Gens (behaviour)

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In animal behaviour, a gens (pl. gentes) or host race is a lineage of a brood parasite species that inherits phenotypic traits adapted for a specific type of host, even though the whole parasite species uses a larger variety of hosts. Brood parasitism is particularly well-known in birds such as the common cuckoo, which lays its eggs in the nests of other birds and exploits the parental effort of the host bird to raise the parasitic offspring.

Many species of avian brood parasite evolve to lay eggs that mimic their hosts' in appearance to reduce the chance that their eggs will be recognised and rejected by the hosts. [1] Brood parasite species that evolve to have gentes are able to evolve close mimicry to a variety of host species with different egg appearances, but individual birds raised by different hosts can breed together without the risk of changing the specialized phenotypes of their eggs. A gens may be specialized to parasitise a few species of hosts with similar eggs, or one host species, or even a smaller subset of a single species with highly variable eggs.

The exact mechanisms of the evolution and maintenance of gentes is still a matter of some research, and it is likely that different species use a mixture of inheritance methods. However, gentes are often distinguished from subspecies when the brood parasite shows some degree of matrilineal inheritance, from mother to daughter. Since it is the female that both lays the eggs and chooses the host nests, this form of inheritance would reliably ensure that eggs with the correct phenotype are laid in the correct nests. This, in turn, reduces the chances of the eggs being rejected by the hosts, with about 5% of well-matched eggs compared to 72% of mismatched eggs rejected by cuckoo hosts. [2] Matrilineal inheritance can be either genetic, based on sex chromosomes or mitochondria, or cultural, with mate choice based on a common host species or nest environment.

In the common cuckoo, it is believed that gens-specific properties are sex-linked and lie on the W chromosome of the female. [3] The male cuckoo, like all male birds, has no W chromosome and could therefore mate with a female from any gens without affecting egg phenotype. However, common cuckoo gentes may also incorporate autosomal genes contributed by both parents. [4] There is stronger evidence for matrilineal inheritance in the greater honeyguide based on whether they parasitize hosts that nest in trees or in burrows, but they also have additional host-specific differences in egg size and shape that are not matrilineal. [5] The cuckoo-finch represents the clearest case of a species in which inheritance of egg phenotype on the W chromosome is probably the primary mechanism for the evolution of gentes. [6] The most recently-diverged cuckoo-finch matrilines are those that specialize even more specifically on different egg phenotypes laid by the same host species, but cuckoo-finches breed as a mixed population regardless of which host they were raised by.

Not all brood parasite species have gentes, although relatively few species have been studied well enough to be certain how common the phenomenon is. Species that are already highly specialized, such as indigobirds or the screaming cowbird, are not likely to have gentes. On the other hand, not all generalist brood parasites that use a wide variety of hosts have gentes either. As in the shiny cowbird, where females show host preferences matched by differences in egg characteristics and which also have some genetic divergence, the distinction can still be unclear. [7] The conditions that a female brood parasite is raised in may affect the egg size of that female later in life, as in the shiny cowbird and greater honeyguide examples, and reinforce a host-specific phenotype based on egg size. Alternatively, some brood parasites may imprint on the habitat or the nest they were raised in, and choose mates and hosts accordingly. [8] Finally, any brood parasite species that uses a large variety of hosts may have subspecies that use a smaller subset of hosts than the whole population, but these are distinguished from gentes because their breeding populations are more isolated from others.

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<span class="mw-page-title-main">Cuckoo</span> Family of birds

Cuckoos are birds in the Cuculidae family, the sole taxon in the order Cuculiformes. The cuckoo family includes the common or European cuckoo, roadrunners, koels, malkohas, couas, coucals, and anis. The coucals and anis are sometimes separated as distinct families, the Centropodidae and Crotophagidae, respectively. The cuckoo order Cuculiformes is one of three that make up the Otidimorphae, the other two being the turacos and the bustards. The family Cuculidae contains 150 species, which are divided into 33 genera.

<span class="mw-page-title-main">Common cuckoo</span> Species of bird

The cuckoo, common cuckoo, European cuckoo or Eurasian cuckoo is a member of the cuckoo order of birds, Cuculiformes, which includes the roadrunners, the anis and the coucals.

<span class="mw-page-title-main">Parrotbill</span> Group of birds

The parrotbills are a family, Paradoxornithidae, of passerine birds that are primarily native to East, Southeast and South Asia, with a single species in western North America, though feral populations exist elsewhere. They are generally small birds that inhabit reedbeds, forests and similar habitats. The traditional parrotbills feed mainly on seeds, e.g. of grasses, to which their robust bill, as the name implies, is well-adapted. Members of the family are usually non-migratory.

<span class="mw-page-title-main">Viduidae</span> Family of birds

The indigobirds and whydahs, together with the cuckoo-finch, make up the family Viduidae; they are small passerine birds native to Africa.

