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  • To Ray Gabriel : subspecies?

    I can't post on the other BTS forum, so Í thought I'd continue Rays question here:

    He asked why isn't subspecies level considered for the Theraphosidae.

    Hi Ray,
    Because at such an early evolutionary level, a species variation has not had a chance to stabilize and continue its form, it could morphologically change practically overnight. Not stable enough to warrant a scientific name. If the entity can create an isolated reproductive mechanism then it will become a species within its own right, but until it does so, it would have to be considered too unstable. For example all it might take for the subspecies to vanish would be an alteration to its geographical barrier(human intrusion could cause this litteraly overnight), allowing it to cross successfully with its other same species counterpart.

    I'm aware that subspecies could be considered for the Theraphosidae and perhaps justifiably so, but perhaps it should also be considered that too little is known of the Theraphosidae at higher levels to even contemplate subspecies at this stage.

    Besides, what morphological characters would be considered for subspecies??? Colour is useless, due to extreme variance, so is size.....

    Cheers,
    Steve Nunn
    Australian Tarantulas website
    http://www.thedailylink.com/australiantarantulas

  • #2
    I'm confused...
    according to the Tarantulas of the World by Heinz-Josef Peters there are several subspecies are recognised...

    Stromatopelma calceatum griseipes
    Selenocosmia javanensis brachyplectra, dolichoplectra, fulva, sumatrana
    Phormictopus cancerides centumfocensis, tenuispina
    Hysterocrates robustus sulcifer
    Heteroscodra crassipes latithorax
    Euathlus vulpinus ater
    Avicularia avicularia variegata

    There are surely also others.
    And I must admit most terms are fysiological or colors but sumatrana isn't

    Greetings Tim

    Comment


    • #3
      Hello,
      Nearly all mygale taxonomists refuse to recognise subspecies due to its instability. You can also add Hysterocrates affinis angusticeps, Avicularia fasciculata clara, Lasiodora trinitatis pauciaculeis and Phoneyusa bidentata ituriensi to the previous grouping.

      As you would imagine they aren't "ruled out"as such, but subspecies are indeed rare in the Theraphosidae.

      Cheers,
      Steve[/i]

      Comment


      • #4
        Tarantula Subspecies

        I fully agree with Steve’s comments regarding tarantula subspecies. There’s little point worrying about subspecies until we’ve sorted out the species first. A taxonomist’s time is far better spent defining/redescribing species than subspecies. As Steve says we can’t adequately define theraphosid subspecies based on variable features such as coloration.

        The classic example is Pterinochilus murinus. Although we know this to be a very colour-variable species, with many geographical colour forms, all museum specimens have long since faded to brown. We are only able to gather reliable geographical data from museum specimens, since pet-trade material typically lacks credible sampling data. Therefore it is currently impossible to define the geographical limits of murinus colour-forms (which probably intergrade where they meet in any case). Exactly where would you draw the line between the subspecies (colour forms)? That wild-caught orange specimen isn’t as orange as that one, but it’s slightly more orange than the typical form?!!? (You see what I’m getting at – totally unworkable). Basically there are 3 murinus colour forms in captivity: typical (sandy yellow), red (orange) and dark (grey). Within each colour form there is some variation (e.g. whether carapace lines are distinct or not, intensity of colour). The best we can hope for is that people maintain the 3 captive colours as separate breeding lines – if only to give us 3 interesting colours to keep, rather than eventually just one.

        We really need to know the geographical limits long before we start applying subspecies names. Many of the existing tarantula subspecies are likely to be elevated to full-species-status or synonymised with other species eventually.

        The only argument where I could see subspecies being valid is where a distinct form occupies an island (cut-off from the mainland population). Even then there’s probably little point in doing so, since you can just state the stock is the “island form.”

        Richard Gallon

        Comment


        • #5
          It may be a little different in different species concepts (Biological, Phylogenetic, etc etc) and different in different orders of organisms, but a subspecies usually is a different form of the species which will/does still interbreed with the nominate form.

          In short I don't see the problem with calling a different colourform a subspecies.
          Especially if the colourform exists in nature despite of interbreeding

          Comment


          • #6
            Unstability seems to me a poor argument.

            If a species would be unstable then it would be a problem (need of protection/ need for revision of taxon etc) But a subspecies is always more unstable be it colourforms (interbreeding) or island forms (genetic drift, inbreeding depressions)

            Recognition is an important purpose of admitting a subspecies.

            recognition of variability in the field, in the species, maybe even different needs. Nature changes constantly and isn't fit to be named with a fixed name. It's a process, not a situation. That implies nothing is stable at all...

