Level Of Parental Investment Research Articles

Pseudo Concorde fallacy in the willow tit?

The predictions of optimal parental investment theory were tested by studying nest defence decisions of willow tits,Parus montanus. As predicted, parental defence intensity increased with offspring age, female parents defended early and middle-season broods more vigorously than late ones and the annual proportion of mobbers correlated significantly with annual means of clutch and brood sizes. Against the predictions, defence intensity was not adjusted to the quality (weight, size and condition) or quantity of offspring, which was also confirmed by brood size manipulation experiments. In this respect, willow tits seemed to commit the so-called Concorde fallacy. A suggested explanation for these non-adaptive responses is that a trait to determine the brood value continuously is not needed, since breeding success is high and predictable every year. In addition, in this population parents with reduced and enlarged broods had the same fitness as those with control broods. Therefore, parents behaved optimally when they did not change their defence intensity according to the manipulations. Thus, this lack of response to unnatural variation in a minor component of lifetime reproductive success could be considered a pseudo Concorde fallacy. These results suggest that parents are able to predict the forthcoming breeding success early in the season, and that this prediction holds quite precisely, with parental investment levels being relatively equal regardless of clutch and brood size.

Evidence of equal maternal investment in the sexes in the polygynous and sexually dimorphic grey seal (Halichoerus grypus)

In polygynous and sexually dimorphic mammals, parents may be expected to bias their investment towards sons because variation in reproductive success is usually higher among males than among females. Moreover, male reproductive success often depends on adult body size, which, in turn, may depend on the level of parental investment. We therefore predicted that in the grey seal (Halichoerus grypus), a polygynous and sexually dimorphic phocid seal, females should invest more in individual sons than in individual daughters. We found that male pups were born heavier than female pups, but that the growth rates and suckling behaviour were similar for the two sexes. The growth rates and the birth weights were not correlated for the pups of either sex. Mothers did not behave differentially towards offspring of the two sexes, except that mothers of male pups spent more time in visual contact with their pups. Male and female pups had similar activity levels and begged at similar rates. We argue that reports of equal expenditure on the two sexes can be accepted as evidence of equal investment, provided that three assumptions are fulfilled. First, parental care must be costly to the parent. Second, energy expenditure must be the most important component of parental investment. Third, there must be no negative correlation between maternal body condition and the ratio of sons to daughters produced. We argue that these assumptions are met in our study, and that our results provide evidence of equal maternal investment in the sexes in grey seals.

Paternal investment affects prevalence of malaria.

Both reproduction and parasite defense can be costly, and an animal may face a trade-off between investing in offspring or in parasite defense. In contrast to the findings from nonexperimental studies that the poorly reproducing individuals are often the ones with high parasite loads, this life-history view predicts that individuals with high reproductive investment will show high parasite prevalence. Here we provide an experimental confirmation of a positive association between parental investment levels of male great tits Parus major and the prevalence of Plasmodium spp, a hematozoa causing malaria in various bird species. We manipulated brood size, measured feeding effort of both males and females, and assessed the prevalence of the hemoparasite from blood smears. In enlarged broods the males, but not the females, showed significantly higher rates of food provisioning to the chicks, and the rate of malarial infection was found to be more than double in male, but not female, parents of enlarged broods. The findings show that there may be a trade-off between reproductive effort and parasite defense of the host and also suggest a mechanism for the well documented trade-off between current reproductive effort and parental survival.

Fledging in altricial birds: parental manipulation or sibling competition?

Abstract. In altricial birds, the period of parental investment covers three distinctly separated phases: incubation, feeding of nestlings, and feeding of fledglings in the family group. The transition between the latter two phases occurs when the brood fledges and leaves the nest. To investigate which party, parents or offspring, initiates nest leaving, different-aged broods were swopped between nestboxes in two passerine bird species, the marsh tit, Parus palustris, and the pied flycatcher, Ficedula hypoleuca. Parents did not try to manipulate nestlings into nest leaving; fledging was thus independent of the level of parental investment. Instead, fledging occurred when one of the nestlings, which had reached a certain threshold size, left the nest in order to approach the parents and obtain additional feedings at the expense of its siblings. It is suggested that the fledging time of altricial birds is determined by energetic considerations and by sibling competition. Since fledging also represents the juvenile's transition from an inactive to an active party in the parent-offspring interaction, it is also to be considered as an escalation of the parent-offspring conflict.

