Reproductive Benefits Research Articles

The efficacy of good genes sexual selection under environmental change.

Sexual selection can promote adaptation if sexually selected traits are reliable indicators of genetic quality. Moreover, models of good genes sexual selection suggest that, by operating more strongly in males than in females, sexual selection may purge deleterious alleles from the population at a low demographic cost, offering an evolutionary benefit to sexually reproducing populations. Here, we investigate the effect of good genes sexual selection on adaptation following environmental change. We show that the strength of sexual selection is often weakened relative to fecundity selection, reducing the suggested benefit of sexual reproduction. This result is a consequence of incorporating a simple and general mechanistic basis for how sexual selection operates under different mating systems, rendering selection on males frequency-dependent and dynamic with respect to the degree of environmental change. Our model illustrates that incorporating the mechanism of selection is necessary to predict evolutionary outcomes and highlights the need to substantiate previous theoretical claims with further work on how sexual selection operates in changing environments.

Attempt to Continue the Modernist Trend Presented on the Example of Multi-Family Housing

While trying to understand the current need for continuity of thoughts and ideas derived directly from the modernist trend with regard to multi-family housing, it is doubtlessly necessary that we need to make a synthetic assessment of the quality of Polish architecture over the last several decades. This period was characterized by an extremely diverse, multi-directional and multifaceted way of a building’s creation. In the face of a generally noticeable regression, the past several years, recognized so far as indisputable paradigms of culture, brought an inconsistent mix of independently consecutive different tendencies and aesthetic needs. The specific state of permutation, peculiar intellectual vacuum created by rejection of the existing rules and shortage of new ones, must have led to anarchy in architecture manifesting in the omnipresent “all-ism”. Against this background, it is difficult but possible, to find a clearly defined style, direction or the need to continue modernist thought on the example of modern housing. Dating back to the seventies of the twentieth century, we can observe activity of the generation of architects, where we can find the attempts to think about architecture on the basis of patterns of contemporary avant-garde world’s architecture. So-called “modernism”, which was in fashion at that time, resulted in frequent borrowings of formal and functional ideas, yet it brought a number of successful realizations of timeless architectural values, expressed in a clear idea and clearly defined form. The second half of the seventies was dominated by the omnipresent classification and prefabrication based on “the systems of industrialized buildings”, which defined the character of the housing architecture. This gave rise to a gradual limitation of individual creativity for the benefit of use and reproduction of typical projects adapted to the needs of particular locations. The economic crisis of the 1980s, as a result of decline of the socialist economy, also resulted in the stagnation of construction activity. An example of the existence of any design process remained the urban design of large housing estates based on the consistently simplified and limited construction systems of multi-family buildings. Thus, monotony and repetition became a ubiquitous standard and the only aesthetic criterion that defined the architectural space of cities at that time. The political and economic transformations that took place after 1989 as well as a strong feeling of freedom, regained after years, triggered off revolutionary changes in thinking that resulted in a multitude of events taking place in architecture, and consequently in the diversity and variability of aesthetic tendencies. Therefore, it is difficult to believe that the buildings constructed at that time were a direct indicator of a post-modernism idea, which, locally, were a sort of specific alibi, resulting from the momentary, deep need to rebuild the times of modernism, unfairly reduced in our reality only down to the criticism and negation of a ubiquitous residential large-panel housing. Luckily, the end of the nineties brought a noticeable reassurance of these tendencies. Uncertainty and indecisiveness, and hence the multitude of ideas and stylistic themes that provoked safe passivity and aesthetic borrowings, have been replaced by escapism from “eclectic postmodernism” towards “neo-modernism” as a more sophisticated form of convention. As a consequence, there appeared objects with a balanced form, not giving in the need to draw directly from classical patterns and not succumbing to the intrusive and chaotic need to recover from the past. Despite the fact that the possibilities of a designer’s creative expressions have become apparently expanded in new, modern economic realities, the designer’s creation has at the same time been very limited. His freedom and free expression were additionally determined by the investor, whose opinion on the social and economic expectations, and thus on the architecture and purely aesthetic issues, has in many cases become superior. However, numerous examples of contemporary multi-family buildings, which are also the result of their own professional experience, offer prospects that the stage of total abandonment of the idea of modernism turned out to be apparent and was provoked by rather temporary emergence of various aesthetic tendencies, which are the result of views denying the architecture, commonly regarded as impersonal.

