C.Gracilis(cuban) or C.gracilis(florida)?

[gromgrom]

The problem with answering these kind of questions is that you need experience or comparison material from the cuban and other populations and I don't have that material, nor have I experience in keeping them

But, there are more knowledgeable people here I think Btw, my name is Michiel, not Michel....I am NOT French

@ Nomad,

PS. Being able to reproduce parthenogenetically alone is not a character in species definition. Most parthenogenetic scorpions have sexual and parthenogenetic populations: Tityus metuendus, Tityus colombianus (a sexual and a parthenogenetic population in the same country), Tityus neblina, T.trivittatus, L.australasiae has a parthenogenetic population in the Philippines and a sexual one in Australia. H.hottentotta has sexual populations in several African countries. etc etc...So it is not impossible that the population from Cuba is parthenogenetic and the Florida population isn't....

My bad on the name. It's how we spell Michael, minus the a, I didnt double check

 

[skinheaddave]

This is one of those cases where it raises some interesting questions and so few answers might be gleaned from what is available:

First off, some background. Centruroides is tough to do morphologically on the whole. Key features that consistently differ between species are hard to find and often seem to be polymorphic within a species rather than diagnostic of species. Often it comes down to proportions or multiple, more qualitative, features.

As a side-note, this leads to a word of caution for those who want to draw conclusions from hobby specimens. In order to get anywhere with this genus you will often need to examine large amounts of material with known collection locales. The biggest issue with Centruroides when it comes to morphology is the effects of size on proportion. You may find two populations -- one large and one small -- and take proportions and come to some conclusion. If, however, you then look at males that mature an instar earlier in the large population you may find they are near identical to males in the smaller population. If you plot this ratio on a graph you may find a continuum in place of a true divide .. and the culprit will be size affecting ratios.

The other key concepts are those of isolation and genetic drift. Most people have at least a little handle on the way selective pressures might lead to change over time (whether you believe it or not, unless you were home-schooled you should have at least had a chapter in a textbook somewhere). It should be noted, however, that selective pressures are not the only path to evolution and speciation. If you take two populations and reduce or remove entirely gene flow between them, chance will start to play a significant role on those genes on which selective pressure doesn't have a strong effect. Genes will tend to diverge and fixate .. purely by chance. So if having one or two granules on some part of some segment doesn't have a strong selective effect (those granules aren't used for stridulation, for example) then two populations with reduced gene flow might fixate on one and two granules respectively.

Of course if there is continued gene flow betweent the two populations, then it will act to negate the effects of genetic drift. The degree of mitigation will depend on the degree of gene flow. Depending on how you feel about such matters, when gene flow becomes far enough reduced you may be tempted to call the two populations "subspecies" or you might argue that they are divergent species at the beginning of their divergence and that there remains a small margin of hybridization.

So let's look at Florida/Cuba. This is a very interesting area of study because there are two species of scorpion shared between the two countries. C.guanensis and C.gracilis. Both are relatively large bark scorpions with similar morphology, habits etc. Perhaps significantly, their distribution in Florida seems to be something of a patchwork with strong localized populations of one or the other but seemingly never/rarely both together. It is entirely possible that they are so close in their niche occupation that they are competative.

I've never looked at C.gracilis from both populations but I have seen a few Cuban C.guanensis and, not surprisingly, they are quite similar but not identical to the FL populations of C.guanensis that are larger and out there on the keys. There are, however, some C.guanensis in FL that start to stray a bit and might be mistaken for C.hentzi given a casual glance. C.gracilis also seem to be variable within FL to some degree. I've certainly seen those collected from mainland FL that differ obviously and superficially in colouration, size etc. as compared to those I've observed in the Keys and Dry Tortugas.

The question really comes down to one of gene flow. It is indisputable that there will be some gene flow between the two populations. Scorpions do raft and hitch rides with boats etc. There will be at the very least a decent amount of gene flow from Cuba to the US with refugee boats. Is this gene flow enough to maintain a single, relatively uniform, species across the two land masses? Likely not .. but who knows. Is it the case that one species has established itself in either area relatively recently (from an evolutionary standpoint) and, though divergent, there may still readily interbreed? Are we, in fact, dealing with different species that are simply morphologically conserved? A good way to go about poking this quesiton would be using molecular techniques to estimate gene flow between populations.

