Category: All Posts Page 59 of 148

Anolis cybotes, female from Barahona, Dominican Republic

Katharina Wollenberg Valero & Ariel Rodríguez

Thermal adaptation is the evolution of the ability to persist in novel thermal environments. Phenotypic characters that allow such adaptation, as well as the resulting shifts in the geographic distributions of species, are an emerging field of study in the midst of a changing global climate. Yet, the genomic basis of such phenotypic adaptation is less well understood, so recent efforts of evolutionary biologists are now aiming at one emerging question: Which genes determine thermal adaptation, and are these the same across different populations and species? Luckily, Anolis is yet again at the forefront of novel discoveries being made in this field (see Campbell-Staton et al., 2017).

Many studies have independently identified genes that are responding to changes in the thermal environment, be it through change of expression under an acute stress, or through changes in the DNA sequence as evolutionary response. In 2014, we gathered information on such thermal adaptation candidate genes from Drosophila to Homo sapiens from the literature.

From the published evidence, we extracted a set of gene functions that potentially underlie climatic adaptation. We were able to match these with functions that are known from phenotypic thermal adaptation (Wollenberg Valero et al., 2014). Interestingly, the products of these genes (Proteins, RNAs) were found to be functionally related with each other thus forming gene networks within the cellular environment.

The Caribbean Anolis cybotes is widely distributed across Hispaniola, and thrives in hot, xeric environments just as well as in cooler and more humid montane environments. The rift valley of Lago Enriquillo heats up to 40.5 °C (104.9 °F), and a few instances of frost were reported at the highest peak (Pico Duarte at 3,098m elevation) – so population survival across these climatic extremes does not seem to be a trivial endeavor.

Populations of this species show pronounced differences between montane and lowland forms in morphology, physiology, behavior, and perch use (Wollenberg et al., 2013; Muñoz et al., 2014), which led us to expect that at least some of this variation should have a genetic basis. Thus, we set up to test whether Anolis cybotes displays any signatures of genomic adaptation to the diverse kinds of environments it inhabits, and whether any genes showing evidence for selection can also be subsumed under the candidate functions we defined previously.

We sampled tissue of these lizards from several high and low elevations (the specimens being the same as in Wollenberg et al., 2013), and looked for variation according to climatic differences via RAD sequencing and subsequent analysis with LFMM. RAD sequencing generates a reduced representation of the target genome, producing thousands of short sequences representing the distribution of the restriction enzyme’s cutting sites throughout the genome. Owing to this property, it cannot be expected that this type of data will necessarily contain “the total set of adaptation genes”; to this effect, detailed genome sequencing is required and such studies have been done in some model organisms (stickleback fish, beech mice, Drosophila, etc.).

Read More

AA reader Jonathan McFarland sent in these disturbing photos with the following remarks:

“I hope you can shed some light on what’s happening to the wild anoles in my Louisiana suburban yard. This week I have found two adolescents with both eyes bleeding or infected. The attached pictures show only one side of the specimens but in each case both eyes appeared as shown. Any info you could provide would be much appreciated.”

Thoughts, anyone?

Jamaican giant anole (Anolis garmani) – one of the many non-native anoles you may see in Miami, FL.

In 2018 it will be nearly ten years since the last Anolis symposium was held at the Museum of Comparative Zoology at Harvard University. Given the rapid advances and exciting new discoveries in Anolis biology, it’s time to organize the 7th Anolis symposium! So, with this official announcement, please mark the weekend of March 17-18th 2018 in your calendars to come and visit the wonderfully tropical lizard-world of Miami, FL!

The aim of the symposium is to bring together Anolis biologists from diverse backgrounds to share their excitement and discoveries for these marvelous lizards. In this symposium, we hope to foster cross-disciplinary collaborations of people working with anoles and to broaden our general understanding of their biology and natural history. Miami was chosen not only for its spectacular anole diversity, but because of its ready access to anolologists living outside of mainland United States.

Miami, FL, is an ideal place in the USA to host this meeting! Over the past 100 years, eight species of Caribbean anoles have joined one native species in becoming established in south Florida. This meeting will be held on the weekend of March 17-18th 2018, which broadly overlaps with at least one weekend of the Spring Break holiday for most US schools, and does not conflict with other major meetings as far as we’re aware. We hope that this will facilitate good attendance! The symposium will be held at the Fairchild Tropical Botanic Gardens, which is home to a diverse community of exotic lizards, including six (!) species of anoles (read more about them here and on Anole Annals here!).

This post serves as a ‘save the date‘ – stay tuned the Symposium page for more information on conference registration, abstract submission for oral and poster presentations, and article submission for the Anolis Newsletter VII.

Puerto Rican crested anoles (A. cristatellus) in Fairchild Tropical Botanic Gardens

The first plate from the Sanger et al. (2008) Anolis staging series.

