Brighter is not always better

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Those that follow the Chipojoblog are familiar with one of our core tenets: strive as best you can to design experiments under natural conditions. This philosophy reflects my own view that behavior should be studied in the field whenever possible. Our recent paper in Current Zoology, “Visual playback of colorfulsignals in the field supports sensory drive for signal detectability,” is a prime of example of the power of this approach, in which an intimate understanding of the ecology and behavior of anoles was used to test a major prediction of the sensory drive hypothesis: are signals locally adapted? In other words, are dewlaps locally adapted to effectively grab the attention of an inattentive receiver?

Over the years we have published a series of papers supporting the hypothesis that dewlap diversity can be partially explained by selection to increase the probability of detection. However, until this paper, experimental evidence from the field was missing, in part because manipulating dewlaps of live anoles is not trivial. Furthermore, even if we were able to successfully manipulate dewlaps, there are still many other signals (e.g., body color, motion pattern, size and posture) that would be out of our control. This problem was solved by researchers working with acoustic signals a long time ago by figuring out ways to play the signal of interest in isolation in what have become known as ‘playback experiments.’ We stole a page from their book and constructed a remote-control dewlap apparatus, which provided an opportunity to display only the dewlap under natural conditions (see gizmo below).  Alex’s building and painting skills was key to the success of this gizmo. He was able to construct dewlaps with similar reflective and transmission properties of real dewlaps while taking into account the visual system of the anoles (please see papers for details). 

Control-remote dewlap display apparatus. A) Acrylic box within which electrical components were housed. B) Electrical components. C) The apparatus at a mesic site with a fake dewlap displayed.

Besides presenting the dewlaps in the field, we wanted to test the hypothesis that the dewlaps are locally adapted. Under this hypothesis, increased detection in one habitat comes at the cost of decreased detection in another habitat. This functional approach to test for adaptive value of a trait is commonly used as robust evidence to support selection favoring the evolution of the trait in question. In this paper we tested if the observed differences in dewlap brightness between xeric and mesic populations of Anolis cristatellus is adaptive. If so, dewlaps from mesic populations should be more detectable in mesic habitats and dewlaps from xeric habitats should be more detectable in xeric habitats. Furthermore, detection probability should decrease in the ‘wrong' habitat. Below are the results of the experiments.  In A. cristatellus individuals from xeric habitats have dewlaps which are darker, that is less brighter,  than individuals from mesic populations.

Responses of free-ranging A. cristatellus to fake dewlaps that mimic the brightness properties of real dewlaps.

Our findings support the sensory drive hypothesis and strongly suggest that the brightness  properties of A. cristatellus dewlaps are locally adapted via selection on signal detectability.  Furthermore, we have demonstrated that a brighter signal is not always the most detectable or effective signal. A common misconception, which is partially the result of not including the sensory system and habitat conditions as part of the analysis. Studies addressing potential functions and selective forces promoting the diversity of dewlaps found in anoles have flourished over the last decade,  nevertheless, these results are the best experimental evidence that we have to support the hypothesis that diversity of dewlap colors might be partially explained by local adaptions to habitat light conditions and the best smoking gun to support the idea that diversity of dewlap colors can be the result of local adaptations to habitat light conditions.  Additionally, our study once again underlines the need to measure both reflection and transmission when asking questions regarding the potential function of the dewlap because the two combine to determine dewlap coloration (brightness, coloration, etc.) in the real world.

We Need Your Help

If you follow my blog, you may have noticed that my lab conducts a significant amount of research in Puerto Rico. As a Boricua, working in Puerto Rico provides me the opportunity to work with the flora and fauna that I have become familiar with since I was a little kid. Furthermore, the anoles from Puerto Rico have a long tradition in scientific research, and studies on them have paved the road for Anolis to become a model system in behavioral, physiological, and evolutionary ecology. In Puerto Rico, the general region around El Verde Field Station can be considered a hot-spot in anole research, and the station itself has hosted many of the pioneers of West Indian Anolis biology, including Stan Rand, George Gorman, Paul Hertz, Ray Huey, Ernest Williams, Judy Stamps, Harold Heatwole, and Joan Roughgarden to name a few. In fact, a Google search returned approximately 4000 anoles papers, for which some of the data was collected at El Verde. Like most of Puerto Rico, the field station was badly damage by Hurricane Maria. We, researchers that have worked at El Verde, are trying to raise funds to re-build and maintain the station, if you can help, it would be greatly appreciated.

https://www.gofundme.com/evfs-repairs-and-operating-costs

The University of Puerto Rico was also badly damage, and the AAAS is raising funds that will be used to help the reconstruction of the science buildings. You can donate following this link.

https://www.aaas.org/news/aaas-contributes-rebuilding-puerto-rico-s-scientific-infrastructure?utm_source=64&utm_medium=social&utm_campaign=AAAS-(@aaas)&utm_term=SciPak&utm_content=AAAS

Muchas gracias por la ayuda.  

