Lifetime Fitness Research Articles

Lifetime fitness benefits of breeding site fidelity and low costs of inbreeding permit inbreeding tolerance in an avian cooperative breeder.

Inbreeding, or breeding with close relatives, often decreases individual fitness, but mate choice in many species can increase inbreeding risk. Inbreeding is more likely in species with limited dispersal, such as cooperative breeders where non-parental individuals-often offspring from previous broods-provide parental care and frequently breed close to home. We leverage 32 years of data from a population of Florida Scrub-Jays ( Aphelocoma coerulescens ), an avian cooperative breeder, to investigate whether mate choice, and its lifetime fitness outcomes, affects inbreeding tolerance. We find that both sexes show a stronger preference for geographically closer rather than less related mates. While female-biased dispersal mitigates inbreeding risk when pairing for the first time, limited movement away from the breeding territory by both sexes for later pairings (following mate death or divorce) results in higher relatedness between mates than expected under random mating. Males paired with close relatives and females that move longer distances experience equivalently reduced lifetime reproductive success. Fitness benefits of breeding site fidelity and relatively low fitness costs of inbreeding thus permit inbreeding tolerance in Florida Scrub-Jays. Understanding how and why mate choice contributes to inbreeding is crucial for informed conservation action for endangered species like the Florida Scrub-Jay.

Females with attractive mates gain environmental benefits that increase lifetime and multigenerational fitness

Females with attractive mates gain environmental benefits that increase lifetime and multigenerational fitness

Social and metabolic mediation of growth performance in a temperate estuarine fish

Despite the importance of juvenile growth to lifetime fitness, high variability exists within many fish species where some individuals grow markedly faster than others. Here, we explored whether social context mediated growth performance in n = 35 Galaxias maculatus by manipulating the social environment after identifying different growth phenotypes. We found that initially fast-growing fish slowed their growth rate when pooled with similarly fast-growing individuals, whereas none of the initially slow-growing fish markedly improved their growth when pooled with other slow-growers. We examined for any metabolic underpinnings to the findings by measuring standard, routine, and maximum metabolic rates (SMR, RMR, and MMR) at two time points separated by ~4 months. SMR and RMR positively correlated with growth rates when the fish were pooled into growth phenotypes, but not when they were returned to their original (mixed) social groups. We highlight research directions to further elucidate how social context and metabolism interact to govern growth phenotype.

Optimal polyandry in fruit flies.

The study of polyandry has received increasing scientific attention with an emphasis on the fitness benefits and costs that females derive from mating with multiple males. There are still gaps in our understanding of how polyandry affects female fitness, however, as many previous studies compared the fitness outcomes of a single mating vs. two or three matings and did not separate the consequences of multiple mating from the costs of sexual harassment. We therefore conducted controlled mating trials with female fruit flies (Drosophila melanogaster) that could mate at either low (every eight days), medium (every four days), or high (every other day) rates while controlling for exposure to harassment from males. We found that female lifetime fitness was highest under the high followed by the medium mating-rate conditions. Moreover, we did not detect reductions in lifespan as a consequence of higher rates of polyandry. Our results demonstrate that even at realistically high rates, polyandry can lead to net fitness benefits for females, which can have major implications for sexual selection. Specifically, we discuss the significance of our findings as they relate to competition and the evolution of secondary sex characteristics in females, and sperm competition amongst males.

Effectiveness of Lifetime Fitness Course Activities in Improving Movement Efficiency

University physical education courses are meant to teach the fundamentals of various sports and exercise techniques. The main purpose of this study was to determine how effective lifetime fitness (LF) courses in higher education can enhance movement efficiency (ME). Eleven participants performed the Fusionetics movement efficiency test at the beginning, middle, and end of the academic semester. Overall ME scores showed a significant effect, whereby the scores increased from the pre- to the mid-test but fell from the mid- to the post-test. Both the 1- and 2-leg squat subtests revealed a similar pattern. The second half of the semester's increased use of endurance-based class activities may have caused the ME score to decline.

The Lifetime Fitness Program: Structured Physical Activity for Older Adults and Meaningful Experiential Learning for Kinesiology Students

Physical activity is associated with improvements in both health and longevity and is highly recommended for older adults. Public health and nonprofit organizations have invested considerable efforts to promote physical activity among this population. The present manuscript describes the specifics of the first university-based adult fitness program (Lifetime Fitness Program) and how this program promotes healthy aging through physical activity while serving as an important venue for experiential learning among students. Thus, the goal of this paper is to provide a “road map” to guide strategies and methods to promote physical activity and healthy aging in an academic setting and provide students with meaningful experiential learning opportunities.