Long time readers of this blog will likely remember the many posts I’ve made trumpeting the utility of anoles for integrative analysis of anatomical diversity, studies that gain perspective from disparate biological fields. The community has come a long way since we published the first staging series of anole embryology only nine years ago. To some this may be old news, but I still find this pace exciting and personally motivating. Decades of ecological and evolutionary studies have created a strong foundation upon which to build new insights about the molecular and developmental underpinnings of anatomical diversity. My lab’s questions boil down to trying to shed light on the developmental origins of adaptive anatomical variation. Otherwise stated, where did the requisite phenotypic variation arise from during the adaptive radiation of anoles. The inherently comparative nature of these studies led me to use anoles as a “model clade,” a group of species that provides the capacity to obtain evolutionary insights the way that “model species” have provided pure developmental biologists and geneticists the power to deduce insights in their areas.

One of the highest hurdles to the progression of Anolis as a model system has been long-term access to living embryos. Although comparative biology is a powerful approach for evolutionary studies, one of the hallmark lessons of modern Evo-devo is the need to experimentally validate the candidate molecular changes associated with anatomical evolution. If I hypothesize that Gene X underlies some phenotypic difference between two species, I must 1) show that it is expressed at the time when the difference arises and 2) somehow tweak the expression of Gene X at that time and in that tissue to show that the changes parallel those observed in nature. To do this you must have access to an embryo in culture, unencumbered from its opaque shell.

Over the past several years several people have been working on ways to gain access to lizard embryos. The first report of a culturing method was by Tschopp et al., who used lentivirus to trace cell migration into the genitalia and limbs. I have not personally been able to consistently replicate those conditions, especially for later embryos. Bonnie Kircher and I, however, recently published two relatively “simple” culturing protocols as part of a new book, Avian and Reptilian Developmental Biology. One of the challenges of earlier culturing attempts was bacterial and fungal growth. As a first step to combatting these invaders, we developed a protocol to sterilize the eggs, soaking the eggs in a weak bleach solution (yes, a literal bleach solution). From there we were off and running.

The first method we describe, following from advice from Raul Diaz, has worked on eggs a few days old to those that are nearly half way through their incubation period. Using a fine pair of scissors, we separate the outer opaque lays of the shell from the inner membranes that surround the embryo and yolk. This bag-of-embryo is then transferred to a small culture dish with a nutrient rich media and drugs to further combat bacterial and fungal contamination. This culturing system has worked well for up to ten days, roughly from the time the limbs are developing digits to the time that the limbs have visible scales on them. (Check out the video!) In principle, this method will allow better access to the embryo for viral injection or the application of small molecule inhibitors that disrupt particular signaling pathways.

Be warned, the second method is a little more Frankensteinian. Because the membranes cover the embryo, visualizing development remains difficult. To circumvent this problem, we developed a protocol where we explant a piece of anole tissue, such as the developing

A developing A. sagrei foot explanting onto a chicken embryo

limb, to a chicken embryo. Both anole and chicken seem to fare well at 33 degrees Celsius, below the standard incubation conditions of the chicken and above that of our anoles. Development appears to proceed normally in the explanted tissue, just as it does would in an embryo within its own shell. These experiments still have a relatively low success rate, but when the explant takes, it works well. To better visualize the tissue for imaging we also stained the tissue with a vital fluorescent dye before the transfer, giving the tissue a wonderful Halloween feel.

The work is far from over. These culturing protocols are just the first step and will not work for all applications. More technically challenging steps especially await those that want to manipulate the anole genome or target distinct patterns of gene expression. This is only the start of what’s to come. For more details about these protocols you can download the chapter here.

Photo by Joel Sartore

The knight anole is really getting around these days: Turks & Caicos, Grand Bahama, Grand Cayman and many other islands. Now they’ve  made it to Abaco, Bahamas, where one individual was captured and possibly two others seen (see article in IRCF Reptiles and Amphibians). Abaco Scientist has an insightful discussion of introduced reptiles and amphibians on Abaco.

Photo from Daffodil’s Photo Blog

Photo from Daffodil’s Photo Blog

Photo-chronicler of Floridian natural history Karen Cusick has done it again. We’ve been captivated by her backyard photos before, but here’s photo of a female green anole with sand on its snout. Been digging holes to bury her eggs, maybe? And while Karen observed the little lady lizard, it suddenly darted into the bushed and emerged with a meal!

The plant in question

Well, at least one A. sagrei did. Gavin Hanke’s, Curator of Vertebrate Zoology at the Royal BC Museum in Victoria, BC, reported on the arrival of one stowing away in a tropical plant. Anoles do seem to have a knack of getting around in plants, fruit and other contrivances.

Lizards are active creatures, often running around in new territories to explore and find food. Sometimes they encounter challenges that keep them from running too far. When they wander away from home, how do they get back? It’s a question that’s led researchers to study this topic.

After watching the daily routines of Anolis lizards by using tracking devices placed on their backs, researcher Manuel Leal learned that they return to the same home again and again. This established the next question which was to find out how the lizards knew how to get back. Birds have a similar ability to find their way home. Although the exact method has not been discovered, it’s possible that lizards have similar abilities and functioning as birds in finding their own again.

