Size-number Trade-off Research Articles

Paternal Effects on Offspring Fitness Reflect Father’s Social Environment

In many species, males influence phenotypic traits in their offspring through non-genetic paternal effects. Such effects can represent a form of paternal investment, and males may benefit by adjusting the effects depending on environmental parameters, such as operational sex ratio, so as to maximize offspring fitness. In the neriid fly Telostylinus angusticollis, fathers reared on a nutrient-rich larval diet produce larger offspring, independent of the rearing environment of the offspring. Here we asked whether this paternal effect was influenced by the social environment to which fathers were exposed. We found significant interactions of the effects of paternal larval diet quality and social environment (same-sex vs. mixed-sex groups) on offspring fitness-related traits. Fathers reared on a nutrient-rich diet produced larger male offspring when housed in mixed-sex groups. However, fathers reared on a nutrient-rich diet produced more viable offspring (or more viable sperm) when housed in same-sex groups prior to mating. These results suggest that fitness-enhancing paternal effects can trade off, consistent with parental investment theory on the offspring size-number trade-off, which suggests that these traits represent alternative investment options and parents are selected to optimize the balance based on a range of environmental variables. This is the first study to show that males can facultatively modulate paternal effects based on the social environment.

Twig size-number trade-off among woody plants in Tiantong region, Zhejiang Province of China

Aims The branch size-number trade-off among woody plants has implications for both the formation of plant architecture and biomass allocation in response to environment stresses.Our objective was to examine how the twig size-number relationship varies among woody plants in subtropical broad-leaved evergreen forests in south-eastern China.Methods The study site is located in Tiantong National Forest Park(29°52' N,121°39' E),Zhejiang Province,in Eastern China.We measured twig length,twig diameter,number of twigs and length and diameter of branches from which the twigs were sampled for 76 woody species in a 1-hm-2 plot.Standardized major axis(SMA) analysis was conducted to examine the quantitative relationship between twig size(cross-sectional area) and the number of twigs at a given twig size(twig intensity).Important findings A significantly negative allometric scaling relationship was found between twig intensity and its cross-sectional area.Under level-Ⅱ light exposure(LE-Ⅱ,40%-80% of the plant under direct light),ever-green species had a much higher twig intensity than deciduous species.However,there was no difference in twig intensity between these two life forms under LE-Ⅰ(40% ehxposure) or LE-Ⅲ(80% exposure).Higher twig intensity was found in evergreen species under LI-Ⅲ than under both LE-Ⅰ and LE-Ⅱ.In contrast,twig intensity of deciduous species was not different among any of the light exposure levels.Shrubs 4 m height had higher twig intensity than sub-trees and trees 4 m at a given twig size.We conclude that the twig size-number trade-off across woody plants in Tiantong was consistent with the Corner's rule(that describes the relationship between twig size and the number of twigs),but might differ among different life forms.Both evergreen species and shrubs are inclined to develop higher twig intensity,which indicates their adaptation to environment stress caused by limitations in light availability.

Larval Food Supply Constrains Female Reproductive Schedules inHippodamia convergens(Coleoptera: Coccinellidae)

AbstractReproductive schedules are a critical aspect of life history intrinsically linked to a species' ecology. We explored dynamic trajectories of daily fecundity, egg size, and egg fertility in three size classes of Hippodamia convergens Guerin-Meneville produced by varying larval access to food, eggs of Ephestia kuehniella Zeller. Adult pairs were held with ad libitum food and eggs were collected daily, counted, and a subsample measured. Egg fertility declined steeply over 25 clutches in small females, gradually in large females, but remained relatively stable in medium females. In small females, egg size and daily fecundity declined in a linear manner. There was no clear indication of an egg size-number tradeoff. In medium females, both egg size and daily fecundity peaked around the 16th day of oviposition, after which both declined. Large females began oviposition earlier and achieved peak egg size about day 7, and peak fecundity around day 12. Large females thus expressed a larger proportion of their reproductive effort early in adult life, a strategy inferred to be adaptive in the context of aphidophagy; a larger proportion of progeny would develop early in the exponential growth phase of the prey population when food is most abundant. Increases in egg size during this period may improve the survival of later-developing progeny; prey become scarce as aphid outbreaks decline and competition intensifies, favoring offspring with a larger body size at eclosion. Larval diet restriction appeared to constrain these presumably adaptive changes in egg size and daily fecundity, largely through effects on maternal body size.

