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Lizard Signals Adapt to the Environment: Habitat-Dependent Variation in Motion Signal Structure between Lizard Populations

Habitat characteristics influence the efficacy of animal signals, which means that populations of the same species occurring in distinct habitats are likely to show differences in signal structure as a form of local adaptation. This kind of variation in signal structure has been well-studied for sound and colour signals, including in several species of anoles, but had not been reported for motion-based signals until recently.

Jacky dragons (Amphibolurus muricatus) are Australian agamid lizards well-known for the complex motion-based displays performed by males. These displays comprise five distinct motor patterns utilised in sequence: tail flicks, backward limb wave, forward limb wave, push up and body rock (A. muricatus display video). A study conducted by Barquero et al. (2015) found evidence of temporal and structural variation in the core display of three populations of A. muricatus. These differences were not related to genotypic differences between populations, so they suggested they might be a consequence of local habitat structure.

The Jacky dragon

The Jacky dragon

Concurrently, Richard Peters and I were developing a methodology to accurately quantify the effect of background noise on the motion based signals of different Australian agamids (see Ramos & Peters 2017a; b). Our approach calculates the speed distributions of the motion produced by lizard signals and the environmental noise independently. It then compares these distributions to obtain a measure of signal-noise contrast. This is accomplished by recording lizard behaviour and reconstructing its motion in three dimensions before comparing it against the motion produced by the surrounding windblown plants, which are the main source of noise for motion based lizard signals. This methodology stands out from other approaches for quantifying motion signals because it does not assume that the camera is ideally placed when recording the displays, but instead provides an accurate representation of the motion from any angle or viewing position.

Building upon the work by Barquero et al. (2015), we applied our novel approach to a couple of populations of Jacky dragons with distinct habitat characteristics. Croajingolong National Park in Victoria (Australia) is densely vegetated coastal heath with tall grasses and shrubs on a sandy substrate. Conversely, Avisford Nature Reserve in New South Wales (Australia) is mostly open woodland with an understory of scattered grasses and small shrubs, and rocky outcrops spread throughout the park.

The habitats of (a) the Jacky dragon. (b) Croajingolong National Park, in coastal Victoria, Australia. (c) Avisford Nature Reserve, in New South Wales, Australia.

The habitats of (a) the Jacky dragon. (b) Croajingolong National Park, in coastal Victoria, Australia. (c) Avisford Nature Reserve, in New South Wales, Australia.

Our results revealed that lizards from the densely vegetated habitat (Croajingolong NP) performed displays of longer duration and introductory tail flick components, and also produced a significantly greater amount of high speeds. However, when we calculated the signal-noise contrast for both populations at their respective habitat, we found no difference. This means that the signals from both populations are equally effective when used within their intended habitat, regardless of their structural differences.

Differences in signal structure between populations. (a) Mean bout and tail flick durations for both lizard populations. (b) Mean tail flick to bout ratio for both lizard populations. (c) Average kernel density functions for both lizard populations.

Differences in signal structure between populations. (a) Mean bout and tail flick durations for both lizard populations. (b) Mean tail flick to bout ratio for both lizard populations. (c) Average kernel density functions for both lizard populations.

As mentioned before, our approach records animal signals and environmental noise independently, which allowed us to consider signals not only in the environment where they were filmed, but also in the habitat of the other lizard population. Consequently, to highlight the effects of the environment on lizard signals, we calculated signal-noise contrast for the signals belonging to one population in both habitats (densely vegetated vs. open woodland). As expected, both lizard populations performed worse in densely vegetated habitat, probably because the complex understory is producing greater motion noise and negatively affecting signal efficacy. Another way of looking at these data, but this time focusing on the displays rather than the habitat, was to compare the signal-noise contrast of both lizard populations in a single habitat. Lizards originating from the densely vegetated habitat produced higher contrast scores in both habitats, indicating that their displays are more effective overall.

Taken together, our results are consistent with the local adaptation hypothesis. Lizards from Croajingolong NP produce displays with longer durations and characterised by faster speeds in order to communicate effectively in a dense and noisy habitat. Conversely, lizards from Avisford NR have adapted to a less noisy environment and do not require such lengthy or energetically expensive displays. Such population level differences in signal structure due to habitat variation represent novel findings for motion-based lizard signals.

