Parental Investment In Relation Research Articles

Invasive predators induce plastic and adaptive responses during embryo development in a threatened frog

Invasive predators can strongly affect native populations. If alien predator pressure is strong enough, it can induce anti-predator responses, including phenotypic plasticity of exposed individuals and local adaptations of impacted populations. Furthermore, maternal investment is an additional pathway that could provide resources and improve performance in the presence of alien predators. We investigated the potential responses to an alien predator crayfish (Procambarus clarkii) in a threatened frog (Rana latastei) by combining field observations with laboratory measurements of embryo development rate, to assess the importance of parental investment, origin and exposure to the crayfish cues. We detected a strong variation in parental investment amongst frog populations, but this variation was not related to the invasion status of the site of origin, suggesting that mothers did not modulate parental investment in relation to the presence of alien predators. However, cues of the invasive crayfish elicited plastic responses in clutches and tadpoles development: embryos developed faster when exposed to the predator. Furthermore, embryos from invaded sites reached Gosner’s development stage 25 faster than those from non-invaded sites. This ontogenetic shift can be interpreted as a local adaptation to the alien predator and suggests that frogs are able to recognise the predatory risk. If these plastic responses and local adaptation are effective escape strategies against the invasive predator, they may improve the persistence of native frog populations.

Parental Investment Under Predation Threat in Incubating Common Eiders (Somateria mollissima): A Hormonal Perspective

Predation risk affects the costs and benefits of prey life-history decisions. Predation threat is often higher during reproduction, especially in conspicuous colonial breeders. Therefore, predation risk may increase the survival cost of breeding, and reduce parental investment. The impact of predation risk on avian parental investment decisions may be hormonally mediated by prolactin and corticosterone, making them ideal tools for studying the trade-offs involved. Prolactin is thought to promote parental care and commitment in birds. Corticosterone is involved in allostasis and may either mediate reduced parental investment (corticosterone-fitness hypothesis), or promote parental investment through a reallocation of resources (corticosterone-adaptation hypothesis). Here, we used these hormonal proxies of incubation commitment to examine the impact of predation risk on reproduction in common eiders (Somateria mollissima) breeding in the Baltic Sea. This eider population is subject to high but spatially and temporally variable predation pressure on adults (mainly by the white-tailed eagle Haliaeetus albicilla and introduced mammalian predators) and nests (by the adult predators and exclusive egg predators such as hooded crows Corvus cornix). We investigated baseline hormonal levels and hatching success as a function of individual quality attributes (breeding experience, female and duckling body condition), reproductive investment (clutch weight), and predation risk. We expected individuals nesting in riskier environments (i.e., on islands where predation on adults or nests is higher, or in less concealed nests) to reduce their parental investment in incubation, reflected in lower baseline prolactin levels and either higher (corticosterone-fitness hypothesis) or lower (corticosterone-adaptation hypothesis) baseline corticosterone levels. Contrary to our predictions, prolactin levels showed a positive correlation with nest predation risk. The unexpected positive relationship could result from the selective disappearance of low-quality females (presumably having low prolactin levels) from risky sites. Supporting this notion, female body condition and hatching success were positively correlated with predation risk on females, and baseline prolactin concentrations were positively correlated with duckling body condition, a proxy of maternal quality. In line with the corticosterone-adaptation hypothesis, baseline corticosterone levels increased with reproductive investment, and were negatively associated with nest predation risk. Hatching success was lower on islands where nest predation risk was higher, consistent with the idea of reduced reproductive investment under increased threat. Long-term individual-based studies are now needed to distinguish selection processes occurring at the population scale from individually plastic parental investment in relation to individual quality and variable predation risk.

