scholarly journals How to evade a coevolving brood parasite: egg discrimination versus egg variability as host defences

2011 ◽  
Vol 278 (1724) ◽  
pp. 3566-3573 ◽  
Author(s):  
Claire N. Spottiswoode ◽  
Martin Stevens
Keyword(s):  
Visual Cues ◽  
Field Experiments ◽  
Brood Parasite ◽  
Arms Races ◽  
Egg Discrimination ◽  
Fitness Advantage ◽  
Evolutionary Trajectories ◽  
Negative Frequency Dependent Selection ◽  
Egg Mimicry ◽  
Host Rejection

Arms races between avian brood parasites and their hosts often result in parasitic mimicry of host eggs, to evade rejection. Once egg mimicry has evolved, host defences could escalate in two ways: (i) hosts could improve their level of egg discrimination; and (ii) negative frequency-dependent selection could generate increased variation in egg appearance (polymorphism) among individuals. Proficiency in one defence might reduce selection on the other, while a combination of the two should enable successful rejection of parasitic eggs. We compared three highly variable host species of the Afrotropical cuckoo finch Anomalospiza imberbis , using egg rejection experiments and modelling of avian colour and pattern vision. We show that each differed in their level of polymorphism, in the visual cues they used to reject foreign eggs, and in their degree of discrimination. The most polymorphic host had the crudest discrimination, whereas the least polymorphic was most discriminating. The third species, not currently parasitized, was intermediate for both defences. A model simulating parasitic laying and host rejection behaviour based on the field experiments showed that the two host strategies result in approximately the same fitness advantage to hosts. Thus, neither strategy is superior, but rather they reflect alternative potential evolutionary trajectories.

scholarly journals Egg Discrimination in the Yellowhammer

The Condor ◽  
2004 ◽  
Vol 106 (2) ◽  
pp. 405-410 ◽  
Author(s):  
Petr Procházka ◽  
Marcel Honza
Keyword(s):  
Brood Parasitism ◽  
Host Responses ◽  
Brood Parasite ◽  
Cuculus Canorus ◽  
The Czech Republic ◽  
Egg Discrimination ◽  
Emberiza Citrinella ◽  
Interspecific Brood Parasitism ◽  
Egg Mimicry ◽  
A Minor

Abstract In a coevolutionary arms race between a brood parasite and its host, both species evolve adaptations and counteradaptations, such as egg mimicry and egg discrimination. The Yellowhammer (Emberiza citrinella) is a minor host of the Common Cuckoo (Cuculus canorus) in Europe. We studied egg discrimination in the Yellowhammer in the Czech Republic where it is parasitized only occasionally. To investigate host responses to parasitic eggs, we added either a nonmimetic (blue) or a mimetic (conspecific) egg to 50 nests. The hosts rejected nonmimetic eggs at a higher rate (92%) than mimetic eggs (32%). Neither intraclutch variation nor contrast between mimetic and host eggs had a significant effect on rejection behavior. There is no evidence for intraspecific brood parasitism in this species. The ability to reject mimetic eggs has therefore most likely evolved as an adaptation against interspecific brood parasitism and may be the reason why the Yellowhammer is parasitized only occasionally. Discriminación de Huevos en Emberiza citrinella Resumen. En una carrera armamentista co-evolutiva entre un ave parásita y su hospedador es previsible que ambas especies desarrollen adaptaciones y contraadaptaciones tales como el ovomimetismo y la ovodiscriminación. Emberiza citrinella es un huésped menor de Cuculus canorus en Europa. Estudiamos la capacidad discriminatoria de los huevos, por parte de Emberiza citrinella, en la República Checa, donde la especie es parasitada sólo ocasionalmente. Con objeto de investigar la respuesta del hospedador a los huevos parásitos, añadimos un huevo no mimético (azul) o uno mimético (coespecífico) a 50 nidos. El hospedador rechazó los huevos no miméticos en una proporción más elevada (92%) que los miméticos (32%). Ni la variación de la apariencia del huevo dentro de la puesta, ni el contraste entre los huevos miméticos y los del hospedador, parecen tener algún efecto significativo en el comportamiento de rechazo. No hay evidencias de la existencia de parasitismo intraespecífico en esta especie. Por tanto, la habilidad de Emberiza citrinella para rechazar huevos miméticos probablemente ha evolucionado como una adaptación contra el parasitismo interespecífico y esta puede ser la razón de por qué la especie es parasitada sólo de manera ocasional.

scholarly journals Host–parasite coevolution beyond the nestling stage? Mimicry of host fledglings by the specialist screaming cowbird

2012 ◽  
Vol 279 (1742) ◽  
pp. 3401-3408 ◽  
Author(s):  
María C. De Mársico ◽  
Mariela G. Gantchoff ◽  
Juan C. Reboreda
Keyword(s):  
Survival Rates ◽  
Plumage Colour ◽  
Brood Parasite ◽  
Primary Host ◽  
Brood Parasites ◽  
Molothrus Bonariensis ◽  
Egg Mimicry ◽  
Host Parasite ◽  
Host Rejection

