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Cichlid speciation attributed to “plasticity” now

mbuna cichlids/Haplochromis, GNU

See this abstract from Molecular Ecology*:

There is increasing evidence that phenotypic plasticity can promote population divergence by facilitating phenotypic diversification and, eventually, genetic divergence. When a ‘plastic’ population colonizes a new habitat, it has the possibility to occupy multiple niches by expressing several distinct phenotypes. These initially reflect the population’s plastic range but may later become genetically fixed by selection via the process of ‘genetic assimilation’ (GA). Through this process multiple specialized sister lineages can arise that share a common plastic ancestor – the ‘flexible stem’. Here, we review possible molecular mechanisms through which natural selection could fix an initially plastic trait during GA. These mechanisms could also explain how GA may contribute to cryptic genetic variation that can subsequently be coopted into other phenotypes or traits, but also lead to nonadaptive responses. We outline the predicted patterns of genetic and transcriptional divergence accompanying flexible stem radiations. The analysis of such patterns of (retained) adaptive and nonadaptive plastic responses within and across radiating lineages can inform on the state of ongoing GA. We conclude that, depending on the stability of the environment, the molecular architecture underlying plastic traits can facilitate diversification, followed by fixation and consolidation of an adaptive phenotype and degeneration of nonadaptive ones. Additionally, the process of GA may increase the cryptic genetic variation of populations, which on one hand may serve as substrate for evolution, but on another may be responsible for nonadaptive responses that consolidate local allopatry and thus reproductive isolation. (paywall) – Ralf F. Schneider, Axel Meyer, How plasticity, genetic assimilation and cryptic genetic variation may contribute to adaptive radiations, More.

What’s interesting about this account is the relatively relaxed (thus more correct) attitude to speciation, an oblique sign of weakening Darwinism. Darwinism depends on the concept of speciation. When speciation just isn’t very clear, Darwinism just isn’t very clear.

* Special issue: Molecular Mechanisms of Adaptation and Speciation: Integrating Genomic and Molecular Approaches

See also: Are there really 1000 “species” of cichlid?

Red wolf not endangered, a hybrid?


Nothing says “Darwin snob” like indifference to the mess that the entire concept of speciation is in

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ppolish, Ok, I see now. Thank you. Dionisio
If it walks like a design and quacks like a design - it's a design. Sorry. https://en.m.wikipedia.org/wiki/Duck_test ppolish
ppolish, What does IIWLADAQLAD – IAD mean? I really don't know. Dionisio
Yep, Dionisio, WYSIWYG. And IIWLADAQLAD - IAD:) Thanks for the link although I was already following that great thread. ppolish
ppolish @2:
“But it is only the APPEARANCE of a design attribute!”.
Watch out! Appearances are deceiving! :) However, sometimes WYSIWYG, right? We ain't seen nothing yet. The best is still ahead. See posts @1102-1111 here: https://uncommondescent.com/evolution/a-third-way-of-evolution/#comment-621874 Dionisio
Plasticity is a key design attribute. Instead of only weasels we get weasels and ferrets and moles. "But it is only the APPEARANCE of a design attribute!". Oh my. ppolish
Duh! Why did it take them so long to figure that out? The whole environmental adaptation story is associated with interwoven functional frameworks built-in within the biological systems. It was designed that way: top-down, not bottom-up. That's all. Just complex complexity. Let's keep the serious research going! Keep it on! We ain't seen nothing yet. The best is still ahead. OK, enough chatting. Back to work! :) Dionisio

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