Reporting on the Reptiles of Redonda

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I’m back from Redonda and the expedition was a great success! I’m happy to report there were many Anolis nubilus boulder-hopping out of the way of the black rats and even blacker ground lizards on the island. In many ways the trip was even more challenging than expected but we came out with quite a lot of data so we have a great sense of the current status of the reptiles on the island and a baseline for comparisons into the future. I have even more stories and some videos going up on my blog to keep watch over there if you want even more details about Redonda.

redonda

To refresh your memories, Redonda is an island of Antigua and Barbuda and was completely denuded by rats and goats over the last century. Despite the dearth of vegetation, three endemic reptiles had been hanging on: Anolis nubilusAmeiva (Pholidoscelis) atrata, and an as-yet unnamed Sphaerodactylus dwarf gecko. The government of Antigua and Barbuda, in collaboration with Fauna & Flora International and local NGO the Environmental Awareness Group, has decided to undertake a massive restoration effort by eradicating the rats and relocating the goats. My job was to get some baseline data on the current lizard populations so we can figure out how they change into the future.

helicopter inside

Helicoptering to the island was every bit as exciting as I’d hoped. The Jurassic Park theme was playing through my head the whole way down. See that grassy patch with slightly fewer large rocks – that was the little tiny helipad, but our pilot was a pro and set us down perfectly. Almost as soon as we were out of the helicopter, we deposited our bags by our tents and set about catching Anoles.

nubilus

Anolis nubilus is at first blush a relatively innocuous member of the genus. They’re perfectly camouflaged in this environment, which is to say they’re drab gray and brown. Their dewlaps are cream-colored (which is really just my nice way to say drab gray-yellow) and the most decorated of the females sport faint dorsal stripes. Males did fairly regularly display impressive crests behind their heads, but nonetheless, the species at first and second glance is considerably less flashy than many of their cousins on nearby islands.

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Photo: Geoffrey Giller

All that said, there’s still a lot of cool stuff going on with nubilus. As Skip mentioned in his article 45 years ago, there’s a casuarina tree right next to the remains of the mine manager’s house that hosts an abundance of the few Redonda tree lizards living up to their name. The tree is still there and the lizards are still eagerly defending their precious few branches (see above).

There are actually quite a few trees still on Redonda, some of which are native Ficus trees. For the most part they’re in fairly inaccessible areas, but that really just means you need to bring a longer noose pole and don’t look down. I caught a lizard on this tree below with a perch height of approximately 350 meters (that’s really going to mess with the averages). Truth be told, after catching the lizard my knees were so wobbly I had to go find a nice big boulder and just had Geoff and Anthony shout me data for a while.

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After a week on the island and many, many Anoles, we got morphometric and performance data, diet data, extended focal-animal behavior videos, two mark-recapture density studies and two permanent transects established, thermal ecology data, habitat use data, and flight behavior data. We even exhaustively determined whether nubilus likes Chuckles! (But that’s a story for another post).

I know this is an Anole blog, but there were some pretty cool things going on with the other reptiles on the island, too. The ground lizards were jet black and really big. Here’s a picture of Anthony Herrel trying to get a tail measurement:

atrata tail

Photo: Geoffrey Giller

The atrata spent their days cruising around scavenging. We saw one eating a hermit crab, and we heard rumor of another that managed to get a sardine away from one of the crew working on the eradication effort! Analyzing the stomach contents of these guys is going to take quite a lot of detective work.

We also were able to gather the first natural history data on this unnamed dwarf gecko species. They’re strangely beautiful with an unlovely shovel-face and semi-transparent, too-squishy, gelatinous body. You wouldn’t guess it but they’re quick!

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Photo: Geoffrey Giller

In all, the reptiles of Redonda were fascinating and getting to explore the island was a unique privilege. I can hardly wait to return next year, and many years after, to see how the lizards change with the island.

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“What about us?” Technically these guys are reptiles too, but c’mon, the lizards are so much cooler. Photo: Geoffrey Giller

A Bit of Extra Swag? Unusual Color Spot on a Brown Anole

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Figure 1. Male brown anole with an unusual orange spot on the shoulder.

In the past, numerous anole enthusiasts have posted photos of atypical color variants (1, 2, 3, 4). While sampling small spoil islands in the intracoastal waterway last October, I caught a male brown anole with an unusual splash of color on the shoulder (Fig 1). Reports of sagrei that are completely orange have been noted (5, 6); however, those animals appear to represent a more intense version of the ‘rusty red’ that many of these lizards commonly display on their bodies,  particularly on the head. The orange on this male, however, is unlike anything I’ve seen on a brown anole, save for the coloration outlining the dewlap.  I’m curious to know if anyone has seen something like this before.

