Female Life-history Traits Research Articles

Breeding phenology drives variation in reproductive output, reproductive costs and offspring fitness in a viviparous ectotherm.

Phenological advances are a widespread response to global warming and can contribute to determine the climate vulnerability of organisms, particularly in ectothermic species which are highly dependent on ambient temperatures to complete their life cycle. Yet, the relative contribution of breeding dates and temperature conditions during gestation on fitness of females and their offspring is poorly documented in reptiles. Here, we exposed females of the common lizard Zootoca vivipara to contrasting thermal scenarios (cold versus hot treatment) during gestation and quantified effects of parturition dates and thermal treatment on life-history traits of females and their offspring for one year. Overall, our results suggest that parturition date has a greater impact than thermal conditions during gestation on life history strategies. In particular, we found positive effects of an earlier parturition date on juvenile survival, growth and recruitment suggesting that environmental dependent selection and/or differences in parental quality between early and late breeders underlie seasonal changes in offspring fitness. Yet, an earlier parturition date compromised the energetic condition of gravid females, which suggests the existence of a mother-offspring conflict regarding the optimisation of parturition dates. While numerous studies focused on the direct effects of alterations in incubation temperatures on reptile life-history traits, our results highlight the importance of considering the role of breeding phenology in assessing the short- and long-term effects of thermal developmental plasticity.

Effects of social environments and female life history traits on sex allocation in a spider mite

Sex allocation in spider mites (Tetranychus sp.) is of interest to many researchers. They are haplodiploid species where the mated females can lay fertile and infertile eggs that develop to daughters and sons, respectively. Females tend to fertilise larger eggs (Macke et al. 2011) and adjust the offspring sex ratio under various social environments (e.g., population size and density) (e.g., Weerawansha et al. 2022a, 2022b, 2022c).

Photoperiod affects female life history traits in temperate populations of Aedes aegypti from South America

Abstract In many insects, short photoperiods induce females to lay diapausing eggs, which are associated with a reduction in female fecundity, and/or with an increase in their growth rate, allowing for a larger size at adulthood. The effects of short photoperiods may also differ among populations, depending on the different selection pressures imposed by the winter conditions. Thus, this study aimed to experimentally assess the effects of short photoperiods on Aedes aegypti, an invasive mosquito species that also vectors several viral diseases. We compared life history parameters of the females reared from the first larval instar under contrasting photoperiods, in two populations from the temperate region of Argentina, one with a milder winter (BA) and the other with a harsher winter (SB). The results showed a significant increase in the time to oviposition, a trend to a larger size of females (significant only for SB) and higher inhibition of egg hatching (more pronounced in SB), in response to short photoperiods. No differences in fecundity were detected among treatments. The different reaction norms of the populations in female body size and egg hatching response suggest an adaptation to local conditions, which might favour a further expansion of A. aegypti towards colder climates.

The glucocorticoid response to environmental change is not specific to agents of natural selection in wild red squirrels

Evolutionary endocrinology aims to understand how natural selection shapes endocrine systems and the degree to which endocrine systems themselves can induce phenotypic responses to environmental changes. Such responses may be specialized in that they reflect past selection for responsiveness only to those ecological factors that ultimately influence natural selection. Alternatively, endocrine responses may be broad and generalized, allowing organisms to cope with a variety of environmental changes simultaneously. Here, we empirically tested whether the endocrine response of female North American red squirrels (Tamiasciurus hudsonicus) was specialized or generalized. We first quantified the direction and magnitude of natural selection acting on three female life history traits (parturition date, litter size, offspring postnatal growth rate) during 32 years of fluctuations in four potential ecological agents of selection (food availability, conspecific density, predator abundance, and temperature). Only three of the four variables (food, density, and predators) affected patterns of natural selection on female life history traits. We then quantified fecal glucocorticoid metabolites (FGMs) across 7 years and found that all four environmental variables, regardless of their effects on patterns of selection, were associated with glucocorticoid production. Our results provide support for a generalized, rather than specific, glucocorticoid response to environmental change that can integrate across multiple co-occurring environmental stressors.

