Covariation Of Life History Traits Research Articles

Do different rates of gene flow underlie variation in phenotypic and phenological clines in a montane grasshopper community?

Species responses to environmental change are likely to depend on existing genetic and phenotypic variation, as well as evolutionary potential. A key challenge is to determine whether gene flow might facilitate or impede genomic divergence among populations responding to environmental change, and if emergent phenotypic variation is dependent on gene flow rates. A general expectation is that patterns of genetic differentiation in a set of codistributed species reflect differences in dispersal ability. In less dispersive species, we predict greater genetic divergence and reduced gene flow. This could lead to covariation in life‐history traits due to local adaptation, although plasticity or drift could mirror these patterns. We compare genome‐wide patterns of genetic structure in four phenotypically variable grasshopper species along a steep elevation gradient near Boulder, Colorado, and test the hypothesis that genomic differentiation is greater in short‐winged grasshopper species, and statistically associated with variation in growth, reproductive, and physiological traits along this gradient. In addition, we estimate rates of gene flow under competing demographic models, as well as potential gene flow through surveys of phenological overlap among populations within a species. All species exhibit genetic structure along the elevation gradient and limited gene flow. The most pronounced genetic divergence appears in short‐winged (less dispersive) species, which also exhibit less phenological overlap among populations. A high‐elevation population of the most widespread species, Melanoplus sanguinipes, appears to be a sink population derived from low elevation populations. While dispersal ability has a clear connection to the genetic structure in different species, genetic distance does not predict growth, reproductive, or physiological trait variation in any species, requiring further investigation to clearly link phenotypic divergence to local adaptation.

A critique of life history approaches to human trait covariation

Abstract Covariation of life history traits across species may be organised on a ‘fast-slow’ continuum. A burgeoning literature in psychology and social science argues that trait covariation should be similarly organised across individuals within human populations. Here we describe why extrapolating from inter-species to inter-individual trait covariation is not generally appropriate. The process that genetically tailors species to their environments (i.e. Darwinian evolution) is fundamentally different from processes that tailor individuals to their environments (e.g. developmental plasticity), so their outcomes in terms of trait covariation need not be parallel or even related. We discuss why correlational selection, physical linkage, pleiotropy, and non-random mating do not substantively affect this claim in the context of complex human traits. We also discuss life history trade-offs and their relation to inter-individual trait covariation. We conclude that researchers should avoid hypotheses and explanations that assume trait covariation will correspond across and within species, unless they can mount a theoretically coherent argument to support this claim in the context of their research question.

Primate enamel evinces long period biological timing and regulation of life history

The factor(s) regulating the combination of traits that define the overall life history matrix of mammalian species, comprising attributes such as brain and body weight, age at sexual maturity, lifespan and others, remains a complete mystery. The principal objectives of the present research are (1) to provide evidence for a key variable effecting life history integration and (2) to provide a model for how one would go about investigating the metabolic mechanisms responsible for this rhythm. We suggest here that a biological rhythm with a period greater than the circadian rhythm is responsible for observed variation in primate life history. Evidence for this rhythm derives from studies of tooth enamel formation. Enamel contains an enigmatic periodicity in its microstructure called the striae of Retzius, which develops at species specific intervals in units of whole days. We refer to this enamel rhythm as the repeat interval (RI). For primates, we identify statistically significant relationships between RI and all common life history traits. Importantly, RI also correlates with basal and specific metabolic rates. With the exception of estrous cyclicity, all relationships share a dependence upon body mass. This dependence on body mass informs us that some aspect of metabolism is responsible for periodic energy allocations at RI timescales, regulating cell proliferation rates and growth, thus controlling the pace, patterning, and co-variation of life history traits. Estrous cyclicity relates to the long period rhythm in a body mass-independent manner. The mass-dependency and -independency of life history relationships with RI periodicity align with hypothalamic-mediated neurosecretory anterior and posterior pituitary outputs. We term this period the Havers-Halberg Oscillation (HHO), in reference to Clopton Havers, a 17th Century hard tissue anatomist, and Franz Halberg, a long-time explorer of long-period rhythms. We propose a mathematical model that may help elucidate the underlying physiological mechanism responsible for the HHO.

