Cuando era estudiante de pregrado en Colombia, estaba tratando de decidir qué hacer para mi tesis. En Colombia—o al menos en mi alma mater, la Universidad Icesi—es obligatorio hacer una tesis para graduarse. Durante ese tiempo, me encontré con tres de mis artículos favoritos: Janzen (1967), Ghalambor et al. (2006) y Muñoz et al. (2014). Después de leer estos artículos, una pregunta surgió en mi mente: ¿Pasa lo mismo en los Andes? Específicamente, ¿la tolerancia al frío disminuye con la elevación mientras que la tolerancia al calor permanece sin cambios?

Compartí esta idea con mis mentores de tesis, María del Rosario Castañeda y Gustavo A. Londoño, y les dije: ¡Quiero hacer esto! Quiero ver cómo los límites térmicos y la rango la tolerancia térmica varían con la elevación tanto dentro como entre las especies de Anolis.

Para abreviar, recolecté datos sobre tolerancia al frío y al calor para 14 especies de anolis en cinco sitios diferentes de Colombia. Sin embargo, debido a restricciones en la Universidad Icesi, solo pude utilizar datos de cuatro especies para mi tesis. Avancemos un año atrás, cuando estaba discutiendo este conjunto de datos con mi mentor de doctorado, Jonathan Losos. Me dijo: deberías usar estos datos para uno de tus capítulos de doctorado. Así que lo hice. Ahora, está publicado en el Evolutionary Journal of the Linnean Society: Salazar et al. 2024.

Ahora, hablemos uno de los Anolis de los Andes colombianos. La mayor parte de lo que sabemos sobre la fisiología térmica de anoles proviene de Anolis caribeños. Hay una notable falta de información sobre los límites térmicos de los anoles que habitan en los Andes. Solo un puñado de artículos se ha publicado sobre este tema: Méndez-Galeano y Calderón-Espinosa 2017, Méndez-Galeano et al. 2020, Montoya-Cruz et al. 2024 y Pinzón-Barrera et al. 2024. Sin embargo, la mayoría de estos se centran en una sola especie.

Entre 2016 y 2017, varios estudiantes de pregrado y yo visitamos cinco localidades diferentes en Colombia para medir la tolerancia al frío y al calor en los anoles andinos. Pasamos casi siete meses en el campo durante un año y medio. Medimos 367 individuos—machos, hembras y juveniles—de 14 especies a lo largo de dos clados: Draconura (cinco especies) y Dactyloa (nueve especies) a lo largo de un gradiente de elevación (200–3000 m). Nuestro estudio abordó dos preguntas clave:

1. ¿Cómo predice la variación térmica a través de la elevación la evolución de dos rasgos fisiológicos clave en los ectotermos tropicales del continente?
2. ¿Cómo ha evolucionado la fisiología térmica en la radiación andina de los anoles?

Antes de adentrarnos en los resultados, permítanme compartir algunas historias de campo. Si alguna vez han buscado Anolis en el Caribe o en los Andes, sabrán lo desafiantes que son. Antes de mis saludas de campo, Rosario me llevó en una de las suyas para enseñarme lo básico. Pasamos unos días en el campo y encontramos un par de lagartijas. En ese momento, pensé: ¡Nunca voy a encontrar suficientes lagartijas para escribir una tesis!

Encontrar anoles en los Andes es difícil. Durante el día, casi son imposibles de ver, y si logras ver uno, atraparlo es otra historia. Como rara vez tuvimos éxito durante el día, cambiamos a trabajo de campo por la noche. Incluso entonces, en algunos lugares no vimos lagartijas durante días. Para maximizar la colecta de datos, decidí capturar y medir a cada individuo que encontrase y evaluar si la lagartija era lo suficientemente grande o saludable para ser medida.

Caminando por la noche en los Andes colombianos; Parque Nacional Natural Tatamá – 2000 m. El anole que tengo en la mano es un Anolis princeps, mi especie favorita.

Aquí va una historia adicional: Rosario una vez me contó lo diferente que era atrapar Anolis en el Caribe. Dijo que allí es más fácil verlos y atraparlos, e incluso puedes decidir en el momento cuál medir. No le creí—hasta que me uní a Kristin Winchell en la República Dominicana. ¡Nunca había visto tantos anoles en un solo lugar—fue increíble! Aún así, me encanta buscar anoles en los Andes, aunque sea más desafiante. No estoy seguro de por qué, pero los Andes siempre tendrán un lugar especial en mi corazón—quizás porque uno de mis sitios de campo está a solo 30 minutos de la casa de mis padres, probablemente nunca lo sabré, jaja.

¿Qué encontramos? Como esperábamos, descubrimos que la tolerancia al frío (CTmin) y la tolerancia al calor (CTmax) aumentan con las temperaturas ambientales y operativas, pero disminuyen con la elevación. Sin embargo, contrariamente a lo que han reportado otros estudios, la tolerancia al calor no permanece sin cambios con la elevación. A diferencia de sus contrapartes caribeñas, los anoles andinos no parecen usar un mecanismo de regulación conductual para limitar la divergencia en la tolerancia al calor a través de las elevaciones—un fenómeno conocido como el efecto Bogert (Muñoz et al. 2022). Es posible que los anoles andinos no regulen su temperatura conductualmente de la misma manera que lo hacen las especies caribeñas, aunque esto aún requiere más investigación (pero véase Méndez-Galeano y Calderón-Espinosa 2017).

