Evolution of life history traits in Leporidae: a test of nest predation and seasonality hypotheses

Recently, it has been proposed that adult mortality schedules may be responsible for latitudinal patterns of life history variation in passerine birds, whereas nest predation only could explain within latitude patterns. Unfortunately, no independent test has been performed regarding the importance of nest predation with different taxa. In the present study, seasonality and nest predation hypotheses explaining variations in gestation time and litter size in 17 lagomorph species were tested. Among latitude patterns were analysed using the phylogenetic independent contrast method of Felsenstein and within latitude patterns were analysed by the pairwise comparative method. The results obtained indicate that latitudinal patterns observed in both variables are explained by different factors: seasonality for litter size and nest predation for gestation time. Litter size variations within latitudes are also explained by differences in nest predation, supporting previous hypotheses. In conclusion, the present study suggests that, when compared among latitudes, different life history traits (e.g. litter size and gestation time) may be shaped by different selective forces and that the effects of nest predation may be high both within and between latitudes.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 603–610.     

Environmental networks,compensating life histories and habitat selection by white-footed mice

Summary Analysis of 6 years' data on a population of free-living white-footed mice documents both phenotypic and environmental control of litter size. Litter size was positively correlated with maternal body size. Maternal size depended upon both seasonal and annual variation. Paradoxically, the proportion of small versus large litters varied among habitats independently of the effects of body size. The result is an influence of habitat on life history that yields patterns of reproduction and survival opposite to the predictions of demographic theory. The habitat producing the largest litters had a relatively high ratio of adult/juvenile survival. Litter size was small in the habitat where the adult/juvenile survival ratio was smallest. All of these anomalous patterns can be explained through density-dependent habitat selection by female white-footed mice. Life-history studies that ignore habitat and habitat selection may find spurious correlations among traits that result in serious misinterpretations about life history and its evolution.     

Living fast and dying young: A comparative analysis of life-history variation among mammals

Recent comparative studies point to the importance of mortality schedules as determinants in the evolution of life-history characteristics. In this paper, we compare patterns of mortality from natural populations of mammals with a variety of life histories. We find that, after removing the effects of body weight, mortality is the best predictor of variation in life-history traits. Mammals with high levels of natural mortality tend to mature early and give birth to small offspring in large litters after a short gestation, before and after body size effects are factored out. We examine the way in which life-history traits relate to juvenile mortality versus adult mortality and find that juvenile mortality is more highly correlated with life-history traits than is adult mortality. We discuss the necessity of distinguishing between extrinsic sources of mortality (e.g. predation) and mortality caused by intrinsic sources (e.g. costs of reproduction), and the role that ecology might play in the evolution of patterns of mortality and fecundity. We conclude that these results must be explained not simply in the light of the demographic necessity of balancing mortality and fecundity, but as a result of age-specific costs and benefits of reproduction and parental investment. Detailed comparative studies of mortality patterns in natural populations of mammals offer a promising avenue towards understanding the evolution of life-history strategies.     

Reproductive traits of riverine shrimps may explain the impact of altered flow conditions

1. The response of a species to environmental disturbance is largely mediated by its life history traits that have evolved within a particular habitat template. Altered flow seasonality, as a direct consequence of river regulation, is a major environmental disturbance and has been implicated in the redistribution of a range of riverine organisms. An understanding of the reasons for species‐specific responses, however, has proved elusive. 2. Here, we investigated the reproduction of three riverine shrimp species (Paratya australiensis, Caridina mccullochi and Macrobrachium australiense) that show contrasting patterns in distribution and abundance in regulated Australian rivers. 3. In all three species, breeding females were largest, and fecundity was greatest early in the breeding season (November–December). Fecundity and egg size subsequently declined, with lower investment (overall and per offspring) perhaps indicating that conditions for larvae were more favourable later in the breeding season (a time normally characterised by low flow, warm water and high productivity). 4. Interspecific differences in absolute values of reproductive traits were, however, striking. Paratya australiensis has typically ‘opportunistic’ traits (small body size, small eggs and high fecundity), whereas M. australiense has more ‘equilibrium’ traits (larger body size, larger eggs and moderate fecundity). Caridina mccullochi is intermediate, having neither high fecundity nor large size, and has limited swimming ability when young. This species is now absent from at least one heavily regulated river in south‐eastern Australia, and we hypothesise that its life history may explain this absence. 5. Studies involving aspects of life history, such as reproductive traits, are likely to improve our understanding of a range of organisms and assist in the management of disturbed or altered environments.     

