Accelerated Life History Research Articles

Reproductive motivation in the context of the COVID-19 epidemic: Is there evidence for accelerated life history dynamics?

One of the key life history assumptions is that mortality rates are positively associated with fast life history dynamics. Since the COVID-19 pandemic has elevated mortality rates throughout the world, we tested this assumption using reproductive motivation (desired number of children and desired age of first reproduction) as a key output measure using a repeated cross-sectional design. We assessed reproductive motivation in Serbian young adults before the pandemic started (N = 362), during the pandemic-caused state of emergency (the peak of the epidemic's first wave: N = 389) and after the state of emergency (i.e., after the first wave: N = 430). Furthermore, in the third time-point we measured experiences during the state of emergency and additional measures of reproductive motivation (reasons for and against parenthood). Subsamples were matched by sex, education, and the sampling procedure. We found the between-group differences which are congruent with life history theory: the desired age of first reproduction was lowest after the state of emergency compared to the 2 previous time-points. However, there were no differences in the desired number of children. Furthermore, the analysis of the links between experiences during the epidemic and reproductive motivation yielded the results which are incongruent with life history theory-adverse experiences during the state of emergency were negatively related to the reproductive motivation. Since the findings were only partially in accordance with life history theory, we discuss possible reasons which may explain the heterogeneity of results. (PsycInfo Database Record (c) 2021 APA, all rights reserved) Impact Statement One of the key assumptions of life history theory is that elevated mortality rates should produce faster life history dynamics which should reflect in higher fertility. This hypothesis is important not only for understanding evolutionary processes in an ecological context but also for predicting demographic trends as well. This assumption was tested by examining the links between COVID-19 epidemic and reproductive motivation (desired number of children and desired age of first reproduction) in young adults. The results showed mixed support for the life history predictions and provide useful guidelines for future studies in this topic. (PsycInfo Database Record (c) 2021 APA, all rights reserved)

Sex-specific movement ecology of the shortest-lived tetrapod during the mating season

Sex-specific reproductive strategies are shaped by the distribution of potential mates in space and time. Labord’s chameleon (Furcifer labordi) from southwestern Madagascar is the shortest-lived tetrapod whose life-time mating opportunities are restricted to a few weeks. Given that these chameleons grow to sexual maturity within about three months and that all individuals die soon after breeding, their mating strategies should be adapted to these temporal constraints. The reproductive tactics of this or any other Malagasy chameleon species have not been studied, however. Radio-tracking and observations of 21 females and 18 males revealed that females exhibit high site fidelity, move small cumulative and linear distances, have low corresponding dispersal ratios and small occurrence distributions. In contrast, males moved larger distances in less predictable fashion, resulting in dispersal ratios and occurrence distributions 7–14 times larger than those of females, and males also had greater ranges of their vertical distribution. Despite synchronous hatching, males exhibited substantial inter-individual variation in body mass and snout-vent length that was significantly greater than in females, but apparently unrelated to their spatial tactics. Females mated with up to 6 individually-known mates, but frequent encounters with unmarked individuals indicate that much higher number of matings may be common, as are damaging fights among males. Thus, unlike perennial chameleons, F. labordi males do not seem to maintain and defend territories. Instead, they invest vastly more time and energy into locomotion for their body size than other species. Pronounced variation in key somatic traits may hint at the existence of alternative reproductive tactics, but its causes and consequences require further study. This first preliminary study of the mating system of a Malagasy chameleon indicates that, as in other semelparous tetrapods, accelerated life histories are tied to a mating system with intense contest and scramble competition among males.