Temperature effects during development on a polyembryonic parasitoid and its host

Ambient temperature can influence development through effects on metabolic rate and by inducing physiological stress. In this study, we assessed temperature effects on a host–parasitoid interaction and on the body size and brood size of emerging wasps. By examining the development at two different temperatures of the koinobiont parasitoid, Copidosoma bakeri, and its host, Agrotis ipsilon, we asked: (1) Does the growth response to temperature by A. ipsilon depend on whether the moth caterpillar is parasitized? (2) Does the allocation pattern of body size and brood size in C. bakeri change with temperature? To answer these questions, we exposed A. ipsilon larvae parasitized by C. bakeri to high or low non-lethal temperatures when A. ipsilon was in early or late larval stages and measured their development time and body mass for all four treatment combinations. We also examined the brood size and body mass of emerging wasps. Whether parasitized or not, A. ipsilon larvae decreased development time, but generally did not decrease final body mass, at the higher temperature. When parasitized A. ipsilon was exposed to the higher temperature only late in their development, enlargement of the host by the parasitoid was reduced. C. bakeri brood size significantly increased when the higher temperature was applied early in host development. We did not detect a shift with temperature in the allocation pattern of the size–number trade-off for wasp offspring, suggesting that this trade-off relationship may be under selection strong enough to yield insensitivity to temperature.

Life history trade‐offs and evidence for hierarchical resource allocation in two monocarpic perennials

The evolution of floral display is thought to be constrained by trade-offs between the size and number of flowers; however, empirical evidence for the trade-off is inconsistent. We examined evidence for trade-offs and hierarchical allocation of resources within and between two populations each of the monocarpic perennials, Cardiocrinum cordatum and C.giganteum. Within all populations, flower size-number trade-offs were evident after accounting for variation in plant size. In addition, variation in flower size explained much variation in flower-level allocation to attraction, and female and male function, a pattern consistent with hierarchical allocation. However, between population differences in flower size (C.cordatum) and number (C.giganteum) were not consistent with size-number trade-offs or hierarchical allocation. The population-level difference in C.cordatum likely reflects the combined influence of a time lag between initiation and maturation of flowers, and higher light levels in one population. Thus, our study highlights one mechanism that may account for the apparent independence of flower size and number in many studies. A prediction of sex allocation theory was also supported. In C.giganteum: plants from one population invested more mass in pistils and less in stamens than did plants from the other population. Detection of floral trade-offs in Cardiocrinum may be facilitated by monocarpic reproduction, production of a single inflorescence and ease of measuring plant size.

Within-species leaf size–number trade-offs in herbaceous angiosperms

Leafing intensity—number of leaves produced per unit of supporting (nonleaf, aboveground) dry mass—determines the size of a plant’s “bud bank”, i.e., the number of axillary meristems per unit plant body or shoot size. This in turn determines the plant’s capacity for flexible and economic meristem deployment strategies as vegetative or reproductive structures. From recent research, it is now widely established that leafing intensity has a strong and isometrically negative relationship with individual leaf mass at the between-species level for both woody and herbaceous species. In the present study of 24 natural populations of herbaceous angiosperms, we show that these two traits also have a general trade-off relationship at the between-plant level within a species. Smaller resident reproductive (i.e., mature) plants generally produced smaller leaves, and plants with smaller leaves generally had higher leafing intensity, in most cases involving an isometric trade-off. For several species, however, the trade-off was allometric—i.e., plants with smaller leaves, which also had generally smaller body sizes, had generally greater than proportionally higher leafing intensity. This parallels results of an earlier study at the between-species level suggesting that, when plant body size is relatively small, there may be a premium—in terms of maximizing fitness—on relatively high leafing intensity. The latter, it is proposed, may function in maximizing the capacity for “reproductive economy”, i.e., successful reproduction despite intense size suppression owing to competition.