One strategy does not fit all: determinants of urban adaptation in mammals

Urbanisation exposes wildlife to new challenging conditions and environmental pressures. Some mammalian species have adapted to these novel environments, but it remains unclear which characteristics allow them to persist. To address this question, we identified 190 mammals regularly recorded in urban settlements worldwide, and used phylogenetic path analysis to test hypotheses regarding which behavioural, ecological and life history traits favour adaptation to urban environments for different mammalian groups. Our results show that all urban mammals produce larger litters; whereas other traits such as body size, behavioural plasticity and diet diversity were important for some but not all taxonomic groups. This variation highlights the idiosyncrasies of the urban adaptation process and likely reflects the diversity of ecological niches and roles mammals can play. Our study contributes towards a better understanding of mammal association to humans, which will ultimately allow the design of wildlife‐friendly urban environments and contribute to mitigate human‐wildlife conflicts.     

Geographic variation of body size and reproductive patterns in Continental versus Mediterranean asp vipers, Vipera aspis

The occurrence of variation in body size and reproductive traits of Vipera aspis was assessed by analysing 74 reproductive females of different populations, collected throughout a large part of the distribution range of the taxon, from central‐western France to central Italy. Six populations were analysed, two of plain habitats, in France and Italy, characterized by a Continental climate, whereas the other four derived from two coastal and two inland, hilly Italian habitats, respectively, showing a Mediterranean climate. Females of the French area showed the smallest mean body size, whereas the pre‐ and post‐partum body masses of females from the coolest, central Italic area were significantly higher. Litter size varied among habitats and was significantly correlated with maternal body size. If the snout–vent length feature varied largely among offspring of different habitats (with the longest size occurring in representatives of the coastal, central Italian area), the average of both body mass and total mass of offsprings did not exhibit any clear pattern among populations colonizing different habitats. Nevertheless, relative litter mass was higher in the French continental populations, and lower in the coolest, Mediterranean, Italian ones. It is worth emphasizing the positive correlation between the snout–vent length feature of females and the total litter mass to environmental factors, such as hottest month temperature and total rainfall. The available literature records that female body size affects offspring size and fecundity. If the present study bolsters this correlation, it also rules out any other effect of female body size on the offspring characteristics analysed. Finally, evidence is provided for the role of climatic factors on life‐history traits (e.g. pre‐partum body mass) of asp vipers, although confounding effects pursued, for example, by food availability may occur. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96 , 383–391.     

Quantitative genetics of immunity and life history under different photoperiods

Insects with complex life-cycles should optimize age and size at maturity during larval development. When inhabiting seasonal environments, organisms have limited reproductive periods and face fundamental decisions: individuals that reach maturity late in season have to either reproduce at a small size or increase their growth rates. Increasing growth rates is costly in insects because of higher juvenile mortality, decreased adult survival or increased susceptibility to parasitism by bacteria and viruses via compromised immune function. Environmental changes such as seasonality can also alter the quantitative genetic architecture. Here, we explore the quantitative genetics of life history and immunity traits under two experimentally induced seasonal environments in the cricket Gryllus bimaculatus. Seasonality affected the life history but not the immune phenotypes. Individuals under decreasing day length developed slower and grew to a bigger size. We found ample additive genetic variance and heritability for components of immunity (haemocyte densities, proPhenoloxidase activity, resistance against Serratia marcescens), and for the life history traits, age and size at maturity. Despite genetic covariance among traits, the structure of G was inconsistent with genetically based trade-off between life history and immune traits (for example, a strong positive genetic correlation between growth rate and haemocyte density was estimated). However, conditional evolvabilities support the idea that genetic covariance structure limits the capacity of individual traits to evolve independently. We found no evidence for G × E interactions arising from the experimentally induced seasonality.     

Does seasonality explain the evolution and maintenance of delayed implantation in the family Mustelidae (Mammalia: Carnivora)?