The problem in putting this all together, of course, is that the US and Cuba have .. frosty ... relations. It isn't as simple even as researchers wanting to look at something like P.boreus across the US/Canada border (also tricky but ultimately doable, I suspect). The number of cuban specimens in US collections is paltry and the reverse is, I suspect, also true. There is(was?) some work along these lines being done but it is a large undertaking with several potential barriers and we shall see what the end result is in time. If estimates of gene flow can be gotten for both species then it would be interesting to compare C.guanensis to C.gracilis. One would expect similar levels given their relatively distribution here (I don't know about the Cuba side) and their similarity in size, habits etc. If the rates were found to be significantly different then you'd have a truly great mystery on your hands .. one that would likely yield some greater insight into the world around us.

Cheers,
Dave

 

[Nomadinexile]

@ Nomad,

PS. Being able to reproduce parthenogenetically alone is not a character in species definition. Most parthenogenetic scorpions have sexual and parthenogenetic populations: Tityus metuendus, Tityus colombianus (a sexual and a parthenogenetic population in the same country), Tityus neblina, T.trivittatus, L.australasiae has a parthenogenetic population in the Philippines and a sexual one in Australia. H.hottentotta has sexual populations in several African countries. etc etc...So it is not impossible that the population from Cuba is parthenogenetic and the Florida population isn't....

Thanks for info! I understand and agree with the above. What I am arguing here is a little different from that though, and I would love to hear your (and dave's) opinion on this, as I'm not 100%.

What I am arguing, is that because Parthenogeneticism is controlled through genetics (right?), that if a species is Parthenogenetic in any of its ranges, then it must be able genetically, to do so in the other ranges if the habitat changes and the need arises. If this ability does not exist in all ranges, then their must 2 different species in the conversation, because the Genetics are not the same. (right?)

I am aware however, that this is difficult to study. I would guess that there has been however, a parthenogetic birthing in Florida by C. gracilis. If it has been observed in Cuba, then the same possibility must exist in the florida populations. All it should take is a bad winter, hot summer, forest cut down, something like that, to trigger it.

Am I way off base here?

 

[Kris-wIth-a-K]

Cuba and FL have basically the same Climate. So Sp dont have to really adapt to each other. If it was as dramatic climate change such as Cuba to Arizona then yes things would be differently adapted. I think you are just overthinking things.

 

[Nomadinexile]

Kris, if you are responding to me:

If it's exactly the same (or close), then why did Parthenogetic trait express itself in Cuba, but not Florida? That trait has to be expressable in other populations, or their genes aren't the same as I understand it, though I am waiting for answers..

 

[skinheaddave]

because Parthenogeneticism is controlled through genetics (right?)

Yes. No. Maybe so.

Let's assume for the moment, though, that it is since this makes for the most simple approach and allows us to touch on gene flow once again.

The first thing we need to realize is that gene flow is like a faucet, not a switch. Yes, it can be turned entirely on (small population in very small region with good interbreeding) or entirely off (two flightless bird populations on different, distant, islands). There are also inbetween states, though. For example, nearby islands may show enough rafting etc. that while the two populations are divergent to some degree, there is sufficient gene flow that the populations do not become either fixated or reproductively isolated.

Now, in simplest terms, "species" is defined based in part on reproductive capability. If two populations can and do mate and produce fertile offspring, they are generally considered a species. If two populations can but don't mate (for example, due to a recent geographic separation) then they are often considered subspecies. They may be divergent but they are reproductively isolated based on external, not genetic, criteria. Subspecies is a difficult taxa, though, because unless that barrier is removed, the long-term prospects of those two populations is to drift and fixate and ultimately become reproductively isolated and separate species.

