Ol’ Blue Eyes: Convergence In Frank Sinatra And Anoles

Anolis stratulus

Anolis stratulus

evermanni eyes

Anolis evermanni

Anolis gundlachi

Anolis gundlachi

Ok, this post has nothing to do with Frank Sinatra other than his nickname. But what about blue eyes in anoles? They seem to pop up all over anole phylogeny. For example, in my recent trip to Puerto Rico, three anoles had cerulean peepers–A. evermanni and A. stratulus, which are closely related, and A. gundlachi, which is more phylogenetically distant. And blue eyes occur in other anoles, such as A. etheridgei from Hispaniola.

The observation raises two questions:

1) Just how phylogenetically widespread is the occurrence of blue eyes in anoles? I know I’ve noted blue-eyedness from time to time, but I haven’t get tracked and can’t remember in which species. I propose the Anole Annals community take it upon itself to compile a list of blue-eyed anoles. If you know of one, please post a comment and, even better, add a photo.

2) Why? I can’t believe there is an adaptive significance to having blue eyes per se. Is it genetically linked to some other adaptive trait? Could sexual selection have a role (though I don’t know of sexual dichromatism in eye color)? Other animals exhibit interspecific variation in eye color and I bet there’s a literature trying to explain it, but I’m not familiar with it. Would make an interesting project!

Some quick googling reminded me of a few other examples, below. Who am I missing? And does anyone have a good photo of blue-eyed etheridgei?

Anolis transversalis

Anolis peraccae

Anolis oculatus

 

About Jonathan Losos

Professor and Curator of Herpetology at the Museum of Comparative Zoology at Harvard University. I've spent my entire professional career studying anoles and have discovered that the more I learn about anoles, the more I realize I don't know.

32 thoughts on “Ol’ Blue Eyes: Convergence In Frank Sinatra And Anoles

  1. At the mechanistic level, blue eyedness in humans is due to a lack of deposition of brown pigment, which allows the underling blue to be seen. The gene responsible, HERC2, has been mapped in humans, but that gene is not responsible for the same phenotype in lemurs Eiberg et al 2008, Bradley et al 2009). A quick BLAST search turns up the mRNA homolog of that gene in the carolinensis genome. Although it doesn’t answer the evolutionary “why”, it would be cool and pretty straightforward to see if HERC2 is different in blue eyed anoles.

    Eiberg et al 2008 DOI:10.1007/s00439-007-0460-x
    Bradley et al 2009 DOI:10.1002/ajpa.21010

    1. Relatively unlike Anolis evermanni and A. gundlachi, A. stratulus can be quite common in high light areas such as open forest & high in the canopy, and is present in the Virgin Islands (where habitats are typically also open). It is even found in urban areas. For example (although it’s not obvious) the picture below is of an A. stratulus in Old San Juan.

    2. Anolis poncensis , a xeric grass-bush species that inhabits both open and dense forests, also has blue eyes; though this species is closely related to A. gundlachi .

      Anolis rupinae does too .

  2. Darn! Dan beat me to Anolis fowleri. Extending Dan’s point about forest anoles being the ones to have blue eyes and speaking totally off the cuff, is it possible that, that blue eyes in anoles are UV-sensitive? Open habitat anoles would definitely experiences more UV than closed canopy species. Might be a stretch. And A. oculatus inhabits open environments. Well, at least some of the subspecies do.

  3. Following up on Anthony’s comment, a neat comparison can be found in the eye color difference between Anolis gorgonae and its mainland sister (or progenitor?) Anolis chloris. Not only is the body of A. gorgonae blue, the eyes are too. Both traits differ in A. chloris, which is a green anole with a complex iris color including browns, greens, and blues. Check out the photos below. I suspect that the island A. gorgonae lost the ability to produce one or more pigments, like Anthony described. It would be cool to look into that, but what would be really cool would to determine whether the same genetic mechanism is behind the differences in both eye color and body color.

  4. Interesting thoughts on the topic. I have wondered about eye color in Mexican anoles often, partially due to most of my favorite species having odd-colored eyes. There’s a blue eye bias among the most unique anoles in Mexico–alvarezdeltoroi, cristifer, and gadovii. Always thought it was a strange coincidence. Two of those species are fragile and seemingly intolerant of increased body temperatures and we know very little about the third one. All are also rather large for Mexican species.