Diversity and evolution of pollen-ovule production in Cuscuta (dodders, Convolvulaceae) in relation to floral morphology

Cuscuta (dodder, Convolvulaceae) is a genus of about 200 species of obligate stem parasites with subcosmopolitan distribution. The diversity of pollen and ovule production was surveyed in 128 species and ten varieties. Taxa were assigned to Cruden’s mating system categories based on their pollen-ovule ratios. Variation and correlations among floral characters were analyzed using regression and ANOVA, while the mating system categories were subjected to a linear discriminant and canonical variates analysis to assess their cohesiveness. Our data strongly suggest that most Cuscuta species possess a wide range of mixed-mating systems. Whereas four ovules develop in each flower, pollen production varies over three orders of magnitude. Several Cuscuta taxa are highly outcrossing, but no species could be identified that are exclusively selfing. The transition from the one-style flowers of subg. Monogynella to the two-style flowers of subgenera Cuscuta and Grammica, and from simultaneous to sequential maturation of the two stigmas in the latter subgenus, has decreased the role of herkogamy as a facilitator of outcrossing. These evolutionary changes are associated with an increase of species richness in subgenus Cuscuta, and especially in subgenus Grammica. Morphological features were not individually found to have a strong correlation to the mating system, but in general, larger corollas and stigmas were associated with greater pollen-ovule ratios. Cuscuta presents some puzzling results when considered in light of the sex allocation theory, as only some infrageneric lineages demonstrate the predicted pollen size-number tradeoff, while Cuscuta gracillima complex (in subgenus Grammica) displays an unexpected negative relationship between pollen size and style length. The relationship between host range and mating system is discussed, prompting further research into the co-evolution of pollination systems and life history traits between parasites and their host species.

Geographical variation in reproductive traits and trade-offs between size and number of eggs in the king ratsnake, Elaphe carinata

701..709 We collected gravid king ratsnakes (Elaphe carinata) from three geographically separated populations in Chenzhou (CZ), Lishui (LS) and Dinghai (DH) of China to study the geographical variation in female reproductive traits and trade-offs between the size and number of eggs. Not all reproductive traits varied among the three populations. Of the traits examined, five (egg-laying date, post-oviposition body mass, clutch size, egg mass and egg width) differed among the three populations. The egg-laying date, ranging from late June to early August, varied among populations in a geographically continuous trend, with females at the most northern latitude (DH) laying eggs latest, and females at the most southern latitude (CZ) laying eggs earliest. Such a trend was less evident or even absent in the other traits that differed among the three populations. CZ and DH females, although separated by a distance of approximately 1100 km as the crow flies, were similar to each other in most traits examined. LS females were distinguished from CZ and DH females by the fact that they laid a greater number of eggs, but these were smaller. The egg size-number trade-off was evident in each of the three populations and, at a given level of relative fecundity, egg mass was significantly greater in the DH population than in the LS population. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 701-709.

Variability Study on Nut Size and Number Trade-Off Identify a Threshold Level for Optimum Yield in Cashew (Anacardium occidentale L.)

Eleven yield-related plant traits in 33 accessions selected from 3 Nigerian breeding populations were studied to understand the influence of nut size-number trade-off in cashew tree yield. Three-years of data were statistically analyzed for genetic variability estimates and showed that the accessions were significantly different for all the yield-related traits with highest variability in production of hermaphrodite flowers. The pattern of variation was population-specific with sparsely fruiting Brazilian accessions characterized by large nuts and kernels, while the Indian accessions were prolific but with small–medium nuts. Flowering, fruit-set, and fruit-development differed significantly between years suggesting a strong influence of environment on cashew tree production. Consistent relationships were found between nut number and total nut yield at both inter- and intra-population levels, underscoring the importance of the number to nut yield in cashew. However, regression between nut number and nut size confirmed the existence of the size-number trade-off phenomenon in cashew, but the degree varied between populations. Cashew trees with jumbo nuts (>15 kg) were significantly affected by the trade-off, as they exhibited poor flowering and fruit set, in addition to prolonged fruit development. This category of nut size should be discouraged for commercial planting. These preliminary results showed that cashew cultivars with nut sizes between 9.0 and 12.0 g are better, as such trees produced enough nuts per tree to support profitable investments in cashew farming.

