Research Article |
Corresponding author: Armando Sunny ( sunny.biologia@gmail.com ) Academic editor: William Magnusson
© 2024 Armando Sunny, Jaqueline Carolina Martínez-Valerio, Rene Bolom-Huet, Rosa Laura Heredia-Bobadilla, Jonas Alvarez-Lopeztello, Yuriana Gómez-Ortiz, Juan Carlos Guido-Patiño, Javier Manjarrez, María G. González-Pedroza, Hublester Domínguez-Vega.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Sunny A, Martínez-Valerio JC, Bolom-Huet R, Heredia-Bobadilla RL, Alvarez-Lopeztello J, Gómez-Ortiz Y, Guido-Patiño JC, Manjarrez J, González-Pedroza MG, Domínguez-Vega H (2024) Modelling the present and future distribution of Ambystoma altamirani in the Transmexican Volcanic Belt, Mexico. Nature Conservation 56: 275-293. https://doi.org/10.3897/natureconservation.56.139402
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Ambystoma altamirani is a critically endangered, microendemic amphibian species inhabiting the high-altitude rivers and streams of the Trans-Mexican Volcanic Belt (TMVB), a region experiencing severe ecological disturbances. This study aims to assess the current and future distribution of A. altamirani under different climate and land-use change scenarios using ecological niche modelling (ENM). We also evaluate the connectivity of suitable habitats and the overlap with existing natural protected areas (NPAs). Using occurrence records and environmental variables, we modelled the species’ potential distribution under two climate models (CN85 and MP85) for 2050. The results indicate a significant reduction in suitable habitat, particularly in areas such as the Sierra de las Cruces and the Chichinautzin Biological Corridor, with habitat losses projected to reach up to 13.95% by 2050 under the CN85 scenario. Forest cover loss between 2001 and 2023 further exacerbates this threat, especially in municipalities like Tlalpan and Ocuilan. Our analysis highlights the urgent need for targeted conservation efforts, including the preservation of mixed Abies-Pinus forests and the restoration of degraded ecosystems. The findings underscore the critical importance of integrated conservation strategies that address habitat degradation, climate resilience and ecological connectivity to ensure the long-term survival of A. altamirani.
Axolotls, Central Mexico, climate change, conservation strategies, Ecological niche modelling, habitat fragmentation, mole salamanders
Ambystoma altamirani is a critically endangered, microendemic amphibian species native to the high-altitude rivers and streams of the Transmexican Volcanic Belt (TMVB). This region, renowned for its rich biodiversity and high levels of endemism (
The TMVB, like many global biodiversity hotspots, is increasingly impacted by human activities that are driving significant biodiversity loss (
The TMVB is one of Mexico’s primary agricultural regions and the expansion of crops like corn, potatoes and oats has led to the conversion of forested land into farmland (
A total of 198 occurrence records for Ambystoma altamirani, including geographical coordinates, were collected from both fieldwork and several online databases, such as REMIB (http://www.conabio.gob.mx/remib), UNIBIO (http://unibio.unam.mx/), the Global Biodiversity Information Facility (GBIF; https://www.gbif.org), HERPNET (http://www.herpnet.net/), the Vertebrate Network (VerNet, http://vertnet.org/index.html), IREKANI (http://unibio.unam.mx/irekani/) and iNaturalist (www.iNaturalist.com.mx). To ensure consistency, only records from 2000 to 2023 were included, as significant land-use changes and climatic shifts in Mexico have primarily occurred over the last two decades. For example, between 2002 and 2019, Mexico lost 594 thousand hectares of humid primary forest, placing it amongst the top nine tropical countries in terms of primary forest loss (
Environmental niche modelling for Ambystoma altamirani was performed using the Maxent algorithm (
Land-use and vegetation projections for the year 2050 were generated using the Land Change Modeller for Ecological Sustainability (LCMES) module in IDRISI TerrSet, based on land-use and vegetation layers from 2011 (series V;
Based on the results of the ENMeval analysis, the L model with a regularisation multiplier (RM) of 1 was identified as the best-performing model for predicting the current distribution of A. altamirani in 2014, as well as its future distribution under the CN85 climate scenario in 2050. For the MP85 scenario in 2050, however, the optimal model was found to be the L model with a RM of 2 (Table
Predictive performance of present and future ENMeval distribution models for Ambystoma altamirani with two different global climate models and land-cover changes.
