Author: Jonathan Losos Page 11 of 130

The green anole, A. carolinensis, is the only native anole in North America. Over the years, the question of whether it is distinct from the Cuban A. porcatus has been debated–morphological differences are pretty minor, other than the Cubans generally being a bit larger.

Now, in an open access paper published last year in Ecology and Evolution, Johanna Wegener and colleagues have driven the final nail in the coffin of the idea that North American carolinensis is a distinct species.

For some time, we have known that carolinensis is nested phylogenetically in the western clade of porcatus, rending porcatus paraphyletic. This phylogeny indicates that North American populations are the result of a colonization event from western Cuba, perhaps 6-12 million years ago (see references in Wegener et al. paper).

From Wegener et al. (2019). Florida populations are usually referred to as “ carolinensis,” Cuban populations as “porcatus“

The novel contribution of the Wegener et al. paper is to look for evidence of hybridization between recently introduced “porcatus” from Cuba and native “carolinensis.” And she found it in spades! The abstract, pasted at the bottom of this post, provides some more details and, of course, you can read the paper itself.

So, Florida populations of the green anole are derived from Cuban populations, and the two readily interbreed when given a chance. Given these facts, there is no justification for treating North American populations as a distinct species. The morphological differences that do exist–quite minor–are the result of geographic variation. Paraphyly plus no reproductive isolation = one species!

But now here’s where it gets interesting. By the rules of zoological nomenclature, the older name has precedence, and so this single species takes the name Anolis carolinensis. That’s right: A. carolinensis is the correct name for Cuban green anoles! I’m sure that won’t go over so well in some quarters.

But it gets more interesting! Cuban Anolis porcatus as currently recognized is not a monophyletic entity, as shown in the attached figure, based on Glor et al. (2005). As the figure shows, eastern populations of porcatus are more closely related to A. allisoni (remember, North American populations are nested in the western clade). Given that the species-level distinctness of allisoni has not been question, most systematists would recognize the two clades of porcatus as different species. Thus, the eastern clade retains the name porcatus.

Bottom line: both A. carolinensis and A. porcatus occur in Cuba!

Abstract

In allopatric species, reproductive isolation evolves through the accumulation of genetic incompatibilities. The degree of divergence required for complete reproductive isolation is highly variable across taxa, which makes the outcome of secondary contact between allopatric species unpredictable. Since before the Pliocene, two species of Anolis lizards, Anolis carolinensis and Anolis porcatus, have been allopatric, yet thisvperiod of independent evolution has not led to substantial species‐specific morphologicalvdifferentiation, and therefore, they might not be reproductively isolated. Invthis study, we determined the genetic consequences of localized, secondary contactvbetween the native green anole, A. carolinensis, and the introduced Cuban green anole, A. porcatus, in South Miami. Using 18 microsatellite markers, we found that the South Miami population formed a genetic cluster distinct from both parental species. Mitochondrial DNA revealed maternal A. porcatus ancestry for 35% of the individuals sampled from this population, indicating a high degree of cytonuclear discordance. Thus, hybridization with A. porcatus, not just population structure within A. carolinensis, may be responsible for the genetic distinctiveness of this population. Using treebased maximum‐likelihood analysis, we found support for a more recent, secondary introduction of A. porcatus to Florida. Evidence that ~33% of the nuclear DNA resulted from a secondary introduction supports the hybrid origin of the green anole population in South Miami. We used multiple lines of evidence and multiple genetic markers to reconstruct otherwise cryptic patterns of species introduction and hybridization. Genetic evidence for a lack of reproductive isolation, as well as morphological similarities between the two species, supports revising the taxonomy of A. carolinensis to include A. porcatus from western Cuba. Future studies should target the current geographic extent of introgression originating from the past injection of genetic material from Cuban green anoles and determine the consequences for the evolutionary trajectory of green anole populations in southern Florida.

Reader Roger Birkhead has asked for help ID’ing this Costa Rican anole on iNaturalist. Can anyone help?

Photo by Karen Cusick from Daffodil’s Photo Blog.

How horrible! Read all about it on Daffodil’s Photo Blog.

Anole Annals readers no doubt recall All-America Park, where so many anole species cavort in South Miami. Turns out the city is “cleaning it up” which spells no good for our favorite lizards. Local A-A Park resident Christopher Cooke writes:

“I live next door to All America Park in South Miami (6820 SW 64th. Avenue), a formerly well known habitat for lizards – I’ve met people from everywhere who have come to study the lizards here.  I’m battling the City which is “sanitizing” the park and I’m looking for any information or references (past or present) in  lizard literature which  highlights the importance of this property as a wildlife environment.  My goal is to stop the “sanitizing” l and replant habitat material so as to restore a conducive environment for lizards and other wildlife.  Any help you can offer will be much appreciated.    Christopher Cooke, neighbor of Neil Losin – for those who know him.”