Understanding the evolutionary pressures that may have led to the development and retention of delayed implantation in mammals remains an enigmatic puzzle for evolutionary ecologists. Recent studies suggest a strong role of environmental conditions but other attributes of species, notably body size and life history traits, may obscure primary mechanisms. Following the recommendation of Lindenfors et al., we examined environmental correlates related to the evolution of delayed implantation and its subsequent maintenance or loss in the family Mustelidae (Mammalia: Carnivora). We focused on the Mustelidae because evolution and subsequent loss of delayed implantation occurred most commonly within this group. Data on 34 species of mustelids from around the world suggest that delayed implantation may have evolved when optimal times for mating and birthing are separated by more than a gestation period, characteristic of environments with long winters that reduce the opportunities to find mates. Environmental characteristics (seasonality, temperature, snow, latitude, and primary productivity) were highly intercorrelated but seasonality was the best predictor of the evolution or loss of delayed implantation via population traits. Here, structural equations on phylogenetic independent contrasts revealed that high seasonality was correlated with low population density and large individual home range size, which in turn was correlated with presence/absence of delayed implantation. We argue that the evolution of delayed implantation provides the reproductive means to mate during the season (summer) with the greatest prospects for females to ‘choose’ mates when living in high‐latitude seasonal environments that generally reduce these opportunities (i.e. low population density and large ranges). Body mass of female mustelids did not differ between species with and without delayed implantation, refuting the hypothesis that loss of delayed implantation is an evolutionary by‐product of evolving to smaller size. We conclude that understanding the environmental selection pressures responsible for the evolution of life history traits related to density and spacing behaviour allows for a more complete picture of the evolution and subsequent loss of delayed implantation.     

Quantitative genetics and fitness effects of basal metabolism

The physiological requirements of reproduction are predicted to generate a link between energy, physiology and life history traits. Simultaneously, low maintenance costs, measured by energy consumption, are expected to be advantageous. Here we investigated fitness relatedness of traits by estimating genetic correlations between, and inbreeding depression for, body mass, basal metabolic rate (BMR) and other life history characters in a wild rodent, Myodes glareolus. The narrow-sense heritability of absolute and mass corrected BMRs were high for females (h² = 0.48 and 0.42) but low and non-significant for males (0.32 and 0.09). A significant positive genetic correlation between BMR and litter size suggests that traits connected to female fecundity might favour higher metabolism (i.e. support increased intake hypothesis). However, the estimates of inbreeding depression indicate that, while higher values of body mass and female litter size could be positively associated with overall fitness, the association between BMR and overall fitness in bank voles would be negative (i.e. support compensation hypothesis). This result suggests that the advantages of larger litters and larger body mass might be evolutionary constrained by high costs of maintenance of those traits, as reflected by the level of basal metabolism.     

Evolution of alternative insect life histories in stochastic seasonal environments

Deterministic seasonality can explain the evolution of alternative life history phenotypes (i.e., life history polyphenism) expressed in different generations emerging within the same year. However, the influence of stochastic variation on the expression of such life history polyphenisms in seasonal environments is insufficiently understood. Here, we use insects as a model and explore (1) the effects of stochastic variation in seasonality and (2) the life cycle on the degree of life history differentiation among the alternative developmental pathways of direct development and diapause (overwintering), and (3) the evolution of phenology. With numerical simulation, we determine the values of development (growth) time, growth rate, body size, reproductive effort, adult life span, and fecundity in both the overwintering and directly developing generations that maximize geometric mean fitness. The results suggest that natural selection favors the expression of alternative life histories in the alternative developmental pathways even when there is stochastic variation in seasonality, but that trait differentiation is affected by the developmental stage that overwinters. Increasing environmental unpredictability induced a switch to a bet‐hedging type of life history strategy, which is consistent with general life history theory. Bet‐hedging appeared in our study system as reduced expression of the direct development phenotype, with associated changes in life history phenotypes, because the fitness value of direct development is highly variable in uncertain environments. Our main result is that seasonality itself is a key factor promoting the evolution of seasonally polyphenic life histories but that environmental stochasticity may modulate the expression of life history phenotypes.     

