Any non-aggressive folks interested in discussing taxonomy?

Discussion in 'Codex taxinomiae plantarum (CTP)' started by VAAlbert, Feb 17, 2009.

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  1. Feb 18, 2009 #41

    Rick

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    Sharing a "similar" pollinator is generally not good enough to separate species or genera. The common honey bee pollinates a wide array of plant species and genera (and correctly these various genera of plants are not lumped together). Too use the pollinator argument you also need the space and time component of the pollination act coupled with the specific pollinator in question (not just gross groupings such as "flies" or "bees").

    On the other hand, is the split between genera such as Odontoglossum and Oncidium based on flower characteristics or DNA so completely arbitrary, that general fly vs.bee pollination strategies can be used as a "coin flipper" for separating or grouping at the genus level?
     
  2. Feb 18, 2009 #42

    VAAlbert

    VAAlbert

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    I have certainly done many parsimony analyses, and likelihood too -- but I have primarily been a plant developmental genomics scientist for a number of years.
     
  3. Feb 18, 2009 #43

    VAAlbert

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    Any other fun taxonomy topics out there??
     
  4. Feb 18, 2009 #44

    nikv

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    ^ ^
    I'll toss out a topic. Why was Laelia purpurata reclassified as a Sophronitis? Do they really think they belong in the same genus?

    Have at it guys and gals. ;)
     
  5. Feb 18, 2009 #45
    ok, another topic which is always going around my head since long ago... the only example I know very well is in Catasetum, so here I go.

    First an scenario with Paphiopedilum:

    paph. bellatulum x niveum = Paph. Psyche
    Ppah. Psyche x belletulum = Paph. Helice

    now back to Ctsm.

    Catasetum pileatum and Ctsm. macrocarpum are sympatric in a certain area of thier distribution. In this part, hybridization between both species is quite common, and the results is Ctsm. xtapiriceps (same cross, but human made, is called Ctsm. Splendens). It is even accepted that this cross is better adapted to the local environment as both parents.

    Ctsm. xtapiriceps, is very variable and we find plants very close to Ctsm. pileatum and plants very close to Ctsm. macrocarpum, and everything in between. Ctsm. Splendens, is more homogeneus and resemble more Ctsm. pileatum (let's put it more on the "Ctsm. pileatum" extrem of the morphological range of Ctsm. xtapiriceps). So, it is also discussed that the Ctsm. xtapiriceps on the "Ctsm. macrocarpum" are back crosses with this parent (actually, I think there is a huge crossing, back crossing, cross crossing, between all of them here).

    Then we have Cts. pileatum with red spots, or completelly red (let's stay with it as Ctsm. pileatum var imperiale, in order to keep thing easier), and it is widely accepted that the red pigments come from hybridization with Ctsm. macrocarpum.

    If an artificial back cross (see paphiopedilum example) is given a different name, why back crosses in nature keep the same name as the primary hybrid? I know, it is very complex to provide a name to all forms found, and actually the question should be more, why the artificial back crosses, do not keep the same name as the primary hybrids :evil:

    Then, assuming, we accept back crosses keep the same name in nature... Why the Ctsm. pileatum with red spots or completely red (accepted to be back back back crosses with Ctsm. macrocarpum) are not considered another variation of Ctsm. xtapiriceps? In some cases going to the extrem, that instead of keeping the name Ctsm. xtapiriceps, the plant is even considered (by some! like RHS) as a new species: Ctsm. imperiale...

    P.S.- I do not know any (for me) satisfactory answer to this...
     
  6. Feb 18, 2009 #46

    Ernie

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    Yep, as pollinator specificity becomes more specific approaching exclusivity (silly for the pollinator?), the usefulness of the character becomes more and more useful at lower taxonomic ranks.

    -Ernie
     
  7. Feb 18, 2009 #47

    VAAlbert

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    Hi there:

    Laelia purpurata was reclassified as a Sophronitis since the genus Laelia did NOT turn out to be a monophyletic genus upon DNA phylogenetic analysis. See http://www.cassiovandenberg.com/pdfs/2008-vandenberg.pdf, fig. 6, p. 109. You'll see there that Laelia species are found in several places in the phylogenetic tree, rendering the genus evolutionarily unnatural. One can suppose that some morphological traits led the old descriptors to classify all these as Laelia, but what happens more often than not in cases like these, it turns out that these 'defining' traits are actually shared, ancestral traits. So, to preserve monophyly in the circumscription of genera in the Cattleya alliance, Laelia purpurata and other Brazilian Laelias were transferred to Sophronitis. This was necessary (if one wants to preserve monophyly) because the TYPE species of Laelia turned up elsewhere in the tree -- and where it turned up, it and related species there needed to be kept as Laelia. Summary: these taxonomic changes were made to preserve information about evolutionary relationships, in this case, supported by DNA (at least).

    Hope this helps.