Covariation in Life-History Traits: Differential Effects of Diet on Condition, Hormones, Behavior, and Reproduction in Genetic Finch Morphs

The relative contribution of genetic and environmental factors in determining variation in life-history traits is of central interest to evolutionary biologists, but the physiological mechanisms underlying these traits are still poorly understood. Here we experimentally demonstrate opposing effects of nutritional stress on immune function, endocrine physiology, parental care, and reproduction between red and black head-color morphs of the Gouldian finch (Erythrura gouldiae). Although the body condition of black morphs was largely unaffected by diet manipulation, red birds were highly sensitive to dietary changes, exhibiting considerable within-individual changes in condition and immune function. Consequently, nutritionally stressed red birds delayed breeding, produced smaller broods, and reared fewer and lower-quality foster offspring than black morphs. Differences in offspring quality were largely due to morph-specific differences in parental effort: red morphs reduced parental provisioning, whereas black morphs adaptively elevated their provisioning effort to meet the increased nutritional demands of their foster brood. Nutritionally stressed genetic morphs also exhibited divergent glucocorticoid responses. Black morphs showed reduced corticosterone-binding globulin (CBG) concentrations and increased levels of free corticosterone, whereas red morphs exhibited reduced free corticosterone levels and elevated CBG concentrations. These opposing glucocorticoid responses highlight intrinsic differences in endocrine sensitivities and plasticity between genetic morphs, which may underlie the morph-specific differences in condition, behavior, and reproduction and thus ultimately contribute to the evolution and maintenance of color polymorphism.

Variation and covariation of life history traits in aphids are related to infection with the facultative bacterial endosymbiont Hamiltonella defensa

Host-symbiont associations play an important role in insects. In aphids, facultative symbionts affect host plant use and increase thermal tolerance and resistance to natural enemies. In spite of these beneficial effects on aphid fitness, the frequency of facultative symbionts in aphids ranges from low to intermediate. Tradeoffs induced by symbionts could prevent the fixation of symbionts in aphid populations. Therefore, we studied the life history traits and correlations between them in 21 clones of the black bean aphid, Aphis fabae, seven of which were infected with the facultative endosymbiont Hamiltonella defensa. We found that clones harbouring H. defensa exhibited significantly higher body mass at maturity and offspring production, and a marginally higher intrinsic rate of increase. However, development time and offspring body size did not differ between symbiont-free and infected clones. In addition, body mass at maturity was positively correlated with offspring production, offspring body size and intrinsic rate of increase, whereas development time was negatively correlated with body mass at maturity, offspring production and offspring body size. Excluding infected clones had little effect on these correlations; only correlations between body mass at maturity and offspring production, and between development time and offspring body size, became nonsignificant. Therefore, we did not find any evidence for tradeoffs between life history traits induced by symbiont infection. In fact, infected clones had higher overall fitness than symbiont-free clones under the conditions of our experiment, suggesting that symbionts do not impose costs on aphids harbouring them. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 237-247.