Movement and olfactory signals: Sexually dimorphic antennae and female flightlessness in moths

Darwin argued a role for sexual selection in the evolution of male sensory structures, including insect antennae, the strength of which will depend upon the importance of early arrival at receptive females. There is remarkable variation in the nature and degree of sexual dimorphism in moth antennae, with males of some species having spectacular, feathery antennae. Although it is widely assumed that these elaborate structures provide greater sensitivity to chemical signals (sex pheromones), the factors underlying the interspecific diversity in male antennal structure and size are poorly understood. Because male antennal morphology may be affected by several female life–history traits, including flight ability, we conducted a phylogenetic comparative analysis to test how these traits are linked, using data from 93 species of moths across 11 superfamilies. Our results reveal that elaborate antennae in males have evolved more frequently in species where females are monandrous. Further, female loss of flight ability evolved more frequently in species where males have elaborate antennae. These results suggest that elaborate antennae have evolved in response to more intense male competition, arising from female monandry, and that the evolution of elaborate antennae in males has, in turn, shaped the evolution of female flightlessness.

Geographic variation in reproductive investment of seven populations of male Brown frog (Rana kukunoris), endemic to the eastern Tibetan Plateau

Abstract Life-history theory suggests that male anurans living in harsh and unpredictable environmental conditions (e.g., low temperature and/or high seasonality) should decrease reproductive investment because of short periods of activity and poor productivity. Although geographic variations in female life-history traits have been investigated intensively across a wide range of taxa, similar studies in males have been scarce. Here, we examined geographic variation in male testis mass of the brown frog (Rana kukunoris) across seven different altitudes on the eastern Tibetan plateau, and tested the hypothesis that relative size of testis mass should increase with increasing temperature and/or decreasing seasonality. In this study, we found male body condition, age and testis mass did not increase with temperature and temperature seasonality, which do not conform to our previous hypothesis, revealing that differences in temperature and temperature seasonality across populations could not drive the evolution of testis size. However, we found a positive correlation between testis mass and body condition or age when controlling for population and the effect of temperature and temperature seasonality, indicative of a condition-dependent expression of testis size. In addition, a correlation between testis mass and operational sex ratio was not significant, suggesting that male–male competition did not lead to increasing levels of sperm competition.

Causes and consequences of variation in development time in a field cricket.

Variation in development time can affect life-history traits that contribute to fitness. In Gryllus vocalis, a non-diapausing cricket with variable development time, we used a path analysis approach to determine the causative relationships between parental age, offspring development time and offspring life-history traits. Our best-supported path model included both the effects of parental age and offspring development time on offspring morphological traits. This result suggests that offspring traits are influenced by both variation in acquisition of resources and trade-offs between traits. We found that crickets with longer development times became larger adults with better phenoloxidase-based immunity. This is consistent with the hypothesis that crickets must make a trade-off between developing quickly to avoid predation before reproduction and attaining better immunity and a larger adult body size that provides advantages in male-male competition, mate choice and female fecundity. Slower-developing crickets were also more likely to be short-winged (unable to disperse by flight). Parental age has opposing direct and indirect effects on the body size of daughters, but when both the direct and indirect effects of parental age are taken into account, younger parents had smaller sons and daughters. This pattern may be attributable to a parental trade-off between the number and size of eggs produced with younger parents producing more eggs with fewer resources per egg. The relationships between variables in the life-history traits of sons and daughters were similar, suggesting that parental age and development time had similar causative effects on male and female life-history traits.

Aquatic Exposure to Abscisic Acid Transstadially Enhances Anopheles stephensi Resistance to Malaria Parasite Infection.

