Anoles of South America Part 4: Threats, Conservation, and the Path Forward

Now that I have reviewed the diversity of South American anoles north and south of the Andes, I will discuss conservation issues in this region. I will start by identifying some of the major threats to anoles, attempt to identify what makes particular anole species vulnerable, and conclude with discussion of the path forward for work with these species.

Threats

As pointed out in the review of introduced species, the general lack of invasive species means that invasives are of relatively low concern at this time, though this could change if more introduced species become invasive. Rather, the major threats to anoles in South America are probably habitat loss and climate change.

Given that one can fly for several hours and seemingly pass over nothing but intact tracts of Amazonian forest, habitat loss seems like it should be a low concern. However, recall in previous entries in this miniseries I pointed out that many species of anoles are range restricted to just a few areas geographically. Hence, the loss of habitat in just the wrong place could wipe out an entire species in one clearcut or fire event. This is especially true for species close to or adjacent to areas with large human populations, such as southeastern Brazil or around other urban centers. For example, species occurring in the Atlantic rainforest of South America, such as Anolis neglectus, A. pseudotigrinus, A. nasofrontalis, and A. phyllorhinus, are known from only a handful a specimens and only from a handful of localities. Together, these four species have been observed a total of eight times on iNaturalist.org (n = 2, 1, 1, and 4 observations, respectively) indicating just how uncommonly encountered they are in the field.

Beyond the Atlantic Rainforest region of Brazil, another area of concern becomes the valleys coming off the Andes mountains in countries like Peru, Ecuador, Colombia, and Venezuela. Many of the species in mountain valleys only occur in one or a few places as the mountain ridges have created barriers to dispersal both enhancing speciation as well as risk of extinction. For example, a recent paper by Moreno-Arias and colleagues (2023) split Anolis heterodermus into eight separate species all occurring in different parts of the cis-Andean valleys of Colombia. Some of the ranges of these species comprise only a few hundred square kilometers in areas not far from population centers such as Bogotá, Cali, and Medellín and most of these species are only known from a handful of observations. For example, Anolis inderenae near Bogotá has only five observations on iNaturalist while Anolis vanzolini slightly to the south has only three. Even species that are seemingly more abundant are often range limited. For example Anolis chloris has nearly 200 observations on iNaturalist but only occurs in the lowland forests along the Pacific coast of Colombia and Ecuador.

Hence, range-restricted species are probably at greatest risk throughout South America. However, small geographic distribution is not the only thing that threatens lizards of South America. Other factors such as governmental policy can either protect or threaten species.

Policy changes and their impact on local diversity has been well documented including in South America. For example, in the late 1970’s the Brazilian state of Rondonia was opened to colonization for the development of new farmland. As such, deforestation there occurred at an accelerating rate (see data and imagery). The deforestation in the western Amazon dramatically impacted natural environments on which many anole species depend (Fearnside 1982, Fearnside and de Lima Ferreira 1984). This is especially important given the enhanced extinction risk associated with forest-dwelling species (e.g., Cox et al. 2022), which describes many, if not most, anole species. So clearly, establishing protected areas can be of value as well as generally trying to reduce habitat loss.

Another major issue that is only going to grow in importance in future years is climate change. In recent years numerous papers have pointed out the risk of a changing thermal environment on lizards as regions experience both increased temperatures and variation in temperatures. Several papers stand out for discussion (e.g., Huey et al. 2009, Sinervo et al. 2010, Caetano et al. 2022, Cox et al. 2022). For example, in 2020, Diele-Viegas and colleagues pointed out that most lizard clades are vulnerable to extinction despite associated geographic distributions or local climate conditions. Their meta-analysis revealed that Neotropical regions of South and Central America were most at risk of climate-related extinctions. Given that tropical regions have the highest species diversity in general, this is not too surprising. However, vulnerability is hard to assess given that not every species was evaluated for risk. For anoles, only 98 of 427 species were evaluated as part of Diele-Viegas et al. (2010), yet their larger taxonomic clade (Iguania) was considered to be vulnerable in the Neotropical biogeographic realm unlike the Anguimorpha and Gekkota.

So at least some recent meta-analyses suggest anoles are at risk. However, some of the projections from other studies differ slightly with regards to when or where risk will occur. For example, many of the most vulnerable species or clades of lizard occur in low latitudes (Ceballos et al. 2017). However, extreme temperatures are most expected in mid-latitude regions, not the tropics (Murali et al. 2023). Murali and colleagues (2023) reported that 11.9% of environments were predicted to experience extreme thermal conditions for half the year by 2099. Another study (Cosendey et al. 2023) identified species as most at risk if they were tropical, viviparous, thermo-conformers. While not viviparous, the tropical thermo-conforming anoles (which pretty much describes all anoles in South America) are among the clades that are likely at greater risk than, say, desert reptiles. This is because desert reptiles are thought to be pre-adapted to thermal stress (Murali et al. 2023). Though not without controversy, some early projections indicate that by 2080 lizard extinction could reach 20% of all species globally (Sinervo et al. 2010), which would easily qualify as a mass extinction event.

