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Author Topic:   Is this tree leaf evolution?
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Joined: 07-01-2005
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Message 16 of 20 (485459)
10-08-2008 4:19 PM
Reply to: Message 1 by straightree
10-05-2008 11:58 AM

The basic problem with your question is that you seem to be asking if an individual tree is an example of evolution in action.
But individuals do not evolve. Populations evolve. Could this tree be part of a population that is evolving? By definition, yes, because all organisms that reproduce imperfectly evolve over time. New species do not always result, but genetic change in a population over multiple generations is inevitable.
Realistically, every individual organism is an example of a transitional form, existing as a link in the chain from its ancestors to its descendants. Your tree is no different in that respect.

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New Cat's Eye
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Message 17 of 20 (485462)
10-08-2008 4:31 PM
Reply to: Message 15 by straightree
10-08-2008 4:11 PM

Technically, all species are in a constant flux, check out genetic drift, so they are always in a transitional stage. You seem to think that stasis is the default but its not.
This could be the solution to my question.
Right on!
I will document myself more extensively in the subject of genetic drift of species, and will look for some information on maples evolution.
Like I said upthread, we rarely talk about the evolution of plants.
I cannot seem to find much info on maple evolution....
I did find this though:
An angiosperm, the earliest known Acer (A. amboyense) was found in eastern North America from the fossil remains of the late Cretaceous period about 67 MYA. All maple fossils have been located exclusively in the Northern Hemisphere and the trees seem most abundant during the Miocene (Oterdoom 1994).
The closest fossil relative to A. macrophyllum appears to be A. merriamii Knowlton (or A. oregonianum Knowlton) from the Late Miocene around 5 MYA (Macginitie 1969; Oliver 1934). Macginitie (1969) notes the potential for a taxonomic problem with assigning the name of a fossil species to a living species, for although they may be morphologically similar it is difficult to determine if the species are genetically identical.
The flowering and sexual mating of Acer have ranged from wind-pollinated to insect-pollinated and monoecy to dioecy. A. macrophyllum is an insect-pollinated dicot in which female flowers occur before male flowers (Oterdoom 1994).
The form of the leaves in the Acer genus has changed over time. From the Late Oligocene to the Early Pliocene (from around 23 to 5 MYA, including the Miocene) the leaf form evolved from the originally more common 3-lobed maples to 5-lobed maples, as evidenced in the paleobotanical studies of the broadening of the A. tricuspidatum leaf base (Oterdoom 1994).
A. macrophyllum belongs to the deciduous maple Aceraceae family, which has 200 species distributed among 2 genera (van Gelderen et al. 1994). Acer species is believed to have originated in central and western China although no fossils have been located in this area (Oterdoom 1994).
Cladistic analysis has concluded that the Aceraceae family was formed by earlier members of the Sapindaceae like Bohlenia, which was characterized by loss of a stipule and a locule, as well as a change to opposite from alternate leaves. The Dipteronia line of the Aceraceae seems to be more closely related to the Sapindaceae ancestor Bohlenia, except for a change in the secondary venation of its pinnately compound leaves. The A. arcticum line resulted in an actinodromous maple leaf after the fusion of a minimum of three leaflets (Stewart & Rothwell 1993; van Gelderen et al. 1994).
Found HERE
Thank you for your help.
No problem, I'm happy that I could. Welcome to EvC.

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Junior Member (Idle past 5726 days)
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Message 18 of 20 (485975)
10-14-2008 6:03 AM
Reply to: Message 1 by straightree
10-05-2008 11:58 AM

In my point of view your question answer is: evolution happens during reproduction, It is not a growth.
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Edited by Adminnemooseus, : No reason given.

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Member (Idle past 2058 days)
Posts: 63
From: Australia
Joined: 12-08-2004

Message 19 of 20 (510938)
06-04-2009 8:41 PM

Just a late reply.........
Hi everyone.
Essentially the answer to Straight Tree's question is that plants have a high degree of morphological variation, especially when they are in their early stages of growth and especially in their leaves.
Take Eucalypts. When young, eucalypts show such a degree of variation in leaf morphology that it can be a nightmare for a botanist to identify them without recourse to examining other more definitive parts of the plant (like the fruit for example).
I think Straight Tree's example is one of a plethora of variations possible for the species - especially in its formative stages.

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Member (Idle past 4832 days)
Posts: 57
From: Near Olot, Spain
Joined: 09-26-2008

Message 20 of 20 (511124)
06-06-2009 10:23 AM
Reply to: Message 19 by MiguelG
06-04-2009 8:41 PM

Re: Just a late reply.........
Thank you for your reply. I agree with you, but have a further question, or concern. How these morphological variations may be connected to evolution process. Could not it be that some of the variations are lost, wears others retained, so that in a long period of time modification is produced? See that Acer Negundo belongs to a family, maples, consisting of about 120 species, of which almost all have palmate lobed leaves. Looking to Acer Negundo leaves, one has the impression that it is a little bit delayed, but going into the same direction of the rest of maples.

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