Reproductive Constraints Research Articles

Severe fire regimes decrease resilience of ectothermic populations.

Understanding populations' responses to environmental change is crucial for mitigating human-induced disturbances. Here, we test hypotheses regarding how three essential components of demographic resilience (resistance, compensation and recovery) co-vary along the distinct life histories of three lizard species exposed to variable, prescribed fire regimes. Using a Bayesian hierarchical framework, we estimate vital rates (survival, growth and reproduction) with 14 years of monthly individual-level data and mark-recapture models to parameterize stochastic integral projection models from five sites in Brazilian savannas, each historically subjected to different fire regimes. With these models, we investigate how weather, microclimate and ecophysiological traits of each species influence their vital rates, emergent life history traits and demographic resilience components in varying fire regimes. Overall, weather and microclimate are better predictors of the species' vital rates, rather than their ecophysiological traits. Our findings reveal that severe fire regimes increase populations' resistance but decrease compensation or recovery abilities. Instead, populations have higher compensatory and recovery abilities at intermediate degrees of fire severity. Additionally, we identify generation time and reproductive output as predictors of resilience trends across fire regimes and climate. Our analyses demonstrate that the probability and quantity of monthly reproduction are the proximal drivers of demographic resilience across the three species. Our findings suggest that populations surpass a tipping point in severe fire regimes and achieve an alternative stable state to persist. Thus, higher heterogeneity in fire regimes can increase the reproductive aspects and resilience of different populations and avoid high-severity regimes that homogenize the environment. Despite being more resistant, species with long generation times and low reproductive output take longer to recover and cannot compensate as much as species with faster paces of life. We emphasize how reproductive constraints, such as viviparity and fixed clutch sizes, impact the ability of ectothermic populations to benefit and recover from disturbances, underscoring their relevance in conservation assessments.

Dietary differences in males and females of a strongly sexually dimorphic ungulate

Detailed knowledge of dietary preferences in wild species are important both for understanding evolutionary processes as well as for their conservation. By means of DNA metabarcoding analysis of faecal samples, we investigated the diet of Alpine ibex (Capra ibex), a mountain ungulate characterised by strong sexual dimorphism and segregation, and analysed differences between male and female diet. Despite a low level of selectivity, we found differences in the diet of males and females that consumed different plant in different quantities. Differences were maintained during both spring and summer. Males tended to feed more on plants richer in fibres (i.e., grasses and sedges) and showed stronger seasonal differences while females consumed more digestible plant families (i.e., forbs). Differences in diet between male and female Alpine ibex are compatible with the strong sexual dimorphism and segregation typical of the species and with female reproductive constraints. These results also show that conservation actions have to take into account different ecological needs of males and females in species characterized by sexual dimorphism and segregation.

Production systems and breeding practices of Begaria cattle breed as input for a community-based breeding program

This study aimed to describe the production systems and breeding practices of Begaria cattle breeds as a resource for community-based conservation and breeding program. A semi-structured questionnaire and focus group discussions were employed to identify and describe the breeding practice of the farmer. Three kebeles: Almahal, Fanguso, and Mankush were considered for the study. The data were analyzed using R software. Cattle were kept for a variety of reasons, including milk, breeding, meat, cash, and saving. It was typical throughout the study area to see herd mixing and keeping together (4.7 ± 0.33 herds on average), herd movement during the dry season, and breeding bull sharing (1.9 ± 1.55 shared bulls). During the summer season, cattle rearing in the areas was hindered by feed and water shortages. The breed's major reproduction constraints were abortion (24 %), repeat breeding (19), and calf mortality (14). The primary reason for keeping Begaria cattle was for milk (29 %), cash (26), meat (22), and breeding (0.22). The average age at first calving (AFC), calving interval (CI) and milk yield per day of the breed were 41.5 ± 1.63, 16.0 ± 0.43 months, and 3.2 ± 0.12 L respectively. The average age of breeding bull selection was 3 ± 0.1 years, and it was based on several criteria, including their phenotype, growth, and white coat colour. Based on the current findings, it is recommended that a multi-trait selection program be designed with full stakeholder participation.

