Effect of habitat fragmentation on reptile diversity of an orographic island in the Argentinean Pampas

Abstract

Habitat fragmentation is one of the main threats to biodiversity. Studying biodiversity is also useful for evaluating the impacts of anthropogenic activities and guiding conservation decisions. We evaluated the effects of habitat fragmentation on reptile diversity in the Tandilia Mountains, a landscape of isolated grassland patches embedded in an agricultural matrix. Seven isolated patches of native grassland were characterized in terms of their spatial characteristics, land use, and diversity. Then a SIMPER analysis and rank-abundance curves were performed to estimate dissimilarity between patches. A Canonical Correspondence Analysis was conducted to understand how the characteristics of the grassland patches influence reptile species presence. A total of 20 species were found in the selected patches. Amphisbaena kingii, Epictia munoai, and Liolaemus tandiliensis were the most abundant and dominant species. The highest reptile diversity was found in the patches more connected, with low border effect and more native grassland. This study highlights the need to prevent further fragmentation of the remaining grasslands to conserve reptile diversity of Tandilia Mountains. Protecting their habitats could provide umbrella protection to other less-documented or cryptic taxa within the same ecosystems.

Key words
Conservation biology; Lizards; Native grasslands; Snakes

INTRODUCTION

Habitat fragmentation is recognized as one of the main threats to biodiversity (Yuan et al. 2024). It breaks continuous habitats into isolated patches altering environmental factors such as solar radiation, wind, and hydrological regimes, permanently transforming landscape (Wilcox & Soule 1980, Saunders et al. 1991). One of the main biological consequences of habitat fragmentation is that the resulting remnants may be unable to sustain viable populations of many species (Bilenca & Miñarro 2004). Species with specialized habitat requirements are particularly vulnerable, as they have evolved over millions of years to occupy specific environments (Hibbitts et al. 2009).

Agricultural landscapes typically comprise a matrix of croplands interspersed with patches of natural vegetation located in areas unsuitable for cultivation (Tscharntke et al. 2005). These landscapes, shaped by intensive agricultural practices, contribute to the modification and fragmentation of habitats (Herrera et al. 2022). In such landscapes, native grasslands remain as isolated patches, and this transformation can have severe consequences for biodiversity (Haddad et al. 2015, Wilson et al. 2016). These patches become the only suitable habitat for many native species and are exposed to physical changes, the magnitude of which depends mainly on their shape, size, and position within the landscape (Saunders et al. 1991).

The characteristics of habitat remnants (hereafter, used interchangeably with relict, and patch) are key to maintaining local biodiversity (MacArthur & Wilson 1967, Simberloff 1986), as they influence habitat connectivity, diversity and susceptibility to external changes (Saunders et al. 1991). According to the theory of island biogeography, larger areas tend to support more habitats and thus greater number of species (MacArthur & Wilson 1967). However, this is not always the case. Simberloff (1986) argued that a network of smaller patches might contain a broader variety of habitats than a single large area, which may not encompass all habitat types present in a region. Moreover, irregularly shaped patches are more exposed to changes in the surrounding matrix (Williamson 1975). The spatial arrangement of patches is also important, as proximity to other remnants enhances landscape connectivity, facilitating species and supporting biodiversity conservation (Tischendorf & Fahrig 2000). In contrast, human disturbances, such as roads, urbanization, and agriculture, contribute to further fragmentation and reduce habitat quality (Saunders et al. 1991, Noss 1993, Primack et al. 2001). Additionally, invasive exotic plants negatively impact native vegetation, by exerting propagule pressure, reducing habitat suitability, altering ecosystem structure, and disrupting nutrient cycles (Richardson 1998, Ferdinands et al. 2005). Consequently, landscapes with high human disturbance and fragmented, irregular or poorly connected patches are likely to harbor lower biodiversity.

Assessing biodiversity is essential for understanding the structure and function of ecological communities or assemblages (Dodd 2016). Moreover, measuring biological diversity in both natural and disturbed habitats, and comparing patterns across sites, allows researchers to monitor the effects of environmental change. Biodiversity metrics are also useful for evaluating the impacts of anthropogenic activities and guiding conservation decisions (Magurran 1988, Snodgrass et al. 2000, Moreno 2001, Urbina-Cardona et al. 2008). Reptiles are considered valuable model organisms in ecological studies due to their roles as predators and prey, and their relatively limited dispersal ability (Pianka 1986, Dodd 2016). Their sensitivity to environmental change also makes them useful surrogate group (Lewandowski et al. 2010). However, compared to other vertebrate groups, reptile ecology remains underexplored (Dodd 2016).