Effects of Habitat Partitioning on Lizards’ Thermoregulatory Behavior

Habitat partitioning due to species coexistence and its implication for species divergence has been the subject of intense research in evolutionary biology. However, its effect on lizard thermoregulation behavior and effectiveness has largely been neglected. Along with Grigoris Kapsalas, Efstratios Valakos and Panayiotis Pafilis, we recently published a paper in the Journal of Thermal Biology, demonstrating that habitat partitioning is responsible for essential divergence in environmental temperatures, while it also promotes deviations in species thermal preferences and thermoregulatory behavior.

Lake Doxa at Feneos plateau, Peloponnese, Greece (image from: http://www.digiwebart.gr/portfolio_page/der-spiegel-cover-art/).

Lake Doxa at Feneos plateau, Peloponnese, Greece (image from: http://www.digiwebart.gr/portfolio_page/der-spiegel-cover-art/).

This work took place in a narrow mountain site in Peloponnese (Feneos plateau, Lake Doxa), Greece. Despite its small size, Greece hosts one of the richest herpetofauna in Europe with a total of 86 species (15 of which are endemic). On top of that, Feneos plateau is an amazing place were 28 reptile species coexist and is the only area in Europe where seven lizards of the family Lacertidae occur in sympatry. The first survey at Feneos plateau started in late 1990s and since then the area attracted many herpetologists from different countries.

For the past 20 years our group has worked on the Feneos broader area studying how resource partitioning shifts dietary preferences, digestive performance and species locomotion. In line with these studies, here we focused on three Podarcis (the most predominant and diversified reptile group in Europe) lizard species–Podarcis peloponnesiacus, P. tauricus and P. muralis–and explored how habitat thermal heterogeneity affects the species’ ability for accurate and effective thermoregulation. To assess our objectives, we compared body temperatures (Tb), operative temperatures (Te) and set-point body temperatures (Tset) of the three species.

Frequency of field body temperatures (Tb, dark gray) and operative temperatures (Te, light gray). Vertical black solid lines indicate the set-point range temperatures (Tset).

Frequency of field body temperatures (Tb, dark gray) and operative temperatures (Te, light gray). Vertical black solid lines indicate the set-point range temperatures (Tset).

As expected, niche partitioning resulted in differences in the thermal quality of the microhabitats used by the three species, with P. muralis occupying cooler habitats compared to the other two species. The latter resulted in P. muralis being active at lower body temperatures. Yet, all species thermoregulate effectively and keep their field body temperatures close to their preferred temperatures, indicating high thermoregulation accuracy. Interestingly, the preferred temperatures lizards select in the lab were similar for all three species, despite the differences in the microhabitat temperatures and the lower Tb P. muralis achieved in the field. These findings reveal a rather conservative thermal physiology between these three closely related species. We suggest that by selecting cooler microhabitats and being active at suboptimal temperatures, P. muralis probably avoid or reduce competitive interactions with the other two species.

Paper: Sagonas, K., Kapsalas, G., Valakos, E. & Pafilis, P., 2017. Living in sympatry: The effect of habitat partitioning on the thermoregulation of three Mediterranean lizards. Journal of Thermal Biology 65, 130-137.

Rat and Goat Removal Gives Anolis nubilus Another Shot

Colin Donihue and Anthony Herrel just completed their trip to Redonda to study Anolis nubilus and no doubt they’ll report back to us shortly. Meanwhile, a tip of the hat to AA commenter Nathan Manwaring for pointing out this article posted on Fauna and Flora International’s website:

Redonda harbours a number of endemic species that occur nowhere else in the world, including the Redonda tree lizard (Anolis nubilus), Shown here. In 2015 all of the surviving reptile species were evaluated by IUCN as Critically Endangered. Credit: Jenny Daltry/FFI.

Captivating Caribbean island to be given a new lease of life

Posted on: 21.07.16 (Last edited) 5 August 2016

Starving goats and predatory rats to be removed from Redonda to restore this Caribbean island to its former glory.

The Government of Antigua and Barbuda has announced plans to remove goats and invasive rats from its most rugged and remote offshore island to allow endangered wildlife and their habitats to recover.

Redonda is home to a unique array of plants and animals, including rare lizards found nowhere else in the world. The uninhabited and seldom visited island is also formally recognised as an Important Bird Area, supporting globally-significant numbers of seabirds.

