Amazing stuff! Cuckoos do not fly over the cuckoo's nest like in Hollywood! đ
Cuckoo males are promiscuous!
"... Because cuckoos parasitize the nests of over 100 different host species, their eggs come in a wide variety of colors and patterns. But how does the cuckoo evolve eggs that mimic so many hosts while still remaining a single species? To find out, scientists analyzed genomes from nearly 300 European and 50 Oriental cuckoos, then checked which gene variants were associated with different eggshell hues. ...
The analysis revealed that egg color is passed down almost exclusively through the female sex chromosome, thus ensuring that daughters always lay eggs with the same base color as their mothers. As a result, a female can mate with any male without losing their adaptation to a specific host, preventing populations from splitting off into different species. ..."
From the abstract of the perspective:
"Like other obligate brood parasites, common cuckoos (Cuculus canorus) reproduce by depositing eggs in “host” nests, thereby exploiting the parental care of another species. After hatching, the cuckoo chick eliminates its competition by ejecting host eggs (and/or chicks) from the nest.
Given these extreme costs, hosts evolved the ability to recognize and reject foreign eggs, and cuckoos evolved eggs that mimic the appearance of host eggs to better escape detection.
This coevolutionary arms race is complicated, however, by the cuckoo’s exploitation of multiple host species, which presents a puzzle: How does a single cuckoo species evolve eggs that mimic those of many different hosts? On page 527 of this issue, Merondun et al. (2) report genomic data that reveal a complex geographic mosaic of cuckoo-host coevolution, in which maternally inherited genes, autosomal (biparental) genes, and population structure all contribute to the evolution of a diversity of cuckoo egg phenotypes."
From the editor's summary and abstract:
"Editor’s summary
Parasitic cuckoos face strong selective pressure for their eggs and offspring to match their hosts, yet each species parasitizes multiple hosts.
Merondun et al. examined the genetic basis of egg coloration in the common cuckoo (Cuculus canorus) and the oriental cuckoo (C. optatus).
In C. canorus, egg coloration was most strongly influenced by maternal variation across morphs, and all 116 single-nucleotide polymorphisms that associated with a blue egg morph located to the female-denoting W chromosome.
Males mate opportunistically in C. canorus, potentially explaining the benefit of these traits being closely linked in the matriline.
By contrast, this trait appears to be highly polygenic and autosomal in C. optatus, demonstrating the myriad ways that evolution can respond to similar pressures ...
Abstract
Host-parasite arms races facilitate rapid evolution and can fuel speciation. Cuculus cuckoos are deceptive egg mimics that exhibit a broad diversity of counterfeit egg phenotypes, representing host-adapted subpopulations (gentes). Genome analysis of 298 common (Cuculus canorus) and 50 oriental cuckoos (Cuculus optatus) spanning 15 egg morphs revealed that eggshell background coloration is predominantly influenced by matrilineal genetic variation. Recurrent mitochondrial mutations and an ancient W chromosome–linked translocation of an autosomal assembly factor for respiratory complex I provide a tentative link between mitochondrial function and pigment synthesis through the heme pathway.
Biparentally inherited loci contribute to phenotypic variation in both species, mainly for maculation.
The evolutionary tug-of-war over a sex-limited, mimetic trait integrates autosomal components with the nonrecombining, matrilineal genome without catalyzing genome-wide divergence between gentes."
How common cuckoos adapt to multiple hosts (perspective, no public access)
Genomic architecture of egg mimicry and its consequences for speciation in parasitic cuckoos (no public access)
The common cuckoo (Cuculus canorus) has evolved egg features (top row) to mimic eggs of different host species (bottom row).
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