Continuum Of Life History Strategies Research Articles

Geographical variation in pace-of-life in a long-distance migratory bird: implications for population management.

Life-history theory predicts that animals should develop adaptive trade-offs between survival and reproduction to maximize their fitness. This results in a continuum of life-history strategies among species, ranging from slow to fast paces-of-life. The optimal pace-of-life has been shown to vary within environmental gradients, with a commonly observed pattern of a slow-to-fast continuum from the tropics to the poles. Within species, pace-of-life variability has however received much less attention. In this study, we investigated whether or not the pace-of-life of populations within a species follows the expected slow-fast continuum associated with latitude. We analysed the variability of life-history strategies among populations of the European roller Coracias garrulus, a long-distance migratory species, comparing breeding parameters and adult survival between populations across a latitudinal gradient. The findings showed a negative correlation between survival and clutch size in roller populations, with a slower pace-of-life in the northern populations and a faster pace-of-life in the southern populations: a reverse gradient to what might be expected from inter-specific studies. These results suggest that northern populations would benefit from measures enhancing adult survival probability, such as reduction in harvesting rates, while southern populations would respond better to actions favouring reproductive success, such as nesting site provisioning. This study highlights that life-history traits can vary substantially between populations of a single species with a large latitudinal breeding range, and pinpoint how knowledge about this variability may be key in anticipating different populations' responses to threats as well as to conservation strategies.

Spatial variance-mass allometry of population density in felids from camera-trapping studies worldwide

Power laws are cornerstone relationships in ecology and evolutionary biology. The density-mass allometry (DMA), which predicts an allometric scaling of population abundance, and Taylor’s law (TL), which predicts a decrease in the population abundance variation along with a decrease in population density, have enhanced our knowledge of inter- and intra-specific variation in population abundance. When combined, these two power laws led to the variance-mass allometry (VMA), which states that larger species have lower spatial variation in population density than smaller species. The VMA has been predicted through theoretical models, however few studies have investigated if this law is also supported by empirical data. Here, to formally test the VMA, we have used the population density estimates obtained through worldwide camera trapping studies for an emblematic and ecologically important carnivorous taxa, the Felidae family. Our results showed that the VMA law hold in felids, as well as the TL and the DMA laws; bigger cat species showed less variation for the population density than smaller species. These results have important implications for the conservation of wildlife population and confirm the validity of important ecological concepts, like the allometric scaling of population growth rate and the slow-fast continuum of life history strategies.

Rethinking the fast-slow continuum of individual differences

Abstract The idea that individual differences in behavior and physiology can be partly understood by linking them to a fast-slow continuum of life history strategies has become popular in the evolutionary behavioral sciences. I refer to this approach as the “fast-slow paradigm” of individual differences. The paradigm has generated a substantial amount of research, but has also come increasingly under scrutiny for theoretical, empirical, and methodological reasons. I start by reviewing the basic empirical facts about the fast-slow continuum across species and the main theoretical accounts of its existence. I then discuss the move from the level of species and populations to that of individuals, and the theoretical and empirical complications that follow. I argue that the fast-slow continuum can be a productive heuristic for individual differences; however, the field needs to update its theoretical assumptions, rethink some methodological practices, and explore new approaches and ideas in light of the specific features of the human ecology.

Forest dynamics and demography

Tropical Forests Tropical forest succession has been viewed mostly by considering trees in categories of early-, mid-, and late-successional species, corresponding to a fast–slow continuum of life history strategies. Ruger et al. now show that the fast–slow continuum does not capture the demographic strategy of the long-lived pioneer species, an important component of many tropical forests (see the Perspective by Bugmann). They developed a forest model that allows for objective predictions of tropical forest dynamics and validated the model's predictions against independent data. These findings should advance our understanding of tropical forest dynamics and facilitate sustainable tropical forest management. Science , this issue p. [165][1]; see also p. [128][2] [1]: /lookup/doi/10.1126/science.aaz4797 [2]: /lookup/doi/10.1126/science.abb7020

Demographic trade-offs predict tropical forest dynamics

Understanding tropical forest dynamics and planning for their sustainable management require efficient, yet accurate, predictions of the joint dynamics of hundreds of tree species. With increasing information on tropical tree life histories, our predictive understanding is no longer limited by species data but by the ability of existing models to make use of it. Using a demographic forest model, we show that the basal area and compositional changes during forest succession in a neotropical forest can be accurately predicted by representing tropical tree diversity (hundreds of species) with only five functional groups spanning two essential trade-offs-the growth-survival and stature-recruitment trade-offs. This data-driven modeling framework substantially improves our ability to predict consequences of anthropogenic impacts on tropical forests.

A novel growth function incorporating the effects of reproductive energy allocation.