<span class="mw-page-title-main">Brown-headed cowbird</span> Species of bird

The brown-headed cowbird is a small, obligate brood parasitic icterid native to temperate and subtropical North America. It is a permanent resident in the southern parts of its range; northern birds migrate to the southern United States and Mexico in winter, returning to their summer habitat around March or April.

<span class="mw-page-title-main">Asian koel</span> Species of bird

The Asian koel is a member of the cuckoo order of birds, the Cuculiformes. It is found in the Indian Subcontinent, China, and Southeast Asia. It forms a superspecies with the closely related black-billed koels, and Pacific koels which are sometimes treated as subspecies. The Asian koel like many of its related cuckoo kin is a brood parasite that lays its eggs in the nests of crows and other hosts, who raise its young. They are unusual among the cuckoos in being largely frugivorous as adults. The name koel is echoic in origin with several language variants. The bird is a widely used symbol in Indian and Nepali poetry.

<span class="mw-page-title-main">Brood parasitism</span> Animal reliance on other individuals to raise its young

Brood parasitism is a subclass of parasitism and phenomenon and behavioural pattern of animals that rely on others to raise their young. The strategy appears among birds, insects and fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its own, usually using egg mimicry, with eggs that resemble the host's. The strategy involves a form of aggressive mimicry called Kirbyan mimicry.

<span class="mw-page-title-main">Shiny cowbird</span> Species of bird

The shiny cowbird is a passerine bird in the New World family Icteridae. It breeds in most of South America except for dense forests and areas of high altitude such as mountains. Since 1900 the shiny cowbird's range has shifted northward, and it was recorded in the Caribbean islands as well as the United States, where it is found breeding in southern Florida. It is a bird associated with open habitats, including disturbed land from agriculture and deforestation.

An obligate parasite or holoparasite is a parasitic organism that cannot complete its life-cycle without exploiting a suitable host. If an obligate parasite cannot obtain a host it will fail to reproduce. This is opposed to a facultative parasite, which can act as a parasite but does not rely on its host to continue its life-cycle. Obligate parasites have evolved a variety of parasitic strategies to exploit their hosts.

<span class="mw-page-title-main">Koel</span> Genus of birds

The true koels, Eudynamys, are a genus of cuckoos from Asia, Australia and the Pacific. They are large sexually dimorphic cuckoos that eat fruits and insects and have loud distinctive calls. They are brood parasites, laying their eggs in the nests of other species.

<i>Cuculus</i> Genus of birds

Cuculus is a genus of cuckoos which has representatives in most of the Old World, although the greatest diversity is in tropical southern and southeastern Asia.

Habitat selection hypothesis is one of several hypotheses that attempt to explain the mechanisms of brood parasite host selection in cuckoos. Cuckoos are not the only brood parasites, however the behavior is more rare in other groups of birds, including ducks, weavers, and cowbirds.

<span class="mw-page-title-main">Horsfield's bronze cuckoo</span> Species of bird

Horsfield's bronze cuckoo is a small cuckoo in the family Cuculidae. Its size averages 22g and is distinguished by its green and bronze iridescent colouring on its back and incomplete brown barring from neck to tail. Horsfield's bronze cuckoo can be destiguished from other bronze cuckoos by its white eyebrow and brown eye stripe. The Horsfield's bronze cuckoo is common throughout Australia preferring the drier open woodlands away from forested areas. This species was formerly placed in the genus Chrysococcyx.

<span class="mw-page-title-main">Little bronze cuckoo</span> Species of bird

The little bronze cuckoo is a species of cuckoo in the family Cuculidae. It was formerly placed in the genus Chrysococcyx. It is a common brood parasite of birds form the genus Geryone. This cuckoo is found in Southeast Asia, New Guinea and some parts of Australia, where its natural habitat is subtropical or tropical moist lowland forest. It is the world's smallest cuckoo. The pied bronze cuckoo was formerly considered to be a subspecies. Other common names for the little bronze cuckoo include the red-eyed bronze cuckoo and the malay green cuckoo. It has 11 subspecies which are generally recognized.

<span class="mw-page-title-main">Pacific long-tailed cuckoo</span> Species of bird

The Pacific long-tailed cuckoo, also known as the long-tailed cuckoo, long-tailed koel, sparrow hawk, home owl, screecher, screamer or koekoeā in Māori, is a species of the Cuculidae bird family. It is a migratory bird that spends spring and summer in New Zealand, its only breeding place, and spends winter in the Pacific islands. It is a brood parasite, laying its eggs in the nests of other bird species and leaving them to raise its chicks.

<span class="mw-page-title-main">Channel-billed cuckoo</span> Species of bird

The channel-billed cuckoo is a species of cuckoo in the family Cuculidae. It is monotypic within the genus Scythrops. The species is the largest brood parasite in the world, and the largest cuckoo.