Context-specific “silver-spoon” effects of wetlands, climate, and temperature on lifetime fitness in a short-lived temperate-breeding migratory songbird

Drivers of global change are creating strongly contrasting early life conditions for developing offspring, which may have carry-over effects on lifetime fitness. We tested for “silver-spoon” effects of natal conditions (environmental conditions and maternal quality) and individual quality (pre-fledging) on the lifetime reproductive success (LRS) of aerial insectivorous adult tree swallows (Tachycineta bicolor) hatched in distinct populations with contrasting environments in Saskatchewan and British Columbia, Canada. In both populations, LRS of adults was influenced by environmental conditions they experienced as developing nestlings, but silver-spoon effects were context-dependent, indicating population-specific responses to the local environment. Higher natal temperature in Saskatchewan had positive silver-spoon effects on the LRS of adult swallows, but the opposite was observed in British Columbia, likely because the highest temperatures local recruits experienced as nestlings occurred during heat extremes. In Saskatchewan, where wetter conditions reflect higher wetland abundance and food supply, we detected a negative effect of good natal wetland conditions on adult LRS, contrary to our hypothesis. However, since current breeding wetland conditions are a strong driver of adult fitness, and adults experiencing high natal wetland abundance generally bred when wetland abundance was lower, we suspect any potential benefits of natal wetland abundance on LRS were overridden by wetland conditions during breeding. As hypothesized, wetter natal conditions in British Columbia, which reflect an unfavorable environment for developing nestlings, had negative silver-spoon effects on the LRS of adults. No maternal or pre-fledging quality effects were detected at either site. Therefore, LRS of individuals within distinct populations is influenced, at least in part, by carry-over effects of the natal environment that vary locally. Consequently, natal environmental conditions that affect fitness, with putative population-level consequences, may underly spatially-varying population trends of regionally distinct populations within a species’ range.

Maternal Behavior in Sumatran Orangutans (Pongo abelii) is Modulated by Mother-Offspring Characteristics and Socioecological Factors

AbstractMammalian mothers flexibly invest in their offspring to maximize their lifetime fitness. Flexible maternal investment may be particularly important in large-brained species with prolonged maternal care, e.g., in great apes. We investigated the effects of socioecological factors and mother–offspring characteristics on nine maternal behaviors in wild Sumatran orangutans (Pongo abelii; N = 22 mother-offspring pairs; >11,200 hr of focal data from 2007–2022) using generalized linear mixed models. The behaviors fall under four maternal functions: locomotory support (carrying), skill acquisition support (feeding in proximity, food transfer), protective proximity maintenance (body contact and proximity initiation, following), and independence promotion (body contact and proximity termination, avoiding). Mother’s parity was not significantly associated with any maternal behavior. Mothers were more likely to show locomotory support, skill acquisition support, and protective proximity maintenance toward younger than older offspring, whereas they were more likely to promote independence in older than younger offspring. Mothers with male offspring were more likely to show skill acquisition support to their offspring than those with female offspring. With increasing food availability, skill acquisition support reduced. With increasing association size (i.e., the number of individuals within 50 m of each other), mothers were more likely to show protective proximity maintenance and less likely to promote independence. When males were present, mothers were more likely to show locomotory support to their offspring. Sumatran orangutan mothers thus flexibly adjust offspring-directed behavior in response to prevailing socioecological factors and mother–offspring characteristics. Our findings add support to the evolutionary theory that mammalian mothers flexibly invest in their offspring.

Inherent versus random variation in fitness of elephant seals: offspring quality and quantity

Variation in reproductive success is the basis of evolution and allows species to respond to the environment, but only when it is based on fixed individual variation that is heritable. Several recent studies suggest that observed variation in reproduction is due to chance, not inherent individual differences. Our aim was to quantify inherent versus neutral variation in fitness of northern elephant seal ( Mirounga angustirostris (Gill, 1866)) females, including both quality and quantity of their offspring. Using 44 years of observations at Año Nuevo in California, we assembled lifetime pup production of 1065 individual females and mass at weaning for 2120 of their pups. Females varied significantly in mean lifetime mass of their pups, with 28% of the variance due to fixed individual differences among mothers. Variation was repeatable over 6 years of a mother’s lifetime and heritable ( h = 0.48). Moreover, pup mass at weaning was associated with future lifetime fitness, since larger pups had a higher chance of surviving to breed. Larger pups, however, did not produce more offspring once breeding, and lifetime pup production was not heritable. Traits related to offspring quality in elephant seals were inherently different among females, but variation in pup production was neutral.

Anthropogenic and climatic factors interact to influence reproductive timing and effort.