However, the island’s plant and animal populations are disappearing fast thanks in large part to its population of over 5,000 aggressive black rats (an invasive alien species) which prey heavily on the island’s wildlife. Together with the herd of long-horned goats that was brought to Redonda by humans more than a century ago, these mammals have transformed this once-forested island into a moonscape. So few plants survive that even the goats now face starvation.

Redonda from the air. The island, once forested, now looks like a lunar landscape. Credit: Jenny Daltry/FFI.

Redonda from the air. The island, once forested, now looks like a lunar landscape. Credit: Jenny Daltry/FFI.

Redonda is over 50 hectares in area and rises dramatically from the Caribbean Sea, 56 km south-west of Antigua. Goat skeletons litter the island, along with the relics of stone buildings from a guano mining community that lived here until the First World War. With few trees left to stabilise the ground, soil and rocks are crumbling into the sea, threatening nearshore coral reef in the waters below.

“We cannot stand by and watch as a part of our country, part of our history, disappears. We cannot be responsible for decimating animal populations on a regional scale,” says local conservationist Natalya Lawrence of the Environmental Awareness Group (EAG).

The Redonda Restoration Programme has been formed by the Antigua & Barbuda Government and EAG in collaboration with partners from the UK (Fauna & Flora International, British Mountaineering Council), USA (Island Conservation) and New Zealand (Wildlife Management International Ltd).

“I am immensely proud that my ministry has been a driving force in the development of this major initiative,” says Honourable Molwyn Joseph, Minister of Health and the Environment. “Restoring Redonda to its full glory will be a great achievement for our country.”

A new home for starving goats

One of the first steps will be to capture and move the remaining goats to Antigua, where they will be cared for by the Department of Agriculture.

The miners also left behind a herd of long herd goats. Together with the rats, these animals have transformed this once-forested island into a moonscape. So few plants survive that even the goats now face starvation. Credit: Jenny Daltry/FFI.

The miners also left behind a herd of long herd goats. Together with the rats, these animals have transformed this once-forested island into a moonscape. So few plants survive that even the goats now face starvation. Credit: Jenny Daltry/FFI.

“The goats are starving to death on Redonda and must be removed for their own sake,” explains Astley Joseph, Deputy Director of the Department of Agriculture. “We believe it is important to rescue this rare breed because it could have useful drought-adapted genes that would benefit other herds on Antigua and elsewhere.”

Rats will then be eradicated using a rodenticide bait that has previously been used to restore more than 20 other Caribbean islands without harming native wildlife. This is scheduled to be completed by mid-2017.

Black rats are omnivorous, and are known to attack native wildlife, such as ground-nesting birds and reptiles. Credit: Jenny Daltry/FFI/OICP.

Black rats are omnivorous, and are known to attack native wildlife, such as ground-nesting birds and reptiles. Credit: Jenny Daltry/FFI/OICP.

“We and other international organisations have offered our support because we recognise that this is a very challenging yet globally important initiative” says Sophia Steele, Eastern Caribbean Project Coordinator at Fauna & Flora International. “Recent studies have identified Redonda as the most important island to restore in the Eastern Caribbean due to its Critically Endangered wildlife and the high probability of lasting success.”

The new programme is funded by the UK Government’s Darwin Initiative, the National Fish and Wildlife Foundation, the Taurus Foundation and private sponsors. Additional technical and in-kind support is being provided by Caribbean Helicopters and Syngenta Crop Protection AG.

Dr Helena Jeffery Brown of the Department of the Environment says, “Antiguans and Barbudans will be proud as Redonda becomes a role model for regional biodiversity conservation. This will be yet another example of how this country is proactive in meeting the national and international commitments it has made to conserve biodiversity.”

Redonda is also an Important Bird Area thanks to its regionally- and globally-significant colonies of seabirds, including these brown boobies. Credit: Jenny Faltry/FFI/OICP.

Redonda is also an Important Bird Area thanks to its regionally- and globally-significant colonies of seabirds, including these brown boobies. Credit: Jenny Faltry/FFI/OICP.

Antigua and Barbuda has a wealth of experience and success under the ongoing Offshore Islands Conservation Programme which has, since 1995, removed rats and other invasive pests from 15 islets closer to Antigua in the North East Marine Management Area. This has saved the Antiguan racer – once the world’s rarest known snake – from extinction, and enabled an incredible recovery of other native animals and plants. Many tens of thousands of residents and tourists now visit and enjoy Antigua’s pest-free islands every year.