También encontramos que la tolerancia al frío y al calor evolucionaron a tasas similares. El análisis filogenético reveló que los límites térmicos pueden variar entre especies estrechamente relacionadas, lo que desafía la idea del conservadurismo de nicho y señala la flexibilidad en la tolerancia fisiológica a medida que las especies se diversifican a lo largo de los gradientes de elevación. Además, la compleja geografía de los Andes jugó un papel significativo en la diversidad de la fisiología térmica dentro de estos anoles. Comprender cómo la diversidad fisiológica influye en la diversificación de especies podría darnos luz sobre cómo dos clados del mismo género, con historias evolutivas distintas, muestran respuestas similares a la adaptación a ambientes montañosos. Nuestros datos sobre los anoles andinos son consistentes con esta perspectiva: ya sea cerca del nivel del mar o varios kilómetros por encima de él, las especies están fisiológicamente especializadas para sus condiciones térmicas locales y exhiben un rango de tolerancia relativamente estrecho, como se predice para los lagartos tropicales (Huey et al. 2009).

Para responder a esas dos preguntas:

1. ¿Cómo predice la variación térmica a través de la elevación la evolución de dos rasgos fisiológicos clave en ectotermos tropicales de tierras continentales? La tolerancia al frío y al calor disminuye con la elevación.
2. ¿Cómo ha evolucionado la fisiología térmica en la radiación andina de los anoles? Ambos rasgos evolucionan a tasas similares, pero su evolución es independiente de la filogenia.

En un mundo que se calienta rápidamente, la pregunta crítica es si estas especies podrán mantener el ritmo con los impactos acelerados del cambio climático en sus ambientes naturales. La investigación futura debe centrarse en comprender cómo el aumento de las temperaturas y los patrones cambiantes de lluvia influirán en los patrones de actividad, el equilibrio energético y las tasas de crecimiento poblacional de los anoles andinos. Al vincular la variación fisiológica con las tendencias demográficas, podremos predecir mejor cómo estas notables especies de lagartos podrían enfrentar las presiones del cambio global.

Espero que este estudio despierte la curiosidad por explorar más a fondo los anoles andinos—y también los anoles amazónicos, que siguen siendo sorprendentemente poco estudiados.

Una última historia adicional—no estoy seguro de cuántos de ustedes han visto esta foto, pero tomé esa hermosa imagen de Anolis chloris durante uno de mis viajes de campo cuando era estudiante de pregrado.

References:

Salazar JC, Londoño GA, Muñoz MM, et al. The Andes are a driver of physiological diversity in Anolis lizards, Evolutionary Journal of the Linnean Society 2025; 4(1): kzae040. https://doi.org/10.1093/evolinnean/kzae040

Ghalambor CK, Huey RB, Martin PR, et al. Are mountain passes higher in the tropics? Janzen’s hypothesis revisited, Integrative and Comparative Biology 2006; 46: 5-17. https://doi.org/10.1093/icb/icj003

Janzen DH. Why mountain passes are higher in the tropics, The American Naturalist 1967; 101: 233-249. https://www.jstor.org/stable/2458977

Méndez-Galeano MA, Calderón-Espinosa ML. Thermoregulation in the Andean lizard Anolis heterodermus (Squamata: Dactyloidae) at high elevation in the Eastern Cordillera of Colombia, Iheringia, Série Zoologia 2017; 107: e2017018. https://doi.org/10.1590/1678-4766e2017018  

Méndez-Galeano MA, Paternima-Cruz RF, Calderón-Espinosa ML. The highest kingdom of Anolis: Thermal biology of the Andean lizard Anolis heterodermus (Squamata: Dactyloidae) over an elevational gradient in the Eastern Cordillera of Colombia, Journal of Thermal Biology 2020; 89: 102498. https://doi.org/10.1016/j.jtherbio.2019.102498

Montoya-Cruz A, Díaz-Flórez RA, Carvajalino-Fernández JM. Thermal balance in Andean lizards: A perspective from the high mountains, Austral Ecology 2024; 49: 313578. https://doi.org/10.1111/aec.13578

Muñoz MM, Stimola MA, Algar AC, et al. Evolutionary stasis and lability in thermal physiology in a group of tropical lizards, Proceedings of the Royal Society B 2014; 281: 20132433. https://doi.org/10.1098/rspb.2013.2433

Muñoz MM. The Bogert effect, a factor in evolution, Evolution 2022; 76: 49-66. https://doi.org/10.1111/evo.14388

Pinzón-Barrera C, Suárez-Ayala N, Carrillo-Chávez LM, et al. Unveiling critical thermal limits of Anolis tolimensis (Squamata, Anolidae) across an elevational landscape, Current Herpetology 2024; 43: 155-134. https://doi.org/10.5358/hsj.43.115

When I was an undergrad student back in Colombia, I was trying to decide what to do for my thesis. In Colombia—or at least at my alma mater, Universidad Icesi—it’s mandatory to complete a thesis to graduate. During this time, I stumbled upon and read three of my favorite papers: Janzen (1967), Ghalambor et al. 2006, and Muñoz et al. (2014). After reading those papers, a question popped into my mind: Does the same happen in the Andes? Specifically, does cold tolerance decrease with elevation while heat tolerance remains unchanged?

