More spiders eating anoles (for previous aranean saurivory, see this and that). This time it’s a brown anole, A. sagrei (also, this time), falling prey to a ctenid spider in Cuba. This one’s particularly gruesome–the head’s already digested away and eaten! The authors are Elier Fonseca Hernández and Tomás M. Rodríguez-Cabrera and the paper’s just out in the most recent issue of IRCF Reptiles & Amphibians.
As a follow up to my recent posts on lamella scale counts on toepads, I thought I would share a tutorial I created for measuring toepad length and width using the program ImageJ. ImageJ is a free, open-access program that allows you to perform a suite of analyses on pictures or scans. I hope this could be a useful tool for graduate students, as well as research technicians and assistants.
Measuring the width of a Cuban brown anole (Anolis sagrei) toepad using ImageJ
Tutorial: How to measure Anolis toepad length and width using ImageJ
You can download ImageJ from here.
Feel free to use and distribute as you need! If anyone has any comments, or spots any recommendations or improvements that can be made, then please feel free to contact me.
Rather than trying to explain this, I’ll simply post the tweet that alerted me to it.
Everyone knows that geckos are anole wannabees, but here in Asia, there are, sadly, no anoles (except introduced brown anoles in Taiwan and Singapore). So, in their absence, an anolologist is forced to count geckos. Fortunately, in some places, they’re not hard to find. Just how many are there on the ceiling of this building near Khao Sok National Park in Thailand?
I have now compiled the results of the survey I previously posted here on Anole Annals. I asked readers at what point on the image below would they stop counting scales if conducting toepad scale counts?
Fig 1. Lamellae numbered 1-51 on the 4th digit of an Anolis lizard hindfoot
As expected, there was a lot of disagreement! However despite some confusion, scale 32, roughly coinciding with the joining of the second to the third phalanx, was a clear favourite (Fig 2, below) (see Kevin De Quieroz’s comment here regarding some confusion with phalanx numbering).
Fig 2. AA readers choice of where one should stop counting during toepad scale counts.
However, I was most interested in the demography of the surveyors. I have met other graduate students confused about this topic, and relevant guidance material seems limited to anecdotes. Would we then expect there to be most confusion among contributors who have never published scale count data?
Fig 3. Survey data broken down into publication record: a) those that have never published scientific articles which include toepad scale counts (blue), b) those that have published a scientific article including toepad scale count data (red), and c) those which have published but were not responsible for conducting the scale counts (green).
The majority (60%) of votes from published researchers fell among scales 32-33, suggesting fairly high agreement on the general area. Only 40% of non-published voters selected these scales, with moderate confusion from scales 24-33 (although a peak at 32 did mirror those of published researchers). Too few votes from researchers that had published but not conducted scale counts themselves were collected to be interpretable.
This survey was not intended to standardize the position at which researchers should conduct toepad scale counts. The functional significance of toepads changes between species, and therefore that should be an important consideration in respect to the ecological/evolutionary question at hand. Those votes towards the higher end of the spectrum (scales 50-51, comprising a scale count of the entire digit) could be important data for species identification and morphological taxonomy. There could be an opportunity for a neat review/methods paper here, contact me if you are interested in more details!
The second most viewed Anole Annals post of all time is “The proper pronunciation of “anole”” which has been viewed 9,938 times (just 121 views behind the all-time leader. *You’ll have to guess what that one is about. Or click here.).
Well, now there’s a video answering the same question and, frankly, I’m not sure everyone will agree with the answer.
*This post was initially drafted several months ago. In the intervening time, the leading post has gone on a tear, and now is ahead by 1,610 views! Go figure.
Hey, that’s not an anole! American Rubyspot Damselfly (Hetaerina americana). Copyright Steve Collins
My colleagues and I recently published a paper documenting character displacement in Anolis carolinensis following the invasion of A. sagrei into Florida. The former moved up into the trees and evolved larger toepads. We did a lot of work in that paper to show with a high degree of certainty that the interaction between the two species is what led to character displacement in A. carolinensis. However, an open question remains as to exactly what kind of interaction, or interactions, they share. Most likely, the two species are competing for food (i.e. exploitative competition). They may also be interacting indirectly through a shared predator or parasite (i.e., apparent competition), and they are known to eat each other’s hatchlings (i.e., intraguild predation).
Today, I’d like to explore another possible interaction in depth: perhaps the two species have diverged to lessen aggressive interspecific interactions for space and territory (i.e., interference competition). For more, let’s turn to the anoles of the Odonata world (provocative statement, I know!): rubyspot damselflies (Hetaerina spp).
