This NC green anole is on the ground, but mostly they apparently are up in the trees. Photo from http://www.wildherps.com/images/herps/standard/08041129PD_green_anole.jpg
We’ve had a lot of talk here on AA about how green anoles can be found low to the ground in places where A. sagrei has not invaded. But Manuel Leal says that’s not so in sagrei-less North Carolina, where all the ones he saw in the woods were high in the trees. What gives?
Professor of Biology and Director of the Living Earth Collaborative at Washington University in Saint Louis. I've spent my entire professional career studying anoles and have discovered that the more I learn about anoles, the more I realize I don't know.
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Skip Lazell
In Jackson, MS, our winter abode, A. carolinensis can be quite terrestrial, but also climbs up several meters: classic trunk-ground.
Pat Shipman
I commented on the Chipjo Lab website that in Moncure, NC, I see the anoles often at about 1m or less on taller vegetation like bushes, shrubs, or taller plants. They do run up trees, to escape predators, spiraling up the trunks. Here we have the beautiful five-lined skink with a electric blue tail. The skinks seem to prefer leaf-litter, potted plants, and low down possible escape or sunning places on the side of the house or vertical posts. I wonder how much the skinks provide the same sort of competition as A. sagrei would, if we had A. sagrei. The range of sizes of skinks is about the same as that of A. carolinensis. I attach a photo of our gorgeous skink. I can often see both a skink and a anole without moving, so they definitely do share the habitat.
Manuel Leal
Agreed, carolinensis really likes high perches here (NC). As I mentioned before, the carolinensis‘ tendency for high perches might be relevant to the interpretation of the research that has been done looking at the interactions between carolinensis and sagrei (some of which has been presented on Anole Annals).
With that said, I am looking forward to seeing critical discussions to other topics posted in AA — similar to what was generated by the proposed change of Anolis. To get the ball rolling, perch selection by carolinensis might be of interest to many readers of AA. As someone who doesn’t work with carolinensis, should the general idea that sagrei is pushing carolinensis towards the canopy be the most likely explanation of why carolinensis seems to perch higher when the species are sympatric? Couldn’t carolinensis have been using those high perches before sagrei‘s arrival? My experience with porcatus is that individuals are commonly found high in the vegetation, and porcatus and carolinensis are very similar in morphology and possibly behavior. Actually, they are so similar that hybridization between them is not out of the question.
Yoel Stuart
Hey Manuel,
Thanks for your post over at Chipojo Lab. I have a couple of thoughts on this, as it’s germane to my research.
1) Without giving too much away until it’s vetted and published, I’m finding that carolinensis is perching higher on small islands with sagrei compared to control islands that don’t have sagrei. So, at least in my system, sagrei appears to be driving a vertical shift by carolinensis. This is shown by Jessica Edwards and Simon Lailvaux in New Orleans too.
2) As to whether carolinensis could be perching higher up in the absence of sagrei, I wouldn’t be surprised by regional variation. The species range encompasses such wide variation in habitat types and environment that there must be variation in perch height in response to variation in insect availability, other predators, lineage effects, and …
3) It’s getting chilly up here in Boston. How’s the weather in North Carolina? I ask because maybe the lizards you’re seeing up so high are basking in the direct sunlight. This is another important component – what’s the seasonal variation in behavior? By late September, I’d bet the NC lizards are done with their breeding season and probably behaving differently than they would during the breeding season. Year round studies (Sandy’s done these, no?) would reveal seasonal shifts. What are NC Ac doing during the summer?
Regardless, my experimental data have me pretty well convinced that sagrei is driving a vertical shift by carolinensis. I think that it’d be pretty hard to claim that sagrei has no competitive effect on carolinensis (and I don’t think you’re claiming that). As the most abundant vertebrate in Florida, sagrei has got to be having a severe impact on the insect community and carolinensis must be feeling it. Sagrei is also aggressively territorial. Anecdotal reports across Florida suggest that carolinensis are seen much more rarely when sagrei is there (either because they’re high up or their population has taken a hit or both).