Year | RM | FC | 10 percentile training presence | ROC | Partial-ROC |
---|---|---|---|---|---|
2014 | 1 | L | 0.3 | 0.98 | 1.968 (p < 0.001) |
2050 cn85 | 1 | L | 0.3 | 0.98 | 1.968 (p < 0.001) |
2050 mp85 | 2 | L | 0.3 | 0.98 | 1.968 (p < 0.001) |
The most important environmental variables associated with the presence of Ambystoma altamirani.
Variable | Permutation importance | Correlation |
---|---|---|
Bio6 | 51.8 | Positive |
Abies forest | 20.3 | Positive |
Slope | 6.8 | Negative |
Altitude | 6 | Positive |
Arid vegetation | 5.6 | Negative |
Quercus forest | 4.5 | Negative |
Pinus forest | 1.9 | Positive |
Aspect | 1.6 | Negative |
Bio5 | 0.8 | Negative |
Grassland | 0.7 | Positive |
Present and future suitability area (km2) and percentage of area loss of Ambystoma altamirani with two different global climate models and land-cover changes.
60% | 10 percentile training presence | ||||||||
---|---|---|---|---|---|---|---|---|---|
2014 (km2) | 2050 cn85 (km2) | Loss 2014–2050 (%) | 2050 mp85 (km2) | Loss 2014–2050 (%) | 2014 (km2) | 2050 cn85 (km2) | Loss 2014–2050 (%) | 2050 mp85 (km2) | Loss 2014–2050 (%) |
1273.94 | 1096.22 | 13.95 | 1197.19 | 6.02 | 3410.1 | 3082.34 | 9.61 | 3248.65 | 4.73 |
Occurrence records with the block method partition, including the Ambystoma altamirani accessible area (M) represented by grey-scale elevation layer.
Response curves of the variables that influence the potential distribution of Ambystoma altamirani.
Present (2014) and future (2050) potential distribution maps for Ambystoma altamirani, generated for 2014 and under future climate scenarios CN85 and MP85 for 2050.
Gains and losses in the potential distribution of Ambystoma altamirani under two different global climate models (CN85 and MP85) and in response to land-use and vegetation cover changes.
Overall, these findings suggest that A. altamirani is highly dependent on specific environmental conditions, particularly cold temperatures and forested habitats, which are projected to be significantly reduced in the coming decades. The models also underscore the importance of protecting key habitats, especially in the Sierra de las Cruces Forest, where the species faces the greatest risk of habitat loss. Conservation strategies should focus on mitigating the effects of climate change and preserving forested areas to ensure the survival of A. altamirani in the future.
A map was generated depicting the potential distribution of A. altamirani within areas where its occurrence is known (Fig.
Present and future suitability area (km2) and percentage of area loss of Ambystoma altamirani with two different global climate models and land-cover changes in the ANPS.
60% | 10 percentile training presence | ||||||||
---|---|---|---|---|---|---|---|---|---|
2014 (km2) | 2050 cn85 (km2) | Loss 2014–2050 (%) | 2050 mp85 (km2) | Loss 2014–2050 (%) | 2014 (km2) | 2050 cn85 (km2) | Loss 2014–2050 (%) | 2050 mp85 (km2) | Loss 2014–2050 (%) |
930.88 | 810.50 | 12.93 | 883.25 | 5.12 | 2123.67 | 1951.48 | 8.11 | 2083.09 | 1.91 |
Present (2014) and future (2050) potential distribution maps for Ambystoma altamirani, considering known areas of occurrence and locations within protected natural areas, generated for the 2014 baseline and future climate scenarios CN85 and MP85 for 2050.
Percentage of forest cover lost between 2001 and 2023 within the Sierra de las Cruces and the Chichinautzin Biological Corridor, as determined using data from Global Forest Watch, considering the municipalities in the region.