“I am most excited to see the progression of recovery on Redonda once the threat of invasive species is removed,” says local biologist Andrea Otto, who will be part of the research team documenting the recovery process. “I want to see which types of vegetation spring up first and which birds return. From what we have seen on the smaller islands we have restored, the transformation will be incredible.”

For more information, read the press release.

Please support this important work by donating today.

How Do We Know What We Know? Sexual Selection, in Humans and in Lizards

Reposted from my blog.

Over the last few months, there’s been a slow-boiling battle underway between Holly Dunsworth and Jerry Coyne about the evolution of sexual dimorphism in humans, surrounding the question of why male and female humans, on average, differ in size. The battlefield ranged from blogposts to twitter to magazine articles. In a nutshell, Coyne argued that “sexual dimorphism for body size (difference between men and women) in humans is most likely explained by sexual selection” because “males compete for females, and greater size and strength give males an advantage.” His whole argument was motivated by this notion that certain Leftists ignore facts about the biology of sex differences because of their ideological fears, and are therefore being unscientific.

Dunsworth’s response to Coyne’s position was that “it’s not that Jerry Coyne’s facts aren’t necessarily facts, or whatever. It’s that this point of view is too simple and is obviously biased toward some stories, ignoring others. And this particular one he shares…has been the same old story for a long long time.” Dunsworth went on to propose, seemingly off the cuff, alternative hypotheses for sexual dimorphism in body size in humans that were focussed not on men but on women, as examples of the kind of hypothesis that is relatively rarely considered or tested in this field.

Though on the surface this battle may seem to be about specific biological facts (Coyne certainly tries to win by treating it that way), in reality this disagreement is, as Dunsworth argues, about the process by which hypotheses are tested and about how knowledge comes into existence. About which hypotheses are considered for testing in the first place. As a result, the two ended up arguing past each other quite a bit.

As I followed this whole exchange, I shook my head at the timing–I had a paper in preparation that was SO RELEVANT to the centre of this debate! That paper is now available as a preprint, so I can try to outline why I think that Dunsworth is right, and Coyne is being short-sighted. My argument has *nothing* to do with humans, however–I don’t know the human sexual selection literature well enough to weigh in on that. Instead, my argument is by analogy with our knowledge of mating systems in Anolis lizards.

Continue reading How Do We Know What We Know? Sexual Selection, in Humans and in Lizards

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Cuban Anolis – Request for Help with ID

Hello everybody!

I am a biology Student from Switzerland and together with my travel mate Demian, I visited Cuba for 3.5 weeks in January and February 2017. We are birders, but pretty much interested in everything that moves! We were taking pictures of lizards whenever we could, but without specifically looking for them. Back home, I was surprised how difficult the identification can be and so I would be happy if you can confirm, correct or help me with the ID. There are a lot of pictures…
I will report every safely identified lizard, probably with observado.org, together with the name of the expert, who is helping us out.
We will also put a comprehensive trip report on cloudbirders, including the herp list.

Continue reading Cuban Anolis — Request for Help with ID

Early Breeding Season Injuries through Aggressive Interactions in Miami, FL

It’s currently dewlapping mayhem down here at the moment, with all species except the late-rising Cuban knight anoles (A. equestris) out and showing off!

IMG_9836 (2) An adult male Puerto Rican crested anole (A. cristatellus) performing dewlap extension displays in Miami FL

Visual displays such as dewlap extensions are often used to mediate physical interactions by acting as an indication of the relative size, strength, and fitness of each individual. This is beneficial for both parties; dominant individuals do not have to waste energy that a physical interaction would require, and weaker individuals avert the risk of physical injury (of course, both reasons are reciprocal to both individuals also).

However, when two individuals cannot determine dominance through visual communication, for example if two individuals are equally matched in size, then an aggressive and physical confrontation may occur (read a previous account of one such interaction between two equally-sized males here). The results of these interactions are apparent in many injurious forms, for example through extensive bite marks to the body (as previously discussed here and here), or perhaps even to the extent of tail loss (as discussed here).

Yesterday (9 March 2017) I observed this male Puerto Rican crested anole (A. cristatellus) below that looks like another male had taken a good bite at him!

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Of course, there are many avenues through which such an injury may appear. However, the presence of a still-erect nuchal crest paired with how fresh the wound looks (and the time of year!) gives me the impression that this was probably the result of an intraspecific male-male interaction.