I shared this idea with my thesis mentors, María del Rosario Castañeda and Gustavo A. Londoño, and told them, I want to do this! I want to test how thermal limits and thermal tolerance breadth vary with elevation both within and among anole species.

Long story short, I collected data on cold and heat tolerance for 14 anole species across five different sites in Colombia. However, due to restrictions at Universidad Icesi, I could only use data from four species for my thesis. Fast forward to over a year ago, when I was discussing this dataset with my PhD mentor, Jonathan Losos. He said, you should use this data for one of your PhD chapters. So, I did. Now, it’s published in the Evolutionary Journal of the Linnean Society: Salazar et al. 2024.

Now, let’s talk about Colombian Andean anoles. Most of what we know about the thermal physiology of anoles comes from Caribbean species. There’s a noticeable gap in information about the thermal limits of Andean-dwelling anoles. Only a handful of papers have been published on this topic: Méndez-Galeano and Calderón-Espinosa 2017, Méndez-Galeano et al. 2020, Montoya-Cruz et al. 2024, and Pinzón-Barrera et al. 2024. However, most of these focus on a single species.

Between 2016 and 2017, several undergrad students and I visited five different locations in Colombia to measure cold and heat tolerance in Andean anoles. We spent nearly seven months in the field over a year and a half. We measured 367 individuals—males, females, and juveniles—from 14 species across two clades: Draconura (five species) and Dactyloa (nine species) along an elevation gradient (200–3000 m). Our study addressed two key questions:

1. How does thermal variation across elevation predict the evolution of two key physiological traits in tropical mainland ectotherms?
2. How has thermal physiology evolved in the Andean radiation of anole lizards?

Before diving into the results, let me share some fieldwork stories. If you’ve ever searched for anoles in the Caribbean or the Andes, you’ll know the challenges. Before my trips, Rosario took me along on one of hers to teach me the basics. We spent a few days in the field and found a couple of lizards. At the time, I thought, I’ll never find enough lizards to write a thesis!

Finding anoles in the Andes is tough. During the day, they’re almost impossible to spot, and if you do see one, catching it is another story. Since I rarely succeeded during the day, we shifted to fieldwork at night. Even then, in some locations we didn’t see lizards for days. To maximize data collection, I decided to capture and measure every individual I found and assess whether the lizard was big or healthy enough to be measured.

Walking through the night in the Colombian Andes; Parque Nacional Natural Tatamá – 2000m,. The anole I have in my hand is an Anolis princeps, my favorite species.

Here’s a side story: Rosario once told me how different it was to catch anoles in the Caribbean. She said it’s easier to see and catch them there, and you can even decide on the spot which one to measure. I didn’t believe her—until I joined Kristin Winchell in the Dominican Republic. I had never seen so many anoles in one place—it was unbelievable! Still, I love searching for anoles in the Andes, even though it’s more challenging. I’m not sure why, but the Andes will always hold a special place in my heart—maybe it’s because one of my field sites is just 30 minutes from my parents’ house, probably I’ll never know haha.

What did we find? As expected, we found that cold tolerance (CTmin) and heat tolerance (CTmax) increase with environmental and operative temperatures but decrease with elevation. However, contrary to what other studies have reported, heat tolerance does not remain unchanged with elevation. Unlike their Caribbean counterparts, Andean anoles do not appear to use behavioral buffering to limit divergence in heat tolerance across elevations—a phenomenon known as the Bogert effect (Muñoz et al. 2022). It’s possible that Andean anoles do not thermoregulate behaviorally in the same way Caribbean species do, though this still requires further investigation (but see Méndez-Galeano and Calderón-Espinosa 2017).

We also found that cold and heat tolerance evolved at similar rates. Phylogenetic analysis revealed that thermal limits can vary among closely related species, challenging the idea of niche conservatism and pointing to flexibility in physiological tolerance as species diversified along elevation gradients. In addition, the Andes’ complex geography played a significant role in driving the diversity of thermal physiology within these anoles. Understanding how physiological diversity influences species diversification could shed light on how two clades from the same genus, with distinct evolutionary histories, exhibit similar responses to adapting to mountainous environments. Our data on Andean anoles are consistent with this perspective: whether near sea level or several kilometers above it, species are physiologically specialized to their local thermal conditions, and exhibit relatively narrow tolerance breadth, as predicted for tropical lizards (Huey et al. 2009).