At least this is true in Florida. But, it may not be true elsewhere as you suggest. Watching whether there will be a mosaic of selective/behavioral effects as sagrei slowly spreads northwards will be very exciting. And, with data like yours in lots of places, we’ll be able to know whether carolinensis perched higher before the arrival of sagrei or not.
As you know, ecology/behavior is messy and it takes a lot of data over long periods of time to try to get a handle on the system. Most of the data in Florida suggest a sagrei-perch height effect. The sagrei-perch height effect will likely not be clear cut everywhere but I think the effect will hold in most places.
Last, porcatus has been living with sagrei and its equivalents for millions of years. I think that the comparison to carolinensis isn’t a fair one.
Jonathan Losos
I hate to disagree with Manuel, but my observations agree with Pat’s. All the green anoles I have seen in North Carolina have been near the ground: one on the sidewalk near a bush, one on a fence near the beach, and one on a windshield. No doubt if sagrei had been around, the greens wouldn’t have been up to such nonsense.
Manuel Leal
Yoel and JBL,
I might throw in the towel and say “no mas,” but before doing so, here are some responses to both of your comments:
1) I agree that year-round observations will be great. Elise was following lizards in late spring and early summer. Most days it would get close to or in the 90’s, although the mornings were a little cooler (around 70’s). However, she saw no major differences during the day in habitat used. In case this was not clear before, she was following mark individuals, which allowed her to get an idea of their daily activities.
2) Also, part of what she saw, which I am guessing is similar to what you are seeing in FL, Yoel, is that individuals are commonly found in the “leafy” parts of branches, where they appear to be doing a nice amount of foraging and moving between trees. In addition to foraging, she also witnessed territorial disputes taking place at approximately 3.5m high. To be clear, they can also be found on the tree trunk, but a high proportion of their activity seems to occur over leaves or relatively thin perches. From my perspective, it would be really interesting to know how often sagrei is also using the leafy parts of branches regardless of the PH or PD.
3) My take is a little different with regards to what we can learn from porcatus. How about the following scenario: carolinensis is like poracatus, and in the absence of sagrei has expanded its “niche”, which seems to occur without “major” changes in morphology or some aspects of its behavior like the preference for leafy sections of trees or bushes. However, carolinensis is not a replacement of sagrei and in some areas they can also be found higher in the vegetation, as is the case here in NC, which is where you find porcatus, as you suggested in part because of competition, but also because its morphology is not that of a trunk-ground anole.
Yoel Stuart
For point 1, Elise was seeing lizards up high for most of the summer? So there goes the basking hypothesis. How many populations was she following? Regardless, I don’t question the data. Like you, just wondering what would be driving that compared to other parts of the range.
For point 2, I’ve got data on perch type for carolinensis and (somewhat less) sagrei from my islands but haven’t really dived into that question. We found lots of carolinensis in leafy mangrove and buttonwood (although they were still on twigs and branches) and on palm fronds but we also found them quite a bit on palm trunks and petioles and cedar. Regardless, carolinensis do move around a lot as they forage. Sagrei were mostly trunk and large branch dwellers.
For point 3, from the anolis morphospace figures I’ve seen (maybe mostly Thom Sanger’s work but I think elsewhere too), carolinensis tends to be more intermediate in anolis morphospace. So it does seem like it has evolved a bit here. It hasn’t become a trunk ground anole but it’s more trunk ground-like than porcatus. In the same way, it’s behavior/ecology isn’t pure trunk-ground anole but it’s more than its relatives.
Anyways, I’m sure William’s Principle of Unsympathetic Magic is at play for both of us.
Manuel Leal
Yoel, we have observed the same pattern at two sites. I don’t think it has to do with basking sites or insects.
It is great that you have focal observations. It should provide, what I think, should be interesting patterns about habitat preferences. To be clear, I am not expecting a total exclusion, instead differences in proportion of time.
Yes, relative differences are always difficult. I am happy with calling carolinensis a generalists, that has a relatively broad structural niche.
Yoel Stuart
All sounds good Manuel. We’ll just have to continue documenting that broad structural niche with lots of studies from all over the SE US.