Ontogenetic growth functions provide basic information in biological and ecological studies. Various growth functions classified into the Pütter model have been used historically, regardless of controversies over their appropriateness. Here, we present a novel growth function for fish and aquatic organisms (generalised q-VBGF) by considering an allocation schedule of allometrically produced surplus energy between somatic growth and reproduction. The generalised q-VBGF can track growth trajectories in different life history strategies from determinate to indeterminate growth by adjusting the value of the ‘growth indeterminacy exponent’ q. The timing of maturation and attainable body size can be adjusted by the ‘maturation timing parameter’ τ while maintaining a common growth trajectory before maturation. The generalised q-VBGF is a comprehensive growth function in which exponentials in the traditional monomolecular, von Bertalanffy, Gompertz, logistic, and Richards functions are replaced with q-exponentials defined in the non-extensive Tsallis statistics, and it fits to actual data more adequately than these conventional functions. The relationship between the estimated parameter values τ and rq forms a unique hyperbola, which provides a new insight into the continuum of life history strategies of organisms.

Demographic measures of an individual’s “pace of life”: fecundity rate, lifespan, generation time, or a composite variable?

Comparative analyses have demonstrated the existence of a "pace-of-life" (POL) continuum of life-history strategies, from fast-reproducing short-lived species to slow-reproducing long-lived species. This idea has been extended to the concept of a "pace-of-life syndrome" (POLS), an axis of phenotypic covariation among individuals within species, concerning morphological, physiological, behavioral and life-history traits. Several life-history metrics can be used to place species in the fast-slow continuum;here, we asked whether individual variation in POL can also be studied using similar life-history measures. We therefore translated measures commonly used in demographic studies into individual-level estimates. We studied fecundity rate, generation time, lifespan, age at first reproduction, fecundity at first reproduction, and principal component scores integrating these different metrics. Using simulations, we show how demographic stochasticity and individual variation in resources affect the ability to predict an individual's POL using these individual-level parameters. We found that their accuracy depends on how environmental stochasticity varies with the species' position on the fast-slow continuum and with the amount of (co) variation in life-history traits caused by individual differences in resources. These results highlight the importance of studying the sources of life-history covariation to determine whether POL explains the covariation between morphological, physiological, and behavioral traits within species. Our simulations also show that quantifying not only among-individual but also among-population patterns of life-history covariation helps in interpreting demographic estimates in the study of POLSs within species. Significance statement It has been demonstrated that there is a continuum of life-history strategies, from fast-reproducing short-lived species to slow-reproducing long-lived species. This pattern of variation in the tempo of life-history strategies has been named the pace-of-life continuum. Recently, it has been suggested that within a population, variation in pace of life explains differences between individuals in their morphological, behavioral, and physiological traits. This paper provides guidelines on how to quantify the pace of life of individuals using demographic approaches that have been developed to study the pace of life of species.

A comparative study of growth: different body weight trajectories in three species of the genus Eublepharis and their hybrids

An extensive research effort is devoted to the evolution of life-histories and processes underlying the variation in adult body weight; however, in this regard, some animal taxa remain neglected. Here we report rates and timing of growth recorded in two wild-derived populations of a model lizard species, Eublepharis macularius (M, W), other two related species, i.e., E. angramainyu (A) and E. sp. (D), and their between-species hybrids. We detected clear differences among the examined species/populations, which can be interpreted in the terms of “fast – slow” continuum of life-history strategies. The mean asymptotic body size was the highest in A and further decreased in the following order: M, W, and D. In contrast, the growth rate showed an opposite pattern. Counter-intuitively, the largest species exhibited the slowest growth rates. The final body size was determined mainly by the inflexion point. This parameter reflecting the duration of exponential growth increased with mean asymptotic body size and easily overcompensated the effect of decreasing growth rates in larger species. Compared to the parental species, the F1 and backcross hybrids exhibited intermediate values of growth parameters. Thus, except for the case of the F2 hybrid of MxA, we failed to detect deleterious effects of hybridization in these animals with temperature sex determination.

Defining Life Histories of Precocious Male Parr, Minijack, and Jack Chinook Salmon Using Scale Patterns

AbstractMale Chinook salmon Oncorhynchus tshawytscha have multiple life history strategies tied to smolting, age, and size at maturation. Precocious strategies include mature parr, minjacks, and jacks; however, there are conflicting definitions of what constitutes a minijack. We describe the variety of growth and life history patterns in precocious spring–summer Chinook salmon in the Snake River basin as inferred from scale patterns. We found six repeatable patterns on the scales collected that differed in average number of freshwater and saltwater circuli and average spacing of circuli during the period of fastest growth. This represented four life histories with two variations. These life histories were differentiated by length distribution: mature headwater parr that never left their natal stream (8–15‐cm fork length), mature river parr (17–24 cm), minijacks that spent 3–4 months in the estuary or ocean (24–37 cm), and jacks that spent one winter in the ocean (≥36 cm). Thus, male Chinook salmon have a continuum of life history strategies. Mature parr spend their entire life in freshwater, mature headwater parr have parr marks, and the mature river parr are more silver in appearance. Neither of these stages have scale resorption. Some parr stay in headwater streams while others make short‐distance migrations to larger rivers. Minijacks make long‐distance migrations to the estuary or ocean but only stay a few months before returning to the spawning grounds. Jacks spend 1 year in the ocean and have many saltwater circuli. Minijacks and jacks are spotted similar to full‐size spawning adults and have scale resorption consistent with a long spawning migration. Finally, our data demonstrate that minijacks are capable of successfully traveling from Idaho to the Columbia River estuary and back (a minimum of 2,600 river kilometers from the Pahsimeroi River) within approximately 4 months.

