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Author Topic:   Ancestral and daughter species existing simultaneously?
The Dude
Junior Member (Idle past 4241 days)
Posts: 1
Joined: 08-06-2012


Message 1 of 12 (669947)
08-06-2012 4:22 PM


I have a genuine question regarding evolution of new species from an ancestral species.
Suppose species A lives in environment X.
Some specimen of species A (population Ay) reach environment Y, where they are isolated from other members of their species (population Ax).
Y is fundamentally different from X in many ways and exerts selective pressure on Ay.
In the long run, the differences between Ay and Ax accumulate and result in speciation. Population Ay slowly becomes species B.
However, environment X remains mostly constant over all this time, so there is little change in population Ax, which remains the unaltered original species A.
Suppose further that a process similar to the one that converted population Ay into species B will convert a population Az in environment Z into species C. C is different from both A and B.
To summarize, species A is the common ancestor to species A, B, and C. A, B, and C will exist simultaneously at some point in time.
My question is this: Is there any example of such a case in the real world? We all know that, according to the theory of evolution, humans (B) and chimpanzees (C) evolved from a common ancestor (A), however this ancestral species went extinct. This happened because humans and chimpanzees were better adapted to the environments they lived in than the ancestral species.
From an evolutionary point of view, I believe the scenario I described to be plausible and possible. Is there any known case in which an ancestral species (A) and one or many "daughter" species (B, C, D...) existed at the same time? Preferably a case involving creatures that reproduce sexually (because for them the term 'species' is more clearly define IMHO).
Thank you very much!

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Adminnemooseus
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Message 2 of 12 (669949)
08-06-2012 6:37 PM


Thread Copied from Proposed New Topics Forum
Thread copied here from the Ancestral and daughter species existing simultaneously? thread in the Proposed New Topics forum.

  
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 3 of 12 (669950)
08-06-2012 6:54 PM
Reply to: Message 1 by The Dude
08-06-2012 4:22 PM


Mom still around
Yup, both parent species and child species often coexit, at least for awhile. A great recent example is Italian Wall Lizards.

Anyone so limited that they can only spell a word one way is severely handicapped!

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Panda
Member (Idle past 3713 days)
Posts: 2688
From: UK
Joined: 10-04-2010


Message 4 of 12 (669953)
08-06-2012 7:29 PM
Reply to: Message 3 by jar
08-06-2012 6:54 PM


Re: Mom still around
jar writes:
Yup, both parent species and child species often coexit, at least for awhile.
To use TD's nomenclature: that would be an example of A and B existing.
I think TD is after a parent species, child species and a grandchild species (i.e. A, B and C).
Since parent/child examples are easily found, I expect parent/child/grandchild examples to also exist - but be probably be fewer in number.
But an example currently eludes me.
Edited by Panda, : No reason given.

"There is no great invention, from fire to flying, which has not been hailed as an insult to some god." J. B. S. Haldane

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jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 5 of 12 (669954)
08-06-2012 7:38 PM
Reply to: Message 4 by Panda
08-06-2012 7:29 PM


Re: Mom still around
Well, Ring Species would be an example. I'm not sure how many "generations" are involved there but I would imagine far more than three.

Anyone so limited that they can only spell a word one way is severely handicapped!

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herebedragons
Member (Idle past 858 days)
Posts: 1517
From: Michigan
Joined: 11-22-2009


(2)
Message 6 of 12 (669955)
08-06-2012 7:48 PM
Reply to: Message 1 by The Dude
08-06-2012 4:22 PM


Yes, there are
Hey Dude ...
Is there any example of such a case in the real world?
The phenomenon you are describing is refereed to as adaptive radiation. And there are quite a few examples. Islands seem to be common places to find such ancestral species and daughter species existing at one time.
There are more than 800 species of drosophilid flies on the Hawaiian Islands.
The Hawaiian silverswords are another example: about 30 species in three genera - Argyroxiphium, Dubautia, and Wilkesia
Darwin's finches are one of the most famous examples. Note that some say that this is just an example of beak sizes varying, not really speciation. Don't be fooled. There are some species that eat insects, some eat seeds of various sizes, some eat nectar - genera Geospiza, CAmarhynchus, Cactospiza, Platyspiza and Certhidea. There may be a couple more too.
African cichlids are another good example of this also.
source: Evolution, Douglas Futuyma, 2nd edition
Remember though, that the modern version of the ancestral species has probably changed somewhat since the two populations diverged, even with the lack of selection pressure, simply due to genetic drift.
Hope this helps
HBD
Edited by herebedragons, : No reason given.

Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for. But until the end of the present exile has come and terminated this our imperfection by which "we know in part," I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

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herebedragons
Member (Idle past 858 days)
Posts: 1517
From: Michigan
Joined: 11-22-2009


(1)
Message 7 of 12 (669957)
08-06-2012 8:10 PM
Reply to: Message 3 by jar
08-06-2012 6:54 PM


Interestingly, jar, this case turned out to be phenotypic plasticity, or at least the changes were reported to be reversible. I did a paper on it for a class on speciation.
quote:
A study published in 2010 (Vervust, et. al.), showed that at least some of these changes were reversible. Researchers captured a subset population from Pod Mrcaru and housed them in terraria. They were fed a strictly arthropod diet for 15 weeks and the gut morphology was then examined. The small intestine and the hindgut showed a significant reduction in weight. Additionally, no evidence of a cecal valve was found in any of the 20 specimens examined. This group still had a more developed digestive tract than the original population from Pod Kopite, but the authors felt that with a continued arthropod diet, even those differences would be erased
the quote is from my paper
source is here
Still a very interesting case and a great example of the founder effect. I am not sure if any more recent work has been done on this, but I doubt the Pod Mrcaru population has been classified as a separate species, perhaps a variety ???
HBD

Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for. But until the end of the present exile has come and terminated this our imperfection by which "we know in part," I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

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Dr Adequate
Member (Idle past 285 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 8 of 12 (669960)
08-06-2012 8:25 PM
Reply to: Message 1 by The Dude
08-06-2012 4:22 PM


Another example would be the platypus and the echidna. IIRC, the echidna is only fairly recently (i.e. within a few million years) derived from the platypus, which was the basal form.
Of course, you might ask whether modern platypuses are enough like the playtpuses back then to be considered exactly the same species. I'll leave that up to you to decide, but they were definitely platypuses.
Note that it's only the restriction that one of the modern species should be so similar to the ancestral species as to be considered exactly the same species as the ancestral form that makes this question at all challenging to answer. If you allow broader groups, then it becomes easy: for example, you have people alongside monkeys. But no monkey now is exactly the same as the monkeys back then, although some of them are very similar and all of them are recognizably monkeys.
In evolution, things rarely stand perfectly still --- even the finest example of "living fossils" can almost invariably be distinguished from their ancestors on a morphological basis.
Of course, then someone might argue that that doesn't necessarily mean that they're different species according to the Biological Species Concept --- you could tell a poodle from a wolf, but we count them as the same species ... so the question of whether a fossil from the time preceding adaptive radiation is the same species (according to the BSC) as some modern species might in fact be unanswerable.
As a final bit of confusion, some people would argue that the answer should really be "no" by definition, because the common ancestor of (for example) a platypus and an echidna should not be considered to be either no matter how much it looks like a platypus. This bit of cladistic pedantry is, however, probably not something you were thinking of when you asked you question.
Edited by Dr Adequate, : No reason given.

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Blue Jay
Member (Idle past 2698 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 9 of 12 (669969)
08-07-2012 12:36 AM
Reply to: Message 8 by Dr Adequate
08-06-2012 8:25 PM


Hi, Dr A.
Dr Adequate writes:
As a final bit of confusion, some people would argue that the answer should really be "no" by definition, because the common ancestor of (for example) a platypus and an echidna should not be considered to be either no matter how much it looks like a platypus. This bit of cladistic pedantry is, however, probably not something you were thinking of when you asked you question.
Within a species, there are cladistic population structures that would ensure that some populations of the parent species will, at least temporarily, be more closely related to the incipient daughter species than they are to other populations of the parent species, despite remaining members of the parent species according to the biological species concept.
So, use of the biological species concept requires us to accept that species can be paraphyletic with respect to other species.

-Bluejay (a.k.a. Mantis, Thylacosmilus)
Darwin loves you.