In this study, we evaluated the effects of habitat fragmentation on reptile diversity in the Tandilia Mountains, a landscape of isolated grassland patches embedded in an agricultural matrix. This region harbors high biodiversity including endemic plant and animal species. (Bilenca & Miñarro 2004, Herrera et al. 2019, Vera et al. 2021, Aranguren et al. 2023, Trofino Falasco et al. 2023). Despite this, reptile diversity in the area has not been studied, with only general species lists available (Nágera 1915, Vega & Bellagamba 1990, Vera et al. 2021). Moreover, recent studies highlighted the need to investigate how the spatial characteristics of grassland remnants influence the reptile communities they support (Vera et al. 2025). We hypothesize that more fragmented patches (i.e. smaller, more irregular in shape, isolated, heavily impacted by agriculture, and invaded by exotic vegetation) will support lower reptile diversity than larger, more regular, and better connected patches. Therefore, our objectives were: i) Spatially characterize a set of grassland remnants in the Tandilia Mountains and estimate their reptile diversity; ii) establish diversity patterns among the different grassland remnants; iii) identify spatial and environmental characteristics associated with reptile diversity.

MATERIALS AND METHODS

Study area

Tandilia Mountains extend for approximately 350 km in the southern portion of the Pampas ecoregion, one of the most significant grassland regions of the world (Dalla Salda et al. 2006). These mountains are composed of igneous and metamorphic rocks overlain by loess deposits (Teruggi & Kilmurray 1980, Dalla Salda 1999). The climate is temperate, with an average temperature of 21°C in the warmest month and 6.3°C in the coldest. Mean annual precipitation approximately is 850 mm (Valicenti et al. 2010).

Native vegetation consists of a grassland steppe dominated by genera such as Stipa, Piptochaetium, Paspalum, Festuca, and Poa with patches of shrubs (Colletia paradoxa, Baccharis, Eupatorium) and ferns (Anemia tomentosa and Pellaea ternifolia) (De la Sota 1967, Cabrera 1971, Valicenti et al. 2010). The Tandilia highland grasslands host several endemic species, including shrubs (Baccharis tandiliensis), herbs (Lepidium tandilense) (Bilenca & Miñarro 2004, Herrera et al. 2019), and amphibians such as Darwin’s blackish toad (Melanophryniscus nigricans) (Martínez-Aguirre et al. 2021). However, some remnants are affected by invasive woody species, such as Pinus sp., Spartium junceun, Acacia melanoxylon, Genista monspessulana, and Rubus ulmifolius (Márquez et al. 2019).

Data collection

We selected seven sites across the Tandilia Mountains: Ranch Las Mercedes (sites I and II), Trébol de 4 hojas Private Field, Ánimas Mountain, Sierra del Tigre Natural Reserve, Boca de la Sierra Natural Reserve, and Paititi Private Natural Reserve (Fig. 1). These sites represent isolated patches of native grassland. Site selection was based on logistical feasibility, accessibility, and variation in spatial and environmental conditions. Reptile sampling followed a standardized protocol, although effort varied slightly among remnants (i.e., mean ± SD = 17.4 ± 9.2 days). Surveys were carried out using visual encounter surveys (VES) conducted along linear transects, each 500 meters long and 30 meters wide, encompassing all available habitat types (Crump & Scott 1994). Sampling took place between 11:00 and 18:00 during 21 campaigns, each lasting an average of 6 days and involving approximately three observers per day. This effort totaled 138 sampling days and 889 hours of observation (equivalent to 2667 person-hours). In addition to standard VES, we conducted active searches under natural and artificial cover objects -such as logs, rocks, firewood piles. and discarded construction materials- to detect cryptic and fossorial species. The GPS coordinates of each reptile encounter were recorded using a Garmin eTrex 20 GPS (unit with an accuracy of <5 m).

Figure 1
Study area from the Tandilia Mountains. Red polygons: selected grassland patches; 1: Ánimas Mountain; 2: Boca de la Sierra; 3: Ranch Las Mercedes I; 4: Ranch Las Mercedes II; 5: Paititi; 6: Sierra del Tigre; 7: Trébol de 4 Hojas.

Spatial and land use characterization of the sites

For each site, a series of spatial characteristics (i.e., area, connectivity, and shape index) and environmental covariates related to land use (exotic vegetation cover, habitat cover, and agricultural cover) were estimated. All these covariates were processed, measured, and estimated using QGIS 3.30.3 software (QGIS Development Team 2022). The shape index (SI) was calculated using the following formula:

$$SI=0.282\ast \text{perimeter}/\sqrt{\text{area}}$$

where 0.282 is a correction factor such that adjusts the index so that a perfectly circular patch approaches a value of 1 (Usher et al. 1992). This index indicates the edge effect of each remnant. Higher SI values shape index value indicate more irregular shapes and greater edge effect, while lower values suggest more compact and less exposed remnants. Connectivity of each grassland remnant was estimated using the modified Lin Index (2009). This index considers the distance and area of the patches to a given grassland remnant:

