Evolution: the angiosperm gap (Introduction)

by David Turell , Thursday, October 05, 2023, 20:34 (414 days ago) @ David Turell

Darwin decried it: The abrupt appearance of angiosperms bothered Darwin so much He called it an 'abominable mystery'. This article shows all of the plant world appeaered abruptly:

https://theconversation.com/how-did-plants-first-evolve-into-all-different-shapes-and-s...

"How did plants first evolve into all different shapes and sizes? We mapped a billion years of plant history to find out

"Plants range from simple seaweeds and single-celled pond scum, through to mosses, ferns and huge trees. Palaeontologists like us have long debated exactly how this diverse range of shapes and sizes emerged, and whether plants emerged from algae into multicellular and three-dimensional forms in a gradual flowering or one big bang.

"To answer this question, scientists turned to the fossil record. From those best-preserved examples, like trilobites, ammonites and sea urchins, they have invariably concluded that a group’s range of biological designs is achieved during the earliest periods in its evolutionary history. In turn, this has led to hypotheses that evolutionary lineages have a higher capacity for innovation early on and, after this first phase of exuberance, they stick with what they know. This even applies to us: all the different placental mammals evolved from a common ancestor surprisingly quickly. Is the same true of the plant kingdom?

***

"We then analysed all this data, grouping plants based on their overall similarities and differences, all plotted within what can be thought of as a “design space”. Since we know the evolutionary relationships between the species, we can also predict the traits of their extinct shared ancestors and include these hypothetical ancestors within the design space, too.

"For example, we will never find fossils of the ancestral flowering plant, but we know from its closest living descendants that it was bisexual, radially symmetric, with more than five spirally arranged carpels (the ovule-bearing female reproductive part of a flower). Together, data points from living species, fossils and predicted ancestors reveal how plant life has navigated design space through evolutionary history and over geological time.

"We expected flowering plants to dominate the design space since they make up more than 80% of plant species, but they don’t. In fact, the living bryophytes – mosses, liverworts and hornworts – achieve almost as much variety in their body forms.

"This may not be entirely surprising since the three lineages of bryophytes have been doing their own thing for more than three times as long as flowering plants. And despite their diminutive nature, even the humble mosses are extraordinarily complex and diverse when viewed through a microscope.

***

"...some of the distinctiveness of the different groupings in design space is clearly the result of extinction. This is clear if we consider the distribution of the fossil species (black dots in the above figure) that often occur between the clusters of living species (coloured dots in the figure). (my bold)

***

"So does that make plants different from animals, studies of which are the basis for the expectation of early evolutionary innovation and exhaustion? Not at all. Comparable studies that we have done on animals and fungi show that, when you study these multicellular kingdoms in their entirety, they all exhibit a pattern of episodically increasing anatomically variety. Individual lineages may soon exhaust themselves but, overall, the kingdoms keep on innovating.

"This suggests a general pattern for evolutionary innovation in multicellular kingdoms and also that animals, fungi and plants still have plenty of evolutionary juice in their tanks.

Comment: All the plant groups have no known predecessors. Note my bold. The authors simply invent missing fossils! (see their illustration). The author's conclusion that evolution is a drive toward complexity is exactly my thinking. The full article is analyzed in Evolution News:

https://evolutionnews.org/2023/10/plant-evolution-all-gaps-and-miracles/

130,000 observations. 548 traits. 400 species of living and fossil plants. This is what a team of 10 evolutionary biologists investigated in a major project to look for patterns of evolution in the plant kingdom. Publishing in Nature Plants, they reproduced their morphospace map of the major groups of plants. If described in words, it would go:

Bang! Algae
Bang! Bryophytes (mosses, liverworts, and hornworts)
Bang! Lycophytes (vascular plants including clubmosses)
Bang! Ferns (spore-bearing vascular plants)
Bang! Gymnosperms (seed-bearing cycads, ginkgoes, and conifers)
Bang! Angiosperms (flowering plants)

Subsequent to each bang, there were rapid variations, like the sparkly after-effects of complex fireworks. But the disparity between each bang is huge.

Comment: there follows a point by point analysis:

"Forcing the uncooperative data into an “evolutionary pattern” of ancestors and descendants branching into a treelike pattern of universal common ancestry required some imagination. This was easily accomplished using miracle words. Plants emerged. They expanded. They occupied design space. And sometimes, they reversed direction and converged."

The whole article is shown to be a series of magical conjectures.