Parental investment in an anadromous population of threespine sticklebacks: An experimental study

Two previously published field studies of threespine sticklebacks conducted to test predictions of parental investment (PI) theory yielded different conclusions about how males invest in their young. Males of a freshwater population invested more in older/larger broods whereas environmental factors played no role in PI decisions. In contrast, males of an anadromous population adjusted levels of PI in response to environmental factors rather than brood characteristics. The current laboratory study attempts to determine possible reasons for the discrepancy between these two studies. We addressed the following questions. Do males invest more in larger/older broods? Do environmental factors affect levels of parental investment? Males were more aggressive (a measure of PI) in defending eggs than empty nests and free-swimming fry. However, aggression was similar for different-aged eggs and different-aged fry. Moreover, when we manipulated brood sizes (fry), males did not change their level of investment. Males increased their level of aggressive defence in response to a rise in water level, indicating that they can adjust their level of investment in response to changes in environmental conditions that affect brood survival.

Sex differences in vulnerability and maladjustment as a function of parental investment: An evolutionary approach

Sex differences in aspects of mental health are examined as a function of uneven parental investment in children. Relative vulnerability is a new construct mediating the influence of parental investment on mental health. Couples (129) in three stages of the family life cycle are measured by scales for parental investment, relative vulnerability, anxiety, depression, and ten psychosomatic syndromes. Results show a path of positive correlations from the parent's sex to level of parental investment, to level of relative vulnerability, and to levels of anxiety and depression. Women invest more than men, and hence they are more vulnerable, anxious, and depressed. They reach the summit of their vulnerability while they have three young children. Relative vulnerability was found to have positive effects along with the negative ones and to affect women in different ways than it does men. Results are interpreted in terms of different parental strategies selected by evolution for each sex.

The risks of parenthood. I. General theory and applications

We use contemporary life history theory to analyze parental decisions concerned with the defense of offspring, and with the provisioning of offspring in the presence of risk. In achieving the optimal level of parental investment, the parent faces a tradeoff between present and future reproductive success. Our models, which are based on stochastic dynamic programming, lead to predictions of the following kind: (i) offspring will be defended more vigorously as they grow older; (ii) long-lived species will accept fewer risks in caring for offspring than short-lived species; (iii) parents living in permanently riskier environments will defend their offspring more vigorously than parents in less risky environments; (iv) however, temporary increases in risk will result in temporarily less vigorous defense and provisioning of offspring. The models also show that parents and their offspring have different conceptions of the optimal level of parental investment. The flexibility of our modeling approach as a method of analyzing facultative behavior is also emphasized. Finally, we apply the methods of this paper to analyze fledging behavior of Atlantic puffins.

Proximate and Evolutionary Constraints on Energy Relations of Reptiles

Proximate constraints on the energetics of desert lizards and turtles fall into four major categories: (1) absolute resource availability; (2) harvest rate limitations; (3) process rate limitations; and (4) limitation on harvest or processing resources imposed by risk of predation. Patterns of basking behavior and allocation of resources to reproduction and growth of turtles at high latitudes suggest that ambient air and marsh temperatures combine to regulate the timing and rates of energy processing and allocation. Because reptile eggs contain all of the chemical energy available to developing embryos, interactions between the level of parental investment in each offspring and egg size must, by definition, occur. That portion of the egg material that is invested in the egg but functions as parental care of the hatchling after it leaves the egg functions primarily to affect hatchling quality rather than hatchling size. Therefore, with regard to many reptiles, optimal egg-size models would be more aptly co...

Influence of age and territory quality on the reproductive behaviour of male Yellow Warblers

Individual male Yellow Warblers (Dendroica petechia) exhibit differences in their level of parental investment, which correlate with the amount of brown streaking on the breast. We tested two alternative hypotheses to explain these patterns. The age effect hypothesis proposes that the variation in plumage and parental behaviour is an effect of differences in male age. This was tested by analyzing the nest visit rates and plumage scores of banded males present in the study in more than 1 year. The age effect hypothesis is rejected because there was no evidence of significant within-male variation due to increasing age, nor of any consistent directional change in either parental effort or plumage pattern between years. The territory quality hypothesis proposes that the quality of territory occupied has an important proximate influence on male parental effort. By observing the same territories over different years we were able to compare nest visit rates of different males with different plumage scores while holding the effect of territory quality constant. Analysis of variance revealed that male plumage rank had a highly significant effect on nest visit rate, while the effect of territory occupied was not significant. Rejection of these two alternative hypotheses provides further support for the hypothesis that phenotypically different males are using alternative and irreversible lifetime reproductive strategies.