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Lithodid-Man
Member (Idle past 2931 days)
Posts: 504
From: Juneau, Alaska, USA
Joined: 03-22-2004


(2)
Message 10 of 12 (669971)
08-07-2012 6:13 AM
Reply to: Message 1 by The Dude
08-06-2012 4:22 PM


Daughter, parent, and grandparent 'species'
As has been pointed out by Dr. A, the answer to this is yes provided we don't quibble too much about the definition of "species". Might be better to use the term "organizational grades" within clades. Apes are nested within monkeys, and humans are nested within apes, but no modern species is the actual ancestral species of any other modern species (in that example, at least).
My all-time favorite examples of this are found in the right-handed hermit crabs and king crabs. As you are no doubt aware hermit crabs have an elongate, coiled abdomen ("tail") that they hide inside of a snail shell. This abdomen is nearly completely uncalcified except at the tip where it bears a terminal calcified structure and a pair of asymetrical appendages used to anchor the crab to the column of the snail shell. Additionally, hermit crabs tend to have the thoracic (body) segments partially decalcified so that only the front portion (that extends from the snail shell) called the shield is calcified.
King crabs (family Lithodidae, some say superfamily Lithodoidea but I strongly disagree) on the other hand have an abdomen that is partially to completely calcified that is never protected by a snail shell. Additionally the thoracic segments are calcified, at least on the dorsal surface. Despite a superficial resemblance to "true crabs" (Infraorder Brachyura), based on a number of morphological features it has been recognized that king crabs are modified hermit crabs, and more specifically modified right-handed hermit crabs (as opposed to the Diogenoidea, left-handed hermits). This classification has been supported by several molecular analyses. So, this is a case of a daughter group (king crabs) existing alongside the parent group (right-handed hermits), but it is a whole lot more interesting than that.
Within the king crab family there exists a great diversity of body types that have preserved the transitions from a hermit crab-like body to a king crab-type body. For example, the Hapalogastrinae (a subfamily of small, non-commercially important king crabs) have a large, uncalcified abdomen and the carapace margins are soft. In this group the abdomen is protected by being held under the body. Other king crabs have a soft abdomen that is covered in calcified nodules with membrane in between them. In this group we have living representatives where some of these nodules are fused together into plates. In the advanced king crabs these plates are complete with no evidence in the adult of forming from fused nodules (although we see them in the embryos). This same pattern can be seen in the calcification of the thoracic segments, primitive king crabs are partially membranous on the carapace margins, while advanced forms show more complete calcfication and fusion.
Because the highest diversity of king crabs exists in the North Pacific, it is believed that they evolved here. In Alaska we have 20 (perhaps 21) species of king crab, only three of which are common enough and large enough for commercial harvest. We also have 28 species of right-handed hermit crabs including two that exhibit a partial calcification of the abdomen and carapace. Now, it is important to note that I am not saying that any of these are the ancestors of any other, just that the body type of various species preserve the ancestral condition at nearly every step.

Doctor Bashir: "Of all the stories you told me, which were true and which weren't?"
Elim Garak: "My dear Doctor, they're all true"
Doctor Bashir: "Even the lies?"
Elim Garak: "Especially the lies"

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Dr Adequate
Member (Idle past 285 days)
Posts: 16113
Joined: 07-20-2006


Message 11 of 12 (669972)
08-07-2012 6:39 AM
Reply to: Message 9 by Blue Jay
08-07-2012 12:36 AM


Within a species, there are cladistic population structures that would ensure that some populations of the parent species will, at least temporarily, be more closely related to the incipient daughter species than they are to other populations of the parent species, despite remaining members of the parent species according to the biological species concept.
So, use of the biological species concept requires us to accept that species can be paraphyletic with respect to other species.
I'll think about that.
My broad point still stands: there are enough problems with talking about species that it's easier to talk about groups defined morphologically instead: we have men alongside monkeys, giraffes alongside okapis, termites alongside cockroaches, where by robust if naive morphological criteria the ancestors were monkeys, okapis, and cockroaches, respectively. When The Dude put the word species into his post, he made his question harder to answer for reasons that may be irrelevant to what he was trying to ask.

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Jon
Inactive Member


Message 12 of 12 (669975)
08-07-2012 9:27 AM
Reply to: Message 4 by Panda
08-06-2012 7:29 PM


Re: Mom still around
I think TD is after a parent species, child species and a grandchild species (i.e. A, B and C).
Dude mentions no grandchild species.

Love your enemies!

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