Devolution? From ScienceDaily:
A new study offers not only a sweeping analysis of how pollination has evolved among conifers but also an illustration of how evolution — far from being a straight-ahead march of progress — sometimes allows for longstanding and advantageous functions to become irrevocably lost. Moreover, the authors show that the ongoing breakdown of the successful but ultimately fragile pollination mechanism may have led to a new diversity of traits and functions.
That’s well, but it can also lead to extinction.
In evolution, the research shows, selection pressure or pure chance can break a functional relationship among such loosely related traits such as the one Leslie studied, even if that relationship has been working well.
In fact, once this pollination mechanism was lost in a species, Leslie’s analysis found, it never returned.
Instead, though, the evolutionary record suggests that when the mechanism broke down for conifer species, they became “free” to put the traits to other use, or to evolve entirely new ones, a phenomenon Leslie refers to as “stasis and release.”
“In some sense, perhaps, these traits being loosely integrated like this might actually allow them to stumble upon better solutions from time to time,” Leslie said.
Many species now have some but not all three of the traits. Junipers, for example, still emit liquid drops to capture pollen from the wind but they no longer have buoyant saccate pollen and while many have downward facing ovules, some do not, Leslie said. Hemlocks, meanwhile, seem to have moved on completely, evolving pollen that can land anywhere on the cone and grow tubes to make their way to the ovule. More.
In short, the nice thing about Darwinian evolution (natural selection acting on random mutation) is that it can explain any set of events—or, or if it turns out the data collection was poor, its opposite . Or a completely different finding in the same group of life forms.
No wonder so many great thinkers have been suspicious of Darwinism.
Maybe someday we will have a scientific theory of evolution.
Added: Isn’t the information content of a theory that explains everything zero?
Devolution? See also prevolution.
Here’s the abstract:
Integration influences patterns of trait evolution, but the relationship between these patterns and the degree of trait integration is not well understood. In order to explore this further, we study a specialized pollination mechanism in conifers whose traits are linked through function but not development. This mechanism depends on interactions among three characters: pollen that is buoyant, ovules that face downward at pollination, and the production of a liquid droplet that buoyant grains float through to enter the ovule. We use a well-sampled phylogeny of conifers to test correlated evolution among these characters and specific sequences of character change. Using likelihood models of character evolution, we find that pollen morphology and ovule characters evolve in a concerted manner, where the flotation mechanism breaks down irreversibly following changes in orientation or drop production. The breakdown of this functional constraint, which may be facilitated by the lack of developmental integration among the constituent traits, is associated with increased trait variation and more diverse pollination strategies. Although this functional “release” increases diversity in some ways, the irreversible way in which the flotation mechanism is lost may eventually result in its complete disappearance from seed plant reproductive biology. (paywall) – Andrew B. Leslie, Jeremy M. Beaulieu, Peter R. Crane, Patrick Knopf, Michael J. Donoghue. Trait integration and macroevolutionary patterns in the pollination biology of conifers. Evolution, 2015; DOI: 10.1111/evo.12670
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