In a recent issue of the Proceedings of the Royal Society B, Jonathan Drury and Greg Grether investigated the role of aggressive (or agonistic) interactions in driving divergence between two species of rubyspot damselflies.
Previous work [1,2,3] in Grether’s group had shown that male competitor recognition in rubyspot damselflies depends on hindwing coloration, and that cross-species recognition and male wing coloration diverges between species living in the same area. This suggests that aggressive interactions between males of different species have driven divergence in wing color to reduce the frequency of energy-intensive, aggressive interactions between species. This divergence is consistent with a type of character displacement called Agonistic Character Displacement (ACD), which is the divergence between species in some sort of species recognition trait to lessen the negative effects of aggressive encounters.
However, another type of character displacement, Reproductive Character Displacement (RCD) is also consistent with these previous findings. RCD is divergence, usually in some sort of mate recognition trait, between two species. By diverging in such a trait (think anole dewlaps), males and females of different species are less likely to spend precious time courting or mating in wasteful, failed cross-species reproductive efforts.
By this point, you, the astute reader, may have noticed that both ACD and RCD predict changes in signaling traits–the former species recognition traits, and the latter mate recognition traits.
Whenever the same trait functions as a signal for both species and mate recognition, and that does happen often, telling apart the action of these two distinct processes (i.e., selection to reduce wasted aggressive effort versus selection to reduce wasted reproductive effort ) can be very difficult*.
Drury and Grether designed a very nice test for successfully discerning between these two hypotheses.
I’m looking for a bit of help and where else to turn than the dedicated readers of Anole Annals? Does anyone have a short video clip (ca. 10 seconds) of a trunk-ground anole running on either the ground or a trunk that they’d be willing to share? I’d like to use it for a couple of upcoming talks, and for teaching. Proper credit would, of course, be given. Plus I’ll buy you a beer if you ever happen to be in Nottingham. I’ve got a few short clips of sagrei but unfortunately the frame rate went screwy when I tried to convert them, hence the appeal. The point is to contrast a trunk-ground’s movement with this clip of carolinensis (shot by Leslie Bode on the Anhinga Trail, Everglades, FL):
If you have something suitable that you’re willing to share, please either leave a comment, or you can email or tweet me (adam.algar[at]nottingham.ac.uk, @acalgar).
Thanks!
I probably would have never said this a few years ago, but penises are absolutely fascinating. The phalluses of terrestrial vertebrates exhibit an incredible diversity of shapes and sizes with some possessing elaborate coils, barbs, bony spines, and multiple lobes. Many of us learn about the rapid evolution of sexual characters in our undergraduate classrooms, but until recently I, for one, did not fully appreciate the striking diversity of this organ until immersing myself in the subject area.
Many biologists study the penis under the umbrellas of different research disciplines, but relatively little work has been performed to explain its anatomical diversity. For example, how many times has a penis/phallus evolved among terrestrial vertebrates? This may seem like a trivial question, but the diversity in form, function, and physiology in the adult phallus actually makes this question difficult to address. Historically there has been much conjecture, but little data to support whether the mammalian penis, squamate hemipenes, and phallus of turtles, crocodilians, and basal birds share a single evolutionary origin or are independently derived. But where comparative anatomy has struggled, comparative developmental biology has recently forged ahead. Within the last several months two independent groups have published a total of seven new research articles that help us resolve the question of phallus homology.
Figure 1 from Gredler et al. 2014 illustrating phallus diversity among amniotes. The darker lines illustrate the sulcus spermaticus which goes on to become internalized in mammals as the urethra.
I previously wrote about a series of five papers published from the Cohn lab (University of Florida) describing the embryology and gene expression patterns for the developing phallus. Since then this group has published a sixth paper synthesizing this wealth of information, using it to lay out a number of outstanding questions regarding phallus development and evolution. More recently, the Tabin lab (Harvard University) published a paper comparing the cellular-level origins of the genitalia in the laboratory mouse, green anole, house snake, chick, and python. I have had the distinct pleasure of working with both groups as their “anole guy.” Although these studies vary widely in their experimental and comparative breadth, together they have shed much needed light on the evolution of vertebrate genitalia. Here my goal is to discuss how this new wave of research changes what we now know, what we don’t know, and what we think we know regarding the evolution of external genitalia among vertebrates. Take a look at the original research papers for details of the developmental analyses, which represent many technical steps forward in our use of anoles as a laboratory model system and intellectual advancements in our understanding of genital development.
During the gradual transition of life onto land, vertebrates evolved the amniotic egg to facilitate their departure from moist environments.
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