Seasonal population dynamics in Lucilia eximia (Wiedemann) (Diptera: Calliphoridae)

In this study the seasonal variation of fecundity, wing and tibia sizes were investigated in natural populations of Lucilia eximia (Wiedemann) as an attempt to determine the variations in life history of the species associated to seasonality. Specimens of L. eximia were monthly collected in Botucatu, S?o Paulo, Brazil, during two years and the adult females dissected to estimate fecundity. Body size was estimated by measuring wing and tibia. Fecundity and body size were seasonally analysed. A relatively constant temporal trajectory was found for fecundity, wing and tibia size over twenty-four months. Strong positive correlations between wing and tibia size, fecundity and wing and fecundity and tibia were observed. The maintenance of stable values in L. eximia indicates that it has suffered little seasonal influence over the period analysed. This result confirms the demographics and life history stable profile of the species in spite of seasonal climatic changes observed in the study area.     

Scaling of growth and life history traits relative to body size, brain size, and metabolic rate in lorises and galagos (Lorisidae, primates)

A broad range of variation in body size, brain size, and metabolic rate occurs within the primate family Lorisidae, thus providing an opportunity to examine the relationship of these three parameters to variation in growth and life history traits. Data on adult body weight, gestation length, lactation length, age at first estrus, litter size, and growth parameters were collected from a captive colony of four lorisid species, Loris tardigradus, Nycticebus coucang, Galago crassicaudatus, and G. senegalensis. The data presented here constitute the most complete life history information available for these poorly understood prosimian species. Correlation and allometric analyses were performed to determine the relationships between variables. Among the lorisids studied, adult body weight, adult cranial capacity, and relative cranial capacity did not predict variation in life history traits. Adult basal metabolic rate predicted most of the variability in gestation length, lactation length, and growth parameters. Lorisines differ from similarly sized galagines in having lower basal metabolic rates, slower growth rates, slower developmental rates, and smaller litter sizes, resulting in reduced reproductive potential. This may be a consequence of lorisine adaptation to a diet of toxic insects. Metabolic rate and diet may be among the most important parameters to examine in any study of life history evolution.     

Variations in life history traits and flight capacity among populations of the light brown apple moth Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae)

Abstract The empirical study of interpopulation variation in life history and other fitness traits has been an important approach to understanding the ecology and evolution of organisms and gaining insight into possible sources of variation. We report a quantitative analysis for variations of five life history traits (larval developmental time, adult body weight, adult lifespan, age at first reproduction, total fecundity) and flight capacity among populations of Epiphyas postvittana originating from four localities in Australia and one in New Zealand. These populations were compared at two temperatures (15° and 25°C) after being maintained under uniform laboratory conditions for 1.5 generations, so that the relative role of genetic divergence and phenotypic plasticity in determining interpopulation variation could be disentangled. Genetic differentiation between populations was shown in all measured traits, with the greatest divergence occurring in developmental time, fecundity and adult body size. However, these traits were highly sensitive to changes in environmental temperatures; and furthermore, significant interactions between population and temperature occurred in all traits except for flight capacity of female moths. Thus, phenotypic plasticity may be another cause of interpopulation variation. The interpopulation variation for some measured traits was apparently related to climatic differences found where the populations originated. Individuals of the populations from the warmer climates tended to develop more slowly at immature stages, producing smaller and less fecund moths but with stronger flight capacity, in comparison to those from the cooler regions. It seems, therefore, that natural populations of E. postvittana have evolved different strategies to cope with local environmental conditions.     

Life histories of Clethrionomys and Microtus (Microtinae)

Although there have been numerous life-history reviews of mammals at high taxonomic levels (e.g. among families within orders), there are far fewer studies at lower taxonomic levels (e.g. among species within genera). Data on adult weights, litter size, gestation length, neonate weight, age and weight at weaning, growth rate to weaning, maximum life span, and length of the breeding season were compiled from the literature on five species of Clethrionomys and 33 species of Microtus. Variability in litter size and male body weights was not significantly different when compared between cyclic and non-cyclic populations. Coefficients of variation were also calculated for the three species with the most data (C. gapperi, C. glareolus and M. pennsylvanicus ). These values showed that the amount of intraspecific variation differed among traits as well as among species. Gestation length was the most invariable of all traits and variation in adult weights, neonate weight, gestation length, and litter size had similar values to those reported for Peromyscus maniculatus. Five and eight traits differed among Clethrionomys and Microtus species, respectively. Differences in litter size, adult weights and length of the breeding season were common to both genera. Male weight, gestation length and neonate weight as well as length of the breeding season were different between genera. Very few traits covaried within C. gapperi, C. glareolus or M. pennsylvanicus. Similarly, few traits covaried among all Clethrionomys populations. However, among all Microtus populations and Microtus species, 11 and 12 correlations were significant. Many of the patterns found in Microtus involved positive relationships between female weight and some other trait. These patterns have also been found by broader surveys at higher taxonomic levels. Large species of Microtus had larger offspring, a greater litter size and occurred in short-season environments relative to small species of this genus.     