Biophysical ordering transitions underlie genome 3D re-organization during cricket spermiogenesis

Spermiogenesis is a radical process of differentiation whereby sperm cells acquire a compact and specialized morphology to cope with the constraints of sexual reproduction while preserving their main cargo, an intact copy of the paternal genome. In animals, this often involves the replacement of most histones by sperm-specific nuclear basic proteins (SNBPs). Yet, how the SNBP-structured genome achieves compaction and accommodates shaping remain largely unknown. Here, we exploit confocal, electron and super-resolution microscopy, coupled with polymer modeling to identify the higher-order architecture of sperm chromatin in the needle-shaped nucleus of the emerging model cricket Gryllus bimaculatus. Accompanying spermatid differentiation, the SNBP-based genome is strikingly reorganized as ~25nm-thick fibers orderly coiled along the elongated nucleus axis. This chromatin spool is further found to achieve large-scale helical twisting in the final stages of spermiogenesis, favoring its ultracompaction. We reveal that these dramatic transitions may be recapitulated by a surprisingly simple biophysical principle based on a nucleated rigidification of chromatin linked to the histone-to-SNBP transition within a confined nuclear space. Our work highlights a unique, liquid crystal-like mode of higher-order genome organization in ultracompact cricket sperm, and establishes a multidisciplinary methodological framework to explore the diversity of non-canonical modes of DNA organization.

Untimely endangerment in endemic trees of Western Ghats, India: An ecological and biological perspective

The study unravels the ecological and biological parameters leading to untimely endangerment of three endemic and threatened tree species viz. Drypetes malabarica, Hydnocarpus macrocarpus and Prioria pinnata, distributed in the southern Western Ghats. Population structure and diversity along with population dynamics of the target species were explored. The reproductive constraints including insect-pest incidence, low abundance, habitat specificity along with human induced habitat threats upsurges the possibilities of rarity of these species in the Kerala part of the Western Ghats.

Unravelling the influence of annual weather conditions and Mediterranean habitat types on acorn production, availability and predation

Seed production and survival are critical steps in the life cycle of plants, and could become bottlenecks for plant regeneration in case of failure. During regeneration many factors, both abiotic and biotic, intervene and interact with each other. After dispersal, environmental variation affects the success of the plant population, so seedling recruitment can display spatial variability. However, few studies of seed production and availability cover a range of habitat conditions (e.g. mature, transitional and post-fire habitats), which makes it difficult to evaluate the potential of site-production relationships. We study how the heterogeneity of habitat structure and composition affects the phenology, production and availability of acorns, mainly holm oak, in a Mediterranean Natural Park. Our results show that meteorological variables determine the phenology of acorn fall. Habitat types present temporal mismatches in falls since, for example, shrublands required a longer period of time for all seeds to fall. Furthermore, habitats with greater tree density and low understory complexity had higher production but smaller acorns. Lower densities promote higher acorn volume (seedling size) as a consequence of less intraspecific competition and more reserves for germination. The proportion of viable acorns available on the ground also decreased substantially in winter, when the proportion of infested acorns increase because the selective consumption of sound acorns by predators. Acorns from mixed forests and shrublands had less pre-dispersal predation by arthropods and post-dispersal predation by wild boar as a result of oak isolation and understory complexity. Conversely, rodents are more abundant in shrublands, where they find a greater diversity of anti-predator refuges and large nutritious acorns available in autumn and winter. Understanding the reproductive constraints imposed by time and space allows us to infer the consequences of environmental changes on population recruitment and persistence. We thus show that habitats with a high density of oak trees, less plant diversity and understory cover had a greater prevalence of infested acorns, thereby reducing recruitment viability. These habitats also had more available acorns on the ground for seed predators. Therefore, habitat type is an important factor affecting acorn production and should be taken into account in future studies.

Relationship analysis of Scalloped Hammerhead (Sphyrna lewini) from West Aceh Waters using molecular genetics approach

Hammerhead sharks are particularly vulnerable to fishing because of their slow growth rate and reproductive constraints. This type of sharks needs special attention due to its conservation status. This research was aimed to describe the relationships of the hammerhead sharks from West Aceh waters with the hammerhead sharks from other places. Samples of the shark were collected from Ujong Baroh Fish Port, West Aceh. The samples were analysed at the Laboratory of Department of Marine Science and Fisheries, Syiah Kuala University. The laboratory activity was started with extraction of DNA enhanced by Polymerase Chain Reaction method and visualized by an electrolytical. Analysis using BLAST showed that the first sample obtained 94%-95% cover query value and produced a 683 base pair length while the second sample obtained 98% per sample for a cover query value and produced a 658 base pair length. The average nucleotide values of the hammerhead shark were T=32.8, C=26.6, A=25.7 and G=14.9. The phylogenetic tree shows that the hammerhead sharks from the study area were more similar to the hammerhead sharks from Australia and Malaysia. Overall, based on the nucleotide composition, phylogenetic tree and genetic distance, the hammerhead sharks from the study area are unique compared to the populations from the other places.