Extreme Body Size Variation in Pleistocene Dwarf Elephants from the Siculo-Maltese Palaeoarchipelago: Disentangling the Causes in Time and Space

The phenomenon of insular dwarfism in proboscideans is particularly well represented on the Siculo-Maltese Palaeoarchipelago, an island group on which a species complex of palaeoloxodont elephants evolved during the Middle-Late Pleistocene. This likely included three species from Malta, four from Sicily (and possibly its palaeo-islands), and one from Favignana Island, ranging in size from the 1 m-tall Palaeoloxodon falconeri to continental-sized 4m-tall P. antiquus. However, our understanding of the causes for extreme differences in body size among insular samples in such a small geographic region is still limited. Here, I document the full range in size of elephants from the palaeoarchipelago, and discuss the reasons for size differences on the three islands in time and space in relation to predation, competition, resource limitation, accelerated life history, and duration of isolation. Differences in size between larger and smaller Sicilian elephants from Luparello Fissure, as well as possibly also in P. ex gr. P. mnaidriensis from Puntali Cave, San Teodoro Cave, and Favignana Island, may relate to the duration of isolation, or alternatively environmental stressors associated with the Last Glacial Maximum in the case of the Favignana elephant. Additionally, small but significant differences in size observable in Middle Pleistocene P. ex gr. P. falconeri from different localities on Sicily, as well as in Maltese P. ‘melitensis’ may also relate to duration of isolation, highlighting the need for better geochronological data in order to better distinguish macro-ecological causes driving body size change from more subtle effects relating to duration of isolation.

Is the link between endorsement and engagement in sexual coercion associated with life history strategy?

We assess whether traits associated with life history strategy moderate the association between endorsement and engagement of sexual coercion. In a sample of 155 men, we measured engagement in subtle sexually coercive behaviours using a novel measure, where participants reported their likely response when faced with several sexual/dating scenarios (e.g., a situation where the participant is sexually rejected). We also measured participants on mating effort, aggression, socioeconomic status (SES), the dark triad traits (psychopathy, narcissism, and Machiavellianism), and endorsement of sexual coercion through acceptance of rape myths. We found that men high in mating effort, SES, and Machiavellianism were more likely to engage in sexually coercion. As expected, greater endorsement was associated with greater engagement in sexual coercion, and this was significantly moderated by narcissism and Machiavellianism, but in opposite directions, with higher levels of Machiavellianism and lower levels of narcissism associated with a greater association between endorsement and engagement. Overall, there was no consistent pattern between traits associated with an accelerated life history strategy and sexually coercive behaviour.

Fitness effects of spontaneous mutations in a warming world.

Spontaneous mutations fuel evolutionary processes and differ in consequence, but the consequences depend on the environment. Biophysical considerations of protein thermostability predict that warm temperatures may systematically increase the deleteriousness of mutation. We sought to test whether mutation reduced fitness more when measured in an environment that reflected climate change projections for temperature. We investigated the effects of spontaneous mutations on life history, size, and fitness in 21 mutation accumulation lines and 12 control lines of Daphnia pulex at standard and elevated (+4℃) temperatures. Warmer temperature accelerated life history and reduced body length and clutch sizes. Mutation led to reduced mean clutch sizes and fitness estimates at both temperatures. We found no evidence of a systematic temperature–mutation interaction on trait means, although some lines showed evidence of beneficial mutation at one temperature and deleterious mutation at the other. However, trait variances are also influenced by mutation, and we observed increased variances due to mutation for most traits. For variance of the intrinsic rate of increase and some reproductive traits, we found significant temperature–mutation interactions, with a larger increase due to mutation in the warmer environment. This suggests that selection on new mutations will be more efficient at elevated temperatures.

Famine-related mortality in early life and accelerated life histories in nineteenth-century Belgium.

Density-dependent and extrinsic mortality are predicted to accelerate reproductive maturation. The first 5 years of life is a proposed sensitive period for life-history regulation. This study examines the ways in which local mortality during this sensitive period was related to subsequent marriage timing in nineteenth-century Belgium (n women = 11 892; n men = 14 140). Local mortality during the sensitive period was inversely associated with age at first marriage for men and women controlling for literacy, occupational status, population growth and migration. Cox regression indicated decreased time to marriage for women (HR = 1.661, 95% CI: 1.542-1.789) and men (HR = 1.327, 95% CI: 1.238-1.422) from high mortality municipalities. Rising population growth rates were associated with earlier marriage for men and women. Migration in general was associated with later marriage for men and women. Consistent with life-history predictions, harsh ecological conditions during early life such as famine coincided with earlier marriage.

Prenatal stress: Effects on fetal and child brain development.