The ancient stress signaling molecule abscisic acid (ABA) is ubiquitous in animals and plants but is perhaps most well-known from its early discovery as a plant hormone. ABA can be released into water by plants and is found in nectar, but is also present in mammalian blood, three key contexts for mosquito biology. We previously established that addition of ABA to Anopheles stephensi larval rearing water altered immature development and life history traits of females derived from treated larvae, while addition of ABA to an infected bloodmeal increased resistance of adult female A. stephensi to human malaria parasite infection. Here we sought to determine whether larval treatment with ABA could similarly impact resistance to parasite infection in females derived from treated larvae and, if so, whether resistance could be extended to another parasite species. We examined nutrient levels and gene expression to demonstrate that ABA can transstadially alter resistance to a rodent malaria parasite with hallmarks of previously observed mechanisms of resistance following provision of ABA in blood to A. stephensi.

Sperm number assessed by flow cytometry in species of Daphnia (Crustacea, Cladocera)

AbstractDaphnia magna and Daphnia pulex are two important model species in ecotoxicology. In daphniids, studies of the effects of contaminants have mostly focused on female life history traits, yet it would also be important to examine male reproductive traits, particularly in relation to endocrine disruptors. In this study, we developed a protocol that uses flow cytometry to measure sperm number in individual males of different species of Daphnia. We tested our protocol on 114 males from several clones of three common species of Daphnia. Sperm count varied widely among individuals and reached high numbers (up to 1.45 × 105). Positive relationships between male length and sperm number were observed in D. pulex and Daphnia pulicaria, but not in D. magna. Important inter‐clonal differences in sperm production were observed in all species, with some clones producing very little sperm. Duplicated sperm samples showed on average only 6% difference in sperm counts. Sperm counts were stable at least over a 2‐hr period and up to 5 hr for most samples. This sperm isolation protocol and flow cytometric enumeration approach will be of major interest to ecotoxicologists.

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.

Predation effects on matrotrophy, superfetation and other life history traits in Phalloceros harpagos

AbstractThis study investigates the effect of a predation gradient on the female life history traits of the poeciliid live‐bearing fish Phalloceros harpagos from a tropical stream in Brazil. Females’ length at maturity, somatic dry mass, reproductive allotment and fecundity varied significantly among predation sites. Phalloceros harpagos from the high‐predation site showed smaller size at maturity and somatic dry mass, greater reproductive allotment and higher fecundity than the nonpredation site. In all sites, we observed superfetation: pregnant females with two broods at different developmental stages. The presence of superfetation was not observed before in other congeneric species, and it may represent an additional independent evolutionary origin of superfetation in the fish family Poeciliidae. Matrotrophy, the postfertilisation maternal provisioning of nutrients to developing embryos throughout gestation, was observed in all three sites, with values of the matrotrophy index above two. The population under high predation pressure showed the highest degree of matrotrophy (embryos quadruplicate their dry mass during development) and the greatest percentage of females with superfetation (44.4%). Some life history traits responded more strongly to predators’ presence and others to predator density. These results suggest that different predation regimes shape female life history traits, increasing fecundity in high‐predation sites. The results also suggest a link between the cost of reproduction and the evolution of matrotrophy and superfetation, potentially to reduce the risk of predation without reducing fecundity.

Where and what to feed? Differential effects on fecundity and longevity in the invasive Drosophila suzukii

Successful establishment of invasive species requires that the species meet environmental conditions favouring their longevity and fecundity. When juveniles and adults consume different resources, gravid females may have to choose whether to feed or to reproduce. We used a successful invasive species to test whether female life history traits are affected by the potential nutrients found in reproductive sites. The pest species, Drosophila suzukii, lays eggs in fruits that could provide nutrients since fruit exudates are generated during oviposition. We demonstrated that D. suzukii adults cannot survive when they have only access to reproductive sites (i.e. undamaged fruits). But they can find the nutrients necessary for longevity on these reproductive sites if there are larger holes in the exocarp. Egg maturation is low when D. suzukii feeds on nutrients from fruits, even when damaged, suggesting that females cannot acquire sufficient nutrients for egg maturation where they lay their eggs. Finally, a field experiment supported our laboratory results: wild females have a low degree of egg maturation, even when captured near reproductive sites. Our study hence shows constraints on egg production, and therefore on fruit infestation, determined by the nutritional ecology of pest females.