Breeding behaviour and time-activity budgets of Bonelli’s Eagles Aquila fasciata: marked sexual differences in parental activities

ABSTRACT Capsule: Differences in parental investment between sexes and stage of the breeding period were found in Bonelli’s Eagles Aquila fasciata. Aims: To describe the sexual differences in parental behaviour of Bonelli’s Eagles and to assess the sex-specific pattern of variation in parental investment in relation to the breeding period. Methods: Between 2006 and 2016, we monitored the parental behaviour of 11 pairs of Bonelli’s Eagles during the incubation and chick-rearing periods in southeastern Spain. Observations were made using 20–60× telescopes from points overlooking the territory at a distance of about 500–800 m from the nest. Results: Our results reveal a marked division in parental duties in Bonelli’s Eagles. Females invested more effort in incubation, nest attendance, chick feeding and nest-building, while males contributed more to food provisioning. Nest attendance and feeding by females decreased with time, and both parents adjusted their provisioning effort in relation to nestling age. Most changeovers took place during the middle of the day, when male provisioning rates and temperatures reach their maximum. Conclusion: Intersexual differences are discussed in the context of the prey capture difficulty hypothesis, which proposes that intra-pair prey differences, due to large sexual size dimorphism, should be particularly advantageous among raptors that pursue agile prey.

Quantity discrimination in parental fish: female convict cichlid discriminate fry shoals of different sizes.

Numerical abilities have been found to be adaptive in different contexts, including mating, foraging, fighting assessment and antipredator strategies. In species with parental care, another potential advantage is the possibility to adjust parental behavior in relation to the numerosity of the progeny. The finding that many fish vary their parental investment in relation to brood size advocates the existence of a mechanism for appraising offspring number, an aspect that has never been directly investigated. Here we tested the ability of parental female convict cichlid (Amatitlania nigrofasciata) to discriminate between two fry groups differing in number by measuring time spent attempting to recover groups of fry experimentally displaced from the next. Females spent more time trying to recover the fry from larger groups when tested with contrasts 6 versus 12 (1:2) and 6 versus 9 fry (2:3); however, they showed no preference in the 6 versus 8 (3:4) contrast, suggesting that this task exceeds their discrimination capacity.

Opposite differential allocation by males and females of the same species

Differential allocation (DA)-the adjustment of an individual's parental investment in relation to its mate's attractiveness-is increasingly recognized as an important component of sexual selection. However, although DA is expected by both sexes of parents in species with biparental care, DA by males has rarely been investigated. We have previously demonstrated a decrease in the feeding rates of female blue tits Cyanistes caeruleus when their mate's UV coloration was experimentally reduced (i.e. positive DA). In this study, we used the same experimental protocol in the same population to investigate DA by male blue tits in relation to their female's UV coloration. Males mated to UV-reduced females had higher feeding rates than those mated to control females (i.e. negative DA). Thus, male and female blue tits display opposite DA for the same component of parental effort (chick provisioning), the first time that this has been reported for any species.

Factors affecting plasma biochemistry parameters and physical condition of Osprey (Pandion haliaetus) nestlings

We assessed the normal values for 15 blood plasma biochemistry parameters and three indices of body condition (IBCs) in free-living Osprey (Pandion haliaetus) nestlings in Brandenburg (Germany). Values were compared with those of other raptors, and possible sexual and age-related differences were examined. In addition, we looked for possible relationships of habitat quality (measured in terms of foraging conditions and human disturbances) to nestling nutritional condition and productivity. Female nestlings showed higher mean urea levels and lower glucose values than males, which could be related to higher growth rates and nutrient demand of females at the end of the nestling period. Seven parameters also showed variation with age, probably relating to increasing body mass, metabolic rates, and physical activity during the pre-fledging stage. Conversely, the IBCs showed poor correlations with selected nutritional parameters, probably due to the homogeneously acceptable nutritional conditions of the nestlings. Finally, we found that Ospreys did not seem to adjust initial parental investment in relation to habitat quality, since productivity was not affected by habitat indicators. However, in large broods, but not in small ones, nestling nutritional condition improved as foraging conditions improved. These results suggest that females that are in better physical condition seem to produce more and better nourished nestlings in better foraging conditions.