Joint modelling of breeding and survival in the kittiwake using frailty models

Assessment of population dynamics is central to population dynamics and conservation. In structured populations, matrix population models based on demographic data have been widely used to assess such dynamics. Although highlighted in several studies, the influence of heterogeneity among individuals in demographic parameters and of the possible correlation among these parameters has usually been ignored, mostly because of difficulties in estimating such individual-specific parameters. In the kittiwake ( Rissa tridactyla), a long-lived seabird species, differences in survival and breeding probabilities among individual birds are well documented. Several approaches have been used in the animal ecology literature to establish the association between survival and breeding rates. However, most are based on observed heterogeneity between groups of individuals, an approach that seldom accounts for individual heterogeneity. Few attempts have been made to build models permitting estimation of the correlation between vital rates. For example, survival and breeding probability of individual birds were jointly modelled using logistic random effects models by [Cam, E., Link, W.A., Cooch, E.G., Monnat, J., Danchin, E., 2002. Individual covariation in life-history traits: seeing the trees despite the forest. Am. Naturalist, 159, in press]. This is the only example in wildlife animal populations we are aware of. Here we adopt the survival analysis approaches from epidemiology. We model the survival and the breeding probability jointly using a normally distributed random effect (frailty). Conditionally on this random effect, the survival time is modelled assuming a lognormal distribution, and breeding is modelled with a logistic model. Since the deaths are observed in year-intervals, we also take into account that the data are interval censored. The joint model is estimated using classic frequentist methods and also MCMC techniques in Winbugs. The association between survival and breeding attempt is quantified using the standard deviation of the random frailty parameters. We apply our joint model on a large data set of 862 birds, that was followed from 1984 to 1995 in Brittany (France). Survival is positively correlated with breeding indicating that birds with greater inclination to breed also had higher survival.

Individual Covariation in Life-History Traits: Seeing the Trees despite the Forest

We investigated the influence of age on survival and breeding rates in a long‐lived species Rissa tridactyla using models with individual random effects permitting variation and covariation in fitness components among individuals. Differences in survival or breeding probabilities among individuals are substantial, and there was positive covariation between survival and breeding probability; birds that were more likely to survive were also more likely to breed, given that they survived. The pattern of age‐related variation in these rates detected at the individual level differed from that observed at the population level. Our results provided confirmation of what has been suggested by other investigators: within‐cohort phenotypic selection can mask senescence. Although this phenomenon has been extensively studied in humans and captive animals, conclusive evidence of the discrepancy between population‐level and individual‐level patterns of age‐related variation in life‐history traits is extremely rare in wild animal populations. Evolutionary studies of the influence of age on life‐history traits should use approaches differentiating population level from the genuine influence of age: only the latter is relevant to theories of life‐history evolution. The development of models permitting access to individual variation in fitness is a promising advance for the study of senescence and evolutionary processes.

Insurance Eggs versus Additional Eggs: Do Brown Boobies Practice Obligate Siblicide?

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Host-parasite coevolution: comparative evidence for covariation of life history traits in primates and oxyurid parasites.

The environmental factors that drive the evolution of parasite life histories are mostly unknown. Given that hosts provide the principal environmental features parasites have to deal with, and given that these features (such as resource availability and immune responses) are well characterized by the life history of the host, we may expect natural selection to result in covariation between parasite and host life histories. Moreover, some parasites show a high degree of host specificity, and cladistic analyses have shown that host and parasite phylogenies can be highly congruent. These considerations suggest that parasite and host life histories may covary. The central argument in the theory of life history evolution concerns the existence of trade-offs between traits. For parasitic nematodes it has been shown that larger body sizes induce higher fecundity, but this is achieved at the expense of delayed maturity. As high adult mortality would select for reduced age at maturity, the selective benefit of increased fecundity is expressed only if adult mortality is low. Parasite adult mortality may depend on a number of factors, including host longevity. Here we tested the hypothesis concerning the positive covariation between parasite body size (which reflects parasite longevity) and host longevity. To achieve this goal, we used the association between the pinworms (Oxyuridae, Nematoda) and their primate hosts. Oxyurids are highly host specific and are supposed to be involved in a coevolutionary process with their hosts. We found that female parasite body length was positively correlated with host longevity after correcting for phylogeny and host body mass. Conversely, male parasite body length and host longevity were not correlated. These results confirm that host longevity may represent a constraint on the evolution of body size in oxyurids, at least in females. The discrepancy between female and male oxyurids is likely to depend on the particular mode of reproduction of this taxon (haplodiploidy), which should result in weak (or even null) selection pressures to an increase of body size in males.

