Nestling recognition via direct cues by parental male bluegill sunfish ( Lepomis macrochirus)

The scent of offspring: chemical profiles of larvae change during development and affect parental behavior in a burying beetle

Chemical cues and signals, especially in insects, play a pivotal role in mediating interactions between individuals. Past studies have largely focused on adult semiochemicals and have neglected those of juvenile stages. Especially in the context of parental care, the larval odor might have a profound impact on parenting behavior, guiding parents in how much resources they should allocate to the different developmental stages. However, whether ontogenetic changes occur in subsocial species and whether larval-emitted scents influence parent-offspring interactions is largely unknown. Using 3 different sampling techniques, we analyzed the cuticular and VOC profile of the 3 larval instars of the burying beetle Nicrophorus vespilloides, which is known for its elaborate parental care. We found distinct differences in the cuticular and VOC profiles across the 3 larval stages. Second-instar larvae, which receive more frequent feedings from parents than the other larval stages, released greater amounts of acetophenone, methyl geranate, and octanoic acid isopropyl ester than the first and third instar. Additionally, using a newly developed bioassay with automated video tracking, we found that adding the odor of second-instar larvae to first-instar larvae increased the number of maternal feeding trips. Our results suggest that the odor produced by larvae plays an important role in mediating parent-offspring interactions. Given these findings, burying beetles might emerge as a promising candidate for identifying a potential begging pheromone.

Prolactin modulates changes in parental care behaviour in response to perceived paternity in bluegill sunfish (Lepomis macrochirus)

Prolactin is a hormone conserved across all vertebrates and is renowned for its role in reproduction and parental care. Previous studies on prolactin in fish have primarily relied on administration of mammalian prolactin and have suggested that increases in prolactin lead to greater parental care. However, the influence of endogenous prolactin on fish parental care remains unknown. Here, we measure circulating concentrations of endogenous prolactin during parental care in a fish and link these concentrations to parental care behaviour. We provide evidence that male bluegill sunfish with higher circulating concentrations of prolactin provide more parental care to their offspring. Furthermore, we show that nesting males with experimentally reduced perceived paternity have lower circulating prolactin concentrations and perform fewer parental behaviours, facilitating an adaptive investment in offspring in response to paternity cues. Our findings not only confirm the role of endogenous prolactin in modulating parental care behaviour in a fish but also provide a mechanism underlying the adaptive changes in parental care made in response to perceived paternity.

Sensory Mechanisms of Parent-Offspring Recognition in Fishes, Amphibians, and Reptiles

Parental care is important for offspring survival and success. Recognition of offspring by parents is critical to ensure parents direct care behaviors at related offspring and minimize energy lost by caring for unrelated young. Offspring recognition of parents prevents possible aggressive interactions between young and unrelated adults and allows offspring to direct begging behaviors toward the correct adult. Despite its importance and widespread nature, much of the current research has focused on a small range of species, particularly mammals and birds. We review the existing literature on the sensory mechanisms of parent-offspring recognition in fishes, amphibians, and reptiles. Within these groups, there is diversity in the presence and strategies for parent-offspring recognition. Future studies should continue to identify these mechanisms, as well as the neural and endocrine underpinnings in non-model organisms to expand our knowledge of this behavior and inform our understanding of the evolution of parent-offspring recognition.

Parental care behaviour in response to perceived paternity is not mediated by 11-ketotestosterone in bluegill sunfish

Parental care is critical for the survival of many young animals, but parental care can be costly to the individual providing care. To balance this cost, parents can allocate their care to offspring based on their value, which can be dependent on the offspring's relatedness to the parent. Bluegill (Lepomis macrochirus) is a fish characterized by uniparental male care and high levels of cuckoldry. While parental males of this species have been shown to adaptively adjust their care in response to paternity, the mechanisms for this adjustment are not well understood. Androgens are steroid hormones that are associated with parental care behaviours in many species including bluegill. Here, we test the hypothesis that circulating androgen concentrations mediate the adjustment in care provided by bluegill parental males by manipulating perceived paternity and then measuring circulating 11-ketotestosterone concentration and parental care behaviour. We show that males with higher perceived paternity provide higher levels of nurturing and nest defense behaviour, but contrary to expectations, we found that these males had lower concentrations of 11-ketotestosterone. Furthermore, we found positive correlations between individual circulating plasma 11-ketotestosterone concentrations and nurturing behaviour, but not with the aggressive behaviours that differed between paternity treatments. While bluegill make behavioural changes in response to perceived paternity, these changes do not appear to be modulated by 11-ketotestosterone.