Review of the botany, traditional uses, pharmacology, threats and conservation of Zanthoxylum armatum (Rutaceae)

• The high medical value of Zanthoxylum armatum has raised concern for its long-term sustainability. • The study reviews botany, uses, and threats, and offers suggestions for the sustainable utilization of the species. • Pharmaceutical potential of the species is well explored and reproductive constraints are well recognized. • Viable cultivation methods and sustainable harvesting techniques are urgently needed for its conservation. Zanthoxylum armatum has fascinated the botanical world due to its significance as the ‘toothache relieving tree'. The high medical value of the species has raised concern for its long-term sustainability. The genus Zanthoxylum is represented by 225 species, distributed throughout the globe. Among others, Z. armatum is a high-value species, facing threats due to destructive harvesting and constraints in its reproduction. This study reviews botany, traditional uses, pharmacology, threats, and offers suggestions for the sustainable utilization of the species. Findings indicate that the pharmaceutical potential of the species is well explored and reproductive constraints are well recognized. Overharvesting is a major threat to its existing populations. Viable cultivation methods and sustainable harvesting techniques are urgently needed for its conservation and sustainable utilization.

When the "satisficing" is the new "fittest": how a proscriptive definition of adaptation can change our view of cognition and culture.

Since Darwin’s theory of evolution, adaptationism is frequently invoked to explain cognition and cultural processes. Adaptationism can be described as a prescriptive view, as phenotypes that do not optimize fitness should not be selected by natural selection. From an epistemological perspective, the principle of a prescriptive definition of adaptation seems incompatible with recent advances in epigenetics, evolutionary developmental biology, ethology, and genomics. From these challenges, a proscriptive view of adaptation has emerged, postulating that phenotypes that are not deleterious will be evolutionary maintained. In this epistemological investigation, we examine how the shift from adaptationism to a proscriptive view changes our view of cognition and culture. We argue that, while adaptationism leads to cognitivism and a view of culture as strategies to optimize overall fitness, the proscriptive definition favors embodied theories of cognition and a view of culture as the cumulative diffusion of behaviors allowed by the constraints of reproduction.

Active season body mass patterns of little brown and northern myotis bats.

Animals are expected to adjust their behavioral patterns to improve fitness outcomes, such as fecundity or offspring survival. For long-lived hibernators, decisions made in each annual cycle may reflect considerations not just for concurrent survival and reproduction but also the pressure to maximize overwinter survival and future reproductive success. We examined how these elements manifest themselves in the body mass variation patterns of North American northern latitude temperate bats, whose size and roosting habits present considerable monitoring challenges. We characterized and compared the summer and fall mass variation patterns of little brown myotis (Myotis lucifugus) and northern myotis (M. septentrionalis) from a historic dataset. In summer, the estimated date of parturition was strongly associated with spring foraging conditions (low wind, low precipitation, and warm temperatures), and mass gain associated with female reproduction conferred considerable differentiation between the mass variation patterns of females and males. In fall, differences were most apparent among species, although adults exhibited a greater capacity for rapid mass gain than juveniles. These results demonstrate how reproductive constraints and interannual survival have important influences on the behavior of temperate bats. Future work should seek to quantify the fitness benefits of patterns identified in this study, such as the rate of prehibernation mass gain.

The cost of host genetic resistance on body condition: Evidence from divergently selected sheep.