    Of course, some of you might say that the characteristics are more important than a DNA tree -- but I for one want my genera to reflect evolutionary relationships, and DNA phylogenetic techniques address such relationships in a rather objective manner.

    As I have argued elsewhere, in any case, it is the species name that is ALWAYS there (if it was validly published); genera an be viewed as merely 'packets' of information that group together species that should be linked because of shared common ancestry. Again, the species is the primary unit of diversity. So whatever Laelia purpurata became as a Sophronitis doesn't affect the fact that an entity was considered distinct at some point and described as this species.

    Best wishes,

    Vic.
     
  8. Feb 18, 2009 #48

    Ernie

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    Interesting. I'd say the Catasetum back cross should have a new hybrid name (even if a "small x", natural hybrid name). I'm stumped, but don't know the background.

    -Ernie
     
  9. Feb 18, 2009 #49

    VAAlbert

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    Well if Catasetum x tapiriceps was validly described, and described as the primary hybrid equal to the RHS name, then C. x tapiriceps is the correct name. The RHS name is simply for horticultural use.

    As for tweezing out the evolutionary/taxonomic issues you mention, this sounds completely like a population genetic question that would require considerable sampling of genetic variation in nature.

    Note still that natural hybrids can certainly be described as species if the botanical author considers them stable enough across observed variation to provide a Latin diagnosis and/or description. Again, another case of 'you choose'.
     
  10. Feb 18, 2009 #50

    VAAlbert

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    A great example here is Paph. wenshanense AKA Paph. x conco-bellatulum. However, I don't know if 'hybrid' status for this entity was ever established. If we assume it is a hybrid, you could certainly accept the species name if you believe that the entity is stable in the key characters used for its description.
     
  11. Feb 18, 2009 #51
    VAAlbert, this is indeed a very interesting example in population genetic and "delimitation" of species... As. Catasetum pileatum var. imperiale, it has been validly described both as Var. imperiale and as Ctsm. imperiale (I think it has never been considered as equivalent to xtapiriceps, even though it is accepted to have inherited the red from macrocarpum) This variety is found normally in a very small region in Venezuela, where a red variant form of macrocarpum is also present.

    One of the reasons I like this example so much (independently of the nomenclature issue) is because it shows how "artificial" the concept of species can be in some cases. Catasetum is a Genus with several species, which (my opinion!) are not so apart genetically from each other. (here are several cases as the one explained with xtapiriceps, but including other species.

    The way I see it (and the way I treat my plants) is that the extrems, e.g a white Ctsm. pileatum and a Ctsm. macrocarpum with a very well defined trident, are the ones to be considered as species, and everything else in between should be considered as "Hybrid XXX Complex" (giving a single name to each cross, and back cross, and crossed bac back cross, and so on, would be imposible in tehse cases). Only, if you have a plant getting out this rangem and living where non of the other components of the colex is present, this should be considered as a variety or forma, e.g. a hypothetical Ctsm. pileatum with red petal and green albellum found where there is no other Ctsm species found.

    I recall, I have read somewhere that there is a similar case with Paphiopedilum (I think Paph. wenshanense / Paph Conco-bellatulum), but am not sure where I read that.
     
  12. Feb 18, 2009 #52
    oops... I had not seen this before writting the previous message :)

    I think that what I read is that (again RHS) accepts wenshanense for teh natural hybrid (including crosses, back crosses and back back crosses, but Conco-bellatulum for the artificial primary hybrid... orsomething like that.. as I said, I have this in my mind, but cannot recall where I read that...
     
  13. Feb 18, 2009 #53
    Interesting posts and points, sorry I did not have too much time to respond.

    But to put some input in Ramon's question regarding Natural Hybrids. Yes, it is true (and does not always make sense), but when you find a population of plants in the wild that is considered a natural hybrid , it is probably never, or at least seldom a first generation natural hybrid (Species A x Species B). In most cases we are dealing with a hybrid swarm, so there can be cross pollination going on between plants that are natural hybrids, and cross pollination between the natural hybrid and either original species parent, so you get plants within your natural hybrid swarm that are not 50/50 species A and species B. All plants within the natural Hybrid swarm however get the same name. I think it will get too complicated to determine what the exact genetic makeup of plants is within a hybrid swarm and give each plant with a different genetic makeup a different name; It makes more sense when you find a population of plants that you know is of hybrid origin between 2 species to give them all the same natural hybrid name.

    It is true if you would recreate those plants by artificial pollination, each cross will get a different name. For instance say Paph. wenshanense for the point of this debate is considered the natural hybrid between Paph. concolor and Paph. bellatulum (even though there is some debate if this is really the case or not):

    Man Made Hybrids:
    Paph. concolor x Paph. bellatulum = Paph. Conco-bellatulum
    Paph. Conco-bellatulum x bellatulum = Paph. Concon Bell
    Paph. Conco-bellatulum x concolor = Paph. Hsinying Concon

    In nature/Wild:
    Paph. concolor x Paph. bellatulum = Paph. wenshanense
    Paph. wenshanense x bellatulum = Paph. wenshanense
    Paph. wenshanense x concolor = Paph. wenshanense

    This is why when you look at different plants of Paph. wenshanense, some resemble more Paph. concolor, while others resemble more Paph. bellatulum.