Reproduction, although absolutely essential to a species' persistence, is in itself challenging. As anthropogenic change increasingly affects every landscape on Earth, it is critical to understand how specific pressures impact the reproductive efforts of individuals, which directly contribute to the success or failure of populations. However, organisms rarely encounter a single burden at a time, and the interactions of environmental challenges can have compounding effects. Understanding environmental and physiological pressures is difficult because they are often context-dependent and not generalizable, but long-term monitoring across variable landscapes and weather patterns can improve our understanding of these complex interactions. We tested the effects of urbanization, climate, and individual condition on the reproductive investment of wild side-blotched lizards (Uta stansburiana) by measuring physiological/reproductive metrics from six populations in urban and rural areas over six consecutive years of variable precipitation. We observed that reproductive stage affected body condition, corticosterone concentration, and oxidative stress. We also observed that reproductive patterns differed between urban and rural populations depending on rainfall, with rural animals increasing reproductive investment during rainier years compared to urban conspecifics, and that reproductive decisions appeared to occur early in the reproductive process. These results demonstrate the plastic nature of a generalist species optimizing lifetime fitness under varying conditions.

Comparing the migration behavior and survival of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) smolts.

Many organisms rely on migrations between habitats to maximize lifetime fitness, but these migrations can be risky due to a suite of factors. In anadromous salmonids, the smolt migration from fresh water to sea is a critical life stage, during which smolts can experience high mortality from multiple sources. This study investigated the migratory behavior and survival of Atlantic salmon (Salmo salar) and anadromous brown trout (Salmo trutta) smolts during their seaward migration using acoustic telemetry between March and May 2021. Due to the extinction of wild salmon in the River Gudenaa after the construction of the Tange hydropower plant, this study used hatchery-reared salmon originating from a nearby Danish river. A total of 75 hatchery-reared salmon smolts, 75 hatchery-reared trout smolts, and 75 wild trout smolts were tagged with acoustic transmitters and released into River Gudenaa, Denmark. The downstream movements of tagged fish were monitored using acoustic receivers deployed in the river and fjord. Hatchery-reared trout initiated migration first, followed by hatchery-reared salmon, with wild trout being the last to migrate. There was no difference in riverine progression rates among the three smolt groups, but noticeable differences emerged once in the fjord: trout (wild and hatchery) slowed down, whereas hatchery-reared salmon maintained their speed. Riverine migration was predominantly nocturnal for all smolts; however, daytime migration increased at the fjord arrays. Day-of-year significantly influenced diurnal patterns in the river and fjord, where daytime migration increased later in the year. Hatchery-reared salmon and wild trout had reasonably good overall survival from river to sea entry (≥66%), whereas hatchery-reared trout had poor survival (c.26%). The fjord was the major bottleneck for survival of hatchery-reared trout. We found no strong evidence for differences in progression rate or diurnal patterns between wild and hatchery-reared trout to explain the lower survival. This study demonstrates that salmon and trout differ in their life-history strategy already in the post-smolt phase, and that stocking is a sub-optimal strategy to aid wild populations.

A comparative genomic analysis of Fructobacillus evanidus sp. nov. from bumble bees

The increase in studies on bee microbiomes is prompted by concerns over global pollinator declines. Bumble bees host core and non-core microbiota which may contribute to increased lifetime fitness. The presence of Fructobacillus in the gut microbiomes of bumble bee workers, or the replacement of core symbionts with Fructobacillus bacteria, has been considered a marker of dysbiosis. A phylogenomic analysis and functional genomic characterization of the genomes of 21 Fructobacillus isolates from bumble bees demonstrated that they represented four species, i.e. Fructobacillus cardui, Fructobacillus fructosus, Fructobacillus tropaeoli, and the novel species Fructobacillus evanidus sp. nov. Our results confirmed and substantiated the presence of two phylogenetically and functionally distinct Fructobacillus species clades that differ in genome size, percentage G + C content, the number of coding DNA sequences and metabolic characteristics. Clade 1 and clade 2 species differed in amino acid and, to a lesser extent, in carbohydrate metabolism, with F. evanidus and F. tropaeoli genomes featuring a higher number of complete metabolic pathways. While Fructobacillus genomes encoded genes that allow adhesion, biofilm formation, antibacterial activity and detoxification, other bacteria isolated from the bumble bee gut appeared better equipped to co-exist with the bumble bee host. The isolation and identification of multiple Fructobacillus species from several bumble bee gut samples in the present study also argued against a specific partnership between Fructobacillus species and their bumble bee hosts.

Born with an advantage: early life and maternal effects on fitness in female ground squirrels.