To answer those two questions:

1. How does thermal variation across elevation predict the evolution of two key physiological traits in tropical mainland ectotherms? Cold and heat tolerance decreases with elevation.
2. How has thermal physiology evolved in the Andean radiation of anole lizards? Both traits evolve at similar rate, but their evolution is independent of the phylogeny.

In a rapidly warming world, the critical question is whether these species can keep pace with the accelerating impacts of climate change on their natural environments. Future research should focus on understanding how rising temperatures and shifting rainfall patterns will influence the activity patterns, energy balance, and population growth rates of Andean anoles. By linking physiological variation to demographic trends, we can better predict how these remarkable lizards might fare under the pressures of global change.

I hope this study sparks curiosity to further explore Andean anoles—and even Amazonian anoles, which remain surprisingly understudied.

One last side story—I’m not sure how many of you have seen this picture, but I took that beautiful shot of Anolis chloris during one of my field trips as an undergrad.

References:

Salazar JC, Londoño GA, Muñoz MM, et al. The Andes are a driver of physiological diversity in Anolis lizards, Evolutionary Journal of the Linnean Society 2025; 4(1): kzae040. https://doi.org/10.1093/evolinnean/kzae040

Ghalambor CK, Huey RB, Martin PR, et al. Are mountain passes higher in the tropics? Janzen’s hypothesis revisited, Integrative and Comparative Biology 2006; 46: 5-17. https://doi.org/10.1093/icb/icj003

Janzen DH. Why mountain passes are higher in the tropics, The American Naturalist 1967; 101: 233-249. https://www.jstor.org/stable/2458977

Méndez-Galeano MA, Calderón-Espinosa ML. Thermoregulation in the Andean lizard Anolis heterodermus (Squamata: Dactyloidae) at high elevation in the Eastern Cordillera of Colombia, Iheringia, Série Zoologia 2017; 107: e2017018. https://doi.org/10.1590/1678-4766e2017018  

Méndez-Galeano MA, Paternima-Cruz RF, Calderón-Espinosa ML. The highest kingdom of Anolis: Thermal biology of the Andean lizard Anolis heterodermus (Squamata: Dactyloidae) over an elevational gradient in the Eastern Cordillera of Colombia, Journal of Thermal Biology 2020; 89: 102498. https://doi.org/10.1016/j.jtherbio.2019.102498

Montoya-Cruz A, Díaz-Flórez RA, Carvajalino-Fernández JM. Thermal balance in Andean lizards: A perspective from the high mountains, Austral Ecology 2024; 49: 313578. https://doi.org/10.1111/aec.13578

Muñoz MM, Stimola MA, Algar AC, et al. Evolutionary stasis and lability in thermal physiology in a group of tropical lizards, Proceedings of the Royal Society B 2014; 281: 20132433. https://doi.org/10.1098/rspb.2013.2433

Muñoz MM. The Bogert effect, a factor in evolution, Evolution 2022; 76: 49-66. https://doi.org/10.1111/evo.14388

Pinzón-Barrera C, Suárez-Ayala N, Carrillo-Chávez LM, et al. Unveiling critical thermal limits of Anolis tolimensis (Squamata, Anolidae) across an elevational landscape, Current Herpetology 2024; 43: 155-134. https://doi.org/10.5358/hsj.43.115

Read all about it in the Journal of Herpetology:

Abstract:

 Pre-Pleistocene fossils of Anolis lizards from the mainland of the Americas are exceedingly rare: only two specimens referred to a single species have been described previously. Here we report on a third specimen, preserved (as are the other two) in Miocene amber from Chiapas, Mexico, and consisting primarily of the anterior vertebrae of the caudal sequence. Despite the fragmentary nature of the fossil, it preserves key osteological characters that permit confident referral to the Anolis clade and further suggest placement within the Dactyloa subclade in a clade of three extant species within the Anolis aequatorialis series. The Chiapan provenance of the fossil indicates that the geographic distribution of the Dactyloa clade (and possibly that of the A. aequatorialis series) extended considerably farther north during the Miocene. Although the new fossil represents a different part of the body than the two fossils representing the fossil species Anolis electrum, its inferred phylogenetic relationships are the same as one of the several possible phyloge 

The key sentence: “As a newly minted urologist in 1988 I saw male patients with challenging sexual problems. I was curious about testosterone (T) therapy (TTh) due to my prior research restoring sexual behavior in the castrated male lizard, Anolis carolinensis, with intracranial T pellets.” Read the two-page paper here.

Anolis porcatus collected in Brazil, and comparison with the native anole A. punctatus. A, male A. porcatus showing green coloration. B, male A. porcatus showing brown coloration. C, the pink dewlap of male A. porcatus. D, female A. porcatus. E, male A. punctatus, a native anole species. F, the yellow dewlap of male A. punctatus. Picture credits: A–D, Mauro Teixeira Jr.; E, Renato Recoder. For more information, see this Anole Annals post or read on below.