Parent-offspring cannibalism throughout the animal kingdom: a review of adaptive hypotheses

Parents that kill and consume their offspring often appear to be acting against their own reproductive interests. Yet parent-offspring cannibalism is common and taxonomically widespread across the animal kingdom. In this review, I provide an overview of our current understanding of parent-offspring cannibalism, which has seen a proliferation in adaptive hypotheses over the past 20 years for why parents consume their own young. I review over four decades of research into this perplexing behaviour, drawing from work conducted on fishes, reptiles, insects, birds, and mammals among other taxa. Many factors have been hypothesised to explain parent-offspring cannibalism in nature, including poor parental energy reserves, small or large brood sizes, low or uncertain parentage, and high brood densities, and additional factors are still being uncovered. Parent-offspring cannibalism does not appear to have a single predominant explanation; rather, the factor, or set of factors, that govern its expression is largely taxon specific. Parents may either consume all offspring under their care (full-brood cannibalism) or consume a fraction of their offspring (partial brood cannibalism). These forms of cannibalism are thought to provide adaptive benefits to cannibals under a range of circumstances, primarily by allowing parents to allocate parental efforts more optimally - energy from eating (some of) one's current offspring can be redirected to other offspring, or to parental growth, survival, and ultimately to other future reproductive endeavours. Thus, parent-offspring cannibalism is a phenotypically plastic trait that responds to changing environmental, social, and physiological conditions. The expression of parent-offspring cannibalism in any given system is intimately linked to the reproductive value of current young relative to parents' expectations for future reproduction, and also to whether parental care is predominantly depreciable or non-depreciable. Furthermore, parent-offspring cannibalism has the potential to generate conflict between the sexes, and I briefly discuss some consequences of this conflict on patterns of mate choice. Finally, there still remain many aspects of this behaviour where our understanding is poor, and I highlight these topics to help guide future research.

Spatial asymmetry of the paternity success in nests of a fish with alternative reproductive tactics

Guard-sneaker tactics are widespread among fish, where territorial males defend a nest and provide parental care while sneakers try to steal fertilizations. Territorials and sneakers adopt diverse pre- and post-mating strategies, adjusting their ejaculate investment and/or behavioural responses to the presence of competitors. The relative distance of competitors from the spawning female plays a major role in influencing male mating strategies and the resulting paternity share. However, territorial male quality and sneaking intensity do not fully account for the variability in the relative siring success occurring among species. An often neglected factor potentially affecting sneakers proximity to females is the nest structure. We conducted a field experiment using the black goby, whose nests show two openings of different size. We found that territorial males defend more and sneaking pressure is higher at the front, larger access of the nest than at the back, smaller one. Moreover, microsatellite paternity analysis shows that territorials sire more offspring at the back of their nest. Such a predictable spatial distribution of the paternity share suggests that nest structure might work as an indirect cue of male relative siring success, potentially influencing the territorial male investment in parental care and/or the female egg deposition strategy.

Nest defense in the face of cuckoldry: evolutionary rather than facultative adaptation to chronic paternity loss

Background

Raising unrelated offspring is typically wasteful of parental resources and so individuals are expected to reduce or maintain low levels of parental effort when their parentage is low. This can involve facultative, flexible adjustments of parental care to cues of lost parentage in the current brood, stabilizing selection for a low level of paternal investment, or an evolutionary reduction in parental investment in response to chronically low parentage.

Results

We studied parental care in Variabilichromis moorii, a socially monogamous, biparental cichlid fish, whose mating system is characterized by frequent cuckoldry and whose primary form of parental care is offspring defense. We combine field observations with genetic parentage analyses to show that while both parents defend their nest against intruding con- and hetero-specifics, males and females may do so for different reasons. Males in the study group (30 breeding pairs) sired 0–100% (median 83%) of the fry in their nests. Males defended less against immediate threats to the offspring, and more against threats to their territories, which are essential for the males’ future reproductive success. Males also showed no clear relationship between their share of defense and their paternity of the brood. Females, on the other hand, were related to nearly all the offspring under their care, and defended almost equally against all types of threats.

Conclusion

Overall, males contributed less to defense than females and we suggest that this asymmetry is the result of an evolutionary response by males to chronically high paternity loss in this species. Although most males in the current study group achieved high parentage in their nests, the average paternity in V. moorii, sampled across multiple seasons, is only about 55%. We highlight the importance and complexity of studying nest defense as a form of parental care in systems where defense may serve not only to protect current offspring, but also to ensure future reproductive success by maintaining a territory.