Testing for Local Adaptation to Spawning Habitat in Sympatric Subpopulations of Pike by Reciprocal Translocation of Embryos.

We tested for local adaption in early life-history traits by performing a reciprocal translocation experiment with approximately 2,500 embryos of pike (Esox lucius) divided in paired split-family batches. The experiment indicated local adaptation in one of the two subpopulations manifested as enhanced hatching success of eggs in the native habitat, both when compared to siblings transferred to a non-native habitat, and when compared to immigrant genotypes from the other subpopulation. Gene-by-environment effects on viability of eggs and larvae were evident in both subpopulations, showing that there existed genetic variation allowing for evolutionary responses to divergent selection, and indicating a capacity for plastic responses to environmental change. Next, we tested for differences in female life-history traits. Results uncovered that females from one population invested more resources into reproduction and also produced more (but smaller) eggs in relation to their body size compared to females from the other population. We suggest that these females have adjusted their reproductive strategies as a counter-adaptation because a high amount of sedimentation on the eggs in that subpopulations spawning habitat might benefit smaller eggs. Collectively, our findings point to adaptive divergence among sympatric subpopulations that are physically separated only for a short period during reproduction and early development—which is rare. These results illustrate how combinations of translocation experiments and field studies of life-history traits might infer about local adaptation and evolutionary divergence among populations. Local adaptations in subdivided populations are important to consider in management and conservation of biodiversity, because they may otherwise be negatively affected by harvesting, supplementation, and reintroduction efforts targeted at endangered populations.

Habitat or prey specialization in predatory ladybird beetles: a case study of two closely related species

This study examines the niche and diet breadth of two closely related sympatric aphidophagous ladybirds: Adalia decempunctata and A. bipunctata. The degree of habitat specialization of these species is investigated, and its effect on life history traits of females is explored. The importance of prey quality in determining the diet breadth is also examined. The niches occupied by these species in three countries, the UK, Belgium and southern France, are similar: A. decempunctata is an arboreal habitat specialist with a narrower set of prey than A. bipunctata, which is commonly found on several types of vegetation. The niches of the two species overlap on trees. Experiments indicate that habitat specialization has resulted in A. decempunctata investing more in each of its offspring than A. bipunctata. A. decempunctata females lay, relative to their body size, heavier eggs than those of the more generalist A. bipunctata, which results in A. decempunctata having bigger larvae. In addition, A. decempunctata larvae are better at surviving starvation than A. bipunctata larvae. In contrast to the expected pattern in food specialization, our study failed to demonstrate a better efficiency of the specialist when fed its usual prey and a detrimental effect when fed on prey that it is unlikely to encounter in the field. The reproductive performance of the specialist ladybird was better when fed an aphid that it was unlikely to regularly feed on in the field. Therefore, the narrow diet of the specialist ladybird is most likely a consequence of it occupying a narrow habitat rather than the quality of the prey. Although further studies on specialization in predatory insects are needed, the results indicate that unlike the role of plant quality in host specialization in herbivorous insects, prey quality has not been the main determinant of ecological specialization in these predatory insects.

Life history ofGambusia vittata(Pisces: Poeciliidae)

Viviparous fishes of the family Poeciliidae have been model systems in the study of life histories because of their remarkable variation in life-history traits both within and among species, and because of the diversity of selective environments that they occupy. However, the life histories of several poeciliids remain unknown. In this study, we describe the life history of Gambusia vittata, a poorly known poeciliid endemic to eastern Mexico. We analyze variation in number of embryos per reproductive female, size of individual embryos, size at maturity, reproductive effort, the amount of maternal transfer of nutrients to developing embryos, and the relationship between female size and life-history traits. We collected individuals from three sites across 3 months. We found that brood size varied significantly across sites and that brood size, embryo mass, and reproductive allotment varied across months within sites. Brood size, embryo mass, and reproductive allotment all increased with female size. We found that this species exhibits moderate matrotrophy, meaning that females transfer small amounts of nutrients to embryos during development. We compare our results to other poeciliid species and provide tentative explanations for the patterns of intraspecific variation that we observed in the life history of G. vittata.