In North America, especially in places like Florida, invasions of introduced species have revealed novel insights into the competition between species as well as the formation of non-analog species assemblages during such events. Anolis lizards, in particular, have demonstrated a strong ability to invade novel environments possibly even displacing native species in many cities in the United States. Yet the same appears not to be true in South America possibly because similar invasions are only just now occurring. In previous posts I considered diversity of cis– and trans-Andean South American anoles. In this post, I will review what can be inferred about the introduced species of anoles in South America using data accumulated on iNaturalist.org.

Certain introductions have been reported, but not yet observed on iNaturalist, such as Anolis sagrei in Rio de Janeiro (Oliveira et al. 2018). However, there are a handful of examples of anole introductions in South America that can be explored in terms of their progress as becoming invasive. As it turns out, most of the anole introductions appear to be fairly early along in the process of invasion making their documentation a useful exercise for future study by anole enthusiasts.

Despite the lowland Amazon rainforest’s vast size, introduced anoles have not been an issue there until very recently. Where introductions do appear to be occurring in South America, they seemed to have started in coastal cities. The first area of interest are the coastal cities in the northeast of South America.

Anolis aeneus in Guyana

Anolis aeneus has been known from Guyana for several decades and is possibly over a century old (review by Williams 1977, see also Schwartz and Henderson 1991). This species appears to be established in Georgetown, Guyana, and has been observed on iNaturalist since 2012. By the end of 2024 there were still only 34 observations of this species in all of Guyana, but this includes at least a pair of observations away from Georgetown in the interior of that country. So, while A. aeneus is considered introduced in Guyana (see image below), it does not appear to be far along in the process of invasion at this point or moving especially rapidly.


Figure above shows all iNaturalist observations of introduced anoles in Guyana, Suriname, and French Guiana.

Anolis marmoratus and A. sagrei in Suriname and French Guiana

A larger ongoing invasion appears to involve the introduced Guadeloupean Anole (Anolis marmoratus) in French Guiana (see image above). Anolis marmoratus was first reported in French Guiana in 1975 as already well established in Cayenne, French Guiana (Hoogmoed and Lescure 1975). On iNaturalist, this species has been reported in the vicinity of Cayenne since at least 2004 but with only a handful of observations each year until very recently.

Annual observations of A. marmoratus from 2021-2023 were 7, 6, and 8, respectively, including one or two additional observations in Kouro about 40 km along the coast to the northwest. However, in 2024 observations jumped to 18 and came from every neighborhood of the twin cities of Cayenne and Remire-Montjoly as well as another seven observations in Roura 15 km to the south and eight in Kouro. While A. marmoratus appears to be established and spreading in French Guiana, it might begin experiencing competition from another well-known invasive anole that appears to be recently introduced in the area: Anolis sagrei.

The first report of Anolis sagrei in northeast South America came from Paramaribo, Suriname, in 2022 when a single observation was added to iNaturalist from within that city. This species was not among those listed as introduced to Suriname by Hoogmoed (1980), although other species of anoles were mentioned, but not yet observed on iNaturalist in Suriname.

In 2024, three observations of A. sagrei were made in the same area of French Guiana. In both cases, it is too early to tell if these are established populations and if they will spread, but the known invasive habits of A. sagrei in places like south Florida make this seem a likely occurrence.

Anolis sagrei in Guayaquil, Ecuador

In western South America, there have been occasional single observations of Anolis sagrei in places like Zamona, Ecuador, along the Napo River in the Amazon occurred in 2022. However, this observation has not been corroborated so far. Until additional observations are made, it is not possible to determine if we are seeing the beginnings of invasions in any of these places. Yet, A. sagrei already has a well-established foothold in another South American location that is worth examining: Guayaquil, Ecuador, reviewed recently by Narváez et al. (2024)(see image below).


Figure above shows all iNaturalist observations of Brown Anoles in the vicinity of Guayaquil, Ecuador. Image courtesy Jaime Camacho via iNaturalist.

Anolis sagrei was first observed on iNaturalist in 2007 in a park in Guayaquil, in southwestern Ecuador, but first reported in about the year 2000. This observation was of a lizard on the peninsula formed by the confluence of the Daule, Babahayo, and Guayas Rivers. It was not observed again until 2016 in that same park, but soon it became apparent it was probably there all along, which is why continued monitoring is essential for understanding invasions.

In 2017 Anolis sagrei was observed six additional times, but had now expanded to occur in several different places in the city having moved about 4 km from the original location and even jumped the Daule River. That same year also saw a single observation of A. sagrei in the northwestern Ecuador city of San Lorenzo, but this has never been repeated so it is hard to tell if this the beginnings of a new invasion or not. By 2018 it was at least 6 km from the original site and in 2019 A. sagrei was observed 17 times having reached the forested outskirts of Guayaquil to the west some 10 km from original location. Thus, even as late as 2019, A. sagrei appears to have been in the early stages of the invasion, but with a big leap forward in 2020.

In 2020, A. sagrei appears to have begun moving along the roads to the north and west of Guayaquil and tripled its occurrence to 49 observations in and around the city. Half of those observations in 2020 occurred on the peninsula where the species was first noted in iNaturalist. But 2020 also saw a leap for this species with an observation for the first time in Portoviejo nearly 200 km to the northwest of Guayaquil.

