It almost feels like researchers think it is okay now to just doubt Darwin. It seems, we’re a long way from the “Darwin himself said” rubbish that used to deface media releases even a few years ago.*
A key concept in Darwin’s theory of evolution which suggests nature favors larger females that can produce greater numbers of off-spring must be redefined according to scientists behind ground-breaking new research.
The study, published in the scientific journal Biological Reviews, concludes that the theory of ‘fecundity selection’ — one of Charles Darwin’s three main evolutionary principles, also known as ‘fertility selection’ — should be redefined so that it no longer rests on the idea that more fertile females are more successful in evolutionary terms. The research highlights that too many offspring can have severe implications for mothers and the success of their descendants, and that that males can also affect the evolutionary success of a brood.
Farmers could have told us that, but who listens to them?
Darwin’s theory of fecundity selection was postulated in 1874 and, together with the principles of natural selection and sexual selection, remains a fundamental component of modern evolutionary theory. It describes the process of reproductive success among organisms, defined by the number of successful offspring which reach breeding age.
How did a theory remain a fundamental component of evolution theory without taking into account factors like this: The more members of a species in a natural ecology who reach breeding age, the fiercer will be the competition for food—with serious effects on the offspring of the new adult generation.
To say nothing of th fact that, in times of hardship due to overgrazing or overhunting, herd or pack discipline could break down, with more species members lost in the chaos.
Note: A possible exception may exist when the life form succeeds via producing overwhelming numbers for a short time only, thus dislodging another life form. That is, it succeeds as a hort term, not a long term strategy.
So, did all those researchers just agree to be feckless in Darwin’s name?
After years of research, an evolutionary biologist from the University of Lincoln, UK, has proposed a revised version of the theory of fecundity selection which recommends an updated definition, adjusts its traditional predictions and incorporates important new biological terms.
Why bother? Why not just say the theory is another Darwin dud and there is no sense trying to rescue it?
See also: Talk to the fossils: Let’s see what they say back
Here’s the abstract:
Fitness results from an optimal balance between survival, mating success and fecundity. The interactions between these three components of fitness vary depending on the selective context, from positive covariation between them, to antagonistic pleiotropic relationships when fitness increases in one reduce the fitness of others. Therefore, elucidating the routes through which selection shapes life history and phenotypic adaptations via these fitness components is of primary significance to understanding ecological and evolutionary dynamics. However, while the fitness components mediated by natural (survival) and sexual (mating success) selection have been debated extensively from most possible perspectives, fecundity selection remains considerably less studied. Here, we review the theoretical basis, evidence and implications of fecundity selection as a driver of sex-specific adaptive evolution. Based on accumulating literature on the life-history, phenotypic and ecological aspects of fecundity, we (i) suggest a re-arrangement of the concepts of fecundity, whereby we coin the term ‘transient fecundity’ to refer to brood size per reproductive episode, while ‘annual’ and ‘lifetime fecundity’ should not be used interchangeably with ‘transient fecundity’ as they represent different life-history parameters; (ii) provide a generalized re-definition of the concept of fecundity selection as a mechanism that encompasses any traits that influence fecundity in any direction (from high to low) and in either sex; (iii) review the (macro)ecological basis of fecundity selection (e.g. ecological pressures that influence predictable spatial variation in fecundity); (iv) suggest that most ecological theories of fecundity selection should be tested in organisms other than birds; (v) argue that the longstanding fecundity selection hypothesis of female-biased sexual size dimorphism (SSD) has gained inconsistent support, that strong fecundity selection does not necessarily drive female-biased SSD, and that this form of SSD can be driven by other selective pressures; and (vi) discuss cases in which fecundity selection operates on males. This conceptual analysis of the theory of fecundity selection promises to help illuminate one of the central components of fitness and its contribution to adaptive evolution. Open access – Daniel Pincheira-Donoso, John Hunt. Fecundity selection theory: concepts and evidence. Biological Reviews, 2015; DOI: 10.1111/brv.12232
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