They Claim Their Homes

Anolis lizards, especially males, claim trees as home territories, fighting to keep any newcomers off their bit of land. They’ve proven that they remember exactly where they stake out their claim, and like all animals, they like structure in their environment, including the location of where they spend their days and nights. Some studies prove that after disorienting the lizards and placing them a far distance from their home, they can still find their way back within 24 hours.

Then They Listen

U.S.  Geological Society geologist John Hagstrum proposed that in order to get back home, pigeons use sounds wave; extensive studies on pigeons show that they use low-frequency sound waves to create an acoustic map of where they are. This way, they can identify predators and safe spaces to land. Some have wondered whether  Anolis lizards might have similar capabilities that are advantageous for homing.

It’s hard to argue that lizards use any other method to get where they came from. Tests have proven shown results that indicate that lizards don’t have the ability to use any magnetic senses or distinguish polarizing light. Still, they manage to baffle scientists who wonder at their complex societies and developed capabilities.

If you want to learn a little more on the topic of how Anolis lizards find their way home, you can see a short film done by Days Edge Productions that follows Leal as he conducts his study.

Note: the watch on the bottom right is not one of ours!

It’s that time again. For one day only, Zazzle.com is offering 50% off the Ecomorph line of watches. Sale Code:

COOLZAZSTYLE

And we’re open to suggestions for new species to feature on a lovely wrist fob. Suggest away!

Red-legged wandering spider (Cupiennius coccineus) consuming a house gecko (Hemidactylus frenatus) at Sirena Biological Station, Corcovado, Costa Rica

When someone first asked me about the major predators of anoles, my first thought was to talk about curly-tailed lizards (Leiocephalus carinatus) in the Caribbean, vine snakes (Oxybelis spp.) in the neotropics [see my previous post on anole predation by O. aeneus at La Selva], and birds. I think that as herpetologists, we tend to fall into the trap of thinking of invertebrates as “lesser” taxa to be preyed upon by small vertebrates like lizards, and in turn for small vertebrates to be eaten by larger vertebrates.

I, too, when thinking about how selective pressures shape morphological variation in mainland and island habitats turned to fellow herps and birds as the primary predation pressure for mainland anoles. However, it wasn’t until I arrived in Costa Rica that I discovered the high prevalence of voracious arthropods, and I realized that our beloved lizards had much more to fear!

Orange wandering spider (Cupiennius getazi) with egg sac at La Selva Biological Station, Costa Rica

Red-legged wandering spider (Cupiennius coccineus) eating a pink katydid (Tettigoniidae: Phaneropterinae) at La Selva Biological Station, Costa Rica

A large adult female mantis (Phasmomantis championi) at La Selva Biological Station, Costa Rica

Conehead katydid (Tettigoniidae: Conocephalinae: Vestria sp.) at La Tarde, Osa Peninsula, Costa Rica

In a single night at La Selva, I could easily find dozens of large wandering spiders (Ctenidae), and if I pointed my headlamp higher in the trees I could see eyeshine from hundreds of spiders. Given the high density of large ctenids at La Selva, it is not unlikely that anoles and small tree frogs constitute a major portion of their diet. In fact, I wouldn’t be surprised if large arthropods are one of the most common predators of mainland anoles in some regions.

The same might be the case for giant mantids of the genera Macromantis and Phasmomantis, and conocephaline katydids sporting fearsome mandibles (e.g. Copiphora spp.). Since the invasive Chinese mantids (Tenodera sinensis) in North America are well documented to prey on hummingbirds almost equal in size to the mantids [see Nyffeler et al. 2017], surely larger and bulkier species in the neotropics can take lizards much smaller than themselves. Even though wandering spiders and conehead katydids are primarily nocturnal hunters, I have heard many stories of these arthropods being implicated in anole and tree frog predation. Research looking into how ctenids and nocturnal katydids forage would help determine if they can actually detect sleeping anoles or if predation events occur from the arthropods simply running in to the anoles while on the move.

If anyone here on Anole Annals has any anecdotal or photographic records, please comment below.

To throw a twist on this discussion, is it possible for a spider to prey on a lizard two and a half times its size? A new paper about a vertebrate-eating jumping spider (Salticidae) describes just that! Considering arthropods as possible major players in anole predation could shed light on behavioral and ecological studies of mainland anoles.

Figure 1 from Nyfeller et al. 2017, showing female jumping spiders (Phidippus regius) consuming Carolina anoles (Anolis carolinensis) and Cuban tree frogs (Osteopilus septentrionalis)

Here are a few more spider photos to wrap up this blog post.

Jumping spider (Salticidae: Phiale cf. guttata) eating an assassin bug (Reduviidae)

Another angle of a red-legged wandering spider (Cupiennius coccineus) consuming a house gecko (Hemidactylus frenatus) at Sirena Biological Station, Corcovado, Costa Rica

Threat display of a Brazilian wandering spider (Phoneutria boliviensis) from Tárcoles, Costa Rica. A ctenid with medically significant venom.