The relationship between maternal ornamentation and feeding rate is explained by intrinsic nestling quality

In altricial birds, parental feeding is essential, and its amount may depend on the quality of both parents. A relationship between parental quality and feeding rate is generally attributed to an active adjustment by parents in order to retain good quality mates or ensure high fitness through raising high-quality offspring. However, the behaviour and need of young may also change with parental quality, and this may affect parental behaviour. A further problem is that most studies have investigated post-hatching parental investment in relation to the secondary sexual signals of males, but not females. In a cross-fostering experiment, we examined the feeding rates of rearing parents in relation to the size and ornamentation of both original and rearing parents in collared flycatchers (Ficedula albicollis). Using this setup, we could examine whether the observed feeding patterns were the results of the decision of the parents based on their own and their partner’s traits or the constraints imposed by the behaviour or need of offspring. When correcting for clutch size and year, we found that feeding rate of both foster parents correlated with the wing patch size of the original female. This implies that original maternal quality had an offspring-mediated indirect effect on investment of foster parents, that is intrinsic nestling quality may constrain parental feeding decisions. This explanation should not be overlooked in future studies on preferential parental investment, and our results also point out that maternal ornaments deserve more attention in such studies.

Sexual dimorphism, survival, and parental investment in relation to offspring sex in a precocial bird

Differential growth rate between males and females, owing to a sexual size dimorphism, has been proposed as a mechanism driving sex‐biased survival. How parents respond to this selection pressure through sex ratio manipulation and sex‐biased parental investment can have a dramatic influence on fitness. We determined how differential growth rates during early life resulting from sexual size dimorphism affected survival of young and how parents may respond in a precocial bird, the black brant Branta bernicla nigricans. We hypothesized that more rapidly growing male goslings would suffer greater mortality than females during brood rearing and that parents would respond to this by manipulating their primary sex ratio and parental investment. Male brant goslings suffered a 19.5% reduction in survival relative to female goslings and, based on simulation, we determined that a female biased population sex ratio at fledging was never overcome even though previous work demonstrated a slight male‐biased post‐fledging survival rate. Contrary to the Fisherian sex ratio adjustment hypothesis we found that individual adult female brant did not manipulate their primary sex ratio (50.39% male, n = 645), in response to the sex‐biased population level sex ratio. However, female condition at the start of the parental care period was a good predictor of their primary sex ratio. Finally, we examined how females changed their behavior in response to primary sex ratio of their broods. We hypothesized that parents would take male biased broods to areas with increased growth rates. Parents with male biased primary sex ratios took broods to areas with higher growth rates. These factors together suggest that sex‐biased growth rates during early life can dramatically affect population dynamics through sex‐biased survival and recruitment which in turn affects decisions parents make about sex allocation and sex‐biased parental investment in offspring to maximize fitness.

Parental investment in relation to offspring quality in the biparental cichlid fish Pelvicachromis taeniatus

Theory predicts that parents should adjust their parental investment to the reproductive value of the brood. Previous studies have mainly investigated the relationship between brood size, brood age and the intensity of care. However, the impact of brood quality traits such as the offspring’s average body size on parental investment has received relatively little attention. We examined the parental response to brood quality in the biparentally brood-caring cichlid fish Pelvicachromis taeniatus. We manipulated offspring quality by manipulating the food availability for the free-swimming fry and measured the parental response over 4 weeks. Generally, care decreased over the 4 weeks suggesting that parents adjust care to decreasing offspring vulnerability. However, parents of relatively low-quality broods, that is, of broods with relatively small average individual body size, showed a greater reduction in care than parents of high-quality broods resulting in a significant difference in care provided in the fourth week. The result suggests that parents adjust their care to brood quality and supports the predictions of the parental investment theory. Furthermore, mothers of high-quality fry were significantly more aggressive towards their partner than mothers of low-quality fry. This result is discussed in the context of parental response to brood value. Generally, females invested more in brood care than males.

Experimental evidence for adjustment of parental investment in relation to brood sex ratio in the blue tit

Parents should allocate parental investment in relation to the expected reproductive value of their offspring. We used a cross-fostering experiment to see whether factors influencing offspring reproductive value (brood size, nestling sex, age or paternity) were related to parental investment in nest defence in the blue tit, Cyanistes caeruleus . Although brood size and the incidence of extrapair paternity did not influence the nest defence behaviour of parents, we found a significant difference in the way male and female parents responded to the experimental change in sex ratio of the brood; the nest defence response of males was faster at nests with an increased proportion of sons, but the response of females was unrelated to changes in brood sex ratio. Furthermore, there was no relation between the original sex ratio of the brood, before manipulation, and the nest defence response of the male, indicating that paternal investment in this behaviour was a direct response to the manipulated brood sex ratio.