$$CI=\sum Ai\ast (1/Di)$$

where Ai and Di are the area and the distance from a given remnant to each of its nearest neighbors. In other words, distance penalizes and larger area size benefits connectivity. The connectivity index was standardized using the following formula:

$$CIs=(xi-\overline{x})/SD$$

where xi is the connectivity value of a given patch,  is the mean of all the connectivity values, and SD is the standard deviation. Land use data were obtained from the MapBiomas Pampa Initiative project website (Baeza et al. 2022). Then, the satellite image downloaded was processed in QGIS 3.30.3 to estimate the percentage of each land use type (exotic vegetation, habitat, and agriculture/pasture) in each grassland remnant.

Alpha diversity

To describe the reptile assemblages of each grassland remnant, we calculated species richness and relative abundance (i.e., the proportion of individuals of a species relative to the total individuals at the site). Species richness was based on the total count of species per site. This approach is suitable for small habitats and has been widely used in studies of mammals, reptiles and fish in temperate zones (Krebs 1989). Captured individuals were marked to avoid overcounting and to enable the estimation of species abundance. Marking methods followed Crump & Scott (1994) and Lobos et al. (2013) and were selected based on individual size and weight: a) PIT tag nanochip (passive integrated transponder) when the nanochip did not exceed 2-3% of the animal’s weight; b) scale cauterization was used when the chip weight exceeded this threshold.

The following diversity indexes were calculated using PAST 3.14 software (Hammer et al. 2001). The Simpson’s Dominance Index, ranges from 0 (all species equally present) to 1 (one species dominates). The Shannon-Wiener diversity a widely used heterogeneity index sensitive to rare species (Krebs 1989). One common issue in the literature regarding the Shannon-Wiener index is its unit type, which is a measure of system entropy, making its interpretation and comparison difficult (Krebs 1989, Moreno 2001). Hill numbers were also calculated to express diversity in terms of the effective numbers of species (Hill 1973). They were calculated for each grassland remnant (N0 = species richness; N1 = number of equally abundant species (exponential (H’)), N2 = number of very abundant species (1/D)). This series of numbers measures the effective number of species in a sample, where each species is weighted by its abundance (Moreno 2001). As the number of species increases, less weight is given to rare species, resulting in lower values for N1 and N2 (Hill 1973). Pielou’s evenness index was used to evaluate the evenness of species distribution at each site. Values range from 0 to 1, where 1 indicates that all species are equally abundant (Magurran 1988, Moreno 2001).

Diversity patterns

We conducted a similarity percentage analysis (SIMPER) in PAST 3.14 software to assess beta diversity. This analysis identifies the species contributing most to the dissimilarity among the grassland remnants (Clarke 1993). An Analysis of Similarities (ANOSIM), a non-parametric test, was used to evaluates whether observed differences in species composition between sites were statistically significant (Clarke 1993). In addition, we plotted rank-abundance curves to visualize abundance distribution patterns across remnants (Urbina-Cardona et al. 2006).

Remnant characteristics and reptile diversity

We performed a Canonical Correspondence Analysis (CCA) to understand the relationship between reptile species and environmental characteristics of grassland remnants. The analysis used two matrices: 1) Site x Species matrix, including the abundance of each species recorded at the seven sites; 2) Site x Environmental Covariates matrix, including area, connectivity, shape index, and land cover percentages (exotic vegetation, habitat, and agriculture). CCA allows for the identification of species-environment relationships and helps infer which environmental gradients influence species distribution patterns (Legendre & Legendre 1998). The analysis was conducted using PAST 3.14 software.

RESULTS

Spatial and land use characterization of the sites

The spatial and land use characteristics differed across the selected sites (Table I): Ánimas Mountain exhibited the highest percentage of exotic vegetation, cover, indicating a significant degree of invasion. Ranch Las Mercedes I was the smallest grassland remnant in terms of area, while the Paititi remnant was the largest. This latter site also had the highest shape index value, suggesting a more irregular and fragmented outline. In contrast, Ranch Las Mercedes I showed the highest connectivity index and the lowest shape index, suggesting a more compact shape and stronger connection to nearby grassland remnants.

Table I
Landscape features (area, CI: connectivity index, SI: shape index) and land use coverage of the selected grassland remnants in Tandilia Mountains.

