New Species, Original Remains

Browsing some rubbish on Facebook, I came across the question, “When has a species mutated, but the original remained?”. The answers implied some confusion as to what the question meant but I took it to mean, “Is there any evidence of an existing species mutating to a new one yet leaving the old one behind?”

For larger animals I see that as problematic, in that the new species is presumably more fit for a given environment and would therefore tend to out-compete the original, wiping them out but maybe, some kind of variation on Gould’s punctuated equilibrium could result in two species that somehow get permanently separated thus allowing for different evolutionary paths; don’t shoot me, it’s just an idea.

With smaller organisms, bacteria or similar, I’m guessing there are examples but I honestly don’t know.

I just like to know if any of you brain boxes have some ideas or even examples on this :slight_smile:

UK Atheist

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You just described allopatric speciation, which has been a concept in circulation in evolutionary biology for decades. :slight_smile:


Oh! First I’ve heard of it :slight_smile:

UK Atheist

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Here’s how allopatric speciation operates.

You start with a population of organisms, that are all members of the same species. Each individual in that population, can choose a mate from the rest of the population, and if successful, can produce fertile offspring with that choice of mate.

Now, an event occurs that results in the population being split in two. Call these new, separated populations A and B.

The event in question could be the emergence of a physical barrier preventing the two populations from meeting, or it could be the emergence of a behavioural trait resulting in what is known as “assortative mating” taking place between two different phenotypes in the population. The exact details of the barrier don’t actually matter - what matters is that a barrier comes into existence between the two populations.

Because there is no gene flow between the newly separated populations, there is no magic force compelling those populations to be genetically identical to each other from that point on. The populations will diverge from each other as a result.

Indeed, the two separated populations need not be genetically identical at the start, and almost certainly won’t be. Hypothesise, for example, that your organisms can have either blue or red spots on the side of the body, and that this trait is controlled by a single gene. There almost certainly won’t be an identical number of blue-spotted and red-spotted individuals in each of the separated populations to begin with (it would be a pretty remarkable occurrence if this were the case), and so, the two populations will not even start as genetically identical with respect to this one gene alone. Repeat this for every gene with multiple alleles, even if they don’t result in an easily observable phenotye, and you quickly realise that the separated populations will begin with differences in place.

Those differences will, of course, increase with each new generation in the separated populations.

Eventually, those differences will reach the point where individuals from population A, will be unable to produce fertile offspring with individuals from population B. We now have a speciation event in place.

Now matters get slightly complicated at this point. If we conduct a genetic audit trail, and arrange for pre-split ancestors to be preserved in a manner allowing their revival, we could find ourselves with the following scenarios:

[1] Population A can produce fertile offspring with its ancestors, but Population B cannot. Population A therefore retains its original species identity, and Population B acquires a new species identity.

[2] The roles of the two populations above are reversed. In this case, Population B retains its original species identity, and it’s Population A that acquires a new species identity.

[3] Both Populations A and B fail to produce fertile offspring with their original ancestors. The original species has effectively disappeared, and we have two new species in their place. But, because ancestors of the original species are still alive, this is characterised as a “pseudo-extinction”. A species only truly becomes extinct, when it leaves no descendants.

Incidentally, scientists know which genes are likely to trigger speciation events as they diverge. An important class being the Major Histocompatibility Complex (MHC) of genes - these are the immune system genes responsible for distinguishing between “self” and “non-self” when, for example, bacteria infect organisms, and are responsible for tissue types. MHC genes are among the quickest to diverge when populations split.

Related, albeit somewhat distantly, are the fertilin genes, which are genes responsible for determining egg and sperm compatibility. These actually form part of an extended family of genes known as the ADAM genes (in this case, ADAM is an acronym for “A Disintegrin And Metalloproteinase Domain”, which is a common feature of these genes). That domain allows the gene products to adhere to various cell substrates, and genes in this family are responsible for a range of cell-cell and cell-matrix interactions.

For example, muscle formation and neurogenesis (formation of parts of the central nervous system) are all mediated by genes in this family. In the case of humans, the ADAM2 gene (also known as fertilin beta) is part of the outer integument of sperm cells, and plays an important role in interactions between sperm and egg. Mutations in this gene will of course ultimately lead to fertility changes in a population, and homologues/orthologues of this gene an be found pretty much across every lineage of organisms that rely upon sperm and egg based reproduction.

So endeth my quick guide to allopatric speciation. :slight_smile:


Wow! While I have a [very old] Applied Biology degree, my genetics was never that brilliant so well done for explaining it in terms I could mostly understand.


UK Atheist

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Glad to be of service :slight_smile:


I’m not sure if this qualifies, but consider the measels virus and another disease (of cattle) called rinderpest.

Rinderpest was eradicated around 2011, but please note that rinderpest also mutated into measels around 500 A.D. or so, and we’ve had both rinderpest and measels together as two separate and distinct diseases until rinderpest was eradicated in 2011.

As another example (if I understand your question correctly), there is an invasive species of freshwater crayfish called the “marbled crayfish.”

It can–evidentally–clone itself without mating, and is distinct from other crayfish.

Yet it didn’t exist before the 1990’s, as it is the result of a hybrid between two other species of crayfish from different parts of the world, and probably happened in an aquarium before the asshole pet owner released the crayfish into the wild.

See below:

Another example may be a specific venomous snake in the Phillipines that lives in Lake Taal.

Lake Taal was a saltwater bay that got closed off from the ocean by a volcanic eruption, and gradually turned into fresh water.

In this process, some sea animals became freshwater versions of their saltwater ancestors, which still exist now.

A specific example is a highly venomous freshwater “sea snake” that can no longer exist as a saltwater species. Since it is reproductively distinct from its saltwater ancestor and has anatomical differences, it probably is an example of a different specie that exists alongside it’s ancestor. This animal didn’t exist before around 1500 or so, as that’s when the volcano closed off the bay and turned it into a freshwater lake.

Please see below:

Another example from Lake Taal is that it is the only place in the world known to have freshwater sardines (the locals call them tawilis).

I hope this answers your question?


Ring Species: Speciation occurs as a species travels around an island. As the population expands, it moves to new hunting areas and changes. Each species on each side of the evolved species can mate; however, as you make your way around the island, the first species can not mate wtih the last.

Stickleback Fish , Amazon River Fish. Speciation occurs because of pools of isolated waters.

Oh, of course… We artificially produced new species in fruit flies.

Those are the few that come to mind, There are many others. The biologists on the site can give you more info. These are the only ones I recall reading about.

Oh hey! You have the underwater iguanas? Can they mate with regular iguanas? (I found another one for you… Just off the top of my head. Wow! Surprised myself.

" There are two types of iguana in the Galapagos Islands, which are separated by what could be as many as 10.5 million years of evolution: the marine iguana and the terrestrial iguanas. Nevertheless, it was recently proven that these two completely distinct species are interbreeding on the minute island of Plaza Sur (measuring one-tenth of a square mile), resulting in an extremely unique and unusual lizard."


Wait a minute, how do we know you’re not just making this up? I’m gonna wait for @Sherlock-Holmes to come back and verify this one.

:innocent: :rofl: :rofl: :rofl:

Sorry couldn’t resist.


Regarding Lake Taal, I would be interested to explore the lake and see if they have freshwater sea anenomes or freshwater octopus.