An expanded theory of Alzheimer's caregiving.

The ancient and cross-culturally prevalent pattern of caregiving suggests that long-term caregiving is species characteristic for humans. If so, then an evolutionary account of the adaptation(s) that underwrite this caregiving is necessary, particularly for the one-sided and long-term nature of Alzheimer's caregiving. Four standard evolutionary explanations are evaluated: kin selection theory, the grandmother hypothesis, direct reciprocity, and indirect reciprocity. Each is found inadequate to explain caregiving because of the lack of reproductive benefits. These evolutionary accounts also assume that relationships are only valuable to the degree that they provide benefits and that relationship partners are predominantly motivated by self-interest. Attachment provides another explanation, which evolved initially to ensure infant protection and nurturance, but was exapted for important adult relationships. Attachment relationships naturally include caregiving and engender long-term relational commitment. Yet attachment theory is ambiguous about whether relationships are maintained for the sake of security benefits or because they have inherent value. This ambiguity undermines the explanatory value of attachment theory for Alzheimer's caregiving. Therefore, a shared identity theory is offered that highlights the inherent value of the relationship and the loved one, transcending the predominant focus on beneficial individual outcomes. The theory emphasizes the frequent human motivation to benefit others because of their mutual commitment, shared identity, and shared goals. The conclusion is that fully understanding and supporting the arduous efforts of caregiving for loved ones with Alzheimer's requires psychologists to fully appreciate and support the deep and meaningful motivations that often inspire the humanity seen in caregiving. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Reproductive Physiology of Halophytes: Current Standing.

Background: Halophytes possess efficient salt-tolerance mechanisms and can complete their life cycles in naturally saline soils with NaCl contents exceeding 200 mM. While a significant progress have been made in recent decades elucidating underlying salt-tolerance mechanisms, these studies have been mostly confined to the vegetative growth stage. At the same time, the capacity to generate high-quality seeds and to survive early developmental stages under saline conditions, are both critically important for plants. Halophytes perform well in both regards, whereas non-halophytes cannot normally complete their life cycles under saline conditions.Scope: Research into the effects of salinity on plant reproductive biology has gained momentum in recent years. However, it remains unclear whether the reproductive biology of halophytes differs from that of non-halophytes, and whether their reproductive processes benefit, like their vegetative growth, from the presence of salt in the rhizosphere. Here, we summarize current knowledge of the mechanisms underlying the superior reproductive biology of halophytes, focusing on critical aspects including control of flowering time, changes in plant hormonal status and their impact on anther and pollen development and viability, plant carbohydrate status and seed formation, mechanisms behind the early germination of halophyte seeds, and the role of seed polymorphism.Conclusion: Salt has beneficial effects on halophyte reproductive growth that include late flowering, increased flower numbers and pollen vitality, and high seed yield. This improved performance is due to optimal nutrition during vegetative growth, alterations in plant hormonal status, and regulation of flowering genes. In addition, the seeds of halophytes harvested under saline conditions show higher salt tolerance than those obtained under non-saline condition, largely due to increased osmolyte accumulation, more optimal hormonal composition (e.g., high gibberellic acid and low abcisic acid content) and, in some species, seed dimorphism. In the near future, identifying key genes involved in halophyte reproductive physiology and using them to transform crops could be a promising approach to developing saline agriculture.