Resolving variation in the reproductive tradeoff between sperm size and number

Spermatozoa are amongst the most variable cells, and three factors are thought to account for this variation in design: fertilization mode, phylogeny, and postcopulatory sexual selection. In addition, it has long been assumed that a tradeoff exists between sperm size and number, and although postcopulatory sexual selection affects both traits, empirical evidence for a tradeoff has so far been elusive. Our recent theoretical model predicts that the nature of a direct tradeoff between sperm size and number varies with sperm competition mechanism and sperm competition risk. We test these predictions using a comparative approach in two very different taxa with different sperm competition mechanisms: passerine birds (mechanism: simple raffle) and Drosophila fruit flies (sperm displacement). We show that in both groups, males increase their total ejaculate investment with increasing sperm competition risk, but whereas passerine birds allocate disproportionately to sperm number, drosophilids allocate disproportionately to sperm size. This striking difference between the two groups can be at least partly explained by sperm competition mechanisms depending on sperm size relative to the size of the female reproductive tract: in large animals (passerines), sperm numbers are advantageous in sperm competition owing to dilution inside the female tract, whereas in small animals (drosophilids), large sperm are advantageous for physical competition (sperm displacement). Our study provides two important results. First, we provide convincing evidence for the existence of a sperm size-number tradeoff. Second, we show that by considering both sperm competition mechanism and dilution, can we account for variation in sperm size between different taxa.

Ecological implications of a flower size/number trade-off in tropical forest trees.

BackgroundIn angiosperms, flower size commonly scales negatively with number. The ecological consequences of this trade-off for tropical trees remain poorly resolved, despite their potential importance for tropical forest conservation. We investigated the flower size number trade-off and its implications for fecundity in a sample of tree species from the Dipterocarpaceae on Borneo.Methodology/Principal FindingsWe combined experimental exclusion of pollinators in 11 species, with direct and indirect estimates of contemporary pollen dispersal in two study species and published estimates of pollen dispersal in a further three species to explore the relationship between flower size, pollinator size and mean pollen dispersal distance. Maximum flower production was two orders of magnitude greater in small-flowered than large-flowered species of Dipterocarpaceae. In contrast, fruit production was unrelated to flower size and did not differ significantly among species. Small-flowered species had both smaller-sized pollinators and lower mean pollination success than large-flowered species. Average pollen dispersal distances were lower and frequency of mating between related individuals was higher in a smaller-flowered species than a larger-flowered confamilial. Our synthesis of pollen dispersal estimates across five species of dipterocarp suggests that pollen dispersal scales positively with flower size.Conclusions and Their SignificanceTrade-offs embedded in the relationship between flower size and pollination success contribute to a reduction in the variance of fecundity among species. It is therefore plausible that these processes could delay competitive exclusion and contribute to maintenance of species coexistence in this ecologically and economically important family of tropical trees. These results have practical implications for tree species conservation and restoration. Seed collection from small-flowered species may be especially vulnerable to cryptic genetic erosion. Our findings also highlight the potential for differential vulnerability of tropical tree species to the deleterious consequences of forest fragmentation.

Clutch frequency affects the offspring size-number trade-off in lizards.

BackgroundStudies of lizards have shown that offspring size cannot be altered by manipulating clutch size in species with a high clutch frequency. This raises a question of whether clutch frequency has a key role in influencing the offspring size-number trade-off in lizards.Methodology/Principal FindingsTo test the hypothesis that females reproducing more frequently are less likely to tradeoff offspring size against offspring number, we applied the follicle ablation technique to female Eremias argus (Lacertidae) from Handan (HD) and Gonghe (GH), the two populations that differ in clutch frequency. Follicle ablation resulted in enlargement of egg size in GH females, but not in HD females. GH females switched from producing a larger number of smaller eggs in the first clutch to a smaller number of larger eggs in the second clutch; HD females showed a similar pattern of seasonal shifts in egg size, but kept clutch size constant between the first two clutches. Thus, the egg size-number trade-off was evident in GH females, but not in HD females.Conclusions/SignificanceAs HD females (mean = 3.1 clutches per year) reproduce more frequently than do GH females (mean = 1.6 clutches per year), our data therefore validate the hypothesis tested. Our data also provide an inference that maximization of maternal fitness could be achieved in females by diverting a large enough, rather than a higher-than-usual, fraction of the available energy to individual offspring in a given reproductive episode.

QUANTIFYING EVOLUTIONARY POTENTIAL OF MARINE FISH LARVAE: HERITABILITY, SELECTION, AND EVOLUTIONARY CONSTRAINTS

For many marine fish, intense larval mortality may provide considerable opportunity for selection, yet much less is known about the evolutionary potential of larval traits. We combined field demographic studies and manipulative experiments to estimate quantitative genetic parameters for both larval size and swimming performance for a natural population of a common coral-reef fish, the bicolor damselfish (Stegastes partitus). We also examined selection on larval size by synthesizing information from published estimates of selective mortality. We introduce a method that uses the Lande-Arnold framework for examining selection on quantitative traits to empirically reconstruct adaptive landscapes. This method allows the relationship between phenotypic value and fitness components to be described across a broad range of trait values. Our results suggested that despite strong viability selection for large larvae and moderate heritability (h(2) = 0.29), evolutionary responses of larvae would likely be balanced by reproductive selection favoring mothers that produce more, smaller offspring. Although long-term evolutionary responses of larval traits may be constrained by size-number trade-offs, our results suggest that phenotypic variation in larval size may be an ecologically important source of variability in population dynamics through effects on larval survival and recruitment to benthic populations.