Diet-dependent cannibalism in the omnivorous phytoseiid mite Amblydromalus limonicus

Amblydromalus limonicus (Garman & McGregor) (Acari: Phytoseiidae) is a commercially available predator of key pests in protected crops, particularly of thrips and whiteflies. Basic information on the developmental and reproductive performance of the predator as a function of food is largely lacking. In the present study, development, reproduction and growth rates were determined for A. limonicus on four economically important pests: Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) and two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). The life history traits of females fed on these different target prey were compared with those of females offered Carpoglyphus lactis L. (Acari: Carpoglyphidae), which is the standard food source for mass-producing this predator. Additionally, three commercially available non-prey food sources with potential for use in the mass production or as supplementary food to sustain populations of the predator in the field were tested: the commercial pollen product Nutrimite (consisting of pollen of narrow-leaved cattail, Typha angustifolia L.), frozen eggs of the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and frozen eggs of the Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae). Survival rates of immature A. limonicus were high (>94% survival) on all tested foods except on T. vaporariorum and T. urticae (76.0% and 17.1%, respectively). The fastest development was obtained when mites were fed on T. angustifolia, whereas the longest developmental times were obtained on T. urticae and T. vaporariorum. When females were offered P. latus, no reproduction was observed, despite a high prey consumption in both the juvenile and adult stages. The reproductive performance of A. limonicus fed on T. vaporariorum was significantly lower than that on F. occidentalis. Furthermore, no second generation could be obtained on a diet solely consisting of T. vaporariorum. Population growth rates were highest when A. limonicus was fed on Nutrimite, E. kuehniella or C. lactis, and exceeded those on a diet consisting of their natural prey, F. occidentalis. The phytoseiid showed cannibalistic behavior when maintained on E. kuehniella and C. capitata eggs and T. angustifolia pollen, with females consuming their own eggs. The rate of cannibalism was dependent on the food source offered, but always resulted in reduced population growth rates. This cannibalistic behavior should be taken into account when selecting food sources for mass rearing of A. limonicus or supporting its populations in the field.

Impacts of diet quality on life‐history and reproductive traits in male and female armed beetle, Gnatocerus cornutus

1. The energy available for reproduction is usually limited by resource acquisition (i.e. condition). Because condition is known to be strongly affected by environmental factors, reproductive investments also vary across heterogeneous environments.2. Although the condition dependence of reproductive investment is common to both sexes, reproductive traits may exhibit sexually different responses to environmental fluctuation due to sex‐specific life‐history strategies. However, few direct experimental studies have investigated the condition dependence of reproductive investments in both sexes.3. We investigated the condition dependence of life‐history and reproductive traits of males and females in the beetle Gnatocerus cornutus Fabricus by manipulating larval and adult diet quality. We found that male and female life‐history traits exhibited similar responses to environmental fluctuations.4. By contrast, the sexes exhibit different patterns of condition dependence in reproductive traits (i.e. the adult nutritional environment has a strong impact on the female lifetime reproductive success, whereas larval nutritional environment strongly affects the secondary sexual trait in males).5. This difference in the plasticity of reproductive traits may lead to different selection pressures for each sex, even if both sexes develop and/or live in the same environment.