Lifetime fitness and its determinants are an important topic in the study of behavioral ecology and life-history evolution. Early life conditions comprise some of these determinants, warranting further investigation into their impact. In some mammals, babies born lighter tend to have lower life expectancy than those born heavier, and some of these life-history traits are passed on to offspring, with lighter-born females giving birth to lighter offspring. We investigated how weight at weaning, the relative timing of birth in the season, maternal weight, and maternal age affected the longevity and lifetime reproductive success (LRS) of female Columbian ground squirrels (Urocitellus columbianus). We hypothesized that early life conditions such as offspring weight would not only have lifetime fitness consequences but also intergenerational effects. We found that weight at weaning had a significant impact on longevity, with heavier individuals living longer. The relative timing of an individual's birth did not have a significant association with either longevity or LRS. Individuals born to heavier mothers were found to have significantly higher LRS than those born to lighter mothers. Finally, maternal age was found to be significantly associated with their offspring's LRS, with older mothers having less successful offspring. Our results provide evidence that early life conditions do have lifelong fitness and sometimes intergenerational consequences for Columbian ground squirrels.

Defining fitness in evolutionary ecology.

An understanding of biological fitness is central to theory and practice in ecology and evolution, yet fitness remains an elusive concept to define and challenging to measure accurately. Fitness reflects an individual's ability to pass its alleles on to subsequent generations. Researchers often quantify proxies for fitness, such as survival, growth or reproductive success. However, it can be difficult to determine lifetime fitness, especially for species with long lifespans. The abiotic and biotic environment strongly affects the expression of fitness, which means that fitness components can vary through both space and time. This spatial and temporal heterogeneity results in the impressive range of adaptations that we see in nature. Here, we review definitions of fitness and approaches to measuring fitness at the level of genes, individuals, genotypes, and populations and highlight that fitness is a key concept linking ecological and evolutionary thought.

Lovers, not fighters: docility influences reproductive fitness, but not survival, in male Cape ground squirrels, Xerus inauris

Over their lifetime, individuals may use different behavioural strategies to maximize their fitness. Some behavioural traits may be consistent among individuals over time (i.e., ‘personality’ traits) resulting in an individual behavioural phenotype with different associated costs and benefits. Understanding how behavioural traits are linked to lifetime fitness requires tracking individuals over their lifetime. Here, we leverage a long-term study on a multi-year living species (maximum lifespan ~ 10 years) to examine how docility (an individual’s reaction to trapping and handling) may contribute to how males are able to maximize their lifetime fitness. Cape ground squirrels are burrowing mammals that live in social groups, and although males lack physical aggression and territoriality, they vary in docility. Males face high predation risk and high reproductive competition and employ either of two reproductive tactics (‘natal’ or ‘band’) which are not associated with different docility personalities. We found that although more docile individuals sired more offspring on an annual basis, docility did not affect an individual’s long-term (lifetime) reproductive output. Survival was not associated with docility or body condition, but annual survival was influenced by rainfall. Our findings suggest that although docility may represent a behavioural strategy to maximize fitness by possibly playing a role in female-male associations or female mate-choice, variations in docility within our study population is likely maintained by other environmental drivers. However, individual variations in behaviours may still contribute as part of the ‘tool kit’ individuals use to maximize their lifetime fitness.

Does social information affect the settlement decisions of resident birds in their second breeding attempt? A case study of the Japanese Tit (Parusminor)

Individuals may gather information about environmental conditions when deciding where to breed in order to maximize their lifetime fitness. They can obtain social information by observing conspecifics and heterospecifics with similar ecological needs. Many studies have shown that birds can rely on social information to select their nest sites. The location of active nests and the reproductive success of conspecifics and heterospecifics can provide accurate predictions about the quality of the breeding habitat. Some short-lived species can facultatively reproduce two and/or more times within a breeding season. However, few studies have focused on how multiple-brooding individuals select nest sites for their second breeding attempts. In this study, we use long-term data to test whether the Japanese Tit (Parus minor) can use social information from conspecifics and/or heterospecifics (the Eurasian Nuthatch Sitta europaea, the Daurian Redstart Phoenicurus auroreus and the Yellow-rumped Flycatcher Ficedula zanthopygia) to select a nest site for the second breeding attempt. Our results showed that the nest boxes occupied by tits on their second breeding attempt tended to be surrounded by more breeding conspecific nests, successful first nests of conspecifics, and fewer failed first nests of conspecifics than the nest boxes that remained unoccupied (the control group). However, the numbers of breeding heterospecific nests, successful heterospecific nests, and failed heterospecific nests did not differ between the nest boxes occupied by tits on their second breeding attempt and the unoccupied nest boxes. Furthermore, the tits with local successful breeding experience tended to choose areas with more successful first nests of conspecifics than those without successful breeding experience. Thus, we suggest that conspecifics' but not heterospecifics’ social information within the same breeding season is the major factor influencing the nest site selection of Japanese Tits during second breeding attempts.