The next year, 2021 saw another 50 observations, with over half occurring outside the area where they were first noted. In that year, the suburbs of Guayaquil to the north and west of saw strong growth in observations. Similarly, 2022 added another 48 observations in the vicinity of Guayaquil. In 2022, the population had reached a zoo near Victoria 15-20 km to the north of Guayaquil. Thus, by the early 2020’s A. sagrei had become firmly established in the greater Guayaquil areas and this species took another leap forward in 2023.

In 2023, 85 observations spanned nearly every neighborhood of Guayaquil and its outskirts. Interestingly, even by 2023 A. sagrei had still not jumped the Guayas River to Duran on the east bank. Nor had it colonized the forested reserve of Isla Santay in the Guayas River between these two cities. However, in 2023 A. sagrei did make a big leap northwest to the coastal city of Manta about 20 km west of the aforementioned Portoviejo.

Guayaquil continued to be the center of observations for A. sagrei in 2024 with another 52 observations, but now observations are being reported elsewhere along the coast including Olon, which is about 100 km west of Guayaquil. However, the observations near Manta, Portoviejo, and San Lorenzo have not been repeated so far. Nor has the species appeared to jump the Guayas River to either Isla Santay or Duran.

Isla Santay is of particular interest because of the known population of the native Anolis festae that occurs there. If A. sagrei were to arrive on Santay it could lead to the extirpation of A. festae at that site or at least a novel competitive environment for that native anole. This is where directing a community of observers, such as on iNaturalist, might be of service to monitor these areas for the novel spread of A. sagrei as well as the persistence of A. festae.

If we take 2007 as the initial year of introduction, A. sagrei appears to be expanding its range at about 5 km per year, but with some leaps out beyond that probably via human-aided dispersal. And even though community data such as provided by iNaturalist are not controlled for in terms of effort, they do provide a fascinating window into an ongoing invasion by a known invader. However, A. sagrei isn’t the only invader of South America.


Figure above shows iNaturalist observations of Brown Anoles in Guayaquil, Ecuador binned in three-year intervals.

Anolis porcatus in Santos, Brazil

A lesser-known invasion of South America appears to involve Anolis porcatus in southeastern Brazil. This invasion appears to be even more recent than A. sagrei in Guayaquil and is worth detailing. Anolis porcatus was first observed on iNaturalist in Santos, Brazil (a coastal city just south of São Paulo) in March 2016 at about the same time it was reported in the literature (Prates et al. 2016, Samelo and Barella 2016). This was the only observation of this introduced species until 2018 when five additional observations recorded this species in three separate locations in São Vincente 8-10 km to the west of the original location.


Figure above shows all iNaturalist observations of Cuban Green Anoles in the vicinity of Santos, Brazil. Image courtesy Nereston Camargo via iNaturalist.org.

In 2019, an additional nine observations of A. porcatus occurred in Santos and São Vincente. Thus, by the end of 2019 it appears A. porcatus had established in four different locations. However, observations were still only occasional at this time.

In 2020 A. porcatus jumped to Cubatão, a city another 5 km to the north of São Vincente, and in 2021 it jumped to Praia Grande 5-6 km along the coast to the southwest of São Vincente. By 2023 there were another 21 observations of this species in and around the area including the forested outskirts to the north of Cubatão. In 2024 another 18 observations of the species suggested A. porcatus was now firmly established around Santos.

In addition to the above observations, in October 2024 A. porcatus was noted for the first time southwest along the coast near Itanhaém about 45 km from the original source location in Santos. Thus, similar to A. sagrei in Ecuador, A. porcatus appears to be making leaps from city to city, possibly via human-aided dispersal.

If we take 2016 as the initial year of introduction, A. porcatus appears to be expanding its range at about 5 km per year and should reach the outskirts of São Paulo in another year or two if this rate holds. This introduction does not yet appear to be affecting any of the native anoles since the closest natural populations of any Anolis occur in Rio de Janeiro several hundred km to the northeast.


Figure above shows iNaturalist observations of Cuban Green Anoles in Santos, Brazil binned in three-year intervals.

When A. porcatus does reach Rio, it could begin competing with the native Amazon Green Anole (A. punctatus), which looks and behaves very similarly. The protected forested corridor along the coast means that there is no meaningful barrier to movement from São Paulo to Rio for the introduced A. porcatus at the moment. Likewise, it seems only a matter of time before A. porcatus moves southwest along the coast toward Curitiba some 200 km away.