Photogenic Habitat Selection

On our way into the forest one morning, Deborah made a great "spot" (Noun, Ellee's Field Dictionary: to visualize an anole in a particularly difficult or interesting location). Check out this A. evermanni hatchling enjoying the decorative vegetation around El Verde Field Station!

It's All In The Little Things

 When you spend a lot of time learning about a single species, it is easy to start generalizing. You begin to assume that the individuals are more or less the same. Sure, there is a bit of variation here and there, but your brain seeks categories and determines rough averages:

“Most individuals are this big or that big.”

“In most cases, individuals will behave in this manner.”

But the more time you actually spend with the individuals in their day to day lives, the more you realize that the “bit of variation here and there” can be both substantial, and fascinating.

Deborah and I are trying to catch glimpses of this variation by observing the natural behavior of female Anolis gundlachi lizards. We know each of these lizards by “name”—they have unique IDs that enable us to identify particular lizards day after day. Over time, we get to know each of them. We start to see patterns.

Deborah's Forest "Escritorio"

Ellee's Favorite Observation Rock

We know who is always out—rain, shine, Ellee tromping past, they are always there, on that tree or this rock.

We understand that there are some lizards we will never glimpse until we sit on this rock, that far away, and watch a particular bunch of dead palm leaves with binoculars for 10 minutes. Give her that time and space, and sure enough, she will poke through the leaves and scamper over to the dead tree she seems to like.

And most annoying, we know which male is likely to tromp through the whole plot and mess up all the behavior observations as the females go skittering back into their hidey-holes. “Here comes O1/O2,” we sigh into our tape recorders. “Yep—yep she’s gone.” Poor, lonely O1/O2.

It’s the minor variation that makes things interesting. Why is this female out when the others have hidden? Why does this female run from this male, but the others don’t?

Collecting this kind of data is hard work. It takes time, practice, and a whole lot of patience. Losing lizards under rocks is frustrating, praying to the rain gods only seems to work on Tuesdays, and, on some days, lizards sit on the exact same perch all day long. But it’s the only way to truly capture that variation, and begin to wonder how it plays a role in the lives and history of the animals we all study.

A Usurper’s Tale: The Saga of B30/B31

[It's more fun if read aloud...]

Today I shall tell you the tale of a lizard known as “Blue/Blue.” She’s actually called “Female, LeftB030/RightB031, Tree 3, Plot 1, 6/21/16,” but I know all that matters little you.

An Anolis lizard, she takes hails from the tropics, but of her many behaviors, female-female competition shall be today’s topic.

The Forest Scene for our story. 

When Blue/Blue’s name first came to be, she spent most of her days on a Tree called SP-3.

A modest sierra palm, she seemed happy enough, surrounded by neighbors, and insects, and a whole manner of forest-y stuff.

One of her neighbors, known to all as White/White, lived on Tree 4, but seems to have disappeared during one night!

Whether she carried her bags to a neighboring plot, or met a maniacal lizard cuckoo, I’m afraid we know naught.

Regardless of reason, there resulted a great tizzy, and we suddenly found our day of observations quite busy.

It would seem that Tree 4 is a great perching prize, as we found it was coveted by a great many eyes.

Green/White eyed the vacancy from Tree number 1, but decided it not worth the battle she might not have won.

Green/Green looked upon the great tree with envy, as she and White/White had never been friendly.

Orange/Yellow crawled down the base of tree 2, shook her head and thought “that’s just too much territory for you.”

Yellow/Yellow had always been restless, tree 5 being easy to defend and leaving her quite quest-less.

But it was Blue/Blue who moved quickly to claim the new prize, much to the surprise of neighborly eyes.

On the roots of Tree 4, Blue/Blue perched with pride, but soon found herself drawn to the other side.

Green/Green pranced about, exploring by root and by vine, not content to remain on her palm leaf and pine!

Blue/Blue took offense and began doing push-ups, as she had come too far and cared not for territorial screw-ups.

But it seemed her efforts would be drawn thin, as Yellow/Yellow scampered up seeking to join in!

Blue/Blue would not give up her prize so easily, as she was 45mm long and therefore not measly!

She push-upped, and dewlapped, and stuck her tongue out, daring her foes to seek other routes.