Oviposition and father presence reduce clutch cannibalism by female poison frogs

BACKGROUND

The consumption of conspecific young by adult individuals is a common phenomenon across various animal taxa. Possible adaptive benefits of such behaviour include the acquisition of nutrients, decreased competition for one's own offspring, and/or increased mating opportunities. Clutch cannibalism has occasionally been observed in several species of Neotropical poison frogs, but the circumstances under which this behaviour occurs has rarely been investigated experimentally. Recent experiments with the poison frog Allobates femoralis have shown that males indiscriminately transport all clutches located inside their own territory to bodies of water, but become highly cannibalistic when taking over a new territory. Females are able to indirectly discriminate between their own and foreign clutches by location and take over transport duties of their own clutches only in the absence of the father. Cannibalism by A. femoralis females has not been previously observed. We thus asked if, and under which circumstances, cannibalism of unrelated clutches by female A. femoralis would occur, by manipulating the presence of the clutch's father, the female's own reproductive state, and the female's familiarity with the environment.

RESULTS

Females clearly cannibalize foreign clutches. Cannibalism was most pronounced when the female had not recently produced her own clutch and the father of the foreign clutch was absent. The female's familiarity with the area had no significant influence on the likelihood of cannibalism to occur.

CONCLUSIONS

Our data indicate that both previous oviposition and the father's presence reduce cannibalistic behaviour in A. femoralis females. Cannibalistic females may gain nutritional benefits or enhanced inclusive fitness by preying on other females' offspring. The finding that the father's presence at the clutch site/territory was sufficient to reduce cannibalism by females suggests a prominent role of male territoriality for the evolution of male parental care.

Divergent coevolutionary trajectories in parent-offspring interactions and discrimination against brood parasites revealed by interspecific cross-fostering

In animal families, parents are expected to adapt to their offspring's traits, and offspring, in turn, are expected to adapt to the environment circumscribed by their parents. However, whether such coevolutionary trajectories differ between closely related species is poorly understood. Here, we employ interspecific cross-fostering in three species of burying beetles, Nicrophorus orbicollis, Nicrophorus pustulatus and Nicrophorus vespilloides, to test for divergent co-adaptation among species with different degrees of offspring dependency on parental care, and to test whether they are able to discriminate against interspecific parasites. We found that offspring survival was always higher when offspring were reared by conspecific rather than heterospecific parents. In the case of N. orbicollis raising N. pustulatus, none of the larvae survived. Overall, these results indicate that parent and offspring traits have diverged between species, and that the differential survival of conspecific and heterospecific larvae is because of improper matching of co-adapted traits, or, in the case of N. orbicollis with larval N. pustulatus, because of selection on parents to recognize and destroy interspecific brood parasites. We suggest that burying beetles experiencing a high risk of brood parasitism have evolved direct recognition mechanisms that enable them to selectively kill larvae of potential brood parasites.

The ontogeny of kin-recognition mechanisms in Belding's ground squirrels

Despite extensive research on the functions and mechanisms of kin recognition, little is known about developmental changes in the abilities mediating such recognition. Belding's ground squirrels, Urocitellus beldingi, use at least two mechanisms of kin recognition in nepotistic contexts: familiarity and phenotype matching. Because recognition templates develop from early associations with familiar kin (and/or with self), familiarity-based recognition should precede phenotype-matching recognition even though one template is thought to be used for both mechanisms. I used a cross-fostering design to produce individuals that differed in relatedness and familiarity. Two pups (one female and one male) were exchanged reciprocally between two litters within 48-h of birth. Every five days, from 15 to 30-d of age, young were exposed to bedding and oral-gland odors from their familiar foster mother and an unfamiliar unrelated female (familiarity test) and from their unfamiliar genetic mother and another unfamiliar unrelated female (phenotype-matching test). As expected, discrimination of odors based on familiarity was evident at all ages tested, whereas discrimination based on relatedness was not evident until 30-d. My results provide a first estimate for when phenotype-matching mechanisms are used by young Belding's ground squirrels, and thus when they can recognize unfamiliar kin such as older sisters or grandmothers. Belding's ground squirrels are the first species for which the development of the production, perception and action components is well understood.

