Tuataras and the species problem

by Greg Mayer

Tuataras are very interesting animals: endemic to New Zealand, and the sole survivors of an ancient and once more widespread order of reptiles, the Sphenodontida, whose closest relatives are the squamates (lizards+snakes). I noted some of their distinctive traits in an earlier post. When a friend went to New Zealand for a visit during the holidays, I asked him to get a picture of a tuatara if one came his way, and he obliged.

Tuatara at a North Island, NZ, zoo.

Tuataras are also of interest with regard to the ” species problem”, which Jerry recently addressed with respect to how many species of elephants there are (with follow-ups here and here). Ernst Mayr defined species in 1942 as

Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such group.

This definition, known as the biological species concept, is the one Jerry argued in favor of in his posts (and more extensively in Speciation, his book with Allan Orr). Through most of the 20th century, a single geographically variable species of tuatara, Sphenodon punctatus, was recognized. In 1990, on the basis of morphological and, primarily, allozyme differences, Charles Daugherty and colleagues argued that a second species, S. guntheri, occurring on islands in eastern Cook Strait (see map), should be recognized. (Allozymes are proteins which are different alleles at the same genetic locus, and which are usually distinguished by protein electrophoresis.)

Distribution of tuataras, from Wikipedia. Circles, Sphenodon punctatus; squares, Sphenodon guntheri.

At the time, this bothered me, as I saw it as an application of the old morphological species concept, extended to genetic data: if you can tell them apart, they are different species. This is also what Jerry argued against in the case of elephants: an arbitrary amount of morphological or genetic difference, or inferred time of separation based on the amount of genetic difference, is not a sound basis for a species concept.

Recently (2010), however , further studies of tuataras have been made, including study of their DNA, and the authors of this work conclude that, as had been held earlier, a single geographically varying extant species of tuatara should be recognized (the status of the extinct tuataras from the New Zealand mainland is still up in the air). So we’re back to S. punctatus as the sole surviving species in the Sphenodontida.

This turnaround in tuatara taxonomy is also a nice example of something Jerry considered in a previous post: scientists changing their mind in the light of new evidence, and not being shy about saying so (something which, of course, should not be rare). Two of the authors of the 1990 resurrection of S. guntheri, Charles Daugherty and Jennifer Hay, are also authors of its 2010 sinking.

If you would like to sample more things tuatara, Hillary Miller, a post-doc at the Allan Wilson Centre for Molecular Ecology & Evolution in New Zealand, has been running, unbeknownst to me at the time of my initial post, an interesting series of posts on tuataras at her blog, The Chicken or the Egg.  (Allan Wilson a New Zealander who was a graduate student and later professor at Berkeley, was a pioneer in the application of biochemistry to evolutionary questions.) See also Victoria University of Wellington’s Tuatara Biology page.

______________________________________________________________

Daugherty, C.H.,  A. Cree, J.M. Hay & M.B. Thompson. 1990. Neglected taxonomy and continuing extinctions of tuatara (Sphenodon). Nature 347:177-179. (abstract)

Hay, J.M., S. D. Sarre, D.M. Lambert, F.W. Allendorf & C.H. Daugherty. 2010. Genetic diversity and taxonomy: a reassessment of species designation in tuatara (Sphenodon: Reptilia). Conservation Genetics 11:1063-1081. (abstract)

14 Comments

  1. Hempenstein
    Posted January 23, 2011 at 2:50 pm | Permalink

    Just a bookeeping note – this has been accessible via a link on Facebook for 3hrs, but not directly from the WEIT URL.

    • Matthew Cobb
      Posted January 23, 2011 at 4:18 pm | Permalink

      Thanks, we’d spotted that. It was there, but for some reason got stuck behind the signage post, so you didn’t see it if you went straight to WEIT…

    • TrineBM
      Posted January 24, 2011 at 12:40 am | Permalink

      Off topic: I’ve never been able to find out which of the ten or so fb-pages called Why Evolution Is True is the “real” one. Is it the one with the book featured as profile-pic?

      • whyevolutionistrue
        Posted January 24, 2011 at 6:40 am | Permalink

        I’m not responsible for any of them (I didn’t even KNOW there were any!), so caveat emptor.

        • TrineBM
          Posted January 24, 2011 at 9:54 am | Permalink

          Oh … I see.

  2. Notagod
    Posted January 23, 2011 at 6:02 pm | Permalink

    Hey! An atheist tuatara. Mmmm, baby human is yummy. Leave feet with flip-flops, them not so good.

    • whyevolutionistrue
      Posted January 23, 2011 at 6:53 pm | Permalink

      I’m pretty sure the feet with flip-flops are a reflection in the glass front of the tuatara cage. I’m not sure why there was a body-less pair of feet in front of the cage.