Sperm competition games: Sperm size (mass) and number under raffle and displacement, and the evolution of P2

We examine models for evolution of sperm size (i.e. mass m) and number ( s) under three mechanisms of sperm competition at low ‘risk’ levels: (i) raffle with no constraint on space available for competing sperm, (ii) direct displacement mainly by seminal fluid, and (iii) direct displacement mainly by sperm mass. Increasing sperm mass increases a sperm's ‘competitive weight’ against rival sperm through a diminishing returns function, r( m). ESS total ejaculate expenditure (the product m ⁎ s ⁎) increases in all three models with sperm competition risk, q. If r( m), or ratio r′( m)/ r( m), is independent of ESS sperm numbers, ESS sperm mass remains constant, and the sperm mass/number ratio ( m ⁎/ s ⁎) therefore decreases with risk. Dependency of sperm mass on risk can arise if r( m) depends on competing sperm density (sperm number / space available for sperm competition). Such dependencies generate complex relationships between sperm mass and number with risk, depending both on the mechanism and how sperm density affects r( m). While numbers always increase with risk, mass can either increase or decrease, but m ⁎/ s ⁎ typically decreases with risk unless sperm density strongly influences r( m). Where there is no extrinsic loading due to mating order, ESS paternity of the second (i.e. last) male to mate ( P 2) under displacement always exceeds 0.5, and increases with risk (in the raffle P 2=0.5). Caution is needed when seeking evidence for a sperm size–number trade off. Although size and number trade-off independently against effort spent on acquiring matings, their product, m ⁎ s ⁎, is invariant or fixed at a given risk level, effectively generating a size–number trade off. However, unless controlled for the effects of risk, the relation between m ⁎ and s ⁎ can be either positive or negative (a positive relation is usually taken as evidence against a size–number trade off).

Zebrafish (Danio rerio) and the egg size versus egg number trade off: effects of ration size on fecundity are not mediated by orthologues of the Fec gene

Few studies have demonstrated plasticity of egg size within the confines of an egg size-number trade-off in response to trophic conditions in fishes. Moreover, the physiological mechanisms that govern this plasticity are not known. Growth differentiation factor 9 (Gdf9) and bone morphogenetic factor 15 (Bmp15) are oocyte-specific factors implicated in follicular growth and ovulation in mammals. In order to investigate whether expression levels of these genes were correlated with ration-dependent changes in fecundity in fish, zebrafish (Danio rerio) were subjected to four different feeding regimens. Counts of spawned eggs or vitellogenic follicles were used to estimate fecundity, whereas quantitative polymerase chain reaction analyses were performed to determine Gdf9 and Bmp15 mRNA levels in response to changes in ration size. Both relative fecundity and gonadosomatic index increased significantly with increased ration size, whereas egg size and hatching rate decreased significantly. No significant differences in Gdf9 or Bmp15 transcript abundance were evident between feeding regimens, suggesting that these growth factors do not govern fecundity in fish. However, favourable trophic conditions markedly affected follicle or egg size and number, with important implications for downstream egg quality and survival.

Balancing the Size-Number Tradeoff in Clonal Broods

The trade-off between the number of offspring in a brood and the sizes of those offspring has been documented in a diverse array of species. Here we consider the factors that might account for the way that the trade-off achieves a particular size-number balance for female offspring. In particular, we determine whether bet hedging, along with traits influencing the expected short-term reproductive success of the brood, could select for a brood size and body mass that maximize long-term fitness. We also evaluate whether the optima based on these characteristics agree qualitatively with documented responses to brood resource levels. To develop a model incorporating these phenomena and keep it as simple and general as possible, we consider an organism that produces clonal broods, eliminating the complexities associated with parent-offspring and sibling conflict. We use the polyembryonic parasitoid wasp Copidosoma bakeri as the focal example. We find that bet hedging effects and key reproductive traits (the number of searching females, their host-finding efficiency, and survival prospects) are often sufficient to produce an optimal size-number balance and can account for the frequent tendency of both brood size and body mass to increase with brood resources (host size). Under some conditions, however, balancing the trade-off requires an additional minimum body-size constraint. Future empirical work and spatially explicit models must better establish the parameter magnitudes and functional relationships so that a deeper understanding and more precise predictions are obtained.

