of fitness interactions and the need to study a phenomenon across several taxa.     

Trade‐offs to flight capability in Gryllus firmus: the influence of whole‐organism respiration rate on fitness

Wing dimorphism, where some macropterous long‐winged (LW) individuals can fly whereas micropterous short‐winged (SW) individuals cannot, is common in insects and believed to be maintained in part by trade‐offs between flight capability and reproductive traits. In this paper we examine differences in whole‐organism respiration rate between wing morphs of the sand cricket Gryllus firmus. We hypothesized that maintenance of the flight apparatus would result in elevated CO₂ respired because of the high metabolic cost of these tissues, which, in turn, constrain resources available for egg production in females. As the trade‐off involves calling behaviour in males, we predicted no equivalent constraint on organ development in this sex. We found female macropters (particularly older crickets) had significantly higher residual respiration rates than micropters. In males, we found only marginal differences between wing morphs. In both sexes there was a highly significant effect of flight muscles status on residual respiration rate, individuals with functional muscles having higher respiration rates. Both female and male macropters had significantly smaller gonads than micropters. Whole‐organism residual respiration rate was negatively correlated with fecundity: macropterous females with high respiration rates had smaller gonads compared with macropterous females with lower respiration rates.     

Life-history evolution and the microevolution of intermediary metabolism: activities of lipid-metabolizing enzymes in life-history morphs of a wing-dimorphic cricket

Although a considerable amount of information is available on the ecology, genetics, and physiology of life-history traits, much more limited data are available on the biochemical and genetic correlates of life-history variation within species. Specific activities of five enzymes of lipid biosynthesis and two enzymes of amino acid catabolism were compared among lines selected for flight-capable (LW[f]) versus flightless (SW) morphs of the cricket Gryllus firmus. These morphs, which exist in natural populations, differ genetically in ovarian growth (100-400% higher in SW) and aspects of flight capability including the size of wings and flight muscles, and the concentration of triglyceride flight fuel (40% greater in LW[f]). Consistently higher activity of each enzyme in LW(f) versus SW-selected lines, and strong co-segregation between morph and enzyme activity, demonstrated genetically based co-variance between wing morph and enzyme activity. Developmental profiles of enzyme activities strongly paralleled profiles of triglyceride accumulation during adulthood and previous measures of in vivo lipid biosynthesis. These data strongly imply that genetically based elevation in activities of lipogenic enzymes, and enzymes controlling the conversion of amino acids into lipids, is an important cause underlying the elevated accumulation of triglyceride in the LW(f) morph, a key biochemical component of the trade-off between elevated early fecundity and flight capability. Global changes in lipid and amino-acid metabolism appear to have resulted from microevolutionary alteration of regulators of metabolism. Finally, strong genotype x environment (diet) interactions were observed for most enzyme activities. Future progress in understanding the functional causes of life-history evolution requires a more detailed synthesis of the fields of life-history evolution and metabolic biochemistry. Wing polymorphism is a powerful experimental model in such integrative studies.     

Nutrient absorption and utilization by wing and flight muscle morphs of the cricket Gryllus firmus: implications for the trade-off between flight capability and early reproduction

Absorption efficiency (AD, approximate digestibility, assimilation efficiency) of various macronutrients and conversion of absorbed nutrients to biomass (ECD) were compared among the two types of flightless morph and the flight-capable morph of the cricket, Gryllus firmus. No biologically significant phenotypic or genetic difference in AD for carbohydrate, protein or lipid was observed among morphs fed either a high-nutrient (100%) or a low-nutrient (25%) diet. Thus, previously-documented differences among adult morphs in carbohydrate and lipid content must be caused by processes other than variation in nutrient absorption by morphs during adulthood. Relative absorption efficiency of total dry mass of food by morphs of G. firmus appears to be a valid indicator of relative AD of total calories. Morphs did not differ phenotypically or genetically in the excretion of end products of nitrogen metabolism (uric acid, hypoxanthine plus xanthine) on either the high nutrient or the low nutrient diet. Nutritional indices corrected for excreted nitrogenous metabolites were very similar to uncorrected indices, and the pattern of variation among the morphs was the same for corrected or uncorrected values. Each of the two types of flightless morph converted a greater proportion of absorbed nutrients into body mass, mainly ovaries, and allocated a smaller proportion of assimilated nutrients to respiration than did the flight-capable morph. Moreover, the trade-off between respiration and early reproduction was substantially magnified on the low nutrient diet. These results extend previous findings of a trade-off between flight capability and early reproduction in wing-polymorphic Gryllus species (1) to diets of very different nutrient quantity, and (2) to flightlessness arising from different causes: blockage of flight muscle development in juveniles vs histolysis of fully-developed flight muscles in adults.     