This is all simple text-book stuff and it does get drastically more complicated than that .. but for our purposes it will do. One thing to note is that all members of one species don't have to interbreed with all other members of that same species. Certainly when you are talking about massive ranges, it is quite possible that the frog, for example, at one end of the range will never meet and mate with one frog at the other end of the range. As a result, the frogs at one extreme may develop a call that is disperate from that of the frogs at the other end .. yet each one is close enough to its neighbour that there is no reproductive isolation within the population as a whole -- yet the two extremes would be reproductively isolated if the middle were removed. This sort of thing happens all the time with inverts (where a corn field can represent a massive range) and will often lead to speciation.

All this so far is based on sexual populations. Once you add in parthenogenesis you change the rules. You certainly can't define species that reproduce entirely asexually based on their mating habits .. they don't have them. With populations that can reproduce in both fashions it is perhaps a bit more conventional insofar as you can still argue from the standpoint of reproductive isolation.

Now, remember that not all features themselves will lead to reproductive isolation. Selective pressures, for example, may create a situation where animals lower on a mountain slope tend to be lighter whereas those up higher tend to be darker to absorb more heat. They may still be the same species, though .. there may be constant gene flow from top to bottom but selective pressures result in better survival for one colouration or the other and this, in turn, leads to most animals in either extreme of the range having one or t'other colouration and the animals in the middle tending to be somewhere inbetween (or a mix of two dichotomous states, depending on the underlying genetics).

So now let's look at C.gracilis. It is entirely possible that one population has developed the ability to reproduce asexually but has maintained its ability to reproduce sexually as well. It may still have some gene flow back-and-forth with another population that does not have this ability. It may simply be the case that the genes resulting from the mutation that allowed one popluation to reproduce asexually has never made it over to the other population. It may be the case that even if an asexual animal is rafted over, any progeny which reproduce sexually lose the benefits of the mutation in light of some common genetics held by the other population. So perhaps there is a genetic "switch" that is turned on which allows for asexual reproduction but the other population also has a gene which prevents the syntehsis of some hormone that is also needed .. even those with the "asexual" gene would not be able to produce asexually.

Now, whether such a situation will eventually lead to an entirely asexual population which ends up being reproductively isolated .. who knows. There are numerous possibilities. In short, though, it is quite possible for two populations to exist which we consider to be of the same "species" and between which there is significant gene flow .. yet some traits are divergent, including mating schemes.

Cheers,
Dave

 

[AzJohn]

Kris, if you are responding to me:

If it's exactly the same (or close), then why did Parthenogetic trait express itself in Cuba, but not Florida? That trait has to be expressable in other populations, or their genes aren't the same as I understand it, though I am waiting for answers..

I wouldn't consider parthenogenisis a trait of the Cuban species. From what i understand is that it occured once in a labratory setting. Does that make it a trait of the species. Take some of the other instances of documented parthenogenisis. If i keep a tityus 10 degrees cooler than it would ever be in the wild and it produces a parthenogenic brood, does that make the species parthenogenic? I can see how parthenogenisis that is the result of climate change would be very useful to a species, but if it takes lab conditions to produce a certain outcome is it considered a trait of the species? If the species never produces parthenogenically in the wild is it a trait?

 

[catfishrod69]

ok i see..thanks...

I wouldn't call them florida bark or cuban bark I'd use the scientific names. Bark scorpion is more of a discription of lifestyle and overall apearence than anything else. Their are several gunus that can be considered bark scorpions. Their are at least 3 species of Centruroides in Florida. The one species we are talking about is C gracilis. C gracilis has populations in Florida, Cuba, and Central America. They are the same species and should be nearly impossible to tell the difference. I have C gracilis from Central America and Florida. If I didn't keep them in labled containers I wouldn't be able to tell them apart.

 

[gromgrom]

I wouldn't consider parthenogenisis a trait of the Cuban species. From what i understand is that it occured once in a labratory setting. Does that make it a trait of the species. Take some of the other instances of documented parthenogenisis. If i keep a tityus 10 degrees cooler than it would ever be in the wild and it produces a parthenogenic brood, does that make the species parthenogenic? I can see how parthenogenisis that is the result of climate change would be very useful to a species, but if it takes lab conditions to produce a certain outcome is it considered a trait of the species? If the species never produces parthenogenically in the wild is it a trait?