The impact of stress on brain health begins in the womb. Both animal and human studies have found that prenatal maternal stress affects the brain and behavior of the offspring. Stressful life events, exposure to a natural disaster, and symptoms of maternal anxiety and depression increase the risk for the child having a range of emotional, behavioral and/or cognitive problems in later life. These include depression, anxiety, Attention Deficit Hyperactivity Disorder (ADHD), and/or conduct disorders. There is an increased risk for other outcomes also, including preterm delivery and reduced telomere length, possibly indicative of an accelerated life history. The causal role of prenatal maternal stress on the etiology of the neurodevelopmental disorders is supported by large population cohorts, which have controlled for a wide range of potential confounders, including postnatal maternal mood. More recently, research has begun to explore the biological correlates and mediators of these findings. These studies suggest that the hypothalamic pituitary adrenal (HPA) axis plays a role in mediating the effects of maternal stress on the fetal brain. Further, in vivo brain imaging research reports that maternal stress is associated with changes in limbic and frontotemporal networks, and the functional and microstructural connections linking them. The structural changes include cortical thinning and an enlarged amygdala. While these studies have been conducted on smaller sample sizes and could not control for many confounders, the observed brain changes do plausibly underlie many of the emotional, behavioral and cognitive changes found to be associated with prenatal stress.

Evolutionary effects of fishing gear on foraging behavior and life-history traits.

Fishing gears are designed to exploit the natural behaviors of fish, and the concern that fishing may cause evolution of behavioral traits has been receiving increasing attention. The first intuitive expectation is that fishing causes evolution toward reduced boldness because it selectively removes actively foraging individuals due to their higher encounter rate and vulnerability to typical gear. However, life‐history theory predicts that fishing, through shortened life span, favors accelerated life histories, potentially leading to increased foraging and its frequent correlate, boldness. Additionally, individuals with accelerated life histories mature younger and at a smaller size and therefore spend more of their life at a smaller size where mortality is higher. This life‐history evolution may prohibit increases in risk‐taking behavior and boldness, thus selecting for reduced risk‐taking and boldness. Here, we aim to clarify which of these three selective patterns ends up being dominant. We study how behavior‐selective fishing affects the optimal behavioral and life‐history traits using a state‐dependent dynamic programming model. Different gear types were modeled as being selective for foraging or hiding/resting individuals along a continuous axis, including unselective fishing. Compared with unselective harvesting, gears targeting hiding/resting individuals led toward evolution of increased foraging rates and elevated natural mortality rate, while targeting foraging individuals led to evolution of decreased foraging rates and lower natural mortality rate. Interestingly, changes were predicted for traits difficult to observe in the wild (natural mortality and behavior) whereas the more regularly observed traits (length‐at‐age, age at maturity, and reproductive investment) showed only little sensitivity to the behavioral selectivity.

Hunting regulation favors slow life histories in a large carnivore

As an important extrinsic source of mortality, harvest should select for fast reproduction and accelerated life histories. However, if vulnerability to harvest depends upon female reproductive status, patterns of selectivity could diverge and favor alternative reproductive behaviors. Here, using more than 20 years of detailed data on survival and reproduction in a hunted large carnivore population, we show that protecting females with dependent young, a widespread hunting regulation, provides a survival benefit to females providing longer maternal care. This survival gain compensates for the females’ reduced reproductive output, especially at high hunting pressure, where the fitness benefit of prolonged periods of maternal care outweighs that of shorter maternal care. Our study shows that hunting regulation can indirectly promote slower life histories by modulating the fitness benefit of maternal care tactics. We provide empirical evidence that harvest regulation can induce artificial selection on female life history traits and affect demographic processes.

Body growth and life history in wild mountain gorillas (Gorilla beringei beringei) from Volcanoes National Park, Rwanda.