SEASONALITY MAINTAINS ALTERNATIVE LIFE‐HISTORY PHENOTYPES

Many organisms express discrete alternative phenotypes (polyphenisms) in relation to predictable environmental variation. However, the evolution of alternative life‐history phenotypes remains poorly understood. Here, we analyze the evolution of alternative life histories in seasonal environments by using temperate insects as a model system. Temperate insects express alternative developmental pathways of diapause and direct development, the induction of a certain pathway affecting fitness through its life‐history correlates. We develop a methodologically novel and holistic simulation model and optimize development time, growth rate, body size, reproductive effort, and adult life span simultaneously in both developmental pathways. The model predicts that direct development should be associated with shorter development time (duration of growth) and adult life span, higher growth rate and reproductive effort, smaller body size as well as lower fecundity compared to the diapause pathway, because the two generations divide the available time unequally. These predictions are consistent with many empirical data. Our analysis shows that seasonality alone can explain the evolution of alternative life histories.     

Sex-dependent effects of sibling cannibalism on life history traits of the ladybird beetle Harmonia axyridis (Coleoptera: Coccinellidae)

To investigate the sex-dependent effects of sibling cannibalism on variations in life history traits, I analysed body size, weight and instar interval in relation to the occurrence of sibling cannibalism in the ladybird beetle Harmonia axyridis. Sibling cannibalism at the time of hatching significantly affected the body size and weight of adults. There was a 2.32% and 1.05% increase in the body size of males and females, respectively, and a 3.55% increase and a 2.30% decrease in their respective body weights. Sibling cannibalism also significantly shortened the total and larval instar intervals, by 4.24% in males and by 1.22% in females, mainly due to shortening of the first instar. These results suggest that the effects of sibling cannibalism on life history traits are sex-differentiated and are greater in males than in females. A simulation of aphid density indicated that shortening the instar interval affected larval survival; the aphid density when the larvae completed development was 39.71% and 10.52% larger for cannibalistic males and females, respectively, than for non-cannibals. These results suggest that sibling cannibalism promotes more rapid development and larger adult size, although the effect was more pronounced in males than in females. Faster development may be adaptive for resource tracking, and the large adult size may increase fecundity in females and mating success in males through female mate choice, both resulting in an increase in the fitness of cannibals.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 349–360.     

Explaining the seasonal decline in litter size in European ground squirrels

In European ground squirrels Spermophilus citellus as in many ground squirrel species. late born litters are composed of fewer young than early born litters. Two alternative though not mutually exclusive hypotheses may explain this seasonal pattern of change in litter size. On the one hand. the production of few large young late in the season may be an adaptation to time limitations on the offspring. that have to complete growth and fattening prior to hibernation. Then one would expect a trade-off between offspring number and size as the breeding season progresses. At its extreme. this hypothesis would predict that total maternal effort should be equal independent of litter size. Alternatively. litter size may be determined by physiological limitations on the mother. in that highly constrained mothers breed later and produce smaller litters. Then one would expect reduced overall maternal effort in highly constrained mothers of smaller litters. In this case. a trade-off between litter size and offspring size would not be expected. We found that total maternal effort in terms of gestation length and the duration of lactation increased with increasing litter size. thus supporting the second hypothesis. Lactation was not terminated at natal emergence. It extended a relatively long period of time beyond the time of first litter emergence depending on litter size. During prolonged lactation. individual young of large litters made up body mass to young of small litters. As a consequence. juvenile weaning body mass was unaffected by litter size although offspring body mass at natal emergence was inversely related to litter size. This additional weight gain in young of large litters compensated for initial survival disadvantages and presumably affected fecundity at yearling age.     

