Thursday, 22 October 2015

Earliest Flowering Plants But No Bouquet for Creationists

Montsechia fossil

Photo: Bernard Gomez/Lyon University, France
Montsechia, an ancient aquatic angiosperm

I often used to start these sorts of blogs off with a comment about it being yet another bad week for creationism, but quite honestly it's increasingly difficult to find a week which hasn't been relentlessly bad for creationism.

No wonder they have just about given up trying to refute the scientific evidence against their crackpot notion and have tended to concentrate on trying to discredit the scientific method and even science itself, or simply trying to get away with ancient creationist articles that were long ago refuted by science, in the hope that they'll find a few ignorant dupes who don't know enough to know they've been refuted.

For example, this paper has pushed back the date of the earliest ancestors of flowering plants to about 130 million years ago. It is the result of an analysis of about 1000 examples of the common fossil found in abundance in deposits in Spain of Montsechia, previously considered to be a conifer. Will it be acknowledged by creationist pseudoscientists and incorporated into their thinking? Of course not. That would harm their income stream.

The importance of very early aquatic flowering plants is not well understood currently and is poorly documented. Here we present details of the morphology and reproductive biology of Montsechia, an extremely early fossil angiosperm that, because it is so ancient and is totally aquatic, raises questions centered on the very early evolutionary history of flowering plants. This paper challenges the paradigm of how we view the early evolution of basal angiosperms and particularly the role of aquatic habitats in the very early evolution and diversification of flowering plants.

The early diversification of angiosperms in diverse ecological niches is poorly understood. Some have proposed an origin in a darkened forest habitat and others an open aquatic or near aquatic habitat. The research presented here centers on Montsechia vidalii, first recovered from lithographic limestone deposits in the Pyrenees of Spain more than 100 y ago. This fossil material has been poorly understood and misinterpreted in the past. Now, based upon the study of more than 1,000 carefully prepared specimens, a detailed analysis of Montsechia is presented. The morphology and anatomy of the plant, including aspects of its reproduction, suggest that Montsechia is sister to Ceratophyllum (whenever cladistic analyses are made with or without a backbone). Montsechia was an aquatic angiosperm living and reproducing below the surface of the water, similar to Ceratophyllum. Montsechia is Barremian in age, raising questions about the very early divergence of the Ceratophyllum clade compared with its position as sister to eudicots in many cladistic analyses. Lower Cretaceous aquatic angiosperms, such as Archaefructus and Montsechia, open the possibility that aquatic plants were locally common at a very early stage of angiosperm evolution and that aquatic habitats may have played a major role in the diversification of some early angiosperm lineages.

Montsechia, an ancient aquatic angiosperm
Bernard Gomez, Véronique Daviero-Gomez, Clément Coiffard, Carles Martín-Closas, and David L. Dilcher
PNAS September 1, 2015 vol. 112 no. 35 10985-10988. doi: 10.1073/pnas.1509241112

The scientific significance of this finding is that is supports the idea that flowering plants evolved as aquatic plants and only later moved onto the land to become dependent on insect, wind, etc for pollination.

The conifers and flowering plants (angiosperms) are closely allied groups of plants which evolved out of the gymnosperms (ferns, etc). The botanical distinction between them is that angiosperms have an enclosed seed, as their Latin name implies.

At this stage in their evolution, the term 'flowering plant' is something of a misnomer since there was little that we would recognise today as a flower, never-the-less, all the basic elements out of which flower parts evolved were there. The reason there was no flower as such was because this group had not yet established its relationship with insects or other pollinating agents such as wind. There is a very good reason plants which depend on wind for pollen dispersal don't have colourful petals - these have evolved to attract insects (and sometimes birds or even bats). Petals on wind-pollinating plants would be a drain on resources.

Just so with our early angiosperms which were aquatic plants. In the early days of plant evolution fertilisation was only possible in the presence of water as the male gametes are motile and swim to the female gamete or ovule so it is not surprising that angiosperms arose in aquatic plants. It is believed the pollen would have simply floated to the female flowers. There was no role for petals so nothing to drive the evolution of petals. These, together with nectar, etc, evolved later in response to an environment which had insects in it.

Now, we can make a few assumptions here about the aquatic environment in which these plants would have lived. We can assume that, if they did indeed depend on passive pollen dispersion, they lived in still or very slowly flowing water. Pollen shed into flowing water would quickly flow downstream so the species as a whole could not move into flowing rivers. This is also the reason fossils of these plants are abundant in what would have been silt deposits of ancient lakes.

So, another tiny piece of the jigsaw falls into place and yet again it is entirely consistent with the scientific view of evolution by natural selection and descent with modification from a common ancestor.

It is, of course, entirely inconsistent with how the bronze Age goat-herders who wrote the Bible guessed life had been created.

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