Effects of Periconceptual Omega-3-Fatty Acid Supplementation on in Vitro Fertilization Success and Miscarriage Rates in Patients of a German Fertility Centre

Long-chain omega-3 fatty acids have been positively related with improvement of fertility in both women and men. Primary natural source of omega-3- fatty acids is seafood. As this also can bei the source of toxicants like f.e. lead, mercury and cadmium, reproductive benefits may be counteracted. Therefore, our approach was to supplement pharmaceutical grade omega-3-fatty acids in order to assess potential benefits of omega-3-fatty acids on modulation of IVF-success by dietary measures in a well-defined group of patients of a German Fertility Centre. A group of 52 IVF-patients with a history of at least two miscarriages or unsuccessful in vitro fertilization approaches received periconceptual omega-3-fatty acid supplementation for a time period of at least 3 weeks. The “historical” control group, consisting of 1109 patients without omega-3-fatty acid supplementation, was generated out of the Fertility Centre´s patient database. The same inclusion criteria (history of at least two miscarriages or unsuccessful in vitro fertilization approaches) were applied for both groups. Omega-3-fatty acid supplementation lead to significantly enhanced in vitro fertilization success rates as well as to reduction of miscarriage rates compared to patients of the control group. The results encourage to design further age-matched, double-blinded prospective studies in order to verify a positive influence of dietary intervention and lifestyle modification on fertility rates.

Effect of avocado and yogurt in diet media on wing length, ovariole number and progeny production of Drosophila melanogaster

Dietary constituents are known to have profound effect on physiological activities including reproductive fitness, fecundity and body size of the organism. In the present study, the flies of Drosophila melanogaster were reared in yogurt and avocado supplemented media to understand its effect on the wing length, ovariole number and progeny production. The results showed that the wing length, ovariole number and progeny production were significantly higher in those reared on avocado+ yogurt media followed by yogurt supplemented media. This suggests that avocado and yogurt as a combination followed by yogurt alone provided required nutrients to the flies to grow larger in size and have a greater number of ovarioles, and produce greater number of progeny than the flies grown in wheat-cream agar media. These results suggest that avocado and yogurt as a combination provide reproductive fitness benefits followed by yogurt media alone.

Wolbachia Infection Associated with Increased Recombination in Drosophila.

Wolbachia is a maternally-transmitted endosymbiotic bacteria that infects a large diversity of arthropod and nematode hosts. Some strains of Wolbachia are parasitic, manipulating host reproduction to benefit themselves, while other strains of Wolbachia exhibit obligate or facultative mutualisms with their host. The effects of Wolbachia on its host are many, though primarily relate to host immune and reproductive function. Here we test the hypothesis that Wolbachia infection alters the frequency of homologous recombination during meiosis. We use D. melanogaster as a model system, and survey recombination in eight wild-derived Wolbachia-infected (strain wMel) and Wolbachia-uninfected strains, controlling for genotype. We measure recombination in two intervals of the genome. Our results indicate that Wolbachia infection is associated with increased recombination in one genomic interval and not the other. The effect of Wolbachia infection on recombination is thus heterogenous across the genome. Our data also indicate a reproductive benefit of Wolbachia infection; infected females show higher fecundity than their uninfected genotypic controls. Given the prevalence of Wolbachia infection in natural populations, our findings suggest that Wolbachia infection is likely to contribute to recombination rate and fecundity variation among individuals in nature.

Overweight May Have Some Positive Reproductive Benefits as Compared to Obese Represented by Higher Sperm Progressive Motility in Infertile Men

Overweight May Have Some Positive Reproductive Benefits as Compared to Obese Represented by Higher Sperm Progressive Motility in Infertile Men

Queen Longevity and Fecundity Affect Conflict with Workers over Resource Inheritance in a Social Insect.

Resource inheritance is a major source of conflict in animal societies. However, the assumptions and predictions of models of conflict over resource inheritance have not been systematically tested within a single system. We developed an inclusive fitness model for annual eusocial Hymenoptera that predicts a zone of conflict in which future reproductive workers are selected to enforce nest inheritance before the queen is selected to cede the nest. We experimentally tested key elements of this model in the bumblebee Bombus terrestris. In colonies from which queens were sequentially removed, queen tenure was significantly negatively associated with worker male production, confirming that workers gain direct fitness by usurping the queen. In unmanipulated colonies, queen fecundity decreased significantly over the latter part of the colony cycle, confirming that workers' indirect fitness from maintaining queens declines over time. Finally, in an experiment simulating loss of queen fecundity by removal of queens' eggs, worker-to-queen aggression increased significantly and aggressive workers were significantly more likely to become egg layers, consistent with workers monitoring queen fecundity to assess the net benefit of future reproduction. Overall, by upholding key assumptions and predictions of the model, our results provide novel empirical support for kin-selected conflict over resource inheritance.