Life History Variation in Mosses: Water Relations, Size and Phylogeny

We evaluate the influences of gametophyte size, taxonomic affiliation (as an indicator of phylogenetic relationship), and water relations on variation and covariation of five life history traits among 335 moss species representing the orders Funariales, Polytrichales, and Pottiales. Size effects, though statistically significant, account for a relatively small proportion of the variation in most life history traits. Canonical Correlation Analyses, conducted across all species as well as within orders and larger families, reveal significant relationships between patterns of covariation in life history traits and variation in morpho-anatomical traits associated with water relations. Water relations account for 40-50% of life history variation depending on taxonomic group, but patterns of relationships between the two sets of variables are broadly similar, irrespective of the taxonomic group in which they were examined. The first water relations variate is a gradient describing water uptake/retention capacity. The life history variate associated with this is an axis that arranges species from those that are monoicous, short-lived and produce few large spores to those having the opposite suite of traits. The second water relations variate represents an endo-ectohydric gradient, which correlates with a life history variate describing differential investment in spores as a function of life expectancy. We used Nested Analyses of Variance and Covariance to partition variance in the life history traits into taxonomic components and evaluate whether size and water relations differences among particular groups mediate apparent taxonomic effects. Generic influences on all traits are strong, and independent of size and water relations effects ; together, genus and water relations account for >50% of the variation in each of the life history traits considered. Apparent ordinal effects largely disappear after adjustment for size and water relations, while substantial family level effects exist for spore number and spore size. Variation among species within genera is modest. These results suggest that most of the diversification in moss life histories occurred at the level of genus and that life histories have been relatively conserved in the process of subsequent cladogenesis. The persistent occurrence of water relations effects at several taxonomic levels, and the relatively large proportion of variance in life history traits, independent of taxonomic affiliation, for which these effects account, may imply adaptive coevolution of water relations and life history. These ideas can best be tested in an explicitly phylogenetic framework.

Covariation in life-history traits, demographics and behaviour in ischnuran damselflies: the evolution of monandry

Covariation in life-history traits, demographics and behaviour in ischnuran damselflies: the evolution of monandry

Covariation in life-history traits, demographics and behaviour in ischnuran damselflies: the evolution of monandry

Abstract The apparent erratic variation in life history traits, coloration patterns, and behaviours that exists among species within the damselfly genus Ischnura is shown to be interpretable when the species are partitioned into three groups. One group consists of species whose males are missing a pair of stout basal spines on the penultimate segment of their accessory penes. These are the only ischnurans in which males, by tandem guarding females, prevent sperm displacement. The other two groups can be recognized by the relative frequency with which mating occurs: monandrous species mate infrequently, polyandrous species more often. Compared to polyandrous species, monandrous species contain smaller size individuals, have greater sexual size dimorphism, have shorter duration copulations, do not have male biased operational sex ratios at aquatic sites, and are more likely to contain monochromatic females. Females belonging to the monandrous species tend to develop a characteristic form of pruinescence at maturity that obscures their underlying colour, and mature at a younger age. We propose that copulation serves only for sperm addition in monandrous species, for both sperm addition and displacement in polyandrous tandem guarding ischnurans, and for contact guarding as well as sperm addition and displacement in polyandrous species that do not tandem guard.

Avian Life History Evolution in Relation to Nest Sites, Nest Predation, and Food

Food limitation is generally thought to underlie much of the variation in life history traits of birds. I examined variation and covariation of life history traits of 123 North American Passeriformes and Piciformes in relation to nest sites, nest predation, and foraging sites to examine the possible roles of these ecological factors in life history evolution of birds. Annual fecundity was strongly inversely related to adult survival, even when phylogenetic effects were controlled. Only a little of the variation in fecundity and survival was related to foraging sites, whereas these traits varied strongly among nest sites. Interspecific differences in nest predation were correlated with much of the variation in life history traits among nest sites, although energy trade—offs with covarying traits also may account for some variation. For example, increased nest predation is associated with a shortened nestling period and both are associated with more broods per year, but number of broods is inversely correlated with clutch size, possibly due to an energy trade—off. Number of broods was much more strongly correlated with annual fecundity and adult survival among species than was clutch size, suggesting that clutch size may not be the primary fecundity trait on which selection is acting. Ultimately, food limitation may cause trade—offs between annual fecundity and adult survival, but differences among species in fecundity and adult survival may not be explained by differences in food abundance and instead represent differing tactics for partitioning similar levels of food limitation. Variation in fecundity and adult survival is more clearly organized by nest sites and more closely correlated with nest predation; species that use nest sites with greater nest predation have shorter nestling periods and more broods,yielding higher fecundity, which in turn is associated with reduced adult survival. Fecundity also varied with migratory tendencies; short—distance migrants had more broods and greater fecundity than did neotropical migrants and residents using similar nest sites. However, migratory tendencies and habitat use were confounded, making separation of these two effects difficult. Nonetheless, the conventional view that neotropical migrants have fewer broods than residents was not supported when nest site effects were controlled.