It seemed Yellow/Yellow would be first up to battle, her own pushups making her palm perch rattle.

They darted and bit and ran round in circles, and if lizard faces could show fatigue, they’d both have been purple!

It lasted ten minutes and filled me with fright, but eventually Yellow-Yellow gave up, and left the fight.

With wounded pride she slunk back to tree five, promising she’d be back when she felt more alive.

But the woes of Blue/Blue were far, far from finished, as Green/Green remained, causing a menace.

She push-upped and crawled closer, drawing Blue/Blue ever nearer, thinking her chance to own tree number 4 had never been clearer.

Drawing un-lizardly strength from her ectotherm soul, Blue/Blue quickly retaliated, never forgetting her goal.

Darting this way and that, she harried her opponent, declaring “This is my throne, and you shall never own it!”

She jumped to the palms that were Green/Green’s home turf, and incited an interaction that became quite a tryst.

Five minutes it lasted, all puffed chests and tongues out, as these two former neighbors battled it out.

Blue/Blue emerged triumphant and Green/Green did run, and with some victory push-ups she shouted “What, leaving the fun?”

She returned to her tree, all pride and all glee, taking stock of the goods in her new territory. 

She slept soundly that night, nestled amongst the leaves, thoughts of her triumphs filling her dreams.

It was good that she rested,

for as you all know,

the Usurper will always be tested,

by friend and by foe. 

A xenomorph moment with an anole (EDIT: Video link provided below)

Late last night, I returned to home base after capturing anoles at several sites for additional mate-preference trials. I started to organize the lizards that I captured and process them before placing them into their cages.

In addition, I had one male Anolis krugi that I held captive for a two days from a previous collection night. I try to catch extra male A. krugi when I can because they’re by far the rarer demographic that I need for my trials and can be used as insurance in case I can’t find enough for the following capture-session. This anole, from the northern hills of Yauco, was a beautiful 53mm-SVL whopper and he wasn’t at all shy to eat the crickets I fed him during his time in captivity.

As I was about to remove him from his cup container to assign him his trial cage I noticed something protruding out of the side of his torso. And that something was moving. “Is that a bot fly?!?” I exclaimed in my thoughts. The larva was just idling with its head (assuming it’s the head end) sticking out of the anole. As many biologists might do if they have the equipment, I ran to my car and grabbed the camcorder and some tweezers.

With the camcorder on and recording, I took the anole out of his container. But as the lizard briefly squirmed in my grasp, it stimulated the larva to flee the scene. I would’ve uploaded the video here of the scene but my current internet provider cannot handle the byte-load. So here is a screen shot. 

After squirming a bit, the lizard calmed down while the larva inched its way out of the hole.

It was pretty like a slightly boring, calm rendition of the scene from the 1979 film, Alien - but the lizard survived the ordeal albeit with a large dry wound exposing his raw musculature.

I decided not to use him for trials and put him back in his cup container. I procured the wiggly larva from the floor, sampled it into a vial and alcohol, and continued on to process the rest of the lizards for the night.

Once all the lizards were measured and in their cages, I briefly googled what this parasitic larva could be. Turns out it is not likely to be a botfly species such as the human botfly (Dermatobia hominis) of family Oestridae, but of a different yet closely related family, Sarcophagidae, the flesh flies.

I found that a fellow anole researcher, Dr. Travis Ingram, reported a similar case with an Anolis pulchellus at El Verde field station with an outcome more fitting of a Ridley Scott movie. The pictures he provided of the larvae seemed just as girthy as the one that emerged out of my A. krugi. Looking at the comments of his post, it appears there have been at least several of these observations in A. carolinensis and A. pulchellus.

Dr. Ingrams’s own googling led him to a paper by Irschick et. al. (2006) which provides insight on the parasitism of a Anolis carolinensis by a sarcophagid fly. Dr. Ingram went the extra kilometer and provided his parasitic larvae with substrate to complete their life cycle and managed to observe the adult fly stage, possessing the characteristics similar to sarcophagid flies.

And just as Dr. Ingrams’s also noted, I noticed nodules bulging from under the same A. krugi’s skin. Perhaps they are other larvae? Has anyone ever seen this in an A. krugi?

The following morning, I checked on the A. krugi male and saw he was still kicking and seemed that he’ll get to live another day at his home site. This was definitely a cool thing to observe, though I much prefer ‘not’ to observe it happen to the rest of my anoles for the rest of the season.

The next morning the wound was dry but still open.

This guy had at least two nodules at the edge of his ventral side.

-Eddie Ramirez

EDIT - 3/October/2016 : Click here to watch the larvae exiting from its host!