Adaptive changes in sexual signalling in response to urbanization.

Urbanization can cause species to adjust their sexual displays, because the effectiveness of mating signals is influenced by environmental conditions. Despite many examples that show that mating signals in urban conditions differ from those in rural conditions, we do not know whether these differences provide a combined reproductive and survival benefit to the urban phenotype. Here we show that male túngara frogs have increased the conspicuousness of their calls, which is under strong sexual and natural selection by signal receivers, as an adaptive response to city life. The urban phenotype consequently attracts more females than the forest phenotype, while avoiding the costs that are imposed by eavesdropping bats and midges, which we show are rare in urban areas. Finally, we show in a translocation experiment that urban frogs can reduce risk of predation and parasitism when moved to the forest, but that forest frogs do not increase their sexual attractiveness when moved to the city. Our findings thus reveal that urbanization can rapidly drive adaptive signal change via changes in both natural and sexual selection pressures.

Food quality matters: Interplay among food quality, food quantity and temperature affecting life history traits of Aurelia aurita (Cnidaria: Scyphozoa) polyps

Understanding the interaction between organisms' life history traits and environmental factors is an essential task in ecology. In spite of the increasing appreciation of jellyfish as an important component in marine ecosystem, there are still considerable gaps in understanding how the phase transition from the benthic polyp to the pelagic medusa stage is influenced by multiple environmental factors, including nutrition. To investigate survival, growth, and phase transition of Aurelia aurita polyps, we designed a factorial experiment manipulating food quantity (20μg C, 5μg C and 1.5μg C polyp−1 every other day), food quality (Artemia salina and two dietary manipulated Acartia tonsa), and temperature (13°C, 20°C, and 27°C). Temperature was the key factor determining phase transition of polyps and negatively affecting their survival rate and growth at 27°C, which reflected a summer heatwave scenario. Furthermore, at polyps' optimum tolerance temperature (20°C) in our study, budding reproduction benefits from high food concentrations. Interestingly, polyps fed with food containing high level highly unsaturated fatty acid (HUFA) were able to compensate for physiological stress caused by the extreme temperature, and could enhance budding reproduction at optimum temperature. Moreover, benthic-pelagic coupling (strobilation) was determined by temperature but affected significantly by food conditions. Mild temperature together with optimum food conditions contributes to inducing more polyps, which may potentially bring about great ephyrae recruitments during overwintering. In contrast, heatwave events can potentially regulate plankton community structure accompanied by changes of nutritional conditions of primary and secondary producers and thus, negatively affect the population dynamics of polyps. We suggest a novel polyp tolerance curve, which can help to understand jellyfish population dynamics in different seasons and ecosystems. This sets up a baseline for understanding how anticipated global warming and food conditions may affect the population size of benthic polyps and consequently pelagic medusae.

A long winter for the Red Queen: rethinking the evolution of seasonal migration.