    Robert
     
  14. Feb 18, 2009 #54

    NYEric

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    Thanx
    Clear as mud! :rollhappy:
     
  15. Feb 19, 2009 #55

    Rick

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    In many orchid cases the increase in pollinator exclusivity does not mean exclusivity of the reproductive requirements of the pollinator. For instance the co opting of various species of hover flies to pollinate paph species doesn't have any impact on the reproductive isolation of a given hover fly species since the fly doesn't depend on the paph for its reproductive needs. It's getting tricked to lay its eggs on a fake aphid colony (presumed) which has nothing to do with the various ecological forces that isolate this particular hover fly species, shaping it into it's own form of reproductive isolation.

    In short I think the orchid pollinatees evolve to take advantage of the available insect pollinators rather than a co-evolution shaping both organisms to greater specificity.

    It may be a curious hypothesis to predict that you might find an increase in genetic barriers (fertility issues) for plant species that have non specific pollinators than for plant species that have very specific pollinators.
     
  16. Feb 19, 2009 #56

    Ernie

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    Cool. Makes sense.

    -Ernie
     
  17. Feb 20, 2009 #57

    VAAlbert

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    The evolution of (relatively nonspecific) fly pollination from within specialized bee pollination is known from the euphorb Dalechampia:

    Title:
    Switch from specialized to generalized pollination
    Authors:
    Armbruster, W. Scott; Baldwin, Bruce G.
    Publication:
    Nature, Volume 394, Issue 6694, pp. 632 (1998). (Nature Homepage)
    Publication Date:
    08/1998
    Origin:
    NATURE
    Abstract Copyright:
    (c) 1998: Nature
    DOI:
    10.1038/29210
    Bibliographic Code:
    1998Natur.394..632A
    Abstract
    The once prevalent view that the evolution of extreme ecological specialization is accompanied by a loss of potential for adapting to new conditions, and thus is irreversible, has been challenged by several recent examples,,. However, we know of no modern phylogenetic studies showing reversal in pollination relationships from extreme specialization to generalization, although such reversals are theoretically expected,. Here we present molecular phylogenetic evidence for an evolutionary shift in Dalechampia (Euphorbiaceae) vines from a highly specialized relationship (pollination by one or a few animal species,) with resin-collecting bees to generalized pollination by a variety of pollen-feeding insects. This shift was associated with dispersal from Africa to Madagascar, where the specific resin-collecting pollinators are absent. These results show that plants dispersing beyond the range of their specific pollinators may succeed by evolving more generalized pollination systems.


    In slipper orchids, phylogenetic relationships tell us that fly pollination has evolved from bee pollination at minimum three times, within Paphs (Barbata, e.g.), Phrags (longifolium, etc.), and Cyps (margaritaceum, etc.). The commode-lipped species have the ancestral morphology, i.e., Selenipedium, Cyp. irapeanum (etc.), Phrag. schlimii, Mexipedium, Paph. delenatii (etc.) -- which at the 'bottoms' of their subtrees in the family tree.

    Best wishes,

    Vic.
     
  18. Feb 20, 2009 #58

    VAAlbert

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    .. lie ...

     
  19. Feb 21, 2009 #59

    Rick

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    Not sure of the definition of "non-specific".?

    As such, flies are not going to orchids for the purpose of pollinating them. So I guess they are not specifically pollinators (i.e. they are not specifically in the business of pollinating flowers for a living).

    However, there are thousands of species of flies (probably many more species than bees)with differing shapes, sizes, life histories, feeding strategies.....so the shift to "flies" does not automatically mean a shift to generalized pollinators. For instance rothchildianum is apparently pollinated by hover flies (species not known to me). Furthermore it appears to be pollinated by the female rather than male that tries to lay its eggs amidst the "aphid mimic". The size of the roth flower compared to other sympatric paph species is pretty big, so would probably need a good size hover fly to get the pollinia placed properly. The same sized hover fly would probably get stuck in the sympatrics if they weren't separated temporarily (different blooming seasons).

    It is possible that supardii, stonei, and kolopakingii flowers could mechanically be pollinated by the same species. But then you need to look at normal home ranges of the hover flies which I suspect are rather small in comparison to many bee species.

    I believe you sent me the paper on pollination of Cyp species in southern China (euglosine bee pollinated), and I believe there were 7 some odd bee species in question, but although all 7 could be attracted by any of the Cyp species, the sizes of the bees was different enough to restrict the successful pollination events to only a couple per Cyp species.
     
  20. Feb 21, 2009 #60

    kentuckiense

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    Well, any idea of the exit orifice dimensions? Not being sarcastic here. Flower size is irrelevant, exit orifice size (and perhaps distance beneath stigma) is what really matters.
     

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