<span class="mw-page-title-main">Cuckoo-finch</span> Species of bird

The cuckoo-finch, also known as the parasitic weaver or cuckoo weaver, is a small passerine bird now placed in the family Viduidae with the indigobirds and whydahs. It occurs in grassland in Africa south of the Sahara. The male is mainly yellow and green while the female is buff with dark streaks. They lay their eggs in the nests of other birds.

<span class="mw-page-title-main">Screaming cowbird</span> Species of bird

The screaming cowbird is an obligate brood parasite belonging to the family Icteridae and is found in South America. It is also known commonly as the short billed cowbird.

<span class="mw-page-title-main">Egg tossing (behavior)</span> Behavior observed in some species of birds

Egg tossing or egg destruction is a behavior observed in some species of birds where one individual removes an egg from the communal nest. This is related to infanticide, where parents kill their own or other's offspring. Egg tossing is observed in avian species, most commonly females, who are involved with cooperative breeding or brood parasitism. Among colonial non-co-nesting birds, egg-tossing is observed to be performed by an individual of the same species, and, in the case of brood parasites, this behavior is done by either the same or different species. The behavior of egg tossing offers its advantages and disadvantages to both the actor and recipient.

<span class="mw-page-title-main">Eivin Røskaft</span> Norwegian evolutionary biologist

Eivin Røskaft is a Norwegian evolutionary biologist, academic, and author. He is a professor emeritus in evolutionary biology at the department of biology at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. Røskaft's research is focused on the application of evolutionary biology to conservation, which has led to projects in Asia and Africa that pertain to human-wildlife conflict, animal population dynamics, and animal behaviour in relation to human activities. He has authored or co-authored several publications, including the books Conservation of Natural Resources: Some African & Asian Examples, and Northern Serengeti Road Ecology, and is an honorary professor at Hainan University, Haikou, China, and Palacký University Olomouc, Czech Republic. He is also an elected member of Royal Norwegian Scientific Society, and the recipient of their Scientific Award.

References

  1. ↑ Davies, Nicholas B. (2000). Cuckoos, cowbirds and other cheats. London: T & A D Poyser. ISBN   978-0-85661-135-3.
  2. ↑ "Cuckoos and Gentes". www.goodhelpclinic.com. Retrieved 2022-11-07.
  3. ↑ Gibbs, H. L.; Sorenson, M. D.; Marchetti, K.; Brooke, M. D.; Davies, N. B.; Nakamura, H. (2000-09-14). "Genetic evidence for female host-specific races of the common cuckoo". Nature. 407 (6801): 183–186. Bibcode:2000Natur.407..183G. doi:10.1038/35025058. ISSN   0028-0836. PMID   11001055.
  4. ↑ Fossøy, Frode; Anton, Antonov; Moksnes, Arne; Røskaft, Eivin; Vikan, Johan R.; Møller, Anders .; Shykoff, Jacqui A.; Stokke, Bård G. (2011). "Genetic differentiation among sympatric cuckoo host races: males matter". Proceedings of the Royal Society B. 278 (1712): 1639–1645. doi:10.1098/rspb.2010.2090. PMC   3081775 . PMID   21068043.
  5. ↑ Spottiswoode, Claire N.; Stryjewski, Katherine Faust; Quader, Suhel; Colebrook-Robjent, John F. R.; Sorenson, Michael D. (2011-10-25). "Ancient host specificity within a single species of brood parasitic bird". Proceedings of the National Academy of Sciences. 108 (43): 17738–17742. doi: 10.1073/pnas.1109630108 . ISSN   0027-8424. PMC   3203796 . PMID   21949391.
  6. ↑ Spottiswoode, Claire N.; Tong, Wenfei; Jamie, Gabriel A.; Stryjewski, Katherine F.; DaCosta, Jeffrey M.; Kuras, Evan R.; Green, Ailsa; Hamama, Silky; Taylor, Ian G.; Moya, Collins; Sorenson, Michael D. (2022-04-26). "Genetic architecture facilitates then constrains adaptation in a host–parasite coevolutionary arms race". Proceedings of the National Academy of Sciences. 119 (17): e2121752119. doi: 10.1073/pnas.2121752119 . ISSN   0027-8424. PMC   9170059 . PMID   35412865.
  7. ↑ DE LA COLINA, M. ALICIA; MAHLER, BETTINA; REBOREDA, JUAN CARLOS (2011-01-28). "Differences in morphology and colour pattern of shiny cowbird (Molothrus bonariensis) eggs found in nests of two hosts". Biological Journal of the Linnean Society. 102 (4): 838–845. doi:10.1111/j.1095-8312.2011.01605.x. hdl: 11336/68672 . ISSN   0024-4066.
  8. ↑ Moksnes, Arne; ØSkaft, Eivin r. (1995). "Egg‐morphs and host preference in the common cuckoo ( Cuculus canorus): an analysis of cuckoo and host eggs from European museum collections". Journal of Zoology. 236 (4): 625–648. doi:10.1111/j.1469-7998.1995.tb02736.x. ISSN   0952-8369.
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