This paper advances an hypothesis that the primary adaptive driver of seasonal migration is maintenance of site fidelity to familiar breeding locations. We argue that seasonal migration is therefore principally an adaptation for geographic persistence when confronted with seasonality-analogous to hibernation, freeze tolerance, or other organismal adaptations to cyclically fluctuating environments. These ideas stand in contrast to traditional views that bird migration evolved as an adaptive dispersal strategy for exploiting new breeding areas and avoiding competitors. Our synthesis is supported by a large body of research on avian breeding biology that demonstrates the reproductive benefits of breeding-site fidelity. Conceptualizing migration as an adaptation for persistence places new emphasis on understanding the evolutionary trade-offs between migratory behaviour and other adaptations to fluctuating environments both within and across species. Seasonality-induced departures from breeding areas, coupled with the reproductive benefits of maintaining breeding-site fidelity, also provide a mechanism for explaining the evolution of migration that is agnostic to the geographic origin of migratory lineages (i.e. temperate or tropical). Thus, our framework reconciles much of the conflict in previous research on the historical biogeography of migratory species. Although migratory behaviour and geographic range change fluidly and rapidly in many populations, we argue that the loss of plasticity for migration via canalization is an overlooked aspect of the evolutionary dynamics of migration and helps explain the idiosyncratic distributions and migratory routes of long-distance migrants. Our synthesis, which revolves around the insight that migratory organisms travel long distances simply to stay in the same place, provides a necessary evolutionary context for understanding historical biogeographic patterns in migratory lineages as well as the ecological dynamics of migratory connectivity between breeding and non-breeding locations.

Convenience polyandry and the role of lone and reciprocal calls in a psyllid

It is widely accepted that receptivity to mating may be asymmetrical between the sexes. While reproductive benefits for males are cumulative, females may not benefit equally from polyandry, especially in species where females can store sperm. Female psyllids (Hemiptera: Psylloidea) are reportedly polyandrous. However, the adaptive significance of this mating strategy has not been thoroughly investigated. Studies involving other insect species indicate that polyandry may be driven by benefits (direct or indirect) or by the need to minimize costs associated with male harassment. Drooping she-oak psyllids, Aacanthocnema dobsoni (Triozidae), use substrate-borne vibrations for mate attraction but they are not a prerequisite for mating. We suspected that polyandry in this species could be driven by male harassment because males exhibit indiscriminate mating behaviour (consistent with a scramble competition mating strategy), often mating with unresponsive (mated) females. We investigated relationships between calling, feeding and mating status to test whether females mate to minimize harassment by males and whether they gain any direct benefits from polyandry. We found that lone calls were commonly, but reciprocal calls were rarely followed by mating. As reciprocal calls should reflect female receptivity, copulations without them highlight the existence of sexual conflict over mating. Observations revealed that feeding females were less likely to resist mating than nonfeeding females. We did not find that females obtained any direct benefits from polyandry. Our results suggest that polyandry in this species may be a consequence of male harassment and that mated females, while feeding, may remate for convenience to minimize costs associated with stylet retraction/penetration and location of new feeding sites.

Factors influencing individual participation during intergroup interactions in mountain gorillas

In group-living species, encounters with extragroup rivals can be one of the riskiest actions in which individuals participate. Different group members often have different incentives to participate during intergroup interactions, and individuals with fewer payoffs of competition, including those of the smaller sex and/or lower rank, may ‘free-ride’ to avoid the costs of conflict. However, there is little evidence for how different types of intergroup interactions (e.g. interactions that do not involve conflict) can influence the participation of individuals. We examined the ecological, demographic and social predictors of individual participation in interactions between 14 fully habituated mountain gorilla groups in Volcanoes National Park, Rwanda from 2003 to 2015. The probability of an individual participating decreased with group size but remained relatively high in aggressive interactions and in multimale groups, illustrating the potential for ‘load lightening’ among group members. Males with fewer mating opportunities participated less often than males with more mating opportunities; however, male participation was significantly higher than female participation across all types of intergroup interactions. Females were more likely to be involved in aggressive interactions with solitary males, possibly to avoid the potential cost of infanticide if a resident male is killed or injured. Both sexes demonstrated more affiliative behaviours towards familiar groups, indicating a benefit of maintaining social relationships with familiar groups. Individuals show considerable variation in behaviour during intergroup interactions, and our results suggest that this variation is primarily driven by intergroup familiarity and individual reproductive benefits, both of which may have long-term consequences for individual fitness.