Great apes show considerable diversity in socioecology and life history, but knowledge of their physical growth in natural settings is scarce. We characterized linear body size growth in wild mountain gorillas from Volcanoes National Park, Rwanda, a population distinguished by its extreme folivory and accelerated life histories. In 131 individuals (0.09-35.26 years), we used non-invasive parallel laser photogrammetry to measure body length, back width, arm length and two head dimensions. Nonparametric LOESS regression was used to characterize cross-sectional distance and velocity growth curves for males and females, and consider links with key life history milestones. Sex differences became evident between 8.5 and 10.0 years of age. Thereafter, female growth velocities declined, while males showed increased growth velocities until 10.0-14.5 years across dimensions. Body dimensions varied in growth; females and males reached 98% of maximum body length at 11.7 and 13.1 years, respectively. Females attained 95.3% of maximum body length by mean age at first birth. Neonates were 31% of maternal size, and doubled in size by mean weaning age. Males reached maximum body and arm length and back width before emigration, but experienced continued growth in head dimensions. While comparable data are scarce, our findings provide preliminary support for the prediction that mountain gorillas reach maximum body size at earlier ages compared to more frugivorous western gorillas. Data from other wild populations are needed to better understand comparative great ape development, and investigate links between trajectories of physical, behavioral, and reproductive maturation.

Ontogenetic and life history trait changes associated with convergent ecological specializations in extinct ungulate mammals

Investigating life history traits in mammals is crucial to understand their survival in changing environments. However, these parameters are hard to estimate in a macroevolutionary context. Here we show that the use of dental ontogenetic parameters can provide clues to better understand the adaptive nature of phenotypic traits in extinct species such as South American notoungulates. This recently extinct order of mammals evolved in a context of important geological, climatic, and environmental variations. Interestingly, notoungulates were mostly herbivorous and acquired high-crowned teeth very early in their evolutionary history. We focused on the variations in crown height, dental eruption pattern, and associated body mass of 69 notoungulate taxa, placed in their phylogenetic and geological contexts. We showed that notoungulates evolved higher crowns several times between 45 and 20 Ma, independently of the variation in body mass. Interestingly, the independent acquisitions of ever-growing teeth were systematically accompanied by eruption of molars faster than permanent premolars. These repeated associations of dental innovations have never been documented for other mammals and raise questions on their significance and causal relationships. We suggest that these correlated changes could originate from ontogenetic adjustments favored by structural constraints, and may indicate accelerated life histories. Complementarily, these more durable and efficient dentitions could be selected to cope with important ingestions of abrasive particles in the context of intensified volcanism and increasing aridity. This study demonstrates that assessing both life history and ecological traits allows a better knowledge of the specializations of extinct mammals that evolved under strong environmental constraints.

Educational expectations and adolescent health behaviour: an evolutionary approach.

Previous research finds adolescents expecting to attend university are more likely to demonstrate health-promoting behaviour than those not expecting university attendance. This suggests public health improvements may be achievable by encouraging adolescents to adopt academic goals. We investigate confounders of this putative relationship, focusing on those identified by evolutionary theory. Multi-level logistic regression was used to analyse the 2010 Scottish Health Behaviour in School-aged Children survey (n = 1834). Adolescents anticipating university attendance exhibited higher levels of engagement in health-protective behaviours (fruit and vegetable consumption, exercise and tooth brushing) and were more likely to avoid health-damaging behaviours (crisps, soft drink and alcohol consumption, tobacco and cannabis use, fighting and intercourse). These relationships persisted when controlling indicators of life history trajectory (pubertal timing, socioeconomic status and father absence). Pupil level: gender, age, perceived academic achievement and peer/family communication and school level: university expectations, affluence, leavers' destinations, exam performance and school climate were also adjusted. Encouraging adolescents to consider an academic future may achieve public health benefits, despite social factors that might otherwise precipitate poor health via an accelerated life history trajectory.

Maternal experience with predation risk influences genome-wide embryonic gene expression in threespined sticklebacks (Gasterosteus aculeatus).

There is growing evidence for nongenetic effects of maternal experience on offspring. For example, previous studies have shown that female threespined stickleback fish (Gasterosteus aculeatus) exposed to predation risk produce offspring with altered behavior, metabolism and stress physiology. Here, we investigate the effect of maternal exposure to predation risk on the embryonic transcriptome in sticklebacks. Using RNA-sequencing we compared genome-wide transcription in three day post-fertilization embryos of predator-exposed and control mothers. There were hundreds of differentially expressed transcripts between embryos of predator-exposed mothers and embryos of control mothers including several non-coding RNAs. Gene Ontology analysis revealed biological pathways involved in metabolism, epigenetic inheritance, and neural proliferation and differentiation that differed between treatments. Interestingly, predation risk is associated with an accelerated life history in many vertebrates, and several of the genes and biological pathways that were identified in this study suggest that maternal exposure to predation risk accelerates the timing of embryonic development. Consistent with this hypothesis, embryos of predator-exposed mothers were larger than embryos of control mothers. These findings point to some of the molecular mechanisms that might underlie maternal effects.