Summary

To summarize, there have not been many instances of introduced anoles in South America for whatever reasons. Nearly all of these start near the coast, likely because invaders are hitching rides in shipping containers or other ocean transport. Right now, the most advanced invasion seems to be taking place in Guayaquil, Ecuador with more recent invasions likely taking place in French Guiana and near São Paulo. Each of these introductions appears to be in the early days of invasion with establishment only clear in and around those locations where originally observed. The expansion of introduced species seems to involve expanding within local areas of these cities and only then expanding by leaps and bounds to nearby cities after several years of establishment. With the rise of community-based observations on platforms such as iNaturalist we can make predictions about when these introduced species will arrive in nearby cities. Likewise, we can leverage the local populace for use in environmental monitoring to better understand potential invasive dynamics of these introduced species for which anoles serve as a useful model system. Whether highly invasive anoles such as A. sagrei can ever invade species-rich environments such as the Amazon or other non-coastal areas remains to be seen. Yet platforms such as iNaturalist may allow us to observe such events in real time if the community of observers can be cultivated and maintained.

Literature cited

Hoogmoed, M.S. 1980. Introduced species of reptiles in Surinam. Notes on the herpetofauna of Surinam VIII. Amphibia-Reptilia 1:277-285.

Hoogmoed, M.S., J. Lescure. 1975. An annotated checklist of the lizards of French Guiana, mainly based on two recent collections. Zoologische Mededelingen 49:141-171.

Narváez, A.E, F. Ayala-Varela, S. Cuadrado, K. Cruz-García, M.H. Yánez-Muñoz, L. Amador. 2024. Updated distribution of the brown anole in continental Ecuador: a case of urban spaces favoring the establishment of an opportunistic exotic species. BioInvasions Records 13:373-384.

Oliveira, J.C.F., T.M. Castro, M.C. Drago, D. Vrcibradic. I. Prates. 2018. A second Caribbean anole lizard species introduced to Brazil. Herpetology Notes 11:761-764.

Prates, I, L. Hernandez, R.R. Samelo, A.C. Carnaval. 2016. Molecular identification and geographic origin of an exotic anole lizard introduced to Brazil, with remarks on its natural history. South American Journal of Herpetology 11: 220-227.

Samelo, R.R., W. Barrella. 2016. Geographic distribution: Anolis porcatus (Cuban Green Anole). Herpetological Review 47:256.

Schwartz, A., R.W. Henderson. 1991. Amphibians and Reptiles of the West Indies: Descriptions, Distributions, and Natural History. Univ. Florida Press, Gainesville.

Williams, E.E. 1977. Anoles out of place. The Third Anolis Newsletter. pp. 110-118.

Two Cuban brown anoles, Anolis sagrei (Credit: Day’s Edge Productions).

By way of Georgia Tech:

Georgia Tech-led study captures two lizard species adapting in response to competition. The study provides some of the clearest evidence to date of evolution in action.

In South Florida, two Caribbean lizard species met for the first time. What followed provided some of the clearest evidence to date of evolution in action.

Lead author James Stroud, anassistant professor in the School of Biological Sciences, was studying Cuban brown anoles (Anolis sagrei) in South Florida when the Puerto Rican crested anole (Anolis cristatellus), suddenly appeared in the region.

Published in Nature Communications, the study documents what happens as the two Anolis lizards adapted in response to the new competitor, while helping to resolve a longstanding challenge in evolutionary biology — directly observing the role of natural selection in character displacement: how similar animals adapt in response to competition.

“Most of what we know about how animals change in response to this process comes from studying patterns that evolved long ago,” Stroud says. “This was a rare opportunity where we could watch evolution as it happened.”

Competition from coexistence 

While these two small, brown lizards diverged evolutionarily between 40-60 million years ago and evolved on completely separate Caribbean islands, the two species are nearly identical, and fill similar ecological niches.

So, when the Puerto Rican crested anole suddenly appeared in Cuban brown anole habitat at Fairchild Tropical Botanic Garden in 2018, the two were competing for similar habitats and food sources.

“When two similar species compete for the same resources, like food and territory, they often evolve differences that allow them to coexist,” Stroud says. But, while scientists have found many examples of similar species developing different traits to ease this overlap, “scientists have rarely been able to observe this process as it unfolds in nature.”

Stroud’s team had already been studying Cuban brown anoles at the Fairchild Tropical Botanic Gardens in Miami, Florida, two years prior to when the crested anoles invaded. The team was able to quickly pivot to observe how the invasion changed both species, analyzing the lizards’ changing diets, measuring if the lizards were moving through foliage or on the forest floor, and recording the different species’ locations relative to each other. For over a thousand lizards, they also measured perch height — the distance from the ground that the lizard is perching — a primary marker of how Anolis lizards divvy up habitat.

“We not only observed how these lizards changed their habitat use and behavior when they encountered each other,” says Stroud, “but we also documented the natural selection pressures driving their physical evolution in real-time.”

Human-made habitats and natural experiments

The research team found that when these lizard species occur together, they divide up their habitat in predictable ways — the Cuban brown anole shifted to spend more time on the ground, and evolved longer legs to run faster in this habitat, while the slightly larger Puerto Rican crested anole lived in vegetation above the ground.

“We found that brown anoles with longer legs had higher survival after crested anoles showed up,” says Stroud. “This matches perfectly with the physical differences we see in populations where these species have been living together for many generations.”