Please make comments on anything that may be useful. Good luck, Christopher!

And while on the topic, here’s a lovely photo by South Miami mayor and neuroethologist extraordinaire Phil Stoddard, taken near the park.

Anolis cristatellus snoozing on a dragonfruit. Photo by Philip Stoddard

Photo by Dee Jacobsen

Dee Jacobsen from southeastern Louisiana sent in these lovely photos. Here’s what went down:
“I came across your site and wondered if you would be interested in see this photo I took in southeast Louisiana of an anole eating and being stung in the tongue by a bee. I was sitting on my porch and this little guy came running toward me to grab that bee by my foot. Scurried off with it and I grabbed the camera. We have so many anoles here that I take lots of shots of them but this one was most unique.”

Charles Leeper from San Antonio writes:
There appears to be a high population of green anoles on our property. While watering some plants, I sometimes spray a large patch of common ivy. What I’ve noticed is green anoles leaping from the above tree limbs onto the ivy leaves in order to drink the water I’ve just sprayed on them. At first, I heard thuds on the ivy and didn’t know what it was, but then I started watching the tree limbs and saw anoles climbing to the edge and leaping off – probably from a height of ten feet. I only notice them jumping from the trees after I’ve watered. I imagine this is typical behavior after a rain, and my water-spraying replicates such an event? I’m sure this is well-documented behavior, but in the case that it isn’t or is unique to a ground covered in a soft landing pad like ivy, I thought I would share it.
Nonetheless, I enjoy observing them and wanted to let you know there is a solid population here!
Charles kindly agreed to take video of some of the action. Thanks, Charles! And here’s his commentary on th videos (two more below):
I captured some footage of the anoles leaping off the trees. The first two videos (the one at the top of the page and the second one below) document them jumping from a branch of only about 4 to 5 feet, and the third one (the first one below) is from a height of perhaps 9 feet (it’s a bit tough to see, but this one shows a very young anole on the center branch – what a dive it takes!). I have seen many more than this (and from heights of probably 15 to maybe 20 feet), but only managed to record these occurrences.
I have not observed them much while it’s raining (a rarity down here in the summer!), but I would imagine they don’t partake in this jumping during or following a rain because either they don’t have to drink from the ivy as the raindrops hit the trees, or they’re already on the ground and not perched/basking in the trees during a storm.
The following is just conjecture, but possibly they smell, hear, or see the water hitting the ivy, and it’s not sprinkling the trees, so they’re drawn down for a drink. As for why they leap off as opposed to crawling down the tree, which does sometimes happen, perhaps they’ve learned the ivy is a soft landing pad and it’s just less energy-intensive to jump, or they’re avoiding bigger green anoles that may be near the base or brown anoles. Although, I’m not sure there are many brown anoles here as I don’t think I have seen them, but I certainly could be wrong.

And here’s a lizard drinking post-spraying:

Photo from Daffodil’s Photo Blog.

Read all about it in the latest post from Daffodil’s Photo Blog.

After a bit of a hiatus, Daffodil’s Photo Blog is back with its splendid anole photos and natural history tidbits. Check out the recent offering.

From the pages of Nova.

BY KATHERINE J. WU TUESDAY, AUGUST 27, 2019 

Compared to mammals, reptiles have a weird way of reproducing—and in the spring of 2017, that put Ashley Rasys in something of a pickle.

For months, the University of Georgia biologist was struggling to come up with a way to tinker with the genes of the brown anole (Anolis sagrei), a petite, pointy-faced lizard native to Cuba and the Bahamas.

The reptile had initially caught Rasys’ eye because of, well, its eyes. People with albinism often have poor vision due to problems with their foveae, the dense pits of cells at the back of the eyes that confer visual acuity. While foveae are lacking in most mammals, they’re present in lizards—making them intriguing candidates for studying the genes that impact foveal function.

There was just one problem: Reptiles aren’t easy to genetically manipulate. In other common laboratory animals, like mice and zebrafish, a tool called CRISPR has made DNA editing a breeze. The procedure typically involves injecting freshly fertilized eggs with gene-editing machinery, creating a change that would propagate when the cell divided.

But a few quirks ruled out that particular strategy in these lizards. Female anoles can store sperm for many months before fertilizing their eggs internally, making it difficult to time the introduction of the CRISPR cocktail. Anole fertilization also cues the formation of a soft, delicate eggshell that’s hard to penetrate without damaging the embryo.

That meant Rasys and her advisor, Doug Menke, had to get creative. So they decided to shift the injection back a developmental step, targeting eggs still maturing in the females’ ovaries. “At this point, they’re just hanging out in the lizard, waiting to be fertilized,” Rasys says.