Fostering relations: first sex and marital timings for children raised by kin and non-kin carers

Kinship fostering is generally preferred to non-kin fostering by policy makers in the U.S. and elsewhere. Researchers and policy makers alike tend to provide several proximate reasons for why this may be, generally neglecting an ultimate evolutionary framework. However, kin selection theory predicts that in the absence of genetically related parents, care from kin will result in the most similar life history outcomes. In low-fertility settings, parents typically favour increased investment in embodied capital and thus delayed reproductive life history strategy. Using archival data from the original Kinsey survey, collected in the U.S. from 1938 to 1963, we used survival analyses to compare the effects of living with kin and non-kin fosterers in childhood on timings of first sex and marriage. Our results support a kin selection hypothesis showing that while fostered children have accelerated life histories compared to children from “intact families”, kin fosterers buffer children from early sexual and reproductive behaviors, compared to children cared for by non-kin.

Invader population speeds up life history during colonization

We explore the long-term developments in population biology and life history during the invasion and establishment of the fish species vendace Coregonus albula in a subarctic watercourse by comparing life-history traits and molecular genetic estimates between the source and the colonist population. The two populations exhibited highly contrasting life-history strategies. Relative to the source population, the colonist population was characterized by slower somatic growth rates, earlier sexual maturation at smaller individual size, higher mortality rates and a shorter life span. The two populations could also be significantly discriminated by the genetic markers. Limited founder effects were detected from heterozygote deficit and reduced allelic richness in the colonist population, but both populations were associated with relatively high genetic diversity. The study reveals that the invasion into a new environment induced large changes in life-history strategy, with typical r-selected traits being more prominent in the colonist than in the source population. We discuss the mechanisms that may explain the observed life-history differences between the source and the colonist population, and argue that the accelerated life history of the colonist population represents an adaptive pioneer strategy aimed at fast population increase during colonization and establishment.

Influence of harvesting pressure on demographic tactics: implications for wildlife management

Summary 1. Demographic tactics within animal populations are shaped by selective pressures. Exploitation exerts additional pressures so that differing demographic tactics might be expected among populations with differences in levels of exploitation. Yet little has been done so far to assess the possible consequences of exploitation on the demographic tactics of mammals, even though such information could influence the choice of effective management strategies. 2. Compared with similar-sized ungulate species, wild boar Sus scrofa has high reproductive capabilities, which complicates population management. Using a perturbation analysis, we investigated how population growth rates (λ) and critical life-history stages differed between two wild boar populations monitored for several years, one of which was heavily harvested and the other lightly harvested. 3. Asymptotic λ was 1·242 in the lightly hunted population and 1·115 in the heavily hunted population, while the ratio between the elasticity of adult survival and juvenile survival was 2·63 and 1·27, respectively. A comparative analysis including 21 other ungulate species showed that the elasticity ratio in the heavily hunted population was the lowest ever observed. 4. Compared with expected generation times of similar-sized ungulates (more than 6 years), wild boar has a fast life-history speed, especially when facing high hunting pressure. This is well illustrated by our results, where generation times were 3·6 years in the lightly hunted population and only 2·3 years in the heavily hunted population. High human-induced mortality combined with non-limiting food resources accounted for the accelerated life history of the hunted population because of earlier reproduction. 5. Synthesis and applications. For wild boar, we show that when a population is facing a high hunting pressure, increasing the mortality in only one age-class (e.g. adults or juveniles) may not allow managers to limit population growth. We suggest that simulations of management strategies based on context-specific demographic models are useful for selecting interventions for population control. This type of approach allows the assessment of population response to exploitation by considering a range of plausible scenarios, improving the chance of selecting appropriate management actions.