Phenotypic plasticity and variation in morphological and life-history traits of antlion adults across a climatic gradient

We report here on two complementary experiments examining the effect of climate on morphological and life-history traits of antlion adults. We first examined whether body size and wing loading of emerging adults are plastic by raising larvae, collected from five antlion populations along Israel's sharp climatic gradient, in two environmental chambers simulating temperature and humidity of desert and Mediterranean climates. The variance in adult morphology was mostly related to body size, with adults of Mediterranean populations being larger than those of desert populations. Wing-to-thorax ratio was negatively correlated with temperature, compensating for the decrease in wing-beat frequency in colder environments. Differences between climatic treatments were significant for body size but not for the wing-to-thorax ratio, suggesting that body size is more plastic than the ratio between different body components. We next investigated how the exposure of antlion pupae to different climatic conditions influences the emerging adults. Adult body mass increased with final larval body mass at a faster rate when exposed to Mediterranean rather than desert conditions. Duration of the pupa stage was positively correlated with final larval mass, but only under Mediterranean conditions. Adult survival increased with initial mass (after eclosion), but was lower under desert conditions. Similarly, adults lost mass at a faster rate when exposed to desert conditions. Notably, the exposure of the pupae to varying climatic conditions had no effect on adult morphology. Climate is a major factor affecting insect life span and body size. Since body size is strongly linked to fecundity and survival, climate thus has a twofold effect on fitness: directly, and indirectly through body size.     

Maternal investment in relation to sex ratio and offspring number in a small mammal – a case for Trivers and Willard theory?

1.  Optimal parental sex allocation depends on the balance between the costs of investing into sons vs. daughters and the benefits calculated as fitness returns. The outcome of this equation varies with the life history of the species, as well as the state of the individual and the quality of the environment.
2.  We studied maternal allocation and subsequent fecundity costs of bank voles, Myodes glareolus , by manipulating both the postnatal sex ratio (all-male/all-female litters) and the quality of rearing environment (through manipulation of litter size by −2/+2 pups) of their offspring in a laboratory setting.
3.  We found that mothers clearly biased their allocation to female rather than male offspring regardless of their own body condition. Male pups had a significantly lower growth rate than female pups, so that at weaning, males from enlarged litters were the smallest. Mothers produced more milk for female litters and also defended them more intensively than male offspring.
4.  The results agree with the predictions based on the bank vole life history: there will be selection for greater investment in daughters rather than sons, as a larger size seems to be more influencial for female reproductive success in this species. Our finding could be a general rule in highly polygynous, but weakly dimorphic small mammals where females are territorial.
5.  The results disagree with the narrow sense Trivers & Willard hypothesis, which states that in polygynous mammals that show higher variation in male than in female reproductive success, high-quality mothers are expected to invest more in sons than in daughters.     

Identifying sources of variation in reproductive and life-history traits among five populations of a Chinese lizard (Takydromus septentrionalis, Lacertidae)

Research on life-history traits of squamate reptiles has focused on North American species, while Asian taxa have been virtually ignored. In order to understand general patterns in reptile life histories, we need a broader data base. Our study on the slender-bodied lacertid lizard Takydromus septentrionalis provides the first detailed information on factors responsible for intraspecific variation in reproductive output and life history in a Chinese reptile. Clutches of recently collected lizards from five widely separated localities in China revealed major divergences in female body size at maturation, mean adult female body size, body condition after oviposition, size-adjusted fecundity, relative clutch mass, and mass and shape of eggs. Most of these geographical differences persisted when the same groups of females were maintained in identical conditions in captivity. Additionally, reproductive frequency during maintenance under laboratory conditions differed according to the animals' place of origin. Thus, the extensive geographical variation in reproductive and life-history traits that occurs within T. septentrionalis is exhibited even in long-term captives, suggesting that proximate factors that vary among localities (local conditions of weather and food supply) are less important determinants of life-history variation than are intrinsic (presumably genetic) influences. The maternal abdominal volume available to hold the clutch may be one such factor, based on low levels of variation in Relative Clutch Mass among populations, and geographical variation in the position of trade-off lines linking offspring size to fecundity.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 443–453.