Re‐examining extreme longevity of the cave crayfish Orconectes australis using new mark–recapture data: a lesson on the limitations of iterative size‐at‐age models

Summary1. Centenarian species, defined as those taxa with life spans that frequently exceed 100 years, have long been of interest to ecologists because they represent an extreme end point in a continuum of life history strategies. One frequently reported example of a freshwater centenarian is the obligate cave crayfish Orconectes australis, with a maximum longevity reported to exceed 176 years. As a consequence of its reported longevity, O. australis has been used as a textbook example of life history adaptation to the organic‐carbon limitation that characterises many cave‐stream food webs.2. Despite being widely reported, uncertainties surround the original estimates of longevity for O. australis, which were based on a single study dating from the mid‐1970s. In the present study, we re‐evaluated the growth rate, time‐to‐maturity, female age‐at‐first‐reproduction and longevity of O. australis using a mark–recapture study of more than 5 years based upon more than 3800 free‐ranging individuals from three isolated cave streams in the south‐eastern United States.3. The results of our study indicate that accurate estimates of the longevity of O. australis are ≤22 years, with only a small proportion of individuals (<5%) exceeding this age. Our estimates for female time‐to‐maturity (4–5 years) and age‐at‐first‐reproduction (5–6 years) are also substantially lower than earlier estimates.4. These new data indicate that the age thresholds for life history events of O. australis are comparable to other estimates for a modest assemblage of cave and surface species of crayfish for which credible age estimate exists, suggesting that a cave environment per se is not required for the evolution of extreme longevity in crayfish.

Volume 137

The idea that individual differences in behavior and physiology can be partly understood by linking them to a fast-slow continuum of life history strategies has become popular in the evolutionary behavioral sciences. I refer to this approach as the “fast-slow paradigm” of individual differences. The paradigm has generated a substantial amount of research, but has also come increasingly under scrutiny for theoretical, empirical, and methodological reasons. I start by reviewing the basic empirical facts about the fast-slow continuum across species and the main theoretical accounts of its existence. I then discuss the move from the level of species and populations to that of individuals, and the theoretical and empirical complications that follow. I argue that the fast-slow continuum can be a productive heuristic for individual differences; however, the field needs to update its theoretical assumptions, rethink some methodological practices, and explore new approaches and ideas in light of the specific features of the human ecology.

Capelin Mallotus villosus (Pisces: Osmeridae), glaciations, and speciation: a nomothetic approach to fisheries ecology and reproductive biology

Capelin Mallotus villosus in the North Pacific and Northwest Atlantic are characterized by a wider latitudinal distribution (cool temperate to subarctic). lower number of vertebrae (64.45 to 68.50), lower biomass, lower fecundity and larger eggs than are capelin in the Central-Northeast Atlantic (exclusively subarctic. 69.16 to 71.54 vertebrae). Capelin in the North Pacific and Northwest Atlantic spawn intertidally over a wider range of latitudes (42 to 72O N), temperatures (1 to 14 'C), salinities (from brackish to oceanic water), and at a higher mean temperature (7.5 C), than do populations in the Central and Northeast Atlantic (offshore spawning, 63 to 76 N, 0.94 to 7 'C , 32.0 % to 34.6 'Ymv, 4 C respectively). These differences indicate that capelin are towards the r-endpoint of the r-k continuum of life history strategies in the North Pacific-Northwest Atlantic and towards the k-endpoint in the Northeast Atlantic. A nomothetic explanation is proposed. During the peak of the last glaciation, the major present-day spawning grounds on the Pacific rim were ice-free. Capelin experienced little change in their accustomed enviromental conditions and spawned intertidally over a wide geographic range. In contrast, North Atlantic spawning grounds were ice-covered. Accordingly, offshore spawning habits evolved. Intertidal spawning in the North Atlantic probably did occur between 40 to 55O N along the European coast and in the Mediterranean Sea where ice did not reach the sea. Capelin populations underwent k-selection, and stenothermy, stenohalinity, low fecundity, large egg size and hlgh biomass evolved in populations of deep-spawning capelin of the North Atlantic in response to the greater environmental predictability in these offshore habitats. During the Holocene hypsithermal, capelin from the Pacific Ocean (intertidal spawning) repopulated Canadian Arctic waters and Northwest Atlantic. Deep-spawning capelin continued to reproduce in the North Atlantic where bathymetry, spawning temperatures and salinities were optimum (Grand Banks, Iceland, Barents Sea). Minor stocks of beachspawning capelin which now inhabit some Norwegian fjords may have been denved from the Northwest Atlantic, via the North Atlantic Drift, and/or from relict populations which spawned intertidally along the ice-free Western EuropeanIMediterranean coast. The implications of this hypothesis for the taxonomic status of capelin are discussed.