Seeking Field Active Body Temperature Data for Anolis chlorocyanus

Hello everyone,

As part of some ongoing work comparing muscle physiology and performance among Anolis species, I am in search of data on the Field Active Body Temperature (Tb) of Anolis chlorocyanus so that I am sure to perform data collection at relevant temperatures. Unfortunately I have been unable to locate Tb data for this species in the literature, so I hoped one of you might have this information and be willing to share it with me. Any help would be greatly appreciated!

Gliding Lizards Use the Position of the Sun to Enhance Social Display

Along with Devi Stuart-Fox, Indraneil Das and Terry Ord, I recently published a paper in Biology Letters showing that arboreal Draco sumatranus lizards orient themselves on the tree trunk perpendicular to the position of the sun during broadcast signalling. This presumably increases the radiance of the translucent dewlap, and likely it’s conspicuousness.

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Figure 1. (a) Draco sumatranus male displaying, showing the transmission of sunlight through the dewlap (photo: T. J. Ord). (b) Perch angle for displaying males, and (c) perch angle for non-displaying males, measured in relation to the sun. Both perpendicular angles (90° and 270°) have been transformed to equal 180°.

Draco lizards are ecologically analogous to the anoles and share similar signalling behaviour (see this recent Draco clip from the BBC’s Planet Earth II). They too possess extendable dewlaps that differ in colour and size between sex / species groups, and they also live in many different habitat types throughout Southeast Asia. I’ve written about my Draco research on Anole Annals before, here and here, if you’re interested – I hope they’re now well accepted as honorary anoles!

Like the anoles, the skin of the dewlap for many Draco species is stretched thin when extended and allows light to pass through.  Leo Fleishman published a Functional Ecology paper in 2015 measuring how the dewlap of Anolis lineatopis appears to glow when positioned with the sun behind them, and how this might improve signalling efficacy. Contrary to expectation, they found the transmission of light through the dewlap doesn’t improve the luminance contrast of the dewlap against the background. The radiance of the dewlap is increased by light transmission (radiance is the sum of the light reflected by the dewlap and any transmitted through the dewlap) – but patches of high radiance are very common in Anolis lineatopis forest shade environment, due to many the little shafts of light shining between gaps in the leaves. Instead they showed that due to the higher total intensity of the dewlap colour (thanks to light transmission) it’s probably easier for a conspecific to discriminate the signal from the natural background colours.

Given this and the similarity between anole and Draco dewlaps, I wondered whether Draco lizards might behaviourally adapt their position on the trunk relative to the position of the sun, to maximise the exposure of the extended dewlap to sunlight. To look at this, I just observed the position of the lizard relative to the sun upon first sighting, and noted whether the lizard was displaying, and if so, whether was it directly to a neighbouring conspecific, or whether it was a territorial broadcast display. We found males were significantly more likely to be oriented perpendicular to the sun when displaying, but not when not displaying (fig. 1).

Of course, signals intended for specific individuals in close-range encounters require the signaller to position themselves such that the receiver is in line of sight – but Draco lizards (and anoles) also give these ‘broadcast signals’ which are not intended for any specific individual, but just as territorial display. For these signals, where there is not another lizard around, they seem to orient themselves perpendicular to the sun, so their extended dewlap is exposed to the most light.

Female D. sumatranus also have dewlaps, but they are small in size and females only very occasionally engage in broadcast display.  I had not expected to see this orientation behaviour in females, as their dewlaps appear opaque and so don’t benefit from light transmission. However, I found the same orientation pattern for females as for males: perpendicular to the sun when displaying, but not when not displaying. This is perhaps because their dewlap reflects UV light (fig. 2) and direct sunlight is richer in UV and shorter wavelengths than light reflected off objects in the surrounding scene. Males have yellow dewlaps, and they too reflect a little UV (though much less than females). Of course, the transmission of light is unidirectional and only increases the radiance of the dewlap for those viewing the dewlap from the opposite side to that of illumination, so the benefit of direct sunlight hitting the UV/yellow male dewlap likely plays a role in this orientation behaviour for males as well.

Figure 2.  a) Draco sumatranus male yellow dewlap colour reflectance; (b) Draco sumatranus female blue dewlap colour reflectance.

Figure 2. a) Draco sumatranus male yellow dewlap colour reflectance;
(b) Draco sumatranus female blue dewlap colour reflectance.