            Comment


            • #7
              Hi Steve
              ,
              >Because at such an early evolutionary level, a species variation has not >had a chance to stabilize and continue its form, it could morphologically >change practically overnight. Not stable enough to warrant a scientific >name. If the entity can create an isolated reproductive mechanism then >it will become a species within its own right, but until it does so, it would >have to be considered too unstable. For example all it might take for the >subspecies to vanish would be an alteration to its geographical barrier>(human intrusion could cause this litteraly overnight), allowing it to cross >successfully with its other same species counterpart.

              Sorry i am not following you with the above,can you try to re explain please maybe with an example species?

              >I'm aware that subspecies could be considered for the Theraphosidae >and perhaps justifiably so, but perhaps it should also be considered that >too little is known of the Theraphosidae at higher levels to even >contemplate subspecies at this stage.

              I dont feel that our lack of knowledge should, prevent subspecies status.
              I have said for a long time i think there are more varients than species, and feel that if we looked at Theraphosids from this angle might make taxonomy much easier

              >Besides, what morphological characters would be considered for >subspecies??? Colour is useless, due to extreme variance, so is size.....

              Good point, i was thinking colour P. murinus dark, normal, red/orange forms, N. carapoensis light and dark form, from different habbitats, but you are correct especially with the variance due to humidity, everyone would be describing thier own spiders as "new" subspecies.

              I suppose then instead of subspecies the term "variety" could be installed to help separate these colour forms in the hobby before they are lost due to hybridising?

              So if this is the route to follow how would we establish recognised varietys, i think they would have to be "peer reviewed" to prevent people making up thier own "varitys".

              The reason i am looking at this is that i have just picked up 5 specimens of naother colour form of P. murinus, it comes from Tanzania and looks like what you might expect from a cross between the "Usumbara" form and the "normal" form. I would like to see this colour form (as i believe all naturally occuring golour forms should be) kept separate and kept pure, much in the way that Breeders of other inverts/reptiles/amphibians do.

              Cheers,
              Ray

              Comment


              • #8
                I almost totally agree with the angel above , but have a few counterpoints:
                Originally posted by angelarachnid

                I suppose then instead of subspecies the term "variety" could be installed to help separate these colour forms in the hobby before they are lost due to hybridising?

                So if this is the route to follow how would we establish recognised varietys, i think they would have to be "peer reviewed" to prevent people making up thier own "varitys".
                The term variety is first of all almost synonymous to subspecies and therefore not necessary. But for use in the hobby of course is fine because every spider has more than one common name already
                Originally posted by angelarachnid
                The reason i am looking at this is that i have just picked up 5 specimens of naother colour form of P. murinus, it comes from Tanzania and looks like what you might expect from a cross between the "Usumbara" form and the "normal" form. I would like to see this colour form (as i believe all naturally occuring golour forms should be) kept separate and kept pure, much in the way that Breeders of other inverts/reptiles/amphibians do.
                It can't be said that colour forms are being kept seperate in nature, that's just the reason why alleged subspecies are so 'unstable'
                The one colourform probably interbreeds with the other and an other is born, which on it's turn is gonna interbreed.

                Comment


                • #9
                  Hi Ray,
                  It would be difficult to give an example, as most variants that have crossed and vanished haven't been recognised to begin with. Because there's no reproductive isolated mechanism (a character or trait that prevents the entity crossing with other similar entities) preventing a cross, it could become very easy for a species variant to vanish. More often then not, a species variant has become isolated from its original population somehow, usually a geographic barrier of some sort (a river or mountain range) , allowing it to begin its own evolutionary process. Maybe colour is the first noticeable (albeit unstable) character in this recently isolated entity (which is pretty much the basis for subspecies, the beginning of a new evolutionary path). But (and this is the argument) because it may have begun its own path, is this stable enough within the Theraphosidae to be considered from a taxonomic standpoint?? Many say no because it really is all too easy for the entity at this early stage to rejoin the original population (unless as Richard has said the geographical barrier is extremely stable, such as an island would be). The species level is what I would consider the ideal taxonomic starting point, simply because at this level the entity has developed certain character/s that prevent it from crossing with other similar entites (when I say crossing I mean that no fertile offspring can be produced).

                  Perhaps calling something a "variety" is a great idea. From a taxonomic standpoint it will be considered irrelevant, but from a hobbyists perspective it would suit nicely.