The procedure took more than a year to perfect. But in the fall of 2018, Rasys, Menke, and the rest of their team hatched the world’s first gene-edited non-avian reptile: a red-eyed albino anole with near-transparent skin. According to the team’s study, published today in the journal Cell Reports, its birth marks a breakthrough for the field of developmental genetics, and hints that similar experiments may be possible in some of the other 10,000-plus species of non-avian reptiles that scuttle the Earth.

“This technology is really important and exciting,” says Martha Muñoz, an evolutionary biologist and anole researcher at Yale University who was not involved in the study. “This really opens up the door for other groups to think outside of traditional model organisms [like mice and zebrafish]…the sky’s the limit.”

With albinism in mind, Rasys and her colleagues set out to mutate the anoles’ tyrosinase gene, which governs pigmentation and has been linked to foveal function in humans. Manipulating this gene, Rasys explains, also made for an easy marker of success: If the procedure ended up generating albino anoles down the line, they’d be pretty tough to miss.

After rounding up 21 female brown anoles from the wilds of Orlando, Florida, the researchers gently anesthetized the lizards and opened them up. In anoles, the ovaries are transparent, making it easy to eyeball their contents “like a train of developing eggs,” Menke says.

The team selected 146 of these growing eggs and injected them with the classic CRISPR recipe: a pair of molecular scissors and a series of DNA-binding “guides” that would show them where to cut—in this case, the tyrosinase gene.

The researchers then had to wait another three months or so for the females to fertilize and lay the eggs. And even when this generation hatched, they thought there’d likely be more work to do, Rasys says. Since the CRISPR concoction had been delivered to eggs that were later fertilized by unaltered sperm, the offspring were expected to be hybrids—half edited, half unedited. These lizards then would need to be bred further to yield albinos, which must inherit the mutation from both parents for the trait to manifest.

But as Rasys watched her first clutch of gene-edited eggs grow, she noticed something strange. About a week before they were due to hatch, most of the embryos had darkened from pink to gray—an indication that they’d started producing pigment. A handful, however, retained their initial pallor, even as they continued to swell in size.

A few days later, Rasys arrived at the lab to find a newly-hatched, inch-long albino, stretching its ghostly pink legs. “It was so exciting to see it,” she recalls. “I thought, ‘It’s so cute.’”

In total, four out of the team’s 146 CRISPR-injected embryos were obvious albinos, surprising the entire team. There’s no way to know exactly what happened, but Menke’s leading theory is that the CRISPR components remained active in some of the eggs long enough to work their magic on both the maternal and paternal copies of the tyrosinasegene.

Genetic screening revealed another five embryos to be the half-edited hybrids the team had initially expected. And when the researchers partnered one of these CRISPR mutts with an unmanipulated mate, the mutation was passed on to some of the pair’s offspring, suggesting the edited gene was heritable.

There’s still plenty of tinkering to do, Menke says. As they report in the study, the team’s gene-editing success rate was around 6 percent—a figure that pales in comparison to the near-perfect efficiency rates that have been reported in zebrafish and mice.

But just showing gene-editing is possible in this system is a big deal, says Ambika Kamath, a behavioral ecologist at the University of California, Berkeley who was not involved in the study. Albinism implications aside, anoles have long been studied by evolutionary biologists and ecologists. In their native Caribbean, the lizards have split into many lineages, but understanding this diversification “has primarily been a historical science…involving stitching together patterns that happened a long time ago,” Muñoz says. “By extending CRISPR to Anolis, we can now mechanistically test some [evolutionary] hypotheses.”

As more applications surface, however, “we don’t want to be releasing CRISPRed lizards into the wild willy-nilly,” Kamath says, without a better understanding of how these sorts of introductions would affect the population at large.

And it might be more than lizard lives at stake. Menke thinks the team’s technique is likely to work in a variety of reptiles, many of which share the anole’s mode of reproduction. There’s even the possibility, he says, that the method could be adapted for birds, which are cut from the same evolutionary cloth. Scientists have hatched CRISPant chicks in the past, but as in lizards, bird embryos are hard to pinpoint at the single-cell stage, making current editing procedures complex and laborious.

Carolyn Neuhaus, a bioethicist at the Hastings Center who was not involved in the study, cautions that as CRISPR continues to be debuted in more and more organisms, the how, when, and in whom of gene editing will need to remain transparent. Though many experiments—including the ones in this study—have the potential to advance science and human health, she says, technology like this shouldn’t be used in a new species “just because it’s there.”

“We rely on scientists to create accurate and reliable knowledge, and that’s a huge responsibility,” she says. “With the CRISPR craze…I just hope it happens as mindfully and carefully as possible.”