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Nephilidae Revision

Discussion in 'True Spiders & Other Arachnids' started by Little Grey Spider, May 15, 2017.

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    Hi, I'm new here. Forgive me if there is another thread on this, but I couldn't find one.
    I'm looking for information on the recent move of (former family) Nephilidae to a subfamily in Araneidae. Anyone know any details about this?

    Thanks in advance!
     
  2. The Snark

    The Snark Dancing with the enemy gods Old Timer

    Here you go. When you have finished digesting this, I'd appreciate you running it past me a few times. Blame the geneticists. Darn finicky trollops.
    http://macroecointern.dk/pdf-reprints/Dimitrov_Cladistics_2016.pdf

    PS Have a glance at the references at the bottom of that white paper. Something one would expect the LHC to barf out on a particularly tasty run.
     
    Last edited: May 15, 2017
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  3. Will do. Currently thumbing through my copy of "Spiders for Dummies" trying to decipher the 30 pages of whatever the heck it is I've just read . Seriously, thank you though. I appreciate your swift response to my query.
     
  4. The Snark

    The Snark Dancing with the enemy gods Old Timer

    Speaking clades, all animals are presently undergoing reclassification right now as genetics takes over the landscape. Huge chunks of what Linnaeus so carefully worked out are being verified, or tossed in the compost bin. As example, sparassids are presently getting the make-over Nephs got in that paper by Senkenberg. Lycosae are also being revisited and re-revisited.
     
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  5. Ungoliant

    Ungoliant Arachnoprince Active Member

  6. schmiggle

    schmiggle Arachnoangel Active Member

    Can't help with the anatomical synapomorphies, but they did all the usual things with the genetics. First, they picked a few sequences that can't change too much because they're probably "housekeeping genes"--genes that, if sufficiently changed, will result in cell death. These genes are assumed to evolve at a fairly constant rate that is unaffected by the environment, because the selective constraint is within the nature of a cell. However, the authors do mention that the way these genes change is partially dependent on the structure of the genes themselves, because a change in the wrong way will result in cell death.

    After they picked this area of the gene, they took three legs each from a number of species of orb weavers, presumably trying to find representatives from a wide taxonomic range, ground them up, and extracted DNA of the sequences they were looking for. After they did that, they plugged all the sequences into a supercomputer and worked out the most likely tree based on the relative similarity of all the genes to each other. They mentioned that the whole process was prone to error relative to the actual taxonomy because the families all split quickly a very long time ago (in evolutionary terms--they split within a few millions years of each other tens of millions of years ago). After doing all that, they have a tree that is the most likely based on a few different statistical analyses. They then do the same thing for cribellate and ecribellate spiders, assigning probabilities for the ancestor being cribellate or ecribellate at each node (based, by the way, entirely on statistical analyses on this data--other relevant data is not included, because that would mess with the math and it would quickly become too complicated), and also for web architecture.

    I hope that was clear, and that I'm not repeating things everyone already knows. The synapomorphies for the families almost don't matter, because they weren't differentiated using synapomorphies.
     
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  7. The Snark

    The Snark Dancing with the enemy gods Old Timer

    Addedendum to @schmiggle Then they, whenever applicable, extract pattern similarities in the trees, tossing out anomalies and refining until they get some pretty accurate profiles.
    They've come a long way from rat liver DNA in a gel in a raceway.
     
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  8. Arachnomaniac19

    Arachnomaniac19 Arachnolord

    648
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    Going off of that, should Menneus be classified as a subgenus of Deinopis?
     
  9. schmiggle

    schmiggle Arachnoangel Active Member

    Based on that tree, that would be the minimum change. Possibly deinopis would be split into several genera; more likely it would be split into several sub-genera, one of which is menneus. Further research would have to be done to determine if menneus is a legitimate grouping at all, or if it's just convergent evolution.
     
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  10. The Snark

    The Snark Dancing with the enemy gods Old Timer

    This is where my brain screeches to a dead halt. How do they delineate precisely what convergence has taken place? The big random number generator got genus X to this place, ... brain locks up.
     
  11. schmiggle

    schmiggle Arachnoangel Active Member

    If the molecular clock says that two species that look different diverged more recently than one of those species and a similar one, then that means the similar looking species are convergent. That's one of the reasons molecular clocks use housekeeping genes--the ancestor to all animals had them, and they are strongly selected to change only in certain ways at a certain speed irrelevant of the environment, so they're highly unlikely to change convergently.
     
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  12. The Snark

    The Snark Dancing with the enemy gods Old Timer

    If they diverged more recently .... then they converged.... I'm going to blame this on brain leaks but that reads as clear as thick pea soup.
     
  13. schmiggle

    schmiggle Arachnoangel Active Member

    Diverging and converging here are talking about different characteristics. They diverged genetically, but then evolved to fill similar niches and so evolved certain similar physical characteristics. In theory they could evolve to be similar genetically as well, but in practice this doesn't seem to happen.
     
  14. The Snark

    The Snark Dancing with the enemy gods Old Timer

    AHA! All becomes clear. I have an extreme left brain mind and think linearly. It gets in my way at times like this. Genetically diverged but environmentally converged. I suspect genetically they will never truly converge but perpetually follow a double helix, circling, close, but never fully convergent.
     
  15. schmiggle

    schmiggle Arachnoangel Active Member

    It turns out that they don't even do that. According to what I've read (though I think further research will be needed to really make a generalization), anatomical convergence usually comes from different genes. For example, they did research on two populations of desert mice that had separately evolved to become black to camouflage with black rocks. Each population had exactly four bases changed from the ancestral population, but the two populations had different changes in different places, even though the result was the same.
     
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