The results indicate that, by 2050, both global climate models (CN85 and MP85) project a reduction in suitable habitat for A. altamirani within protected natural areas, using a 60% threshold. Under the CN85 scenario, the species is expected to experience a significant 12.93% habitat loss, whereas the MP85 model predicts a more moderate reduction of 5.12%. Additionally, using the 10 percentile training presence threshold, the CN85 model shows an 8.11% decrease in suitable habitat, with a smaller reduction of 1.91% under the MP85 scenario. These findings emphasise the considerable impact of climate change on the future availability of suitable habitats for this critically endangered species (Table
The results show varying levels of forest cover loss across four municipalities (Tlalpan, Álvaro Obregón, Jalatlaco and Ocuilan) between 2001 and 2023. Tlalpan experienced the most dramatic increase in forest loss in 2023, reaching 99.29 km2, with a smaller peak in 2022 (21.62 km2). In Álvaro Obregón, the highest deforestation occurred in 2018 (11.05 km2), followed by 2019 (9.82 km2). Jalatlaco had its most significant losses in 2018 (50.97 km2) and 2017 (21.26 km2). Ocuilan showed similarly high levels of deforestation in 2018 (63.75 km2) and 2017 (30.24 km2), with another spike in 2022 (28.56 km2).
The findings of this study underscore the significant threats faced by Ambystoma altamirani, a critically endangered amphibian, whose survival depends on highly specific environmental conditions found in the TMVB (
It is also important to consider that these distribution models are predicting potential suitable areas for the species. However, even though some regions may appear to have the necessary environmental conditions, A. altamirani is not present in many of them. This suggests that the potential distributions predicted by the models might be overestimated. Consequently, A. altamirani could be facing even greater conservation pressures than what these models suggest, given that its actual range might be more restricted than the potential range indicates. This highlights the need for targeted conservation actions that focus on both habitat protection and understanding the species’ real-world limitations within its predicted range. The loss of critical forest cover between 2011 and 2014 and continued deforestation since then have compounded the risk of extinction for A. altamirani, as these forests provide essential microhabitats that are becoming increasingly scarce (
These findings highlight the urgent need for targeted conservation actions to mitigate habitat loss and protect the remaining suitable environments for A. altamirani, especially in areas identified as high-risk through both deforestation trends and species distribution models. Likewise, these areas are known biodiversity hotspots and are critical for maintaining ecological connectivity, which is vital for the species’ survival (
Given the complex combination of threats facing A. altamirani, conservation strategies must adopt an integrated approach that addresses habitat loss, invasive species management and climate resilience. Protecting and restoring temperate forests, particularly those with a high proportion of Abies cover, is critical for maintaining viable populations (
Ambystoma altamirani is at a critical juncture, facing a confluence of threats from habitat loss, invasive species, pollution and climate change. Immediate action is required to protect its remaining habitats and ensure the long-term survival of the species. Conservation efforts must focus on habitat protection, sustainable land-use practices, invasive species management and climate adaptation strategies. By taking a holistic approach, we can help safeguard this unique species and the valuable ecosystem services it provides for future generations.
We are grateful to the editor and two anonymous reviewers for their comments. R.L.H.B was on his postdoctoral stay at UAEMex (CONACYT: 2995280/94/2022). This work was supported by the Secretary of Research and Advanced Studies (SYEA) of the Universidad Autónoma del Estado de México (Grants to AS: 4732/2019CIB and 6801/2022CID). A. S: Adahy Olun Contreras-García, te extraño mucho.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This work was supported by Universidad Autónoma del Estado de México.
All authors contributed to the study conception and design, material preparation, data collection and analysis. The first draft of the manuscript was written by Armando Sunny and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Armando Sunny https://orcid.org/0000-0003-4685-5322
Jaqueline Carolina Martínez-Valerio https://orcid.org/0009-0001-4886-7143
Rene Bolom-Huet https://orcid.org/0000-0003-3371-896X
Juan Carlos Guido-Patiño https://orcid.org/0000-0002-1662-8914
All of the data that support the findings of this study are available in the main text.