The Path Forward

Clearly anoles are at risk, and probably not just the range-limited uncommon or rare species, but even the abundant, widespread species are at some level elevated risk of extinction in coming decades or centuries. So, what conservation measures are called for and what can be done?

Some of the fixes are seemingly obvious regarding reducing the rate of deforestation and enacting strong protective policies to enable conservation of species. However, it is beyond the scope of this post to review all of the possible ways that conservation measures can be enacted. Yet, because I’ve drawn on iNaturalist.org as a site from which species distributions and occurrence data can be inferred, I take this opportunity to point out that iNaturalist and sites like it are in essence community-sourced environmental monitoring that deserves further consideration.

Obviously, demonstrating extinctions such as those predicted above becomes a gargantuan task given the number of species involved and the geographic scope of a global phenomenon such as ongoing environmental alterations. Yet, I firmly believe that with sufficient data provided by community-scientists, such as those who contribute to iNaturalist, it may be possible observe extinctions in real time. Generally, organizations such as the International Union for the Conservation of Nature (IUCN) require censuses be conducted that fail to detect a species for a set amount of time, such as 10 years. However, proving the negative is especially challenging even with a 10-year requirement. As such, species are reported rediscovered from time-to-time mostly because of the poor quality of information regarding species occurrence and the difficulty in demonstrating that something has actually gone extinct for good rather than just occurs at really, really low abundances. As an example, I offer the story of the Golden Toad ([=Bufo] periglenes).

The disappearance and eventual extinction of the Golden Toad is a testament to the difficulty of proving cause-and-effect relationships in science related to extinction. In the late 1980’s, Golden Toads disappeared from their habitat in Costa Rica pretty much from one year to the next. This was part of a global phenomenon of amphibian declines that were poorly understood at the outset (Barinaga 1990). At the time, it was unclear if this was a merely part of a natural fluctuation (populations do go up AND down, afterall) or actual decline and/or loss of populations and species (Pechmann et al. 1991). Part of the problem was general lack of long-term species or environmental monitoring, so inferences were being made from snapshot short-term data.

It wasn’t for another decade that one of the first studies developed causal mechanisms for the disappearance of Golden Toads despite exhaustive efforts at rediscovering the species (Pounds 2001). In that study, Pounds implicated a particularly strong El Niño event that caused alterations in the cloud forest habitat of the Golden Toad and subsequent reproductive failure. Additional research continues to clarify events such as this (Anchukaitis and Evans 2010) and the causal links of factors such as the emergence of the amphibian-specific chytrid fungus continue to aid our understanding of these extinctions (Lips et al. 2005, 2008), but only in retrospect.

The point of the Golden Toad’s demise is this, extraordinary claims, such as a species extinction, require extraordinary evidence and often this is hard to obtain given the limitations of funding, time, and effort. Hence, harnessing the power of a community of naturalists to make observations of the occurrence of species and to use these observations in an attempt to document the continued persistence of or loss of species is laudable despite the pitfalls present in the available data.

The limitations of existing datasets are many. In particular, iNaturalist is not an organized effort by the community and rather haphazard in the species observed. There is no one guiding the efforts of observers to go out and document certain species, though I have found that engaging the community and providing direction can be a useful exercise. In general, I find iNaturalist to be populated by well-meaning and interested observers who want to help, but often don’t know how to help.

Another limitation is that the data on iNaturalist often do not reflect the abundance of species. Observers may see several of a species, but only post one observation. Cryptic species may go unnoticed. In short, effort is entirely uncontrolled for on iNaturalist meaning one can never be sure that the lack of observations means a species is absent, or just overlooked.

Despite these major known limitations, macro-fauna and flora, such as lizards, including anoles, are well represented on this site because of their visibility as well as the presence of a healthy tourist industry in certain select places (e.g., Ecuador, Peru, French Guiana all seem to have a well-developed tourist infrastructure). Hence, identifying the species present in those areas today, monitoring their occupancy at those sites into the future, and attempting to document when and where species just stop being observed is not outside the realm of possibility if professional biologists are willing to invest in the endeavor.