Trade‐offs between host resistance to parasites and host growth or reproduction can occur due to allocation of limited available resources between competing demands. To predict potential trade‐offs arising from genetic selection for host resistance, a better understanding of the associated nutritional costs is required. Here, we studied resistance costs by using sheep from lines divergently selected on their resistance to a common blood‐feeding gastro‐intestinal parasite (Haemonchus contortus). First, we assessed the effects of selection for high or low host resistance on condition traits (body weight, back fat, and muscle thickness) and infection traits (parasite fecal egg excretion and loss in blood haematocrit) at various life stages, in particular during the periparturient period when resource allocation to immunity may limit host resistance. Second, we analysed the condition–infection relationship to detect a possible trade‐off, in particular during the periparturient period. We experimentally infected young females in four stages over their first 2 years of life, including twice around parturition (at 1 year and at 2 years of age). Linear mixed‐model analyses revealed a large and consistent between‐line difference in infection traits during growth and outside of the periparturient period, whereas this difference was strongly attenuated during the periparturient period. Despite their different responses to infection, lines had similar body condition traits. Using covariance decomposition, we then found that the phenotypic relationship between infection and condition was dominated by direct infection costs arising from parasite development within the host. Accounting for these within‐individual effects, a cost of resistance on body weight was detected among ewes during their first reproduction. Although this cost and the reproductive constraint on resistance are unlikely to represent a major concern for animal breeding in nutrient‐rich environments, this study provides important new insights regarding the nutritional costs of parasite resistance at different lifestages and how these may affect response to selection.

Age-related differences in foraging behaviour at sea and interactions with fishing vessels in an opportunistic urban gull

Abstract Fishing activity generates high amounts of fishing discards, a predictable anthropogenic food subsidies used by seabirds. Although the use of discards by these predators has been well studied, there is a lack of knowledge about the ontogenetic differences in their use. We contributed to filling this gap for the yellow-legged gull (Larus michahellis), an opportunistic predator that extensively exploits anthropogenic food subsides. We investigated its foraging behaviour during the early breeding season deploying GPS devices on adults, immatures, and juveniles from the urban population of Barcelona (northwestern Mediterranean Sea) and examining the effect of fishing vessels on their spatial movements using a Vessel Monitoring System. The results revealed age-related differences in distribution and foraging behaviour at sea and an interaction with fishing vessels in this seabird. Age-related differences in behaviour were explained by the reproductive constraints of adults and the ontogenetic differences associated with lower foraging ability in immature and juvenile individuals. We did not find apparent preferences for a specific type of fishing vessel between ages. These results suggest that the reform of the Common Fisheries Policy might affect the entire population of this species, that could lead to an increase in the use of urban environments, increasing the conflicts with human activities.

Dancing drives evolution of sexual size dimorphism in manakins.

Body size mediates life history, physiology and inter- and intra-specific interactions. Within species, sexes frequently differ in size, reflecting divergent selective pressures and/or constraints. Both sexual selection and differences in environmentally mediated reproductive constraints can drive sexual size dimorphism, but empirically testing causes of dimorphism is challenging. Manakins (Pipridae), a family of Neotropical birds comprising approximately 50 species, exhibit a broad range of size dimorphism from male- to female-biased and are distributed across gradients of precipitation and elevation. Males perform courtship displays ranging from simple hops to complex aerobatic manoeuvres. We tested associations between sexual size dimorphism and (a) agility and (b) environment, analysing morphological, behavioural and environmental data for 22 manakin species in a phylogenetic framework. Sexual dimorphism in mass was most strongly related to agility, with males being lighter than females in species performing more aerial display behaviours. However, wing and tarsus length dimorphism were more strongly associated with environmental variables, suggesting that different sources of selection act on different aspects of body size. These results highlight the strength of sexual selection in shaping morphology-even atypical patterns of dimorphism-while demonstrating the importance of constraints and ecological consequences of body size evolution.

Reproductive biology of two threatened and highly traded medicinal plants, Salacia gambleana and Salacia oblonga, from the Western Ghats of India

Salacia is a genus of flowering plants in the family Celastraceae, consisting of woody climbers distributed in tropical America, Africa, and Asia. In India it is represented by 21 species, of which 15 occur in peninsular India. Most species of the genus have been used in traditional medicine, mainly the Ayurvedic system. Apart from overexploitation for medicinal purposes, the low fruit set and infestation of seeds have affected natural regeneration, and led to the rarity of Salacia species in their natural habitats. The reproductive biology of Salacia oblonga and S. gambleana was studied for the first time to understand the reproductive constraints of these threatened and medicinally important species. The flowering phenology, pollen viability, germination, stigma receptivity, and insect-pest interaction were analyzed. The obligatory entomophily coupled with insufficient pollinators and seed pest infestation were found to be the main reproductive constraints responsible for the low fruit set and poor natural regeneration of these species.