Anole Annals — Valentine’s Day Special

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Peter Uetz of the Reptile Database fame sends the following Valentine’s Day greetings:

DSCN3297-2If you or your significant other loves anoles, you may want to show her/him this hearty Anolis distichus (Figure 2960, above) on occasion of today’s Valentine’s Day. It clearly shows a heart on it’s head. Some other specimens such as the couple in Figure 3297 (right, from locality 1 in the Google map), also show a heart although it’s not as pronounced. Also note their blunt coloration which doesn’t seem to affect their affection.

Anolis distichus is pretty variable and even within this subspecies, A. d. dominicensis Reinhardt & Lütken 1863, to which all these specimen belong, there is considerable variation. By the way, the guy with the heart (Figure 2960) is from the same locality 3 as two other specimens which do not have a heart (Figures 2948 and 2968) although they display a similar shape on their heads. Figure 3087 shows yet another specimen for comparison, this time from locality 2.

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2968

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2948

3087

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Various authors have described a dozen subspecies from Hispaniola (reviewed in Schwartz 1971, see map 2 from that paper). The northern half of Hispaniola is almost entirely in the hands of A. d. dominicensis, hence the specimens on the photos have been assigned to that subspecies.

Hispaniola terrain map-2

Note that Glor & Laport 2012 elevated several Dominican subspecies of A. distichus to full species level, namely A. dominicensis, A. favillarum, A. ignigularis, A. properus, and A. ravitergum. The Reptile Database hasn’t followed this yet because their geographic sampling was limited to relatively few localities and they did not provide any updated diagnoses (but their recommendations have been recorded in the database). Also, there seems to be hybridization among several of these populations.

Photo localities:

2948: 3

2960: 3

2968: 3

3087: 2

3297: 1

Acknowledgments

Thanks to Miguel Landestoy and Luke Mahler who helped with the IDs.

References

Glor, Richard E.; Robert G. Laport 2012. Are subspecies of Anolis lizards that differ in dewlap color and pattern also genetically distinct? A mitochondrial analysis. Molecular Phylogenetics and Evolution 64 (2): 255-260.   http://www.sciencedirect.com/science/article/pii/S1055790310004276

Schwartz, A. 1968. Geographic variation in Anolis distichus Cope (Lacertilia, Iguanidae) in the Bahama Islands and Hispaniola. Bull. Mus. comp. Zool. Harvard 137 (2): 255- 309.  http://biodiversitylibrary.org/page/4784182

Schwartz, A. 1971. Anolis distichusCatalogue of American Amphibians and Reptiles (108)

(used to be available online at ZenScientist, and maybe soon at the SSAR website again).

Anolis distichus in the Reptile Database

http://reptile-database.reptarium.cz//species?genus=Anolis&species=distichus

(an extended synonymy and distribution section will appear in the next database release)

The database entry also has another 43 references most of which are available online.

Where Is the Type Locality of Anolis aequatorialis?

A new paper in Zootaxa aims to figure it out, based on the travel journals of its describer, Franz Werner. Here’s the paper’s abstract:

The eminent Austrian zoologist Franz Werner described several new species of amphibians and reptiles from America, including Anolis aequatorialis Werner, 1894 and Hylodes appendiculatus Werner, 1894. Both species were described based on single specimens, with no more specific type localities than “Ecuador” (Werner 1894a,b). After its description, A. aequatorialis remained unreported until Peters (1967) and Fitch et al. (1976) published information on its distribution and natural history. Anolis aequatorialis is currently known to inhabit low montane and cloud forest on the western slopes of the Andes from extreme southern Colombia to central Ecuador, between 1300 and 2300 m elevation (Ayala-Varela & Velasco 2010; Ayala-Varela et al. 2014; Lynch et al. 2014; D.F. Cisneros-Heredia pers. obs.). Likewise, Hylodes appendiculatus (now Pristimantis appendiculatus) remained only known from its type description until Lynch (1971) and Miyata (1980) provided certain localities and information on its natural history. Pristimantis appendiculatus is currently known to occur in low montane, cloud, and high montane forests on the western slopes of the Andes from extreme southern Colombia to northern Ecuador between 1460 and 2800 m elevation (Lynch 1971; Miyata 1980; Lynch & Burrowes 1990; Lynch & Duellman 1997; Frost 2016). To this date, the type localities of both species remain obscure. The purpose of this paper is to restrict the type localities of Hylodes appendiculatus Werner, 1894 and Anolis aequatorialis Werner, 1894 based on analyses of the travel journals of their original collector.