Genetic Analysis of Life-History Constraint and Evolution in a Wild Ungulate Population

Trade-offs among life-history traits are central to evolutionary theory. In quantitative genetic terms, trade-offs may be manifested as negative genetic covariances relative to the direction of selection on phenotypic traits. Although the expression and selection of ecologically important phenotypic variation are fundamentally multivariate phenomena, the in situ quantification of genetic covariances is challenging. Even for life-history traits, where well-developed theory exists with which to relate phenotypic variation to fitness variation, little evidence exists from in situ studies that negative genetic covariances are an important aspect of the genetic architecture of life-history traits. In fact, the majority of reported estimates of genetic covariances among life-history traits are positive. Here we apply theory of the genetics and selection of life histories in organisms with complex life cycles to provide a framework for quantifying the contribution of multivariate genetically based relationships among traits to evolutionary constraint. We use a Bayesian framework to link pedigree-based inference of the genetic basis of variation in life-history traits to evolutionary demography theory regarding how life histories are selected. Our results suggest that genetic covariances may be acting to constrain the evolution of female life-history traits in a wild population of red deer Cervus elaphus: genetic covariances are estimated to reduce the rate of adaptation by about 40%, relative to predicted evolutionary change in the absence of genetic covariances. Furthermore, multivariate phenotypic (rather than genetic) relationships among female life-history traits do not reveal this constraint.

Acclimation of life‐history traits to experimental changes in environmental contaminant concentrations in brown bullhead (Ameiurus nebulosus)

One adaptive mechanism aquatic populations use to facilitate tolerance to environmental contaminants is acclimation. Polychlorinated biphenyls (PCBs) are a globally ubiquitous class of persistent organic contaminants that have been linked to reproductive impairments in fish. The authors used female brown bullhead (Ameiurus nebulosus) to test whether acclimation of reproductive life-history traits occurs in response to changes in sum PCB exposure. They compared egg diameter, gonadosomatic index (GSI), and fecundity of fish directly caught from wild populations exposed to a range of contaminant concentrations (acute), to those collected from the same populations a year before, which were placed in a clean environment to clear their contaminants throughout that year (cleared). Sum PCB concentrations were also determined for each individual. Brown bullhead from acute treatments had significantly greater sum PCB concentrations compared with cleared treatments. Egg diameter and GSI metrics were greater in cleared treatments compared with acute treatments (by 6 and 14%, respectively). Treatment effect (i.e., acute or cleared), as opposed to where the fish were collected from, accounts for 72 to 89% of the variation in the reproductive life-history trait variables. No difference in fecundity was found between acute and cleared treatments. The authors found support that acclimation of reproductive life-history traits occurs to changes in sum PCB concentration. To their knowledge, the present study is the first experimental test of acclimation responses of female life-history traits to contaminants in wild populations.

LIFE HISTORY TRAITS OF ODONTOSTILBE PEQUIRA (STEINDACHNER, 1882) IN THE PANTANAL OF PORTO MURTINHO, MATO GROSSO DO SUL STATE, BRAZIL

This study aimed to analyze the life history traits of females and males of Odontostilbe pequira, and correlate the recruitment of both sexes with the variation in the flood pulse of Paraguay River. The samplings were performed every month between February 2009 to January 2011, along the main channel of Paraguay River and its tributary (Amonguijá River) and the marginal lakes Criminosa and Flores. Length data were taken from 977 individuals of Odontostilbe pequira (564 females and 413 males). The equation that describes the relationship weight/length for females is Total weight=0.0000183*Standard length 2.95, and for males, Total weight=0.0000105*Standard length 3.10 , with isometric growth for females and positive allometric for males. The asymptotic length (L?) estimated for females was greater (39.59mm) than for males (37.57mm). Females also had higher growth rate (k=0.93 year -1 , Rn=0.35) and natural mortality rate (Z=1.56 year -1 ) than males (k=0.82 year -1 , Rn= 0.27, Z= 1.45 year -1 ). Through the growth curves, generated by the distribution of length classes, it was registered 3 complete cohorts for females, with longevity estimated at 3.22 years, and 4 cohorts for males with longevity of 3.65 years. The growth performance index values (?) were close to 3 and similar between females (?= 3.16) and males (?= 3.06). The recruitment pattern was long for females and males of O. pequira , without significant variation in the recruitment distribution (p=0.77) between sexes. The recruitment peak occurred in July and June, for females and males, respectively. There was correlation between the recruitment and the water level of the river for both sexes (females: r=0.91, p