Reproductive constraint in the social aphid Ceratovacuna japonica: Sterility regulation in the soldier caste of a viviparous insect

Differentiation of the non-reproductive caste is a unique feature of eusocial insects. Apoptosis in oocytes plays a major role in constraining the reproductivity of the eusocial insects including bees, ants, and termites. However, the regulation of reproductive constraint in non-reproductives of primitively eusocial insects other than hymenopterans and blattodeans is almost unknown. Here, we investigated the soldier sterility in a hemipteran insect, the social aphid Ceratovacuna japonica. We compared the gonads of soldiers, that are completely sterile, with those of reproductives in their viviparous development. We found that soldiers possess a pair of ovaries and the same number of germaria as reproductives, but soldiers’ ovarioles were small and lacking gastrulating embryos. Unlike in most model social insects, the staining of cleaved Caspase-3 showed apoptosis in the maternal nutritive cells, rather in the oocyte, of soldier ovaries. In addition, the ubiquitous C. japonica vasa1 and piwi2a expression indicates the developmental failure of embryos in soldier ovaries. The absence of posterior nos1, an insect posterior determinant, indicates deficient posterior patterning in soldier ovarioles. Our findings suggest a different mode of reproductive constraint, which regulates both oogenesis and embryogenesis in a viviparous insect ovary. This is the first report of the reproductive constraint in a viviparous social insect at the molecular level.

Assessment on major production constraints, and reproductive performances of camel in West Hararghe Zone Oromia Ethiopia

The study was conducted in Mieso and Bordede districts, in West Hararghe Zone of Oromiya National Regional State with the objectives of assessing major constraints of camel production, reproductive performances, and physicochemical quality of camel milk in the study areas. A total of 120 households (camel owners) were selected purposively for interview (i.e 20 households from each kebeles). Feed shortage, conflict over the scarcity of natural resources, low productivity of grazing land, and water scarcity were the main constraints of camel production. The mean age at first mating for male and female camels was 5.92±2.91 and 4.79±1.84 years respectively, similarly, the average number of services per conception of camels in this finding was 1.73±0.64. The reproductive span of male and female camels in the study area were 20.04±6.50 and 25.20±7.83 years, respectively and the gestation period of camels recorded in this study was 1.73±0.64. The lactation length of a camel was 9.77±2.10 and 17.30±5.66 months in Mieso and Bordede, respectively. Late maturity is reported as the primary reproductive constraint followed by long calving interval, the presence of reproductive disease, low conception rate and the birth of stunted calves in Mieso district. Whereas in Bordede district the primary reproductive constraints were late maturity followed by the presence of reproductive disease, long calving interval, low conception rate and birth of stunted calf. In conclusion, camel is one of the most important livestock for pastoralists’ livelihood as a source of milk, meat and draught power. In order to increase the productivity of camels, the major constraints such as shortage of feed and water, disease problems and others should be given attention.

Aconitum heterophyllum Wall. ex Royle: An Endemic, Highly Medicinal and Critically Endangered Plant Species of Northwestern Himalaya in Peril

: Aconitum heterophyllum is a precious endemic medicinal plant of Northwestern Himalaya. It possesses a number of curative effects and is accounted for having diuretic, hepatoprotective, antipyretic, analgesic, antioxidant, alexipharmic, anodyne, anti-atrabilious, expectorant, immunostimulant, febrifuge, anthelminthic, anti- cancerous, anti-diarrhoeal, anti-emetic, anti-inflammatory, anti-flatulent, anti-periodic, anti-phlegmatic, anti-diabetic, antifungal, antimicrobial, antiviral and carminative properties. Further, it is an important ingredient of many Ayurvedic formulations. Its pharmacological potential may be attributed to of the presence of many biologically active phytochemicals like aconitine, mesaconitine, acetylaconitine, heterophylline A, and heterophylline B. Owing to its high therapeutic uses and market value, the plant is being exploited for its tubers from the wild. Further, there are some reproductive constraints due to which the population of the plant in the wild is waning at a rapid rate. Due to these factors, Aconitum heterophyllum has been categorized as critically endangered; demanding focused conservation strategies and cultivation efforts.