  5. Anolis woodi also has blue eyes.On a side note what about the 16 or so anole species that are able to vocalize,I wonder why this ability hasn’t evolved in each distinct lineage of Anolis and why even in some closely related species groups it seems that only select species are able to do it?

      1. Anolis cybotes is the only cybotoid I knew of that could vocalize so this brings the number up to more than sixteen,Apart from those there are 15 other anoles for which vocalizing ability has been recorded.These are Anolis chlorocyanus ,A.vermiculatus, A.coelestinus, A.hendersoni , A.garmani, A.valencienni, A.opalinus, A.grahami, A.biporcatus A.salvini, A.petersi, A.roquet, A.chocorum A.lucius and A.occultus. Also, even though it has never been recorded to vocalize I once held an unusually large and agitated A.lineatopus which produced a whirring sound with Its mouth closed. I don’t know if this counts or if this is actually something all anoles can do, I have never heard another A.lineatopus do this before or since no matter how agitated and I don’t know what to make of it.

        1. I can confirm vocalizations for all cybotoids except A. breslini and A. haetianus, which I’ve never seen. Anolis haetianus is probably just a morphological variant of A. cybotes anyway. But yeah, I think it’s a fair guess to say that A. breslini vocalizes. I can confirm this for: A. armouri, A. cybotes, A. longitibialis, A. marcanoi, A. shrevei, A. strahmi, and A. whitemani.

          1. Weren’t a few of these taxa grouped into A.cybotes at one point?If this is the case the perhaps the record of Anolis cybotes vocalizing was taken before the split,this may explain why A.cybotes is the only name I have ever seen listed as vocalizing .Then again most of the species I listed above came from one source (http://www.faculty.biol.vt.edu/jenssen/pdfMS/1979_copeia_vocalizations_grahami.pdf) and it may well be that records of vocalization for the other species exist and I simply haven’t found them yet.

    1. Not sure if this counts as vocalization, but A. cristatellus males can sort of hiss at each other while fighting…

  6. Just out of curiosity, is it known if eye color changes during the day or during a lifetime of an Anolis lizard?

  7. By the way Anolis alutaceus also has blue eyes.I have also read that Anolis ahli possesses this trait (its common name appears to be the Escambray Blue-eyed Anole ) but I have never seen a photograph of this species so I don’t know for sure.

    1. Here’s a photo of A. ahli (click to enlarge). There’s some blue in there, but I wouldn’t say pure blue. I only have pictures of this one individual… Does anyone know the original source of the common name?

      1. The Escambray Mountains are a mountain range in central Cuba.This species is found on Cuba so perhaps it is either endemic to or was first described from there.

        1. I was wondering about the “Blue-eyed” part of the name (since the eyes aren’t very blue compared to lots of other Cuban anoles).

          1. Perhaps it is the only blue(ish) eyed species found in that region,or was the first one described from there.I have also seen it referred to as Ahl’s anole by the way.

  8. James – I caught all of those species and so have heard them vocalize. They sort of squeak when you handle them.

  9. With regards to UV sensitive, all of the anoles seems to have a UV photopigment. Also, there is no evidence that the color of the iris predicts and/or influences color perception. It is possible that the lens can serve as a filter, but the lens is not the cause of a blue iris.

  10. I’m surprised no one has mentioned Norops vociferans (Myers 1971). I encountered this species one night among tall grass (the last place I would have thought to look for anoles) in the Reserva Forestal Fortuna, Panama, at about 1200 m elevation. It was asleep at the top of a grass stem. When caught, it opened its mouth and exposed the black lining, all the while emitting a tiny, continuous croak. I did not collect it, however, as it appeared to be a hatchling and I did not wish to sacrifice it.

  11. Anolis anchicayae also has blue eyes (see Poe et al. 2009, Breviora 516, page 8) and this species is very related to A. peraccae.

  12. I know its a little late but incidentally while browsing Anole annals I noticed two more blue eyed species.Anolis fasciatus in this post and , A.allogus here [eyes seem more bluish grey in most pictures].There is also somemething strange about Anolis aquaticus-it has a blue ring around the pupil that shows up in some photos and not at all in others-it’s probably just a light thing.Just thought Id list them in case anyone came along trying to find a full list of blue eyed species.

    1. As well as Anolis alumina, which belongs to the same lineage as A.etheridgei and a.fowleri.in a somewhat similar situation to A.gorgonae and A.chloris above this species has a blue iris while its relative A.koopmani has a blue, green and yellow blotched one.

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