                  Cheers,
                  Steve Nunn
                  Australian Tarantulas website
                  http://www.thedailylink.com/australiantarantulas

                  Comment


                  • #10
                    Tarantula subspecies

                    Hi Guys,

                    If we take Pterinochilus murinus as a working example. It has a huge geographical range and not surprisingly some variability across it (and presumably gene flow too). In the South (Zambia) we see a dark colour-form, Southern Tanzania has sandy yellow coloured specimens and in northern Tanzania we find some of the bright orange ones. Into Kenya we see a sandy yellow form again.

                    Wild caught imports are just "spot samples" from this species' range. So it's not surprising these "spot samples" are different looking. However, if we were able to sample specimens at 10km points along a transect line from Zambia to Kenya I suspect we might find a gradual colour change between the colour-forms (assuming the distribution is unbroken).

                    OK - say we decide subspecies rank in spider taxonomy is ON again . Each "spot sample" population gets a subspecies name (because they look different). What do we call all the intermediates (along the cline) which will eventually be found in the wild? Simply calling them intergrades between two of the "spot sample" subspecies is unlikely to cover all the shades of yellow, grey and orange we'll undoubtedly encounter.

                    A subspecies is a fairly arbitrary classification in my opinion and totally artificial, at least in contiguous mainland 'populations'. Exactly where do you draw the geographical boundaries between the various subspecies? You'd end up with a situation where it'd be impossible to allocate specimens to a subspecies unless you knew exactly where it was collected. Even then what would you call it if it's in a "grey area" between two subspecies. Maybe define it as a new subspecies and let the situation snowball

                    It certainly makes for an interesting discussion. How do you pigeon-hole variability......

                    Cheers, Richard

                    Comment


                    • #11
                      Wow, so much to reply to:

                      I think the points regarding subspecies are all valid, espacially as you are correct in saying it would be very hard to palce them due to colour and what do we call the intergrades inbetween what we have decided as sub-species, yes i can see it snowballing out of proportion.

                      Maybe the characteristics for sub-species status would differ from speies to species.

                      If you remember a few years back there were huge A. versicolour which were uncommon in the hobby, then all of a sudden there were a large amount of a smaller A. versicolour every where, no one kept the two forms distinct and these are now man made "hybrids" of two distinct forms.

                      If we were to keep these separate it would be based on the differeent Islands they came from. either as "varietys" or "sub-species".

                      With Nhandu coloratovillosum, there is the normal form (which if my memory serves me correctly) commes from a wooded area, and a "darker" form where the bands on the legs are much narrower which comes from a "Savanna" area (please correct me if i have got these the wrong way around). This could be variety or subspecies due to habitat.

                      I think it would be really bad if we ended up with more "mongrel" species in the hobby because people are unwilling to keep colour or regional varieties pure.

                      In some of the Lepidoptera ( i think it one of the Pierids), Small White or Green Veined White, which is much more yellow in the Scottish or Irish forms and is called ssp hibernica, this is given subspecies status because of its geographical location, but in other species where the eye spots on the wings, or other markings are "diffused" or indistinct these are given variety status.

                      At the end of the day, i still feel we need to establish something If only from a hobby point of view to keep these different forms separate. Last year the rcf P. murinus and the ncf P. murinus were different species and being bred apart. Now people know they are the same species, there are some people who wont really care about keeping them pure.

                      Now what if and this is purely Hypothetical, a new taxonomic feature was found, which separated these two forms back into species in thier own rights? in the hobby we would have a bunch of hybrids.

                      As every one agrees Theraphosid Taxonomy is very much in its infancy, is now not the right time to start putting in palce the foundations for "sub-species" or "Variety" or "form" status, before other forms are found rather than waiting till it is to late to rectify any hybridisation in the hobby?

                      Comment


                      • #12
                        Now what if and this is purely Hypothetical, a new taxonomic feature was found, which separated these two forms back into species in thier own rights? in the hobby we would have a bunch of hybrids.
                        Hi Ray,
                        I think this is where the defintion of a species could be argued. I believe to have a new species it should be shown that the species can not breed with those close relatives, therefore, it must possess an isolated reproductive mechanism that prevents it hybridising. . You know, there's a strong argument that Brachypelma albopilosum and Brachypelma vagans are one and the same species, all because when crossed, they produce fertile offspring. I guess it depends on what you would call a species.

                        Because of what I would define a species as, a simple physical character might not be enough to warrant a new description, others may disagree.

                        Cheers,
                        Steve Nunn[/quote]
                        Australian Tarantulas website
                        http://www.thedailylink.com/australiantarantulas

                        Comment

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