I think if we can reproduce that ability ourselves, maybe. It would be interesting if we could get some asexual+sexual populations going in the hobby . Pipedream?

 

[Michiel]

Thanks for info! I understand and agree with the above. What I am arguing here is a little different from that though, and I would love to hear your (and dave's) opinion on this, as I'm not 100%.

What I am arguing, is that because Parthenogeneticism is controlled through genetics (right?), that if a species is Parthenogenetic in any of its ranges, then it must be able genetically, to do so in the other ranges if the habitat changes and the need arises. If this ability does not exist in all ranges, then their must 2 different species in the conversation, because the Genetics are not the same. (right?)

I am aware however, that this is difficult to study. I would guess that there has been however, a parthenogetic birthing in Florida by C. gracilis. If it has been observed in Cuba, then the same possibility must exist in the florida populations. All it should take is a bad winter, hot summer, forest cut down, something like that, to trigger it.

Am I way off base here?

I get you now. Basically, yes, if a species from site A reproduces parthenogenetically, the same species from site B should be able to do the same, because if they are same species, they should have inherited the same ability. Habitat destruction, introduction into a new area, lack of males, temperature and food intake manipulation (in the lab) are a couple of examples of possible triggers of parthenogenetic reproduction.

Try to get Lourenco's paper on the life cycle of Tityus neblina. Interesting paper....

 

[skinheaddave]

I get you now. Basically, yes, if a species from site A reproduces parthenogenetically, the same species from site B should be able to do the same, because if they are same species,

Since this directly contradicts what I have said, would you care to comment on my thoughts and suggest where your interpretation differs? I'd hate to think that all that time typing was an utter waste and nobody is bothering to even read it.

Cheers,
Dave

 

[Michiel]

Hi Dave,

what I meant in my last post is that theoretically speaking, both populations should be able to reproduce parthenogenetically physiologically, but that specimens from one population are triggered to reproduce parthenogenetically and others aren't.
I.e. in Colombia you have two populations of Tityus colombianus, on in the North of the country and one in the South. One of the populations reproduces sexually, and the other parthenogenetically. I suspect/ assume that the specimens from the sexual population are theoretically able to do the same, if properly triggered (climate fluctuations, human disturbance of the habitat, lack of males etc). If not, that would indicate that the parthenogenetic population picked up this trait somewhere down the line of evolution and have adapted to a certain situation, that the sexual population didn't...

The interesting thing about the Tityus neblina paper is that males and females where brought to the lab and where mated...A couple of females where separated from the rest and where kept at lower temps and they received food only once in three weeks, instead of weekly.
The latter specimens, these separated females, reproduced parthenogenetically while the former reproduced sexually. Maybe I am drawing the wrong conclusions, but this means that the females adapted surprisingly quickly to colder temps and lower food intake (within the span of the research), and reproduced parthenogenetically. I suspect these females where already able to do so physiologically, because such an adaption normally would take much longer????

I hope to have clarified what I meant earlier....if not, please ask....I read articles and I form an opinion, I am not a parthenogenesis expert lol

Cheers, Michiel

 

[Nomadinexile]

Dave,

I read everything you wrote 3x. I have to say this is part of why I love AB. You all remind me of how little I really know! I spend a lot of time around people who can barely form a complete sentence, so this is good reminder that I'm not that smart. (ego check)

I have a lot of questions and comments, but it is so much to chew on, I want to do it later when I have formed a more complete thought.

~r

 

[GartenSpinnen]

I actually have a pair of Centruroides guanensis and they're two totally different scorpions. They don't even remotely look like gracilis, I can take pictures if needed.

---------- Post added at 03:51 PM ---------- Previous post was at 03:49 PM ----------

Actually, I remember Sam having posted pictures of the guanensis when he was selling them, this is what a guanensis looks like:

Wow! Those are perdy

I want to get me a few!

I used to keep the FL variety for quite some time. They are nice scorps, very colourful after molt. Man I miss my Centruroides

 

[skinheaddave]

Michiel,

Indeed I am sure there are situations where the entire species is capable of parthenogenesis but only certain environmental factors bring it about.