Egg mimicry by obligate avian brood parasites and host rejection of non-mimetic eggs are well-known textbook examples of host–parasite coevolution. By contrast, reciprocal adaptations and counteradaptations beyond the egg stage in brood parasites and their hosts have received less attention. The screaming cowbird ( Molothrus rufoaxillaris ) is a specialist obligate brood parasite whose fledglings look identical to those of its primary host, the baywing ( Agelaioides badius ). Such a resemblance has been proposed as an adaptation in response to host discrimination against odd-looking young, but evidence supporting this idea is scarce. Here, we examined this hypothesis by comparing the survival rates of young screaming cowbirds and non-mimetic shiny cowbirds ( Molothrus bonariensis ) cross-fostered to baywing nests and quantifying the similarity in plumage colour and begging calls between host and cowbird fledglings. Shiny cowbirds suffered higher post-fledging mortality rates (83%) than screaming cowbirds (0%) owing to host rejection. Visual modelling revealed that screaming cowbirds, but not shiny cowbirds, were indistinguishable from host young in plumage colour. Similarly, screaming cowbirds matched baywings' begging calls more closely than shiny cowbirds. Our results strongly support the occurrence of host fledgling mimicry in screaming cowbirds and suggest a role of visual and vocal cues in fledgling discrimination by baywings.

scholarly journals Can't tell the caterpillars from the trees: countershading enhances survival in a woodland

2008 ◽  
Vol 275 (1651) ◽  
pp. 2539-2545 ◽  
Author(s):  
Hannah M Rowland ◽  
Innes C Cuthill ◽  
Ian F Harvey ◽  
Michael P Speed ◽  
Graeme D Ruxton
Keyword(s):  
Visual Cues ◽  
Field Experiments ◽  
Three Dimensional ◽  
Shape From Shading ◽  
The Body ◽  
Colour Pattern ◽  
Free Living ◽  
Background Matching ◽  
Lepidopteran Larvae ◽  
Beech Tree

Perception of the body's outline and three-dimensional shape arises from visual cues such as shading, contour, perspective and texture. When a uniformly coloured prey animal is illuminated from above by sunlight, a shadow may be cast on the body, generating a brightness contrast between the dorsal and ventral surfaces. For animals such as caterpillars, which live among flat leaves, a difference in reflectance over the body surface may degrade the degree of background matching and provide cues to shape from shading. This may make otherwise cryptic prey more conspicuous to visually hunting predators. Cryptically coloured prey are expected to match their substrate in colour, pattern and texture (though disruptive patterning is an exception), but they may also abolish self-shadowing and therefore either reduce shape cues or maintain their degree of background matching through countershading: a gradation of pigment on the body of an animal so that the surface closest to illumination is darker. In this study, we report the results from a series of field experiments where artificial prey resembling lepidopteran larvae were presented on the upper surfaces of beech tree branches so that they could be viewed by free-living birds. We demonstrate that countershading is superior to uniform coloration in terms of reducing attack by free-living predators. This result persisted even when we fixed prey to the underside of branches, simulating the resting position of many tree-living caterpillars. Our experiments provide the first demonstration, in an ecologically valid visual context, that shadowing on bodies (such as lepidopteran larvae) provides cues that visually hunting predators use to detect potential prey species, and that countershading counterbalances shadowing to enhance cryptic protection.

scholarly journals Brood parasitism selects for no defence in a cuckoo host

2011 ◽  
Vol 278 (1719) ◽  
pp. 2777-2783 ◽  
Author(s):  
Oliver Krüger
Keyword(s):  
Brood Parasitism ◽  
Adaptive Behaviour ◽  
Arms Races ◽  
Defence Behaviour ◽  
Egg Mimicry ◽  
Evolutionary Lag ◽  
Thick Shells ◽  
Defence Strategies ◽  
Coevolutionary Arms Race ◽  
Parasite Avoidance

In coevolutionary arms races, like between cuckoos and their hosts, it is easy to understand why the host is under selection favouring anti-parasitism behaviour, such as egg rejection, which can lead to parasites evolving remarkable adaptations to ‘trick’ their host, such as mimetic eggs. But what about cases where the cuckoo egg is not mimetic and where the host does not act against it? Classically, such apparently non-adaptive behaviour is put down to evolutionary lag: given enough time, egg mimicry and parasite avoidance strategies will evolve. An alternative is that absence of egg mimicry and of anti-parasite behaviour is stable. Such stability is at first sight highly paradoxical. I show, using both field and experimental data to parametrize a simulation model, that the absence of defence behaviour by Cape bulbuls ( Pycnonotus capensis ) against parasitic eggs of the Jacobin cuckoo ( Clamator jacobinus ) is optimal behaviour. The cuckoo has evolved massive eggs (double the size of bulbul eggs) with thick shells, making it very hard or impossible for the host to eject the cuckoo egg. The host could still avoid brood parasitism by nest desertion. However, higher predation and parasitism risks later in the season makes desertion more costly than accepting the cuckoo egg, a strategy aided by the fact that many cuckoo eggs are incorrectly timed, so do not hatch in time and hence do not reduce host fitness to zero. Selection will therefore prevent the continuation of any coevolutionary arms race. Non-mimetic eggs and absence of defence strategies against cuckoo eggs will be the stable, if at first sight paradoxical, result.