Patterns of life history variation in the Funariales, Polytrichales and Pottiales

AbstractA combination of Principal Component and Cluster Analyses is used to test for recurring suites of life history variation among 357 species of the Funariales, Polytrichales, and Pottiales. About 85% of among-species covariation in life expectancy, spore size and number, and sexuality is summarized by three Principal Components. Cluster Analyses, using species scores on these three derived variables, identify six groups of species based on similar grades of covariation in life history traits. These groups also differ significantly in water relations, gametophyte size, modes of spore dispersal, and prevalence of asexual reproductive propagules, and apparently are ecologically coherent, at least with regard to spatio-temporal scales of habitat availability and heterogeneity.A number of differences emerge in comparisons of Principal Component Analyses performed separately for each of seven families. In particular, the distribution of overall variance among successive components varies greatly, suggesti...

A Comparative Study of Reproduction and Development in the Polychaete Family Terebellidae.

The reproduction and development of four species of terebellid polychaetes from the west coast of North America were studied and compared with several other terebellid species to reveal the covariation of life history traits in the group, and assess any limitations on terebellid life history evolution that may be imposed by ancestry or body design. The four species in the present study span the range of reproductive and developmental modes known for the family Terebellidae. Eupolymnia crescentis and Neoamphitrite robusta are both free spawners that reproduce during discrete 3-month breeding periods. In E. crescentis, oogenesis takes from 5 to 8 months and spawning occurs from July to September, maximum oocyte diameter is 210 {mu}m, and fecundity reaches {approx}128,500 during a single breeding period. The E. crescentis larva develops near the bottom for about 7 days before settling as a five-setiger juvenile. Neoamphitrite robusta reproduces from April to July after a 12-month oogenic cycle; oocytes in this species measure up to 180 {mu}m, and fecundity reaches ~830,000. The two brooders in the study, Ramex californiensis and Thelepus crispus, brood their larvae in the maternal tube. T. crispus reproduces continuously for at least 6 months, and has up to 51,500 larvae in a single brood. The oocytes in this species (400 {mu}m) give rise to larvae that are brooded to the one-setiger stage and then emerge to undergo a one-day planktonic period before the larvae settle and become juveniles at eight setigers. Ramex californiensis reproduces continuously year round; larvae are brooded in cocoons that are laid sequentially in the tube, with up to 44 larvae in a single cocoon. Development from the 410 {mu}m oocytes is direct, and juveniles have 11 setigers. Unlike E. crescentis and N. robusta, in which oogenesis is synchronized within individuals to produce a peak of large oocytes during the discrete spawning period, R. californiensis and T. crispus females have a wide range of oocyte sizes throughout the year. Correlation analysis and analysis of variance of reproductive and developmental traits of these and several other terebellid species revealed some expected trends. For example, egg size varies according to the mode of reproduction (free spawning, extratubular brooding, or intratubular brooding), and is also correlated with juvenile size. However, egg size does not predict fecundity in terebellids when body size is held constant, and brooding is not restricted to small-bodied species. Indeed, the largest and smallest species in the study brood their larvae intratubularly, suggesting that allometric constraints may not be important in determining mode of reproduction in these polychaetes. The Terebellidae is a diverse family found in all marine habitats, yet all known terebellid larvae are non-feeding; this contrasts with the occurrence of both planktotrophy and lecithotrophy in other polychaete families, and leads to the proposal that larval development in terebellids has been constrained during the evolution of the lineage. The results of this study demonstrate that generalizations regarding complex relationships among life history traits are often inappropriate. The need for more comparative studies of marine invertebrate reproduction and development, and the integration of phylogenetic analyses into the study of life history evolution in marine invertebrates is highlighted.