This, however, is not a guarantee that that is the case in all situations. A common garden experiment would be the way to go about determining whether or not this was the case .. as you might well imagine, this sort of work is not being done.

On the broader point, while it is true that populations of a species must be linked by gene flow, it is not true that species must be genetically uniform. It is obvious that this is not the case individual-to-individual but it is also the case that the proportions of various alleles in different populations may differ drastically and that some alleles may be entirely absent from some populations. In the case of parthenogenesis, any population that developed obligate parthenogeneisis would quickly diverge into its own species .. but as long as it is faculative and gene flow is maintained with other popluations, there may be populations with all individuals being capable of parthenogenesis, some with a mix or some where no individual is capapble.

Cheers,
Dave

 

[Sarcastro]

Maybe we're over thinking and over analyzing the question.
Has anyone thought of Iteroparous brooding? this can be mistaken for parthenogenesis.

 

[Michiel]

Maybe we're over thinking and over analyzing the question.
Has anyone thought of Iteroparous brooding? this can be mistaken for parthenogenesis.

Most people here know the difference between parthenogenetic and iteroparous reproduction. The OP was asking about differences between populations of scorpions and parthenogenesis and afterwards a discussion about parthenogenesis took place. Then you come around telling us we should consider iteroparity. Thanks for the suggestion, but I fail to see the relevance here and I don't think this has anything to do with over thinking or over analyzing

 

[Sarcastro]

Most people here know the difference between parthenogenetic and iteroparous reproduction. The OP was asking about differences between populations of scorpions and parthenogenesis and afterwards a discussion about parthenogenesis took place. Then you come around telling us we should consider iteroparity. Thanks for the suggestion, but I fail to see the relevance here and I don't think this has anything to do with over thinking or over analyzing

The statements I made we're just that, two separate statements. One for the question asked about "Cuban" "Florida" and the other for the discussion referring to reproduction. That is why they were separated by line spaces and not one continuous statement. I do not know why there was such a problem with my post, but to take a condescending and elitist tone and tell someone that their post means nothing is down right rude and uncalled for.

 

[Michiel]

The statements I made we're just that, two separate statements. One for the question asked about "Cuban" "Florida" and the other for the discussion referring to reproduction. That is why they were separated by line spaces and not one continuous statement. I do not know why there was such a problem with my post, but to take a condescending and elitist tone and tell someone that their post means nothing is down right rude and uncalled for.

Wait a minute. I said that I don't see the relevance of your post given the discussion that took place...I did not say your post means nothing etc etc, that is just the way you experience it. I merely corrected you.
That you find this condescending and think I have an elitist tone, says more about you, than about me. I think you can't handle feedback, parthenogenesis just has nothing to do with iteroparity, other than that they are both ways of reproduction, and you become angry when some one says this to you? And this makes the person that gives feedback (in this case me) automatically condescending and an elitist?


I am not out for a dispute or something, but what you did was joining the conversation (no problem, this is a forum intended for these interactions), and you said something that totally has nothing do to with it.....What good is the remark:"maybe we are over thinking, over analyzing the question"? Who are you to ask or suggest this? After all this is a complicated subject. Imagine, two doctors are discussing pathology of a patient, difficult symptoms, hard to diagnose, and then a third comes a long: "Hey aren't you guys over thinking the question or over analyzing it?" Maybe it is the patients' foot instead of it's hand. How would you think these two doctors would respond....

Greetings from a rude, arrogant and obnoxious elitist!

 

[AzJohn]

Maybe we're over thinking and over analyzing the question.
Has anyone thought of Iteroparous brooding? this can be mistaken for parthenogenesis.

Iteroparous is often mistaken for parthenogenisis. In this case however the parthenogenic birth report is documentedand comes from a well respected scientist. That's what makes this species so cool. You have three different populations that could be developing into different species. Each one has different characteristics. For instance the Central Americam population is considered medically significant while the Florida popullation isn't. The Cuban population is possibly parthenogenic while the others are probably not. I'm very interested in this topic, we don't get as many topics likee this as I'd like.