Natures wonders: cuckoo nest theft drives evolution (Introduction)

by David Turell , Friday, May 31, 2024, 15:32 (108 days ago) @ David Turell

Cuckoo chicks resemble host's:

https://theconversation.com/whats-that-in-my-nest-how-the-evolutionary-arms-race-betwee...

"In new research published in Science, we show how this process drives the creation of new species of cuckoos. These birds lay their eggs in the nests of other species, and their chicks mimic the appearance of their host’s chicks to avoid detection.

"The deceptive behaviour of bronze-cuckoos imposes heavy costs on their hosts. They lay their eggs in the nests of small songbirds, such as fairy wrens and gerygones, and abandon their young to the care of the host.

"Soon after hatching, the cuckoo evicts the host eggs or chicks from the nest to become the sole occupant. The host parents not only lose all their own offspring, but also invest several weeks rearing the cuckoo, which eventually grows to around twice the size of its foster parents.

"Not surprisingly, given these high costs, hosts have evolved the ability to recognise and reject odd-looking chicks from their nests.

"Only the cuckoo chicks that most closely resemble the host’s chicks will evade detection, and so with each generation, the cuckoo chicks become a closer and closer match to the host chicks. This is why the chicks of each species of bronze-cuckoo look almost identical to their hosts’ chicks.

"This exquisite mimicry has evolved to an even more fine-tuned level. Within a single species of bronze-cuckoo that exploits several different hosts, the appearance of the chicks tracks that of their hosts.

"In response to chick rejection by hosts, both the little bronze-cuckoo and the shining bronze-cuckoo have diverged into several separate subspecies. Each subspecies exploits a different host and produces a chick that matches that of the host.

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"Our results also suggest that the evolution of cuckoos and their hosts is most likely to drive the creation of new species when the cuckoos impose a high cost on their hosts – such as by killing off all the host’s own offspring. This leads to an “evolutionary arms race” between the host’s defences and the cuckoo’s counter-adaptations.

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"Interactions between exploiters and their victims may be one of the main drivers of biodiversity. The process of speciation we described, in which the exploiter shows very specialised adaptations to their victim, may occur in other parasites and hosts, and in predators and prey. These tightly coupled interactions might even explain why there are millions, rather than thousands, of uniquely specialised species across the globe."

Comment: the photographs of actual chick comparisons are amazing. The study proves microevolution is ongoing.