Life history tactics of darters (Percidae: Etheostomatiini) and their relationship with body size, reproductive behaviour, latitude and rarity

Patterns of covariation of life history traits of darters in the genus Etheostoma are reviewed. The primary pattern is associated with body size. Large darters grow faster, mature at a larger size, produce bigger clutches, and have longer reproductive and life spans, and shorter spawning seasons, than do small darters. When the effects of size are removed statistically, the dominant secondary pattern matched the r‐K continuum from fast‐growing, short‐lived, primarily semelparous species with many small ova and a high reproductive effort (r‐species) to slow‐growing, long‐lived, iteroparous species with few large ova and a low reproductive effort (K‐species). Variation in life history traits is also influenced by reproductive behaviour, latitude, and rarity (as measured by geographic range). There are significant differences in the primary and secondary life history patterns among reproductive guilds. Latitude and rarity are not correlated with these primary and secondary patterns. Instead, they account for variation of tertiary patterns. Rare species may not match the reproductive performance of more common and widely distributed species. Future studies of life history traits in darters should focus on species whose reproductive behaviour differs from that of the species reviewed in this study, and on the demographic characteristics of rare or declining populations.

Intraspecific variation in body size, metabolic rate, and reproduction of deer mice (Peromyscus maniculatus)

Deer mice (Peromyscus maniculatus) from three populations were used to examine patterns of covariation among body size, metabolic rate, and selected reproductive and developmental traits. Mass at birth and at 21 days, growth rates of individual neonates and whole litters, litter size, interlitter interval, and metabolic rates of adult females were used as dependent variables against maternal mass in allometric equations. Litter mass was positively correlated with maternal mass within each of the three populations. Conversely, litter size, litter mass at 21 days, litter growth rate, interlitter interval, and maternal metabolic rate were correlated with maternal mass in only one or two of the populations. Neonatal traits (mean mass of individuals at birth and at weaning and their growth rates) were consistently independent of maternal mass. There was no significant relationship between any of the reproductive parameters measured and metabolic rate of individual females. These results support the view that patterns of covariation in life history traits, metabolic rate, and maternal mass, which are generally evident in interspecific comparisons, are not necessarily apparent at the level of individuals within a single population.

Cost of reproduction and covariation of life history traits in birds

Evolution of life history traits can be studied at two different levels: (1) current selection processes, including trade-offs in life history traits in natural populations as revealed by observations or, preferably, exieriments; and (2) patterns of variation in life history traits with each other and with ecology among extant species. Selection is not evolution, but selection pressures must have caused evolutionary change and led to current patterns of life history traits. These problems are exemplified by recent research on clutch size in birds.

Patterns of Covariation in Life History Traits of Squamate Reptiles: The Effects of Size and Phylogeny Reconsidered

Stearns' (1984) major conclusion was that patterns of covariation in life history traits within squamate reptiles are strongly influenced by classwide correlations with female body length. This res...

The Effects of Size and Phylogeny on Patterns of Covariation in the Life History Traits of Lizards and Snakes

Explanations of patterns of covariation in life history traits have been couched in terms of processes acting within species to produce adaptations to local habitats and mortality schedules. Analysis of the impact of size and lineage on patterns of covariation in the life history traits of reptiles suggests that microevolutionary explanations, while perhaps necessary, are not sufficient to account for the patterns in the data. Patterns of covariation are strongly influenced by classwide correlations with a single trait, average adult female length; they are further influenced by the effects of family and genus, but the differences between the two orders of reptiles analyzed are entirely accounted for by the correlations with size. Thus much of the tendency for traits to covary in the pattern originally thought to have been produced by r- and K-selection can be explained by selection on size alone followed by coadaptive shifts in life history traits. However, the pattern described here is also consistent w...