Hormones, Transcriptomes, Quantitative Genetics, and Anoles

 

Brown Anole

Male (left) and female (right) brown anoles (sizes are not to scale)

Among their many contributions to evolutionary biology, anoles have historically been at the forefront of research on sexual dimorphism. Much of the recent work in this area focuses on a very general question – how do males and females express different phenotypes despite sharing essentially the same underlying genome?

Not surprisingly, the answer often depends on the type of scientist you ask. An endocrinologist might say that the development of sexual dimorphism requires hormones such as testosterone and estradiol. A quantitative geneticist might reply that it involves the reduction of genetic correlations between the sexes. A molecular geneticist might view the problem as one of regulating the expression of shared genes differently in each sex. Can anoles help us put these different perspectives together into a unified framework for sexual dimorphism?

To address this question, our lab at the University of Virginia teamed up with Christian Cox (Georgia Southern), Joel McGlothlin (Virginia Tech), and Daren Card, Audra Andrew, and Todd Castoe (University of Texas, Arlington). The full details are available in The American Naturalist, but here’s a quick rundown of the highlights:

We conducted a breeding study on a captive colony of Anolis sagrei, a species in which adult males average nearly three times the mass of females. We found that the extent to which males and females share heritable variation for body size starts out high early in life, but declines rapidly as sexual dimorphism emerges during development.

Development of sexual dimorphism in Anolis sagreiThis breakdown of genetic constraint is mirrored by a sharp increase in the sex-biased expression of hundreds of autosomal genes in the liver, particularly those genes that regulate growth, metabolism, and cell proliferation. In other words, although male and female anoles share most of the same genes, each sex tweaks the expression of these genes in different ways as development progresses.

How do they do it? We also show that some of the patterns of male-specific gene expression that emerge later in life can be induced by treating juvenile females with testosterone. Putting these pieces together, we propose that hormones help male and female anoles regulate their shared genes in different ways, which allows them to attain dramatically different body sizes and also helps break down genetic correlations that would otherwise constrain their independent evolution. We hope that our study encourages other Anolis biologists to continue building connections between evolutionary genetics, developmental biology, and endocrinology!

A Call, No A Plea, For Anole Eggs and Hatchlings

One of the long-faced members of the carolinensis clade, Anolis brunneus.

One of the long-faced members of the carolinensis clade, Anolis brunneus.

Several years ago, I wrote a series of papers and blog posts about the diversity of anole head shape and its developmental origins. My colleagues and I touched on disparate topics such as whether the head differences among species are similar to post cranial ecomorphology, whether the patterns of cranial modularity are conserved across anoles, and the developmental bases of sexual dimorphism in skull shape.

Since starting my own lab at Loyola University in Chicago last year, I am revisiting these projects on skull evolution. Like in much of science, I have found that my early forays into this area created more questions than answers. Understanding the diversity of skull shape among anoles and other iguanid lizards will be one of the first focal areas of my new lab. We are currently mining museum collections to understand how the variation in anole skulls compares to iguanid lizards more broadly. The ultimate goal, however, is to return to questions about the developmental origins of this variation. Just how many different ways has development been modified to generate all the variation we observe in adult anatomy? We do not yet know.

This is where my attention turns to you. To thoroughly flesh out the developmental origins of anatomical diversity, I must have robust sampling of species across the iguanid phylogeny. I am asking the community to please think of me and my students if you have extra breeding animals, eggs, or hatchlings of any species of anole or another iguanid lizard. I am happy to help offset the cost of the animals or collaborate in a mutually beneficial manner.

One of the most exciting species that have recently had the fortune to work with is Anolis hendersoni. For its body size, this species has one of the longest faces of all anoles. In this case I was contacted by the owner of Backwater Reptiles who had several A. hendersoni adults that we are hoping to get eggs from over the next year at Loyola. The folks at Backwater have been great to discuss “exotic” anoles with as they occasionally receive species like A. woodi, A. cybotes, and Chamaeleolis, all of which could be great additions to my project. This is just one example of how I am trying to broaden the sampling for this project. I ask you, the broader anole community, to help me increase my sampling further. I sincerely thank anyone that has leads for me in advance.

Happy Birthday, Festive Anole!

I got up early this morning to put a video camera on one of our A. sagrei eggs that was looking particularly ripe. About two hours later, this little hatchling crawled out. The whole hatching process took about 25 minutes, and I’ve sped up the video by 30x. The video is much more compelling with sound. I personally like “Also Sprach Zarathustra,”  though “Ranz des Vaches” by Rossini had some enthusiastic support in lab. If you have other music suggestions, add them to the comments!

Happy birthday, little one!