The importance of wood traits and hydraulic conductance for the performance and life history strategies of 42 rainforest tree species

*In a comparative study of 42 rainforest tree species we examined relationships amongst wood traits, diameter growth and survival of large trees in the field, and shade tolerance and adult stature of the species. *The species show two orthogonal axes of trait variation: a primary axis related to the vessel size-number trade-off (reflecting investment in hydraulic conductance vs hydraulic safety) and a secondary axis related to investment in parenchyma vs fibres (storage vs strength). Across species, growth rate was positively related to vessel diameter and potential specific hydraulic conductance (K(p)), and negatively related to wood density. Survival rate was only positively related to wood density. *Light-demanding species were characterized by low wood and vessel density and wide vessels. Tall species were characterized by wide vessels with low density and large K(p). Hydraulic traits were more closely associated with adult stature than with light demand, possibly because tall canopy species experience more drought stress and face a higher cavitation risk. *Vessel traits affect growth and wood density affects growth and survival of large trees in the field. Vessel traits and wood density are therefore important components of the performance and life history strategies of tropical tree species.

A sex‐specific size–number tradeoff in clonal broods

Polyembryonic parasitoids producing single‐sex broods of clonal offspring provide an unusually clear window into the classic tradeoff between the number and size of offspring. We conducted a laboratory study of the encyrtid parasitoid Copidosoma bakeri parasitizing the noctuid Agrotis ipsilon to examine the way that size and number of offspring tradeoff in broods of each sex and to determine how the fit between host and parasitoid brood is achieved. We found that brood mass (wasp body mass ×brood size) was proportional to host mass, independent of brood sex, indicating a tight fit between brood and host and ensuring a size–number tradeoff. By correcting brood size and body mass of each brood for host mass, we demonstrated the expected inverse relationship between wasp variables. We postulated that the wasp brood might achieve the fit to the host by (1) adjusting brood size based on information available early in host development before and during division of the embryo, (2) manipulating host size late in host development after completion of embryo division, or (3) simply adjusting individual wasp mass to fill the host. We evaluated host responses to parasitism – and correlations between brood size and host growth early and late in development – for broods of each sex. The data are consistent with adjustment of brood size to the amount of host growth early in host development and with manipulation of host mass late in host development. The tight link between host mass and brood mass also suggests a final adjustment by parasitoid growth to achieve complete filling. Within the tight fit, female broods were smaller but contained larger individuals than male broods. The sex‐specific balance point of the tradeoff and sex differences in balancing mechanisms and responses to host size suggest different selection pressures on each sex requiring future investigation.

Beyond size-number trade-offs: clutch size as a maternal effect.

Traditionally, research on life-history traits has viewed the link between clutch size and offspring size as a straightforward linear trade-off; the product of these two components is taken as a measure of maternal reproductive output. Investing more per egg results in fewer but larger eggs and, hence, offspring. This simple size-number trade-off has proved attractive to modellers, but our experimental studies on keelback snakes (Tropidonophis mairii, Colubridae) reveal a more complex relationship between clutch size and offspring size. At constant water availability, the amount of water taken up by a snake egg depends upon the number of adjacent eggs. In turn, water uptake affects hatchling size, and therefore an increase in clutch size directly increases offspring size (and thus fitness under field conditions). This allometric advantage may influence the evolution of reproductive traits such as growth versus reproductive effort, optimal age at female maturation, the body-reserve threshold required to initiate reproduction and nest-site selection (e.g. communal oviposition). The published literature suggests that similar kinds of complex effects of clutch size on offspring viability are widespread in both vertebrates and invertebrates. Our results also challenge conventional experimental methodologies such as split-clutch designs for laboratory incubation studies: by separating an egg from its siblings, we may directly affect offspring size and thus viability.

Evolution of maternal effects: past and present.

It has been said that many original ideas reflect a convergence of related thought that coalesces into a unified representation of what many have been thinking. This is certainly true for the subfield of maternal effects evolution. The study of maternal effects has a long history. The first two