THE GENETIC BASIS OF THE TRADE-OFF BETWEEN CALLING AND WING MORPH IN MALES OF THE CRICKET GRYLLUS FIRMUS

Wing dimorphisms exist in a wide range of insects. In wing-dimorphic species one morph is winged has functional flight muscles (LW), and is flight-capable, whereas the other has reduced wings (SW) and cannot fly The evolution and maintenance of wing dimorphisms is believed to be due to trade-offs between flight capability and fitness-related traits. Although there are well-established phenotypic trade-offs associated with wing dimorphism in female insects, there only exist two studies that have established a genetic basis to these trade-offs. The present study provides the first evidence for a genetically based trade-off in male insects, specifically in the sand cricket Gryllus firmus. Because they have to expend energy to maintain the flight apparatus (especially flight muscles), LW males are predicted to call less and therefore to attract fewer females. To be of evolutionary significance, call duration wing morph, and wing muscle condition (size and functionality) should all have measurable heritabilities and all be genetically correlated. Differences between morphs in male G. firmus in the likelihood of attracting a female were tested in the laboratory using a T-maze where females chose between a LW male and a SW male. Call duration for each male was recorded on the sixth day of adult life. A significant difference in call duration was found between SW and LW males (SW = 0.86 ± 0.01, LW = 0.64 ± 0.01 h). SW males attracted significantly more females than did LW males (63% vs. to 37%). All the traits involved in the trade-off had significant heritabilities (call = 0 75 ± 0 33; wing morph = 0.22 ± 007; muscle weight = 0.38 ± 0.09) and genetic correlations (call and wing morph = -0.46 ± 0.20 for SW, -0.68 ± 0.16 for LW; LW call and muscle weight = -0.80 ± 0.14). These results provide the first documented evidence that trade-offs between a dimorphic trait and a fitness-related character in males has a genetic basis and hence can be of evolutionary significance.     

Morph-dependent fatty acid oxidation in a wing-polymorphic cricket: implications for the trade-off between dispersal and reproduction

Although a considerable amount of information is available on the ecology and physiology of wing polymorphism, much less is known about the biochemical-genetic basis of morph specialization for dispersal versus reproduction. Previous studies have shown that the dispersing morph of the wing-polymorphic cricket, Gryllus firmus, prioritizes the accumulation of triglyceride flight fuel over ovarian growth, while the opposite occurs in the flightless morph during the first week of adulthood. In this study, we compared the in vivo rate of lipid oxidation between genetic stocks of flight-capable versus flightless morphs to determine the role of lipid catabolism in morph specialization for flight versus reproduction. During the first five days of adulthood, in the absence of flight, fatty acid oxidation was substantially lower in the dispersing morph relative to the flightless morph, when either radiolabeled acetate or palmitate was used as a substrate. Differences between the morphs in fatty acid oxidation were genetically based, occurred co-incident with morph-specific differences in triglyceride accumulation and ovarian growth, and were observed on a variety of diets. A genetically based trade-off in the relative conversion of palmitate into CO(2) versus triglyceride was observed in morphs of G. firmus. Decreased oxidation of fatty acid and increased biosynthesis of triglyceride, both appear to play an important role in flight fuel accumulation, and hence morph specialization for flight. Conversely, increased oxidation of fatty acid likely fuels the enhanced ovarian growth in the flightless morph. The results of the present study on fatty acid catabolism, and previous studies on triglyceride and phospholipid biosynthesis, provide the first direct evidence that genetically based differences in in vivo flux through pathways of intermediary metabolism underlie a trade-off between flight capability and reproduction--a trade-off of central importance in insects.     

The evolutionary genetics of acquisition and allocation in the wing dimorphic cricket, Gryllus firmus

The evolutionary trajectories of trade-offs are ultimately governed by the evolution of the underlying physiological processes of the acquisition and subsequent allocation of resources. In this study, we focused directly on acquisition and allocation as traits and estimated their genetic architecture in the trade-off between flight capability and reproduction in the cricket, Gryllus firmus. To determine the evolutionary genetics of acquisition and allocation both within and between resource environments, we performed a large-scale quantitative genetic breeding experiment in which families were split over several resource levels. Our findings were fourfold: (1) there was substantial genetic variance in acquisition and allocation, (2) contrary to the assumption of independence between acquisition and allocation, there was a significant genetic correlation between them, (3) the genetic covariance between acquisition and allocation was significantly different in the different food environments, (4) the trade-off, as measured by the genetic correlation between flight muscle mass and ovary mass, was only significant in the food restriction environments. However, when measured directly as the genetic correlation between reproductive allocation and flight allocation, we found a consistent strong negative genetic correlation, demonstrating that when allocation is measured independently of acquisition we find evidence for the trade-off.     