Nathan Turnbough
Manuel and Yoel,
This is a topic of interest to me, since it’s tangentially related to my research into the relative food web impacts of these two species. Here are some thoughts:
The surprising part of the NC carolinensis pattern isn’t their use of high, leafy perches, but their lack of use of lower perches. I suspect that herpers-at-large in the southeastern U.S. observe many green anoles at low perch heights and few at high PH because they typically focus their search efforts on the ground and lower vegetation (at least I speak for myself – perhaps this is untrue for more dedicated anolologists?), not because carolinensis are rare in the canopy. As Sandy Echternacht has pointed out to me many times, we miss who-knows-how-many anoles high up in the vegetation, even when we are looking for them, and our observation bias may affect our impressions—even our measurement—of PH distributions. Based on what I know about TN anoles, it’s probably not unusual to find carolinensis way up in the canopy if you look for them there, but it is weird that they aren’t using lower perches as well.
Could the lack of near-ground carolinensis observations in NC be related to the habitat? My experience with carolinensis outside of FL is pretty limited, but those I’ve observed in sagrei-free TN, GA, and SC have mostly been at relatively low PH (< 2.5 m, including many on the ground, rocks adjacent to water, and cliff bases). Nearly all the observations I can recall, however, have been in edge (or edge-like) environments or relatively open forest habitats (lack of ground cover, sparse understory). The few carolinensis I’ve observed high up in trees have been in forest interiors. Are the NC sites in relatively intact forest? How open is the understory?
Ultimately, to understand variation in carolinensis’ use of low perches (when higher ones are available) and the upwards shift in the presence of sagrei, I suppose we need to know what carolinensis is doing when it uses lower perches in its territory (especially those near the ground). The same activities, with the same frequencies, as when using higher perches? Seeking microhabitats with more abundant or preferentially sought prey? Some other purpose? Although carefully designed experiments are needed to really address this question, you probably have data, Yoel (and Todd Campbell also), that could serve as a take-off point. For example, does the relative frequency of perch type (thin branches, trunks, palm/palmetto leaves, etc.) use differ between carolinensis-only islands and those with sagrei (i.e., can/does carolinensis perch in the same way when it shifts upwards, or does it lose access to certain perch types)?
Jonathan Losos
I think Nate’s on to something here. I remember in Cuba, when entering the deep forest at Soroa, A. porcatus was only seen high in the canopy, but outside the forest it came down much lower. Presumably in the forest it was up at the top where it could bask and stay warm. Particularly in North Carolina, I bet the same thermoregulatory concerns are a major factor in its habitat use in forests.
Martha Munoz
To weigh in on the basking site hypothesis, my understanding is that lizards that want warmer microsites tend to bask or restrict their activities to lower perches in more open areas. See Bauwens et al. 1996, Hertz and Huey 1981, and Angilletta et al. 2009. That being said, I don’t think we have much data on what microsite temperature is like above a few meters. I, for one, would like to see iButton (temperature sensor) data from 0, 1, 2, and 3 meters. I wonder if, depending on the vegetation cover and time of day, a really high perch means more incident sunlight than at about 1 meter up. The fact that A. carolinensis has been observed on the ground would seem to indicate they are seeking warmer microsites down low, rather than high up, but it would be worthwhile to double check.
Jonathan Losos
In a thick forest, the best place to get sun is up in the canopy. Forest plant ecophysiologists have documented that there are huge differences in microclimate up top, in the full sun, compared to the shaded realms below.
Martha Munoz
Certainly makes sense to me! My only doubt about this stems from how wind eddies differ low down from high up in a thick forest. Sites higher up in the canopy tend to get few, large gusts, while sites lower down tend to get many small wind eddies. How those differences in cooling are counterbalanced by greater incident radiation up top still strikes me as requiring the data from copper models (i.e., something with the right shape and thermal inertia as a lizard).
Wayne Sheffield
Five years ago I left my native Florida, and moved up here to Raleigh for Grad School and to escape “The Mouse”. So Yesterday while shopping at my Local Greenhouse, I was shocked to see 2 Brown Cuban Anoles running around. I know my fellow shoppers thought me strange running around the store taking photos. Are they now common to NC, or just to local Garden centers?