Correction: Sex, personality and conspecific density influence natal dispersal with lifetime fitness consequences in urban and rural burrowing owls

Correction: Sex, personality and conspecific density influence natal dispersal with lifetime fitness consequences in urban and rural burrowing owls

Energetics of collective movement in vertebrates.

The collective directional movement of animals occurs over both short distances and longer migrations, and is a critical aspect of feeding, reproduction and the ecology of many species. Despite the implications of collective motion for lifetime fitness, we know remarkably little about its energetics. It is commonly thought that collective animal motion saves energy: moving alone against fluid flow is expected to be more energetically expensive than moving in a group. Energetic conservation resulting from collective movement is most often inferred from kinematic metrics or from computational models. However, the direct measurement of total metabolic energy savings during collective motion compared with solitary movement over a range of speeds has yet to be documented. In particular, longer duration and higher speed collective motion must involve both aerobic and non-aerobic (high-energy phosphate stores and substrate-level phosphorylation) metabolic energy contributions, and yet no study to date has quantified both types of metabolic contribution in comparison to locomotion by solitary individuals. There are multiple challenging questions regarding the energetics of collective motion in aquatic, aerial and terrestrial environments that remain to be answered. We focus on aquatic locomotion as a model system to demonstrate that understanding the energetics and total cost of collective movement requires the integration of biomechanics, fluid dynamics and bioenergetics to unveil the hydrodynamic and physiological phenomena involved and their underlying mechanisms.

Propensity for selfing varies within a population of hermaphroditic snails: coexistence of selfers, outcrossers and mixed-mating individuals.

To understand mating-system evolution in self-compatible hermaphrodites, variation in selfing rates is highly relevant. Empirical studies are rarely designed to capture variation between individuals, instead often comparing species and populations. Yet, evolution primarily occurs within populations, rendering among-individual variation essential. Observed individual selfing rates depend on the environment (e.g. differences in mate availability) and individuals' propensity for selfing. We quantified individual variation in selfing propensity in the snail Radix balthica by conducting laboratory mating trials that manipulated mate availability (low versus moderate) and estimating selfing rates from progeny arrays. We also measured female lifetime fitness. We found substantial among-individual variation in selfing propensity, including pure selfers (32%), pure outcrossers (31%) and mixed-mating individuals that selfed and outcrossed (37%). Experimental levels of mate availability did not significantly affect selfing rates. Selfers had reduced female liftetime fitness. Our results show that the propensity for selfing can differ considerably among individuals, with similar proportions of selfers, outcrossers and mixed maters. As mate availability did not affect selfing, our 'moderate' experimental level of mate availability might still have been too low to prompt selfers to outcross. This and the observed fitness differences also cautiously suggest that investigating the heritability of selfing propensities might be worthwhile in this population.

Field-work reveals a novel function for MAX2 in a native tobacco's high-light adaptions.

Laboratory studies have revealed that strigolatone (SL) and karrikin (KAR) signalling mediate responses to abiotic and biotic stresses, and reshape branching architecture that could increase reproductive performance and crop yields. To understand the ecological function of SL and KAR signalling, transgenic lines of wild tobacco Nicotiana attenuata, silenced in SL/KAR biosynthesis/signalling were grown in the glasshouse and in two field plots in the Great Basin Desert in Utah over four field seasons. Of the lines silenced in SL and KAR signalling components (irMAX2, irD14, irKAI2 and irD14 × irKAI2 plants), which exhibited the expected increases in shoot branching, only irMAX2 plants showed a strong leaf-bleaching phenotype when grown in the field. In the field, irMAX2 plants had lower sugar and higher leaf amino acid contents, lower lifetime fitness and were more susceptible to herbivore attack compared to wild-type plants. These irMAX2 phenotypes were not observed in glasshouse-grown plants. Transcriptomic analysis revealed dramatic responses to high-light intensity in irMAX2 leaves in the field: lutein contents decreased, and transcriptional responses to high-intensity light, singlet oxygen and hydrogen peroxide increased. PAR and UV-B manipulations in the field revealed that the irMAX2 bleaching phenotype is reversed by decreasing PAR, but not UV-B fluence. We propose that NaMAX2 functions in high-light adaptation and fitness optimisation by regulating high-light responses independently of its roles in the SL and KAR signalling pathways. The work provides another example of the value of studying the function of genes in the complex environments in which plants evolved, namely nature.