Sex-specific effects of food supplementation on hibernation performance and reproductive timing in free-ranging common hamsters

Hibernation is characterized by reduced metabolism and body temperature during torpor bouts. Energy reserves available during winter play an important role for hibernation and some species respond to high energy reserves with reduced torpor expression. Common hamsters are food-storing hibernators and females hibernate for shorter periods than males, probably related to larger food stores. In this study, we provided free-ranging common hamsters with sunflower seeds shortly before winter and recorded body temperature using subcutaneously implanted data loggers. We compared hibernation patterns and body mass changes between individuals with and without food supplements and analysed reproductive onset in females. Supplemented males delayed hibernation onset, hibernated for much shorter periods, and emerged in spring with higher body mass than unsupplemented ones. Additional food did not affect hibernation performance in females, but supplemented females emerged earlier and preceded those without food supplements in reproductive onset. Thus, males and females differently responded to food supplementation: access to energy-rich food stores enabled males to shorten the hibernation period and emerge in better body condition, probably enhancing mating opportunities and reproductive success. Females did not alter hibernation patterns, but started to reproduce earlier than unsupplemented individuals, enabling reproductive benefits by an extended breeding period.

Effects of long‐term variation in pollinator abundance and diversity on reproduction of a generalist plant

Abstract Quantifying the benefits of pollinator abundance and diversity for plant reproduction is a critical challenge, especially given recent pollinator declines. Many studies test for pollen limitation (PL), but huge gaps remain in our understanding of how often and why plants experience PL. Most studies are limited to a few sites or years. Little existing research mechanistically links pollinator visitation with plant reproduction. Also, buffering against variability in visitation is a key but largely untested potential benefit of pollinator diversity. Long‐term studies pairing visitation data with PL experiments are essential to addressing these gaps, but extremely rare. I measured pollinator visitation, responses to pollen supplementation, and fruit weights in the generalist plant Scrophularia californica across multiple sites for 8 years. I determined how often S. californica experienced significant PL and tested mechanistic models predicting PL and fruit (capsule) weight from visitation. I then used those models to simulate pollinator loss and evaluate the relative effects of changes in visit quantity and quality. I explored the stabilizing benefits of visitor diversity by quantifying both covariation among pollinators and effects of simulated species loss on variation in PL and capsule weights. Scrophularia showed significant PL in only 26.9% of patch/year combinations tested. Visitation by the most abundant (Apis mellifera) and effective (Vespula pensylvanica) pollinators strongly predicted PL and capsule weights. Both response curves were highly nonlinear, but PL saturated more with increased visitation. Pollinator loss simulations predicted substantially increased PL and reduced capsule weights, mostly because of lower visit numbers rather than changes in visit quality. Visitation rates of individual pollinators varied substantially and without correlation. Simulated pollinator loss increased the spatial and temporal skew in visitation, resulting in higher predicted coefficients of variation for PL and capsule weights. Synthesis. Previous work predicts a nonlinear relationship between pollinator visitation and plant reproduction, but this is the first long‐term study I am aware of that quantifies such a pattern. The analysis of covariance in pollinator visitation combined with my simulation results provide novel empirical support for another important hypothesis, that multiple pollinators can provide stabilizing benefits for plant reproduction.

Sex differences in helping effort reveal the effect of future reproduction on cooperative behaviour in birds.

The evolution of helping behaviour in species that breed cooperatively in family groups is typically attributed to kin selection alone. However, in many species, helpers go on to inherit breeding positions in their natal groups, but the extent to which this contributes to selection for helping is unclear as the future reproductive success of helpers is often unknown. To quantify the role of future reproduction in the evolution of helping, we compared the helping effort of female and male retained offspring across cooperative birds. The kin selected benefits of helping are equivalent between female and male helpers-they are equally related to the younger siblings they help raise-but the future reproductive benefits of helping differ because of sex differences in the likelihood of breeding in the natal group. We found that the sex which is more likely to breed in its natal group invests more in helping, suggesting that in addition to kin selection, helping in family groups is shaped by future reproduction.

Eugenics Redux: "Reproductive Benefit" as a Rationale for Newborn Screening.