Grundsätzliches zur Konzeption einer evolutionären Psychiatrie

Phenomenological, biological and aspects of psychiatric disorders lack an integrative metatheoretical framework. This paper reviews the foundations of evolutionary psychiatry. Many aspects of evolutionary psychiatry are largely based on the fitness theory. Since many biologists argue that the unit of selection is the gene rather than the single organism or a group of organisms, the of inclusive fitness embraces the fitness of an individual plus the fitness of his or her close relatives with whom the individual on average shares a calculable proportion of genes, depending on how close the relationship actually is. Reciprocal altruism, parental investment in relation to sexual selection, and parent-offspring conflict constitute specific problems that guide the evolution of psychological mechanisms and strategies of an organism especially in terms of its behaviour. Such problems have probably contributed to the evolution of the human social brain that developed in the environment of evolutionary adaptedness to solve problems of adaptive significance of ancestral conditions. Despite this seemingly gene-centred view, evolutionary psychiatry may be understood as a metatheory to integrate genetic understanding and causal explanation of psychopathological processes, including neurobiological and psychological findings, because it takes both, the ultimate and the proximate level of evolved cognitive capacities, emotion and behaviour, into account. Many psychiatric disorders may therefore be considered as dysfunctions of the social brain. This could be exemplified by disorders that are characterised by a compromised capacity for inferring the mental states of other individuals, referred to as theory of mind. In real-life situations mental state attribution usually interferes with affective cues which is, for instance, crucial for experience and behaving empathetically. In many severe psychiatric disorders the lack of empathy may therefore at least in part explain why the competence of patients suffering from schizophrenia, for example, is reduced. Although gender-specific differences in prevalence rates and symptomatology of psychiatric disorders are mentioned in the diagnostic manuals of psychiatric disorders to some extent, it is widely underrecognised that some of these differences emerged due to divergent problems of adaptation for men and women. Likewise, some concepts of psychoanalytic such as the Oedipus complex are inconsistent with evolutionary psychiatry. From an evolutionary point of view there is no such conflict between offspring and same-sex parent, however, parents and offspring disagree over the amount of parental investment, e.g. in terms of resource allocation and investment in potential other offspring. Many insights from evolutionary psychology and psychiatry are therefore also therapeutically neglected but may open new opportunities for empirical research.

Begging signals and biparental care: nestling choice between parental feeding locations

The evolutionary conflict over the amount of resources transferred between a parent and its offspring may be resolved by honest signalling of ‘need’ by offspring and parental investment in relation to signalling level. In birds, biparental care is the norm and evidence that male and female parents differ in their investment pattern in individual offspring is growing. In an experiment on great tits,Parus major, we investigated how and why parents differ in food allocation when responding to similar chick signals, which supposedly uniquely reflect the chick's nutritional condition. Nestling hunger level was manipulated by food deprivation and hand-feeding. Subsequent filming revealed that parents fed from significantly different locations on the nest and thereby forced chicks to choose between them when competing for favourable positions. Deprived nestlings approached, and fed ones retreated (or were displaced by siblings) from, positions near the female. No such behaviour was observed towards the male. Females allocated more feeds than males to the food-deprived nestlings. The results are discussed in terms of nestling competition for access to ‘begging patches’. By varying their ‘begging patch’ value, parents may exploit competitive inter-sibling dynamics to influence the outcome of competition among chick phenotypes (e.g. ‘need’, size, sex). Parent birds may thereby exert considerable control over the information content of chick begging behaviour.

Repeatability of mass loss in female Pied Flycatchers Ficedula hypoleuca

The consistency of mass losses from the incubation to the brooding stage in female Pied Flycatchers was analyzed by means of repeatability analyses with the aim of seeing whether mass loss may have a heritable component. Repeatability (R) of mass loss was low and non-significant (R = 0.23, P = 0.12), and, when environmental variables known to influence mass loss were accounted for it, was even lower (R = – 0.10, P = 0.65). We argue that experiments on the significance of mass loss in breeding birds should take into account a wider array of environmental factors contingent on female mass loss than those usually considered (offspring number, feeding rate, female condition), namely territory quality, parental age, condition of the pair mate, and the variation of parental investment in relation to residual reproductive value.

Parental investment in relation to sex

Parental investment in relation to sex