Enamel microstructure in the fossil bovid Myotragus balearicus (Majorca, Spain): Implications for life-history evolution of dwarf mammals in insular ecosystems

The causes underlying the evolution of insular dwarfs and giants are a matter of ongoing debate. Because body size is among the principle life history traits, recent works aim to understand the evolution of insular dwarfs in the framework of life history theory. However, the hypotheses put forward so far are conflicting. Early studies, suggested that dwarfing is a consequence of selection for an increased reproduction associated to an accelerated life history (formerly r-selection). Recent work, however, based on the analysis of bone histology of the fossil insular dwarf bovid Myotragus balearicus (Balearic Islands, Spain), concluded that dwarfing on islands results from a decrease in growth rate associated to a slow life history (formerly K-selection) in response to selective forces peculiar to insular conditions. In the present work, we reconstruct the schedule of certain life history traits by estimating the rate of dental development and eruption times in M. balearicus and, for comparisons, in an extant caprine (Ovis aries). We used histological techniques to calculate crown formation time, daily secretion rate and crown extension rate, in the lower molars. Eruption pattern in M. balearicus was analysed through the radiological images of an ontogenetic series of mandibles. Our results show that dental crowns grew at slower rates and the period of crown formation was more extended in the dwarfed fossil bovid than in other extant caprines, resulting in dental development and eruption time that doubles that of extant bovids of similar body size. This suggests an important delay in life history schedules. Concordant with the delayed dental development, the striking hypsodonty of Myotragus is indicative of an extended lifespan. These results, together with previous findings from long bone histology, provide empirical evidence for a shift towards a slow life history in this insular dwarfed mammal. Density-dependent resource limitation is hypothesized as the main trigger of the life history and body size evolution of Myotragus.

A Faithful Record of Stressful Life Events Recorded in the Dental Developmental Record of a Juvenile Gorilla

The pattern and rate of dental development are critical components of the life history of primates. Much recent research has focused on dental development in chimpanzees and other hominoids, but comparatively little is known about dental development in Gorilla. To date, dental chronologies for Gorilla are based on a sample of 1 and information about variations in the time and timing of crown initiation and completion is lacking. We provide data on dental development in 1 captive, juvenile, female, western lowland Gorilla gorilla gorilla of known age, sex, life events, and date of death (carefully documented as part of zoo records) that experienced various physical insults during her first year of life. The perfect natural experiment allowed us to test the association of the timing of accentuated stress lines in teeth with significant physiological and psychological events during ontogeny of this juvenile gorilla. We analyzed histological sections from 14 permanent teeth (maxillary and mandibular I1-M2) and assessed crown initiation (CI) and crown formation times (CFT) using short- and long-period incremental lines in both enamel and dentine; they are advanced for all teeth compared to previously published chronology. The data suggest a relatively accelerated pace of dental development in gorillas compared to chimpanzees and fit an emerging pattern of an accelerated life history schedule in gorillas. Data on the timing of major accentuated lines in the developing dentition are tightly associated with exact dates of surgical procedures and follow-up hospital visits as recorded on zoo medical records. Our data highlight the importance of captive individuals with well-documented medical records for studying life history.

Life history responses depend on timing of cannibalism in a damselfly

Summary1. Cannibalism has often been suggested as an important mechanism to reach the necessary developmental stage and size before a critical time horizon is reached, but this role has been largely unexplored. We studied effects of cannibalism on the life history of the damselflyLestes viridisunder combinations of a time constraint (by manipulating the perceived time available in the growth season) and a biotic constraint (density).2. Larvae had a faster development and growth rate when reared at high time stress (late photoperiod). They also had a higher growth rate and mass at emergence when cannibalism occurred (density 2 and 4). Cannibalism occurred earlier at higher density. Accelerated life history responses (faster development and growth rate) and a higher mass at emergence were dependent upon the timing of cannibalism. Responses were more pronounced or only present if cannibalism occurred early in the larval period.3. Our data suggest that cannibalism may not only act as a lifeboat mechanism by enabling cannibals to survive detrimental ecological conditions, but may also act as a compensatory mechanism to keep life history variables near‐optimal at life history transitions, even under sub‐optimal conditions.