Staying close to home: Ecological constraints on space use and range fidelity in a mountain ungulate.

Understanding patterns of animal space use and range fidelity has important implications for species and habitat conservation. For species that live in highly seasonal environments, such as mountain goats (Oreamnos americanus), spatial use patterns are expected to vary in relation to seasonal changes in environmental conditions and sex‐ or age‐specific selection pressures. To address hypotheses about sex, age, and seasonality influence on space‐use ecology, we collected GPS location data from 263 radio‐collared mountain goats (males, n = 140; females, n = 123) in coastal Alaska during 2005–2016. Location data were analyzed to derive seasonal and sex‐specific fixed‐kernel home range estimates and to quantify the degree of seasonal range and utilization distribution overlap. Overall, we determined that home range size was smallest during winter, expanded coincident with the onset of green‐up and parturition, and was largest during summer. Home range size of males and females did not differ significantly during winter, but females had larger home ranges than males during summer, a relationship that was switched during the mating season. Pairwise comparisons involving individual females across subsequent years indicated home ranges were significantly smaller during years when they gave birth to offspring. Mountain goats exhibited a strong degree of range fidelity, and 99% (n = 138) of individual animals returned to their previous year's seasonal range with an average annual Bhattacharyya's affinity utilization distribution overlap index of 68%. Similarity of seasonal home range utilization distributions varied in relation to sex and season in some respects. Home range overlap was highest during the summer vegetation growing season, particularly among females. These findings advance our understanding about how environmental variation and sex‐ and age‐related reproductive constraints influence space use and range fidelity among alpine ungulates. Documentation of the high degree of range fidelity among mountain goats has important conservation implications in landscapes increasingly altered by anthropogenic activities.

Sex‐specific migratory behaviors in a temperate ungulate

AbstractSexual segregation has been intensely studied across diverse ecosystems and taxa, but studies are often limited to periods when animals occupy distinct seasonal ranges. Some avian and marine studies have revealed that habitat segregation, when sexes differ spatially or temporally in use of the physical landscape, is common during the migratory period and characterized by sex‐specific differences in migratory behaviors. Recent research highlights the importance of understanding movement patterns in the context of the full annual life cycle and highlights the need to extend relevant theories of sexual segregation to the migratory period. We tested predictions from two leading hypotheses of sexual segregation, the forage‐selection hypothesis (FSH) and the reproductive strategy hypothesis (RSH) as applied to the migratory period. We collected global positioning system (GPS) location data for male and female mule deer (Odocoileus hemionus) in south‐central Wyoming and northwest Colorado and tested the main predictions of the FSH and RSH. Both sexes showed high fidelity to their migratory routes, but route fidelity was more variable in males. Males also started spring migrations earlier, ended spring and autumn migrations later, and spent 22% more time on stopover sites during spring migrations. Consequently, males took twice as long in spring and 44% longer in autumn to complete migration. Our results revealed clear sex‐specific migratory behaviors and supported predictions of the RSH that male foraging behaviors optimize body condition for the autumn rut, and females prioritize foraging while balancing reproductive constraints. Specifically, males timed their movements with spring green‐up as optimally as females, and the timing of male migrations and use of stopovers suggested that males prioritized time in areas of high‐quality forage. This refutes predictions of the FSH during the migratory period that males should consistently choose habitats with abundant, low‐quality forage. Our findings provide an important contribution to sexual segregation theory by extending relevant theories to understand male and female movements during the migratory period.

Experimentally constrained early reproduction shapes life history trajectories and behaviour

The trade-off between current and future reproduction is a cornerstone of life history theory, but the role of within-individual plasticity on life history decisions and its connections with overall fitness and behaviour remains largely unknown. By manipulating available resources for oviposition at the beginning of the reproductive period, we experimentally constrained individual life history trajectories to take different routes in a laboratory study system, the beetle Callosobruchus maculatus, and investigated its causal effects on fecundity, survival and behaviour. Compared to females without resource limitations, females experiencing restricted conditions for oviposition had reduced fecundity early in life but increased fecundity when resources became plentiful (relative to both the previous phase and the control group) at the expense of longevity. Constrained reproduction in early life also affected behaviour, as movement activity changed differently in the two experimental groups. Experiencing reproductive constraints has, therefore, consequences for future reproduction investments and behaviour, which may lead individuals to follow different life history strategies.