Stroud adds that while the research provides some of the strongest observations of evolution in action to date, it also demonstrates how human activities can create natural experiments that help us understand fundamental evolutionary processes — both species of Anolis lizard in the study were originally non-native to South Florida.

“As species increasingly come into contact due to human-mediated introductions and climate change, these studies may be important for predicting how communities will respond,” he says. “By studying these non-native lizards who are meeting each other for the first time in their existence, we had a unique opportunity to see the actual process unfold and connect it to the patterns we observe in nature.”

The annual meeting of the Society for Integrative and Comparative Biology (SICB) is almost here! This year’s meeting will take place in Atlanta, Georgia from January 3-7, 2025. Excitingly (albeit unsurprisingly) this year’s meeting will have a number of anole talks and posters. As we have done in previous years, we plan to have an Anole Annals blog post covering each anole talk; however, we need your help!

If you are attending SICB this year and interested in helping with our anole blogging efforts as an Anole Annals contributor, please email me (Anna Thonis). Below is a list of all anole talks taking place at this year’s meeting – be sure to check them out! 

Additionally, I encourage everyone to check out the fantastic spread of posters focused on anoles at this year’s meeting. Although we will not be blogging about each poster presentation, I am still providing a list of all anole-centric posters below. All poster sessions will take place from 3:30 – 5:30 pm in the Atrium Ballroom. 

Hope to see many of you at SICB!

Anolis nubilus. Photo by Colin Donihue.

From the pages of Popular Science.

Efforts to save Anolis nubilus have been reported previously on Anole Annals and Colin Donihue’s website.

A nearly-extinct Caribbean reptile is showing signs of a comeback following years of conservation efforts. The population of the Sombrero ground lizard (Pholidoscelis corvinus) has increased from less than 100 individuals in 2018, to over 1,600 in 2024. The huge population jump is detailed in a survey released on December 18.

Sombrero ground lizards are a small reptile that primarily eats the eggs of ground-nesting birds, corn, and other plants. It is endemic to Sombrero, the northernmost island of the Lesser Antilles and roughly 34 miles off the coast of Anguilla. This tiny Caribbean island ranks in the top three of the world’s 36 biodiversity hotspots, with several species that are only found on this 94 acre island. The colorful Sombrero Island bee, a to-be-named pygmy gecko, and the Sombrero Island wind scorpion, and numerous others all call this place home. The island also supports large seabird colonies and is designated as an Important Bird Area.

“The Critically Endangered Sombrero ground lizard is an endemic species, which means it’s found only on Sombrero Island and nowhere else in the world,” Farah Mukhida, a natural resources manager and Executive Director at Anguilla National Trust tells Popular Science. “It’s a beautiful little reptile with its black-blue scales.”

A study from 1999 estimated there were only between 396 and 461 individuals left. Sombrero Island was also once on the verge of environmental collapse. Mineral mining, a population of invasive mice, deforestation, and severe hurricanes had all taken their toll.

“That it’s managed to survive decades of phosphate mining, invasive species, and now climate change with longer periods of drought, higher temperatures, and even stronger hurricanes and storm surges that sweep over the island is absolutely astounding and shows just how resilient this lizard is,” says Mukhida.

Major conservation efforts beginning in 2021 have focused on removing the invasive mice and planting more native species on the island. Experts from the Anguilla National Trust, Fauna & Flora, and Re:wild have worked to help the Sombrero ground lizard and its island habitat recover. The lizards are showing huge signs of improvement, with their population increasing roughly 16 times in six years.

 

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“We were absolutely ecstatic when we analysed the results of our population surveys and found this enormous increase in their numbers,” says Mukhida.

The island itself has been declared pest-free and is much more green. Native plants including the sea bean, seagrape, and prickly pear are already showing healthy new growth. The  conservationists are also expressing some cautious optimism for the future.

“This is a remarkable turnaround for this cheeky and charismatic lizard but while we celebrate this recovery, we recognise that there is much more to be done to secure their future and that of other Caribbean wildlife,” Jenny Daltry, Caribbean Alliance Director, Fauna & Flora and Re:wild, said in a statement. “The combined impacts of biodiversity loss and climate breakdown are being felt with greater intensity every year in the Caribbean and around the world. Indeed, we are still busy helping our partners in Jamaica and St Vincent and the Grenadines to recover from the devastation wreaked by Hurricane Beryl earlier this year.”

Efforts will continue to preserve this biodiversity hotspot in the face of a changing landscape. One of the factors helping this recovery is the island’s distance from the mainland and fairly low number of visitors. The team plans constant vigilance to make sure they can respond quickly if more invasive rodents arrive. The continued re-wilding here will also require constant upkeep for the island’s flora, including building soil reserves and sowing additional seeds.

“These restoration interventions have cascading effects: they attract insects which help pollinate plants, they attract birds that drop seeds, they provide food and shelter for lizards that also serve as seed dispersers, pollinators, and nutrient transporters,” says Mukhida. “We’re committed to Sombrero’s recovery, sharing lessons learned, and building on successes.”

How many anoles can you find?