Saturday, 5 August 2017

100 Million Year-Old Flower

The ancestral flower was bisexual with multiple whorls (concentric cycles) of petal-like organs, in sets of threes.

Copyright: Hervé Sauquet/Jürg Schönenberger.
What flowers looked like 100 million years ago.

Flowering plants are by far the most diverse group of plants comprising so 300,000 different species. They were, however, late on the scene in evolutionary terms, only evolving some 140 million years ago.

This puts their evolution towards the end of the age of dinosaurs in the Cretaceous, when the ancestors of mammals were still mammaliform synapsids. The evolution of the first flowering plants is one of those enduring mysteries for evolution to explains, Darwin himself referring to it as "an abominable mystery".

Now an new study coordinated by Juerg Schoenenberger from the University of Vienna and Hervé Sauquet of the Université Paris-Sud has shed more than a little light on what the first flowers looked like. The same study has also reconstructed what flowers at the key divergence point looked like.

The entire study is an application of the Theory of Evolution - so much for creationists' constant assertion that the TOE is a 'theory in crisis', a major plank in the Discovery Institute's political program, the Wedge Strategy. In fact, the entire appearance and diversification of flowering plants can only be explained and understood in terms of evolutionary theory.

The result of the study were published open access a few days ago in Nature Communications:

The researchers also reconstructed what flowers looked like at all the key divergences in the flowering plant evolutionary tree.

Copyright: Hervé Sauquet/Jürg Schönenberger.
Abstract
Recent advances in molecular phylogenetics and a series of important palaeobotanical discoveries have revolutionized our understanding of angiosperm diversification. Yet, the origin and early evolution of their most characteristic feature, the flower, remains poorly understood. In particular, the structure of the ancestral flower of all living angiosperms is still uncertain. Here we report model-based reconstructions for ancestral flowers at the deepest nodes in the phylogeny of angiosperms, using the largest data set of floral traits ever assembled. We reconstruct the ancestral angiosperm flower as bisexual and radially symmetric, with more than two whorls of three separate perianth organs each (undifferentiated tepals), more than two whorls of three separate stamens each, and more than five spirally arranged separate carpels. Although uncertainty remains for some of the characters, our reconstruction allows us to propose a new plausible scenario for the early diversification of flowers, leading to new testable hypotheses for future research on angiosperms.


The international team spent six years analysing the largest data set of floral traits assembled to date, consisting of 13,444 referenced data points. Their samples were from 792 species from 63 orders (98%) and 372 families (86%) of angiosperms. In simple terms, using molecular dating analysis they looked for the most common (therefore likely to be the most primitive) traits across the sample data to arrive at the most likely form of the ancestral flower.

The results were surprising; the ancestral flower seems to have had an arrangement of parts not seen in modern flowers or that previously proposed. It was bisexual with both carpals and stamens and had multiple whorls of petal-like structures or tepals, arranged in layers of three. Close to but not the same as that seen in magnolias, buttercups and laurels. It was probably a reduction in the number of these tepals that allowed flowers to diversify into the huge array of forms we see today.

The team were also able to reconstruct the likely appearance of flowers at the major nodes in this diversification.

So, not much sign of a theory in crisis there to cheer up forlorn creationists still waiting for the entire body of evolutionary biology to disappear and for biologists to turn into Bible-literalist followers of Bronze Age superstitions.


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