The evolution of trade-offs: testing predictions on response to selection and environmental variation

The concept of phenotypic trade-offs is a central element in evolutionary theory. In general, phenotypic models assume a fixed trade-off function, whereas quantitative genetic theory predicts that the trade-off function will change as a result of selection. For a linear trade-off function selection will readily change the intercept but will have to be relatively stronger to change the slope. We test these predictions by examining the trade-off between fecundity and flight capability, as measured by dorso-longitudinal muscle mass, in four different populations of the sand cricket, Gryllus firmus. Three populations were recently derived from the wild, and the fourth had been in the laboratory for 19 years. We hypothesized that the laboratory population had most likely undergone more and different selection from the three wild populations and therefore should differ from these in respect to both slope and intercept. Because of geographic variation in selection, we predicted a general difference in intercept among the four populations. We further tested the hypothesis that this intercept will be correlated with proportion macropterous and that this relationship will itself vary with environmental conditions experienced during both the nymphal and adult period. Observed variation in the phenotypic trade-off was consistent with the predictions of the quantitative genetic model. These results point to the importance of modeling trade-offs as dynamic rather than static relationships. We discuss how phenotypic models can incorporate such variation. The phenotypic trade-off between fecundity and dorso-longitudinal muscle mass is determined in part by variation in body size, illustrating the necessity of considering trade-offs to be multi factorial rather than simply bivariate relationships.     

Juvenile hormone titer and morph-specific reproduction in the wing-polymorphic cricket,Gryllus firmus

Juvenile hormone titers and reproductive characteristics were measured in adult wing and flight-muscle morphs of the wing-polymorphic cricket, Gryllus firmus, during the first week of adulthood. This species has three morphs: one flight capable morph with fully-developed wings and fully-developed flight muscles [LW(F)], one flightless morph with fully-developed wings and histolyzed (non-functional) flight muscles [LW(H)], and another flightless morph with underdeveloped (short) wings and underdeveloped flight muscles (SW). Both flightless morphs [LW(H) and SW] had larger ovaries which contained a greater number of postvitellogenic eggs compared with the flight capable [LW(F)] morph. The juvenile hormone titer was significantly higher in SW compared with LW(F) females on days 3-7 of adulthood. On these days, the JH titer also was significantly higher in the other flightless morph, LW(H), compared with flight-capable [LW(F)] females as determined by one statistical test, but did not differ significantly by another test. The JH titer was positively correlated with ovarian mass or terminal oocyte length, but not with the number of post-vitellogenic eggs. This study is the first direct comparison of juvenile hormone titers in adult wing morphs of a wing-polymorphic insect. Results indicate that an elevated juvenile hormone titer may be at least partly responsible for one of the most distinctive features of wing-polymorphic species, the increased early fecundity of flightless females.     

The trade‐off to macroptery in the cricket Gryllus firmus: a path analysis in males

Among the Orthoptera, wing dimorphism, where one morph is long‐winged and flight capable while the other is short‐winged and flight incapable, is common and believed to be maintained in populations due to trade‐offs to flight capability. In males, macropterous individuals call less than micropterous individuals and as a consequence obtain fewer matings. This trade‐off is hypothesized to be mediated by the energetic costs of calling. In this paper we report results for a path analysis examining lipid weight and DLM (dorso longitudinal muscle) condition of male Gryllus firmus. We found that as DLM condition changes from a nonfunctional to a functional state, call duration decreases, and as lipid weight increases, call duration increases. The most important linked path was wing morph → DLM condition → call duration. This model is consistent with the prediction that the trade‐off between wing morph and call duration is mediated via DLM and lipid stores.     

Effects of suppressed oviposition activity and flight muscle histolysis on food consumption and ovarian development in a wing-dimorphic cricket: an explanation for sporadic conclusions related to physiological trade-offs

The effects of deprivation of oviposition substrate on food consumption and egg production were compared between the long-winged (LW) and the short-winged (SW) morph of a cricket, Modicogryllus confirmatus, to determine how suppressed oviposition activity would influence these traits in each wing morph. Food consumption was greatly suppressed in females deprived of oviposition substrate (-OS) compared to those given access to it (+OS) during the 2-week feeding trial in the SW morph but not in the LW morph. Some LW females shed their hindwings and histolyzed the flight muscles. Such de-alated LW (DLW) morphs tended to consume more food than intact LW (ILW) morphs. In all morphs, ovarian weight was heavier under -OS conditions than under +OS conditions during the second week of adulthood, although the differences were greater in SW morphs than in ILW morphs. In DLW morphs in which flight muscle histolysis was induced by artificial de-alation at adult emergence, the temporal changes in ovarian weight were similar to those of SW morphs.In SW morphs, food consumption was also significantly reduced when ovipositing females were deprived of oviposition substrate for 2 days compared to those allowed to oviposit continuously, but food consumption was not reduced in ILW or DLW morphs. SW females from which one ovary was extirpated at adult emergence, SW (-o), also showed a significant difference in food consumption when treated as above, indicating that food consumption was not determined simply by the number of ovarian eggs. The crop content was positively correlated to food consumption and smaller under -OS conditions than under +OS conditions. The 2-day deprivation of oviposition substrate caused no significant difference in the total number of deposited and ovarian eggs in any group, but the ovarian mass of developing oocytes tended to be smaller under -OS than under +OS conditions, particularly in SW morphs.These results indicate the possibility that some inconsistent results and conclusions discussed in recent studies, concerning the physiological trade-offs between flight capability and reproduction, were caused by the suppressed oviposition activity and failure to recognize the occurrence of flight muscle growth and histolysis in the test crickets.