How can you or anyone invest in the endeavor? Contribute your observations. This is the fodder for all of the biological knowledge and if you have a photo library from fieldwork or other trips, you in essence are helping create a baseline knowledge of where and when things occurred now before the environmental alterations affected the species of interest

Another way to help is by learning to identify observations on iNaturalist. This site has no paid identifiers and any identifications are done on an opt-in basis. Your knowledge about how to recognize and identify certain taxa can help purify the data pool for scientific studies. Are the data created by iNaturalist perfect? Decidedly not (Zani 2024), but they are of a quality that can be improved by the community of observers and identifiers that is willing to invest time and effort for this endeavor. Some institutions are recognizing this and allowing faculty and staff to count observing and identifying under “service to the profession”. As of right now, iNaturalist contributes nearly half the records reported by the Global Biodiversity Information Facility (GBIF). In terms of anoles, as of this writing iNaturalist currently reports 310,000 records of 364 anole species while GBIF report 462,000 records of 455 species. In other words, iNaturalist currently accounts for about 2/3 of the Anolis records on GBIF.

Hence, there are benefits to the data from sites such as iNaturalist beyond just the monitoring for novel introduced species such as the natural movements of species, the biological timing of events, and the presence/absence of species in any one area. Are there pitfalls and limitations? Absolutely, but getting involved in a community such as iNaturalist as on observer or as an identifier has value in that it provided the fodder for future scientific investigation related to species conservation that we are only just beginning to understand.

Literature cited

Anchukaitis, K. J., and M. N. Evans. 2010. Tropical cloud forest climate variability and the demise of the Monteverde golden toad. Proceedings of the National Academy of Sciences, USA 107:5036-5040.

Barinaga, M. 1990. Where have all the froggies gone? Science 247: 1033-1034.

Caetano, G. H. d. O., D. G. Chapple, R. Grenyer, T. Raz, J. Rosenblatt, R. Tingley, M. Böhm, S. Meiri, and U. Roll. 2022. Automated assessment reveals that the extinction risk of reptiles is widely underestimated across space and phylogeny. PLoS Biology e3001544.

Ceballos, G., P. R. Ehrlich, and R. Dirzo. 2017. Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines. Proceedings of the National Academy of Sciences, USA 114:E6089-E6096.

Cosendey, B. N., C. F. D. Rocha, and V. A. Menezes. 2022. Climate change, lizard populations, and species vulnerability/persistence: trends in ecological and predictive climate studies. Environment, Development and Sustainability.

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Fearnside, P. M., and G. de Lima Ferreira. 1984. Roads in Rondonia: highway construction and the farce of unprotected reserves in Brazil’s Amazonian forest. Environmental Conservation:358-360.

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Lips, K. R., P. A. Burrowes, and J. R. M. III. 2005. Amphibian population declines in Latin America: a synthesis. Biotropica 37:222-226.

Lips, K. R., J. Diffendorfer, J. R. M. III, and M. W. Sears. 2008. Riding the wave: reconciling the roles of disease and climate change in amphibian declines. PLoS Biology 6:441-454.

Mi, C., L. Ma, Y. Wang, D. Wu, W. Du, and B. Sun. 2022. Temperate and tropical lizards are vulnerable to climate warming due to increased water loss and heat stress. Proceedings of the Royal Society B 289:20221074.

Moreno-Arias, R. A., M. A. Méndez-Galeano, I. Beltrán, and M. Vargas-Ramírez. 2023. Revealing anole diversity in the highlands of the Northern Andes: new and resurrected species of the Anolis heterodermus species group. Vertebrate Zoology 73:161-188.

Murali, G., T. Iwamura, S. Meiri, and U. Roll. 2023. Future temperature extremes threaten land vertebrates. Journal of Heredity 615:461-467.

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Sinervo, B., F. Méndez-de-la-Cruz, D. B. Miles, B. Heulin, E. Bastiaans, M. V.-S. Cruz, R. Lara-Resendiz, N. Martínez-Méndez, M. L. Calderón-Espinoza, R. N. Meza-Lázaro, H. Gadsden, L. J. Avila, M. Morando, I. J. D. l. Riva, P. V. Sepulveda, C. F. D. Rocha, N. Ibargüengoytía, C. A. Puntriano, M. Massot, V. Lepetz, T. A. Oksanen, D. G. Chapple, A. M. Bauer, W. R. Branch, J. Clobert, and J. J. W. Sites. 2010. Erosion of lizard diversity by climate change and altered thermal niches. Science 328:894-899.

Zani, P. A. 2024. Accuracy of iNaturalist identifications: a test using a geographically ubiquitous and variable species of lizard. Herpetological Review 55:157-162.