Adopt, ignore, or kill? Male poison frogs adjust parental decisions according to their territorial status

Systematic infanticide of unrelated young has been reported in several animal taxa. Particular attention has been given to carnivores and primates, where infanticide is a sexually selected strategy of males to gain increased access to female mating partners. Cannibals must ensure avoiding their own offspring and targeting only unrelated young. Therefore, decision rules are needed to mediate parental and cannibalistic behaviour. Here we show experimentally that male poison frogs adjust their parental responses – care or infanticide – towards unrelated clutches according to their territorial status. Male frogs followed the simple rule ‘care for any clutch’ inside their territory, but immediately switched to cannibalism when establishing a new territory. This demonstrates that simple cognitive rules can mediate complex behaviours such as parental care, and that care and cannibalism are antagonistically linked. Non-parental infanticide is mediated by territorial cues and presumably serves to prevent misdirected care in this poison frog. Our results thus prompt a re-consideration of evolutionary and causal aspects of parental decision making, by suggesting that selective infanticide of unrelated young may generally become adaptive when the risks and costs of misdirected care are high.

An experimental test of in-season homing mechanisms used by nest-guarding male Largemouth Bass following displacement

Through manipulations of sensory functions, researchers have evaluated the various mechanisms by which migratory fish, particularly in lotic systems, locate natal spawning grounds. Comparatively less work has occurred on the ways by which fish in lentic systems locate spawning sites, and more specifically, the ways by which displaced fish in these systems locate their broods post spawning. The primary goal of this research was to determine the sensory mechanisms used by nesting, male Largemouth Bass to navigate back to their brood following displacement. This was accomplished by comparing the ability of visually impaired, olfactory impaired and geomagnetically impaired individuals to return to their nests after a 200 m displacement, relative to control males. All treatments were designed to be temporary and harmless. We analyzed the data using a generalized linear mixed model, and found that the probability of an olfactory impaired individual returning to his nest within a given time interval was significantly lower than the probability of a geomagnetically impaired individual returning. Overall, it appears as though olfaction is the most important sensory mechanism used for homing in Largemouth Bass.

Polyandry and alternative mating tactics

Many species in the animal kingdom are characterized by alternative mating tactics (AMTs) within a sex. In males, such tactics include mate guarding versus sneaking behaviours, or territorial versus female mimicry. Although AMTs can occur in either sex, they have been most commonly described in males. This sex bias may, in part, reflect the increased opportunity for sexual selection that typically exists in males, which can result in a higher probability that AMTs evolve in that sex. Consequently, females and polyandry can play a pivotal role in governing the reproductive success associated with male AMTs and in the evolutionary dynamics of the tactics. In this review, we discuss polyandry and the evolution of AMTs. First, we define AMTs and review game theoretical and quantitative genetic approaches used to model their evolution. Second, we review several examples of AMTs, highlighting the roles that genes and environment play in phenotype expression and development of the tactics, as well as empirical approaches to differentiating among the mechanisms. Third, ecological and genetic constraints to the evolution of AMTs are discussed. Fourth, we speculate on why female AMTs are less reported on in the literature than male tactics. Fifth, we examine the effects of AMTs on breeding outcomes and female fitness, and as a source, and possibly also a consequence, of sexual conflict. We conclude by suggesting a new model for the evolution of AMTs that incorporates both environmental and genetic effects, and discuss some future avenues of research.

Odor-based recognition of familiar and related conspecifics: a first test conducted on captive Humboldt penguins (Spheniscus humboldti)

Studies of kin recognition in birds have largely focused on parent-offspring recognition using auditory or visual discrimination. Recent studies indicate that birds use odors during social and familial interactions and possibly for mate choice, suggesting olfactory cues may mediate kin recognition as well. Here, we show that Humboldt penguins (Spheniscus humboldti), a natally philopatric species with lifetime monogamy, discriminate between familiar and unfamiliar non-kin odors (using prior association) and between unfamiliar kin and non-kin odors (using phenotype matching). Penguins preferred familiar non-kin odors, which may be associated with the recognition of nest mates and colony mates and with locating burrows at night after foraging. In tests of kin recognition, penguins preferred unfamiliar non-kin odors. Penguins may have perceived non-kin odors as novel because they did not match the birds' recognition templates. Phenotype matching is likely the primary mechanism for kin recognition within the colony to avoid inbreeding. To our knowledge this is the first study to provide evidence of odor-based kin discrimination in a bird.

Parental investment without kin recognition: Simple conditional rules for parent-offspring behavior

Species differ widely with regard to parental investment strategies and mechanisms underlying those strategies. The passing of benefits to likely offspring can be instantiated with a number of different computational and behavioral systems. We report results from an agent-based model in which offspring maintain proximity with parents and parents transmit benefits to offspring without the capacity of either parent or offspring to 'recognize' one another. Instead, parents follow a simple rule to emit benefits after reproducing and offspring follow a simple rule of moving in the direction of positive benefit gradients. This model differs from previous models of spatial kin-based altruism in that individuals are modeled as having different behavioral rules at different life stages and benefits are transmitted unidirectionally from parents to offspring. High rates of correctly directed parental investment occur when mobility and sociality are low and parental investment occurs over a short period of time. We suggest that strategies based on recognition and bonding/attachment might serve to increase rates of correctly directed parental investment under parameters that are shown here to otherwise lead to high rates of misdirected and wasted parental investment.

Detective mice assess relatedness in baboons using olfactory cues

The assessment of relatedness may be crucial in the evolution of socio-sexual behaviour, because it can be associated with fitness benefits mediated by both nepotism and inbreeding avoidance. In this context, one proposed mechanism for kin recognition is 'phenotype matching'; animals might compare phenotypic similarities between themselves and others in order to assess the probability that they are related. Among cues potentially used for kin discrimination, body odours constitute interesting candidates that have been poorly investigated in anthropoid primates so far, because of a mixture of theoretical considerations and methodological/experimental constraints. In this study, we used an indirect approach to examine the similarity in odour signals emitted by related individuals from a natural population of chacma baboons (Papio ursinus). For that purpose, we designed an innovative behavioural tool using mice olfactory abilities in a habituation-discrimination paradigm. We show that: (i) mice can detect odour differences between individuals of same sex and age class in another mammal species, and (ii) mice perceive a higher odour similarity between related baboons than between unrelated baboons. These results suggest that odours may play a role in both the signalling of individual characteristics and of relatedness among individuals in an anthropoid primate. The 'biological olfactometer' developed in this study offers new perspectives to the exploration of olfactory signals from a range of species.

Paternity, parental behavior and circulating steroid hormone concentrations in nest-tending male bluegill

Like many teleost fishes, bluegill (Lepomis macrochirus) are characterized by sole male parental care of offspring. In addition, bluegill parental males experience cuckoldry by specialized parasitic male morphs. This cuckoldry has previously been shown to influence the expression of parental care behavior. To better understand some of the proximate mechanisms mediating parental behavior, we examined the relationships between circulating steroid hormones, paternity, and parental behavior during the egg and fry stages of care in parentals that spawned during the first third of the breeding season. During the egg stage of care, we found that males with higher paternity had lower levels of testosterone, but there was no relationship between paternity and either 11-ketotestosterone or cortisol. There also was no relationship between the hormones and care behavior comprising fanning of the eggs, nest rim circles, chases of brood predators, or pecking at the eggs (indicative of egg cannibalism), except for a negative relationship between cortisol and pecking behavior. During the fry stage of care, we conversely found that males with higher paternity had higher levels of testosterone and 11-ketotestosterone. There also was a negative relationship between the concentrations of these two androgens and the defensive behavior of males when exposed to a potential brood predator (a pumpkinseed, Lepomis gibbosus). We discuss these results in relation to previous work in fishes and other vertebrate taxa. Overall, our data suggest a complex relationship between circulating steroid hormone levels, paternity and parental behavior.

Morphometric changes associated with the reproductive cycle and behaviour of the intertidal-nesting, male plainfin midshipman Porichthys notatus

Morphometric changes in body condition, liver, sonic muscle and gonadal development associated with the annual reproductive cycle and behaviour of the intertidal-nesting male plainfin midshipman Porichthys notatus were investigated. Body condition of type I males rapidly increased during the pre-nesting (PN) period, peaked at the beginning of the summer nesting cycle and then gradually declined to lowest levels during the non-reproductive (NR) period. The gonado-somatic index of type I males peaked during PN and then declined during the summer nesting cycle to lowest levels at the end of the nest cycle and during NR. Indices of sonic muscle and liver of type I males were lowest during NR, gradually increased during PN and then peaked during the summer nesting cycle. Results indicate that body condition and fecundity of type I males were positively correlated with body mass at the end of the nest cycle. These findings as they relate to the annual reproductive cycle and behaviour of the type I male P. notatus are discussed.