scholarly journals The ghosts of parasitism past: lingering frontline anti-brood parasite defences in a former host

2021 ◽  
Author(s):  
Matthew H J Chaumont ◽  
Naomi E Langmore ◽  
Justin A Welbergen
Keyword(s):  
Brood Parasitism ◽  
Species Interactions ◽  
Egg Laying ◽  
Arms Race ◽  
Fine Tuning ◽  
Brood Parasite ◽  
Reed Warbler ◽  
Arms Races ◽  
Brood Parasites ◽  
Defensive Behaviors

Abstract Coevolutionary arms races between brood parasites and hosts provide tractable systems for understanding antagonistic coevolution in nature; however, little is known about the fate of frontline antiparasite defences when the host ‘wins’ the coevolutionary arms race. By recreating bygone species-interactions, using artificial parasitism experiments, lingering defensive behaviors that evolved in the context of parasitism can be understood and may even be used to identify the unknown agent of parasitism past. Here we present the first study of this type by evaluating lingering “frontline” nest defences that have evolved to prevent egg laying in a former brood parasite host. The Australian reed warbler Acrocephalus australis, is currently not parasitized but is known to exhibit fine-tuned egg discrimination—a defensive behavior indicative of a past brood parasite-host arms race and common in closely related parasitized species. Here, using 3 D-printed models of adult brood parasites, we examined whether the Australian reed warbler also exhibits frontline defences to adult brood parasites, and whether we could use these defences to identify the warbler’s “ghost of parasitism past”. Our findings provide evidence that the Australian reed warbler readily engages in frontline defences that are considered adaptive specifically in the context of brood parasitism. However, individuals were unable to discriminate between adults of different brood parasite species at their nest. Overall, our results demonstrate that despite a relaxation in selection, defences against brood parasitism can be maintained across multiple stages of the host’s nesting cycle, and further suggest that, in accordance with previous findings, that learning may be important for fine-tuning frontline defence.

scholarly journals Cryptic cuckoo eggs hide from competing cuckoos

2014 ◽  
Vol 281 (1792) ◽  
pp. 20141014 ◽  
Author(s):  
Ros Gloag ◽  
Laurie-Anne Keller ◽  
Naomi E. Langmore
Keyword(s):  
Selective Agent ◽  
High Luminance ◽  
Arms Races ◽  
Low Luminance ◽  
Egg Mimicry ◽  
Egg Removal ◽  
Egg Crypsis

Interspecific arms races between cuckoos and their hosts have produced remarkable examples of mimicry, with parasite eggs evolving to match host egg appearance and so evade removal by hosts. Certain bronze-cuckoo species, however, lay eggs that are cryptic rather than mimetic. These eggs are coated in a low luminance pigment that camouflages them within the dark interiors of hosts' nests. We investigated whether cuckoo egg crypsis is likely to have arisen from the same coevolutionary processes known to favour egg mimicry. We added high and low luminance-painted eggs to the nests of large-billed gerygones ( Gerygone magnirostris ), a host of the little bronze-cuckoo ( Chalcites minutillus ). Gerygones rarely rejected either egg type, and did not reject natural cuckoo eggs. Cuckoos, by contrast, regularly removed an egg from clutches before laying their own and were five times more likely to remove a high luminance model than its low luminance counterpart. Given that we found one-third of all parasitized nests were exploited by multiple cuckoos, our results suggest that competition between cuckoos has been the key selective agent for egg crypsis. In such intraspecific arms races, crypsis may be favoured over mimicry because it can reduce the risk of egg removal to levels below chance.

scholarly journals Evolution of host egg mimicry in a brood parasite, the great spotted cuckoo

2003 ◽  
Vol 79 (4) ◽  
pp. 551-563 ◽  
Author(s):  
JUAN J. SOLER ◽  
JESUS M. AVILES ◽  
MANUEL SOLER ◽  
ANDERS P. MØLLER
Keyword(s):  
Brood Parasite ◽  
Egg Mimicry

A field study of homing and orientation to the home site in Ulvaria subbifurcata (Pisces: Stichaeidae)

1977 ◽  
Vol 55 (9) ◽  
pp. 1551-1556 ◽  
Author(s):  
John M. Green ◽  
Robert Fisher
Keyword(s):  
Home Range ◽  
Field Study ◽  
Visual Cues ◽  
Field Experiments ◽  
Benthic Species ◽  
Homing Behavior ◽  
Orientational Response ◽  
Home Site ◽  
Home Area ◽  
Small Home Range

The movements, homing behavior, and initial orientation to the capture site were investigated in Ulvaria subbifurcata using an underwater habitat and scuba. Field experiments showed that this benthic species restricts its activity to a small home range, less than 3 m2, is capable of returning to that home area after being displaced at least 270 m, and can orient in the direction of the home site after displacements of at least 30 m. The conditions under which the orientation experiments were conducted indicate that visual cues are not necessary for the orientational response.

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