In recent years, as newborn screening has expanded to include conditions for which treatment is questionable, new rationales for screening have proliferated. One such rationale is the potential reproductive benefit to parents from the detection of a genetic condition or carrier status in infants. An unanticipated consequence of invoking knowledge of reproductive risk as a major benefit of screening has been to open newborn screening to the charge that it constitutes state-sanctioned eugenics. Thus, an endeavor that had been viewed as the converse of state programs of selective breeding has come to be seen in some quarters as yet another of its incarnations. The result has been serious and self-inflected harm to the reputation of newborn screening programs.

Subordinate females in the cooperatively breeding Seychelles warbler obtain direct benefits by joining unrelated groups.

In many cooperatively breeding animals, a combination of ecological constraints and benefits of philopatry favours offspring taking a subordinate position on the natal territory instead of dispersing to breed independently. However, in many species individuals disperse to a subordinate position in a non-natal group ("subordinate between-group" dispersal), despite losing the kin-selected and nepotistic benefits of remaining in the natal group. It is unclear which social, genetic and ecological factors drive between-group dispersal. We aim to elucidate the adaptive significance of subordinate between-group dispersal by examining which factors promote such dispersal, whether subordinates gain improved ecological and social conditions by joining a non-natal group, and whether between-group dispersal results in increased lifetime reproductive success and survival. Using a long-term dataset on the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis), we investigated how a suite of proximate factors (food availability, group composition, age and sex of focal individuals, population density) promote subordinate between-group dispersal by comparing such dispersers with subordinates that dispersed to a dominant position or became floaters. We then analysed whether subordinates that moved to a dominant or non-natal subordinate position, or became floaters, gained improved conditions relative to the natal territory and compared fitness components between the three dispersal strategies. We show that individuals that joined another group as non-natal subordinates were mainly female and that, similar to floating, between-group dispersal was associated with social and demographic factors that constrained dispersal to an independent breeding position. Between-group dispersal was not driven by improved ecological or social conditions in the new territory and did not result in higher survival. Instead, between-group dispersing females often became cobreeders, obtaining maternity in the new territory, and were likely to inherit the territory in the future, leading to higher lifetime reproductive success compared to females that floated. Males never reproduced as subordinates, which may be one explanation why subordinate between-group dispersal by males is rare. Our results suggest that subordinate between-group dispersal is used by females to obtain reproductive benefits when options to disperse to an independent breeding position are limited. This provides important insight into the additional strategies that individuals can use to obtain reproductive benefits.

Brood provisioning and reproductive benefits in relation to habitat quality: a food supplementation experiment

Food availability is a major characteristic of habitat quality, linking habitats with demographic parameters such as reproductive performance. Parent birds adjust their food provisioning to both habitat-specific food characteristics and the demands of their young. However, because habitat quality and the brood's food intake are often correlated, the underlying mechanisms of adjustments in parental provisioning remain entangled. How the relationship between habitat quality and parental provisioning behaviour affects the quantity of food available to nestlings and the resulting nestling growth and survival is therefore still incompletely established. We experimentally increased the food intake of little owl, Athene noctua, nestlings in two habitat types differing in food availability and used unsupplemented broods as controls. The food supplementation experiment allowed us to disentangle the effect of habitat type from the effect of the nestlings' food intake on parental provisioning behaviour. Camera traps recording a series of 10 consecutive images for each parental visit allowed us to quantify visiting rates and diet composition by applying a hierarchical multinomial model explicitly accounting for the observation process. Food supplementation caused parents to switch to smaller food items and to increase visiting rates, resulting in similar biomass brought to nestlings in supplemented and unsupplemented broods. Irrespective of the food supplementation, parents in low-quality habitats delivered 63% of the biomass delivered by those in high-quality habitats. Accordingly, we found an increase in nestling survival rates in response to food supplementation in low-quality habitats, but not in high-quality habitats. Our results show that habitat quality affects the biomass of prey delivered to the brood, whereas the nutritional state of the brood affects prey selection or foraging modes of parents. Reproductive output directly reflected habitat quality in terms of food availability, identifying food as the main factor underlying differential reproduction within and between populations.