Energetic Content of Eggs, Larvae, and Juveniles ofFlorometra serratissimaand the Implications for the Evolution of Crinoid Life Histories

Summary This is the first report of egg, larval, and juvenile energetic content in crinoids. Florometra serratissima (A.H. Clark) produces a nonfeeding larva with an unusually low level of parental investment per offspring. The mean egg volume was 7.42 × 106μm3. The eggs contained an average of 4.47 × 10−2 joules egg−1. The mean energetic density of the eggs was 6.02 joules mm−3. There was a loss of 3.61 × 10−2 joules individual−1 (81% of initial content) during the 25 day lecithotrophic period of the pelagic doliolaria and the prefeeding, benthic cystidean. As a result, the pentacrinoid juveniles contained very little organic material (0.86 × 10−2 joules individual−1), and might suffer high mortality rates as a consequence. These results raise a number of questions about the adaptiveness and the evolution of crinoid life histories.

Shared and unshared parental investment, parent-offspring conflict and brood size

Taking as our starting point Trivers' (1974) account of parent-offspring conflict, we develop models of the influence of brood size on the optimal level of parental investment (PI) in the whole brood for parent and offspring, and on the magnitude of conflict between them. A modification of Trivers' model is proposed. In general, the benefit of an act of PI to an offspring in a brood of size N is ( N+1)/ N times the benefit to its parent. Therefore as brood size increases, offspring benefit approaches parental benefit, and this is because an increasing proportion of the offspring's benefit is being gained through siblings, to which offspring and parent are equally related. A distinction is drawn between ‘shared’ and ‘unshared’ types of PI. When PI is shared the total benefit accruing is not directly gained by all offspring but is shared amongst them (e.g. food brought to the young). In contrast, unshared PI can simultaneously benefit some or all of the brood (e.g. types of anti-predator defence). For shared investment, PI and conflict are predicted to increase with brood size. Two models of unshared anti-predator defence are described. If the predator characteristically takes the whole brood when it strikes (e.g. altricial nestlings) PI is predicted to increase and conflict decline with brood size, although this effect is inhibited or even reversed for high risk defence tactics because of the higher cost to larger broods if the parent dies. When the predator takes a single offspring (e.g. precocial birds) the parent's optimum PI is independent of brood size, the offspring's optimum PI declines in larger broods and conflict again declines with brood size. The parent is commonly expected to win the conflict over anti-predator care. Predictions concerning PI levels gain support from existing data, largely for birds, but evaluation of those for conflict must await the collection of new data. The distinction between shared and unshared investment is applicable to altruistic behaviour in general.

Egg Size Distributions Among Closely Related Marine Invertebrate Species: Are They Bimodal or Unimodal?

Previous articleNext article No AccessNotes and CommentsEgg Size Distributions Among Closely Related Marine Invertebrate Species: Are They Bimodal or Unimodal?Frank E. Perron, and Robert H. CarrierFrank E. Perron Search for more articles by this author , and Robert H. Carrier Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 118, Number 5Nov., 1981 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/283865 Views: 6Total views on this site Citations: 23Citations are reported from Crossref Copyright 1981 The University of ChicagoPDF download Crossref reports the following articles citing this article:Ovidio García-Oliva, Florian M Hantzsche, Maarten Boersma, Kai W Wirtz, Lisa Campbell Phytoplankton and particle size spectra indicate intense mixotrophic dinoflagellates grazing from summer to winter, Journal of Plankton Research 44, no.22 (Mar 2022): 224–240.https://doi.org/10.1093/plankt/fbac013Alexander D. Meyer, Alan Hastings, John L. Largier Larvae of coastal marine invertebrates enhance their settling success or benefits of planktonic development – but not both – through vertical swimming, Oikos 130, no.1212 (Nov 2021): 2260–2278.https://doi.org/10.1111/oik.08585Elena K. Kupriyanova, Dmitry Yu. Mikhin Do fecundity-time models really predict extreme optimal egg sizes?, Marine Ecology 36, no.44 (Sep 2014): 873–886.https://doi.org/10.1111/maec.12193Elena K. Kupriyanova What do egg size distributions in marine invertebrates tell us about validity of fecundity-time models?, Marine Ecology 35, no.22 (Aug 2013): 249–253.https://doi.org/10.1111/maec.12064JS McAlister, AL Moran Effects of variation in egg energy and exogenous food on larval development in congeneric sea urchins, Marine Ecology Progress Series 490 (Sep 2013): 155–167.https://doi.org/10.3354/meps10420S. J. Kamel, F. X. Oyarzun, R. K. 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