Site	Area	CI	SI	Habitat (%)	Exotic vegetation (%)	Agriculture (%)
Ánimas Mountain	1857	-0.27	2.2	76.9	22.8	0.3
Boca de la Sierra	2044	-0.28	3.6	92.9	3.4	3.7
Ranch Las Mercedes I	43	1.99	1.2	87.6	11.8	0.6
Ranch Las Mercedes II	156	0.21	2.3	92.1	7.3	0.7
Paititi	5819	-1.29	4.8	64.0	22.3	13.7
Sierra del Tigre	2221	-0.41	3.7	81.0	17.6	1.5
Trébol de 4 Hojas	127	0.05	2.5	95.3	1.7	3.0

Alpha diversity

We obtained 628 reptile records corresponding to 20 different species (Fig. 2, Table II). The most abundant species was Amphisbaena kingii (N=160), representing 25.5% of all the individuals recorded. It was followed by Epictia munoai (N=146, 23.2%) and Liolaemus tandiliensis (N=92, 14.6%). Six species were found at very low frequencies, each representing less than 1% of total individuals (N<6): Amphisbaena angustifrons, Liolaemus absconditus, Lygophis anomalus, Ophiodes vertebralis, Tachymenis ocellata, and Xenodon dorbignyi.

Table II
Reptile species at each remnant (they were numbered as in the Figure 1) in Tandilia Mountains.

Species	Reference	Sites
Amphisbaena angustifrons	Aa	2,5
Amphisbaena darwinii	Ad	3,4,7
Amphisbaena kingii	Ak	1,2,3,4,5,6,7
Bothrops alternatus	Ba	1,2,3,4,6,7
Contomastix celata	Cc	2
Epictia munoai	Em	1,2,3,4,6,7
Erythrolamprus poecilogyrus	Ep	1,3,5
Liolaemus absconditus	La	5
Liolaemus tandiliensis	Lt	1,2,5,6,7
Lygophis anomalus	Lya	3
Ophiodes vertebralis	Ov	1,3,4
Oxyrhopus rhombifer	Or	2,3,4,5
Paraphimophis rusticus	Pr	3,4,5
Phalotris spegazzinii	Ps	1,3,4,5,6
Philodryas agassizii	Pa	3,4,6
Philodryas patagoniensis	Pp	1,3,4,6
Salvator merianae	Sm	1,2,3,6,7
Teius oculatus	To	1,2,6
Tachymenis ocellata	Tao	3,4
Xenodon dorbignyi	Xd	2,6

Figure 2
Reptile abundance of species in the studied patches of the Tandilia Mountains.

Ranch Las Mercedes I had the highest abundance of reptiles and accounted for 70% of the total species richness (14 out of 20 species), followed by Ranch Las Mercedes II, with hosted 55% of the species (11 out of 20 species; Table III). The alpha diversity indexes indicate that the sites Trébol de 4 Hojas and Ranch Las Mercedes I are at opposite ends: the former showed the lowest species evenness and diversity, while the latter presented the highest diversity and more uniform distribution of individuals among species. Similarly, Hill numbers reflected the presence of approximately two very abundant species in Trébol de 4 Hojas, whereas Ranch Las Mercedes I showed a higher effective diversity, with about six very abundant species.

Table III
Alpha diversity of reptiles from the studied patches in the Tandilia Mountains.

	Ánimas Mountain	Boca de la Sierra	Ranch Las Mercedes I	Ranch Las Mercedes II	Paititi	Sierra del Tigre	Trébol de 4 Hojas
Specific richness	10	10	14	11	8	10	6
Abundance	63	89	199	114	64	62	37
Simpson’s Dominance	0.3	0.3	0.2	0.2	0.4	0.2	0.6
Shannon-Wiener	1.7	1.4	2.1	1.7	1.3	1.8	1.0
Pielou’s Eveness	0.7	0.6	0.8	0.7	0.6	0.8	0.5
N0	10	10	14	11	8	10	6
N1	5.6	4.1	8.1	5.6	3.6	6.1	2.6
N2	3.7	2.9	6.3	4.0	2.5	4.1	1.8

Diversity patterns

The SIMPER analysis identified eight species contributing to the dissimilarity among sites: Amphisbaena darwinii, Amphisbaena kingii, Epictia munoai, Liolaemus tandiliensis, Paraphimophis rusticus, Philodryas patagoniensis, Salvator merianae, and Teius oculatus. ANOSIM results revealed significant differences in species composition across 14 site pairs (Table IV). Notably, Trébol de 4 Hojas differed significantly from all other sites, while Ranch Las Mercedes I showed significant differences from all sites except Ranch Las Mercedes II.

Table IV
SIMPER and ANOSIM results of reptiles from the studied patches in the Tandilia Mountains.

Sites	Sierra del Tigre	Ánimas Mountain	Ranch Las Mercedes I	Ranch Las Mercedes II	Boca de la Sierra	Trébol de 4 Hojas	Paititi
Sierra del Tigre		Ak; To; Pp; Lt 77,11%	Ak; Pp´; Em; Ad; Lt 72,81%	Ak; Em; Pr; