Evolution Of Brood Parasitism Research Articles

The evolution of brood parasitism from host egg predation

Abstract Obligate brood parasites pass all their parental duties to foster parents of a host species. While best understood in birds and hymenopteran insects, obligate brood parasitism has evolved independently at least 59 times across many lineages. The ancestors of brood parasites often provided no parental care to their offspring. Instead, a trophic association with their eventual hosts commonly appears to precede the origin of a brood parasitic strategy. Here, we used a game theoretical model to explore the conditions under which brood parasitism can evolve from predation and be maintained in the population. Our model was inspired by the relationship between the cuckoo catfish (Synodontis multipunctatus) parasitizing mouthbrooding cichlid fishes in the African Lake Tanganyika. Our model demonstrates the facilitatory role of host egg predation on the origin and evolutionary maintenance of brood parasitism through the exploitation of the host response to egg predation by brood parasites. We found no conditions under which brood parasitism as a pure strategy is evolutionarily stable, but we describe a range of evolutionarily stable equilibria when predators and parasites coexist. While our model is tailored to the cuckoo catfish, it generally applies to other systems where brood parasitism has evolved from other antagonistic behavior.

Did extreme nest predation favor the evolution of obligate brood parasitism in a duck?

Obligate brood parasites depend entirely on other species to raise their offspring. Most avian obligate brood parasites have altricial offspring that require enormous amounts of posthatching parental care, and the large fecundity boost that comes with complete emancipation from parental care likely played a role in the independent evolution of obligate parasitism in several altricial lineages. The evolution of obligate parasitism in the black‐headed duck, however, is puzzling because its self‐feeding precocial offspring should not constrain parental fecundity of a potential brood parasite in the way that altricial offspring do. We used an experimental nest predation study to test the idea that high nest predation rates played a role in the evolution of brood parasitism in this enigmatic duck. Experimental duck eggs in untended nests suffered massive rapid predation, while eggs in tended nests of the three main hosts, all aggressive nest defenders, had very high success, illustrating the benefits of parasitizing these ‘bodyguard’ hosts.

A siblicidal origin for avian brood parasitism?

We present a model for the evolution of host selection by avian brood parasites from the ecological context of siblicidal brood reduction tactics. Our analysis concentrates on the fitness costs and benefits that permit the evolution of brood parasitism as an adaptive strategy from a state of obligate parental care already featuring siblicide. Limited resources delivered by provisioning parents may incite siblicidal behaviour in offspring, directed towards nestmates regardless of kinship. The extent of siblicidal behaviour (in frequency of occurrence and number of nestmates killed) can extend to the eradication of all nestmates, as has been observed in some raptors and in seabirds. For parents of siblicidal offspring, laying each egg parasitically may maximize offspring survival by eliminating competition between related but siblicidal nest mates. To permit the evolution of conspecific (intraspecific) brood parasitism, costs of siblicide by the offspring of parasitic parents must exceed costs paid by the parasitic parents when losing related conspecifics (host offspring) in a host nest. To permit the evolution of obligate interspecific brood parasitism, costs to fitness from siblicidal offspring or nest reduction of related hosts must exceed costs of heterospecific parental care. Understanding the kin structure between parasites and hosts in conspecific parasitism, and measuring the costs paid by parasitic young due to mismatched incubation, provisioning, and social behaviours by heterospecific foster parents, should provide novel insights into the opportunities and constraints of the evolution of avian brood parasitism.

Continuous variation rather than specialization in the egg phenotypes of cuckoos (Cuculus canorus) parasitizing two sympatric reed warbler species.

The evolution of brood parasitism has long attracted considerable attention among behavioural ecologists, especially in the common cuckoo system. Common cuckoos (Cuculus canorus) are obligatory brood parasites, laying eggs in nests of passerines and specializing on specific host species. Specialized races of cuckoos are genetically distinct. Often in a given area, cuckoos encounter multiple hosts showing substantial variation in egg morphology. Exploiting different hosts should lead to egg-phenotype specialization in cuckoos to match egg phenotypes of the hosts. Here we test this assumption using a wild population of two sympatrically occurring host species: the great reed warbler (Acrocephalus arundinaceus) and reed warbler (A. scirpaceus). Using colour spectrophotometry, egg shell dynamometry and egg size measurements, we studied egg morphologies of cuckoos parasitizing these two hosts. In spite of observing clear differences between host egg phenotypes, we found no clear differences in cuckoo egg morphologies. Interestingly, although chromatically cuckoo eggs were more similar to reed warbler eggs, after taking into account achromatic differences, cuckoo eggs seemed to be equally similar to both host species. We hypothesize that such pattern may represent an initial stage of an averaging strategy of cuckoos, that – instead of specializing for specific hosts or exploiting only one host – adapt to multiple hosts.

Linking nest predation with brood parasitism in captive zebra finches: a multi-pair study

Zebra finches (Taeniopygia guttata) are social, colonial nesting birds with moderate levels of intraspecific brood parasitism reported in both wild and captive populations. In a previous study, individually housed, captive zebra finch pairs responded to nest removal during the egg-laying period by parasitising simulated active conspecific nests. In the study reported here, we investigated the role of nest loss as a proximate trigger for parasitism in a more naturalistic setting: small groups consisting of three pairs per aviary. In three of ten experimental trials, females responded to nest removal during the egg-laying period by laying eggs in active neighbouring nests. This rate of parasitism was lower than that reported previously for individually housed pairs, and aggressive interactions between hosts and putative parasites were also observed. The results provide further support for the Hamilton–Orians hypothesis for the evolutionary origin of brood parasitism and highlight the influence of social context on the expression of brood parasitic behaviour. Together with qualitative descriptions of several previously unreported behaviours associated with nesting and brood parasitism in captive zebra finches, these experiments provide a functional context and methodology for future studies on zebra finches as a potential new model for the ecology and evolution of brood parasitism.

Evolution of brood parasitism in birds: constraints related to prey type

Few birds are obligate brood parasites and one explanation is that the young will not thrive with the food and parental care provided by another species. We addressed this problem by cross-fostering between two passerine birds with similar breeding ecology, viz., the pied flycatcher (Ficedula hypoleuca), and the great tit (Parus major). A previous study showed that pied flycatchers are readily raised by great tit foster parents, but that cross-fostering of great tits to pied flycatcher nests fails. In the present study, great tit nestlings were temporarily placed in pied flycatcher nests and video filmed when three and 10 days old. The parents did not seem to discriminate between the nestlings of the two species but the great tits had more problems handling the prey. Apparently, the offspring of the two species have adapted to different diets, pied flycatchers providing more adult and winged insects to their young than do great tits. We suggest that species with nestlings feeding on prey items that are difficult to swallow are more likely candidates to become interspecific brood parasites than species feeding on soft prey easily ingested.

Experimental support for the role of nest predation in the evolution of brood parasitism

In 1965, Hamilton and Orians (HO) hypothesized that the starting point for the evolution of obligate interspecific brood parasitism in birds was the facultative laying of physiologically committed eggs in neighbouring active nests of con- and heterospecifics, following predation of a bird's own nest during the laying stage. We tested this prediction of the HO hypothesis by using captive pairs of zebra finches (Taeniopygia guttata), a species with evidence for intraspecific parasitism both in the wild and in captivity. As predicted, in response to experimental nest removal, subjects laid eggs parasitically in simulated active conspecific nests above chance levels. Across subsequent trials, we detected both repeatability and directional change in laying patterns, with some subjects switching from parasitism to depositing eggs in the empty nest. Taken together, these results support the assumptions and predictions of the HO hypothesis, and indicate that the zebra finch is a potential model species for future behavioural and genetic studies in captive brood parasite research.

Strategic Variation in Mobbing as a Front Line of Defense against Brood Parasitism

Coevolutionary arms races, where adaptations in one party select for counter-adaptations in another and vice versa, are fundamental to interactions between organisms and their predators, pathogens, and parasites [1]. Avian brood parasites and their hosts have emerged as model systems for studying such reciprocal coevolutionary processes [2, 3]. For example, hosts have evolved changes in egg appearance and rejection of foreign eggs in response to brood parasitism from cuckoos, and cuckoos have evolved host-egg mimicry as a counter-response [4-6]. However, the host's front line of defense is protecting the nest from being parasitized in the first place [7-10], yet little is known about the effectiveness of nest defense as an antiparasite adaptation, and its coevolutionary significance remains poorly understood [10]. Here we show first that mobbing of common cuckoos Cuculus canorus by reed warblers Acrocephalus scirpaceus is an effective defense against parasitism. Second, mobbing of cuckoos is a phenotypically plastic trait that is modified strategically according to local parasitism risk. This supports the view that hosts use a "defense in-depth strategy," with successive flexible lines of defense that coevolve with corresponding offensive lines of the parasite. This highlights the need for more holistic research into the coevolutionary consequences when multiple adaptations and counter-adaptations evolve in concert [11].

Offspring development mode and the evolution of brood parasitism

In the evolution of interspecific social parasites, the shift from facultative to obligate brood parasitism is thought to be driven by the cost of parental investment. Accordingly, avian brood parasites with precocial young are almost exclusively facultative parasites, whereas those with altricial young are almost exclusively obligate parasites. Surprisingly, then, North American cuckoos (Coccyzus spp.) have altricial young but are described as facultative brood parasites. Because little is known about parasitism by Coccyzus cuckoos, we explored the potential importance of heterogeneric brood parasitism to their reproductive strategy. In contrast to the existing set of anecdotal reports of cuckoos parasitizing songbirds, we found no evidence of cuckoo parasitism in 10 197 songbird nests, despite spatial and temporal overlap between cuckoos and potential hosts and despite varied food availability. Experiments revealed a lack of egg-rejection behavior in some of the most common potential hosts, suggesting that parasitic eggs would be accepted if laid and that we would detect cuckoo parasitism if it occurred regularly. We propose that reports of Coccyzus cuckoos parasitizing songbirds stem from errant attempts to parasitize other cuckoos. This resolves a theoretical paradox about interspecific parasitism and mode of offspring development, as we suggest that Coccyzus cuckoos have not evolved to parasitize other species. Key words: altricial, brood parasitism, cuckoo, facultative, obligate, precocial. [Behav Ecol]

Evolution and life-history correlates of female song in the New World blackbirds

Female song is much more prevalent in tropical than in temperate songbirds but, we know surprisingly little about the evolutionary origins of this striking latitudinal difference. Here I reconstruct the evolution of female song in the New World blackbird family (Icteridae) and compare historical changes in this trait to changes in several other life-history characters: social mating system, nesting pattern, and migratory behavior. Reconstructions using both parsimony and maximum likelihood methods show that female song has been lost repeatedly in this clade and that tropical ancestors with frequent female song almost invariably were monogamous, had dispersed nest sites, and were nonmigratory. Losses of female song were not consistently associated with changes in any single life-history characteristic across the family, but rather appear to have occurred for different reasons in different lineages, including the evolution of migration in the oriole genus (Icterus), the evolution of brood parasitism in the cowbirds (Molothrus), and the evolution of polygynous, colonial breeding in the oropendolas (Psarocolius, Gymnostinops) and caciques (Cacicus). These results support previous suggestions that the prevalence of female song in the tropics is largely explained by the life-history traits associated with tropical habitats. Key words: ancestral state reconstruction, comparative methods, duetting, female bird song, life history, phylogeny. [Behav Ecol]

The evolution of sexual dimorphism in parasitic cuckoos: sexual selection or coevolution?

Sexual dimorphism is ubiquitous in animals and can result from selection pressure on one or both sexes. Sexual selection has become the predominant explanation for the evolution of sexual dimorphism, with strong selection on size-related mating success in males being the most common situation. The cuckoos (family Cuculidae) provide an exceptional case in which both sexes of many species are freed from the burden of parental care but where coevolution between parasitic cuckoos and their hosts also results in intense selection. Here, we show that size and plumage differences between the sexes in parasitic cuckoos are more likely the result of coevolution than sexual selection. While both sexes changed in size as brood parasitism evolved, we find no evidence for selection on males to become larger. Rather, our analysis indicates stronger selection on parasitic females to become smaller, resulting in a shift from dimorphism with larger females in cuckoos with parental care to dimorphism with larger males in parasitic species. In addition, the evolution of brood parasitism was associated with more cryptic plumage in both sexes, but especially in females, a result that contrasts with the strong plumage dimorphism seen in some other parasitic birds. Examination of the three independent origins of brood parasitism suggests that different parasitic cuckoo lineages followed divergent evolutionary pathways to successful brood parasitism. These results argue for the powerful role of parasite-host coevolution in shaping cuckoo life histories in general and sexual dimorphism in particular.

Noisy Plasticity and Evolution of Brood Parasitism

Noisy Plasticity and Evolution of Brood Parasitism

Other mothers’ ducklings–why look after them?

Not all female animals look after their own young and the attention devoted to their own offspring varies enormously among species. But even within species with well-developed female parental care, certain females might choose an alternative breeding tactic and leave their offspring in the care of others. Such brood parasitism is particularly common in ducks, where some females (‘hosts’) often receive eggs laid by other females (‘parasites’) of the same species. But why would a female accept someone else's responsibilities? After all, taking care of another female's chicks can sap the caretaker's strength and increase her exposure to predators. Several ideas have been proposed to solve this puzzle, ranging from the simple notion that females might not be able to discriminate between her own offspring and those of others, to the hypothesis that a female might actually enhance the survival of her own progeny by accepting offspring of others. An intriguing idea is that parasites and hosts could be related. As relatives share some of their genes, the costs paid by a host female might be counterbalanced by the propagation of her own genes through the offspring of her related parasite. Although the general importance of ‘kin selection’ was proposed by W.D. Hamilton in the 1960s, and its potential role in the evolution of brood parasitism was identified by Malte Andersson in the early 1980s, this idea still remains a matter of hot debate.

Nestling aggression and the evolution of brood parasitism in altricial birds

Interspecific brood parasitism, in which females lay eggs in the nests of other species, has been observed in many altricial birds. In addition, nestling aggression, in which parasite nestlings attempt to out compete or kill host eggs or nestlings, occurs in many species of interspecific brood parasites. We examine the relationship traits for nestling aggression potentially have to the evolution of obligate brood parasitism. We propose the following: (1) under conditions in which a low number of extra eggs is made possible by being freed from parental care, a stable facultative stage could arise; (2) if aggression arose in a stable facultative parasite, aggression would be selected for if the ratio of the increase in success conferred on young in host nests to the decrease in success suffered by young in the home nest was above some threshold; and (3) once aggression had arisen in the facultative parasite, it could produce strong selection for the evolution of an obligate strategy.

The evolution of brood parasitism: the role of facultative parasitism

The evolution of brood parasitism: the role of facultative parasitism

A Phylogenetic Study of the Blackbirds Based on Variation in Mitochondrial DNA Restriction Sites

We used a generalized parsimony model to estimate the phylogeny of 47 species in the avian subfamily Icterinae using restriction enzyme cleavage sites in mitochondrial DNA (mtDNA). Deep branches in the tree are poorly resolved, either because blackbirds radiated rapidly after the origin of the dade or because substitutions have saturated sites in the mtDNA. Our tree is similar to one published by Lanyon (1994, Evolution 48:679-693) based on mtDNA sequences, which suggests that lack of basal resolution might be attributable to closely spaced speciation events. Both data sets had similar consistency and retention indices, suggesting comparable information content in these two types of data. Neither the restriction-site tree nor the sequence tree support the monophyly of the genus Agelaius. The restriction-site tree suggests that several traditional taxonomic rearrangements are likely based on phenotypic resemblance rather than phylogeny and that the feature viewed as a key innovation of blackbirds (gaping) might not be the basal condition; gaping might be a composite of characters rather than a single homologous condition. The re? striction-site tree suggests that the brood-parasitic cowbird species are not monophyletic, contra the sequence data. A combined analysis of sequences and restriction sites for cowbirds supports the sequence tree of Lanyon (1994); however, we suggest an alternative view of the evolution of brood parasitism that is also consistent with the combined data tree. Polygyny appears to be independently derived within blackbirds. Icterus galbula and I. bullockii, which hybridize and are therefore currently considered a single biological species, are not sister taxa; these are likely phy? logenetic species. (Blackbirds; generalized parsimony; maximum likelihood; brood parasitism; mating systems; phylogenetic species concept.)

On Testing the Hamilton-Orians Hypothesis for the Origin of Brood Parasitism

Brood parasitism has long been of interest to ornithologists, but little is known about its evolutionary origin. Hamilton and Orians (1965) proposed that one factor favoring the evolution of brood parasitism might be nest destruction during egg laying. Because most birds lay a clutch of eggs over a series of days, and because successive eggs are ovulated soon after the previous egg is laid, females become physiologically committed to laying their next egg within hours of laying the previous egg of the clutch. Thus, if the nest is destroyed during the laying period, the female is faced with the problem of where to lay the physiologically committed egg and might benefit by laying it in another bird's nest.