      GCM

      • JohnnieCanuck
        Posted January 23, 2011 at 10:24 pm | Permalink

        Blame the bodiless feet on physics and the human optic system. Not the actual bodies, just the apparently missing parts.

        Note that there are two pairs of feet. The photographer is wearing athletic shoes and tight black pants, while the woman has on lighter capris that show poorly in comparison to the foliage, due to the relative lighting levels.

        Amateur photographers are forever being fooled because their brains do too good a job of ignoring the reflections. The camera doesn’t have that ability, however and what it sees is what you get.

        To minimise reflections, put the camera as close as possible to the glass and don’t use a flash, if possible. Cup your hand around any gap if the reflection is still a problem. Don’t scratch the glass or plastic with the camera.

        If the flash must be used, position yourself at about 45 degrees, vertically or horizontally to the glass and a metre or two away from it so the reflection is off to the side.

        Sometimes the glass upsets the auto focus on the camera, too.

        My family just hates it when I’m the one with the camera. A single picture takes “Like, forever, Dad”.

        • Dominic
          Posted January 24, 2011 at 3:13 am | Permalink

          Thanks for the tips! I often try photos from train windows & it can be very tricky – especially if you use a phone camera.

  3. Posted January 24, 2011 at 12:36 am | Permalink

    I’m quite glad to know it’s one species again. Relict species sounds so much better than relict genus. After 64,000,000 years without speciating, why start now?

    According to a Well Known Search Engine, there are tuatara in San Diego, Auckland, Hamilton and Wellington zoos, and the Southland Museum.

    In Wellington they are also at Zealandia (the Karori Wildlife Sanctuary), on Matiu/Somes Island in the middle of the harbour, and (free to view) at Victoria University of Wellington‘s Von Zedlitz building, Kelburn Parade.

    We (I live on the coast just north of the black line) say those islands off the Marlborough Sounds of the South Island are west of Cook Strait – the strait itself is only 22km across.

    • Sigmund
      Posted January 24, 2011 at 2:54 am | Permalink

      Does anyone know whether the islands were isolated from the NZ mainland for very long periods of time. I suspect that sea level changes during the ice ages would mean that a lot of these islands were connected to the main islands in relatively recent times – so a separation of the order of 12,000 years rather than 65 million might be a lot closer to the correct figure (from a molecular genetics point of view a separation of tens of millions of years will rather inevitably lead to the sorts of genetic drift, chromosomal alterations, etc that would make hybridization virtually impossible.)
      By the way, had anyone tried to breed the two supposed ‘species’ together in captivity?

    • Posted January 24, 2011 at 6:33 am | Permalink

      At the San Diego Zoo? Thanks for the tip! My 10-year-old is in love with the Tuatara (at least since the last post on them–he was thrilled when I pulled up WEIT today:-)). Next time we go to Nana and Grandpa’s, we’ll definitely try to make it to the SDZ to see them!

  4. Dominic
    Posted January 24, 2011 at 3:17 am | Permalink

    Hi Greg – have you seen the news about the Clouded Leopard? Looks worthy of a comment on this topic of speciation from you, or Jerry…

    http://news.bbc.co.uk/earth/hi/earth_news/newsid_9369000/9369238.stm

    And for cat lovers the IUCN cat specialist group…

    http://www.catsg.org/catsgportal/20_catsg-website/home/index_en.htm

  5. Jonathan Losos
    Posted January 24, 2011 at 8:01 am | Permalink

    The issue of Nature that contained the original article by Daugherty et al. in 1990 had a picture of a tuatara (and no flip-flops) on its cover with the sensational headling “Bad Taxonomy Can Kill.” The implicit point was that an unrecognized species of tuatara was not getting the protection it needed because it was not considered to be a separate species. Lots of money and effort was devoted to protecting a population that we no longer think is a different species. I wonder what the new headline should be.


4 Trackbacks/Pingbacks

  1. [...] http://chickenoreggblog.wordpress.com/tag/tuatara/  http://whyevolutionistrue.wordpress.com/2011/01/23/tuataras-and-the-species-problem/ [...]

  2. [...] from Why Evolution is true is a fine post from Greg Mayer about the problem of classifying animals into species (taxonomy): Tuataras are very interesting animals: endemic to New Zealand, and the sole survivors of an [...]

  3. [...] species concept issue, which both Jerry and I mentioned recently (links to Jerry’s posts in mine). The second is a scientific nomenclature issue, one that arose in the infamous Darwinius [...]

  4. [...] Tuataras and the species problem « Why Evolution Is True [...]

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