Cuckoldry incites cannibalism: male fish turn to cannibalism when perceived certainty of paternity decreases

Perceived certainty of paternity is expected to influence a male's behavior toward his offspring: if he is uncertain of his reproductive success with a current brood due to the presence of cuckolders, it may benefit him to invest instead in future reproduction. A decrease in perceived certainty of paternity incites filial cannibalism (the eating of one's own offspring) in some teleost fishes that provide parental care; however, no work has demonstrated that cannibalism increases proportionately with increased levels of cuckoldry. Here we show for the first time in a fish with no parental care that as the number of cuckolders at a spawning event increases, so does the probability that a male will cannibalize eggs. In field observations of Telmatherina sarasinorum, a small fish endemic to Sulawesi, Indonesia, males increased filial cannibalism behavior threefold in the presence of one cuckolder and nearly sixfold in the presence of two or more cuckolders. This suggests that males may use detection of cuckolders as an indication that the paternity of current offspring has been compromised.

Development of individually distinct recognition cues

Despite extensive research on the functions of kin recognition, little is known about ontogenetic changes in the cues mediating such recognition. In Belding's ground squirrels, Spermophilus beldingi, secretions from oral glands are both individually distinct and kin distinct, and function in social recognition across many contexts. Behavioral studies of recognition and kin preferences suggest that these cues may change across development, particularly around the time of weaning and emergence from natal burrows (around 25 days of age). I used an habituation-discrimination task with captive S. beldingi, presenting subjects with odors collected from a pair of pups at several ages across early development. I found that at 21 days of age, but not at 7 or 14, young produce detectable odors. Odors are not individually distinct, however, until 28 days of age, after young have emerged from their burrows and begun foraging. In addition, an individual's odor continues to develop after emergence: odors produced by an individual at 20 and 40 days of age are perceived as dissimilar, yet odors produced at 28 and 40 days are treated as similar. Developmental changes in odors provide a proximate explanation for why S. beldingi littermate preferences are not consolidated until after natal emergence, and demonstrate that conspecifics must update their recognition templates as young develop.

Visual acuity, environmental complexity, and social organization in african cichlid fishes

The authors studied the effects of habitat complexity and social organization on visual acuity in closely related cichlid fishes (the Ectodini clade). The authors quantified habitat complexity among sand, intermediate, and rock habitats using chromatic difference measures (intensity analysis). Visual acuity was measured behaviorally, using optomotor/optokinetic responses to rotating square-wave stimuli. The rock-dwelling Asprotilapia leptura exhibited the best visual ability, compared with the intermediate and sand-dwelling species, Xenotilapia spilotera and Xenotilapia flavipinnis. The authors then compared effects of social organization. The lek-forming, polygamous Enantiopus melanogenys showed better visual acuity than that of the pair-bonding, monogamous X. flavipinnis. The authors' results are the first to demonstrate that species-specific differences in visual acuity are associated with differences in both the physical and social environment.

Stabilizing selection on genomic divergence in a wild fish population

Conservation programs use breeding protocols to increase genomic divergence (by mating genetically dissimilar individuals) in an attempt to circumvent population declines resulting from inbreeding depression. However, disruption of either beneficial gene complexes or local genetic adaptations can lead to outbreeding depression, and thus, there should be a reduction in fitness of individuals at either end of the genomic divergence continuum. Although such simultaneous inbreeding and outbreeding depression has been observed in plant populations, it rarely has been demonstrated in animal populations. Here, I use both genetic and phenotypic measures to show that there is stabilizing selection on genomic divergence in a wild population of bluegill sunfish (Lepomis macrochirus). I also show that breeding individuals that exercise mate choice produce offspring that are closer to the optimal level of genomic divergence than random mating alone would predict.

Decisions about parental care in response to perceived paternity

Evolutionary ecologists are attempting to explain how parents make behavioural decisions about how much care to provide to their young. Theory predicts that when genetic relatedness to young is decreased by cuckoldry, for example, parents should reduce their care in favour of alternative broods that provide greater reproductive success. Experimental manipulation of perceived paternity has been used to test the theory, but such studies have generated mixed results. Some manipulations can fail to alter a parent's perceived paternity, whereas others may directly affect parental behaviour when, for instance, the manipulation involves capturing the parent. No study has demonstrated parental care adjustment in a manner uncomplicated by experimental design or life history correlates. Here I test the theory using the fact that nest-tending parental male bluegill sunfish (Lepomis macrochirus) can assess their paternity using both the visual presence of parasitic cuckolder males during spawning, and olfactory cues released by newly hatched eggs. By manipulating both types of cues I show that parental males dynamically adjust their parental care, favouring broods that are apparently most closely related. These results confirm the importance of genetic relatedness in parental care decision-making.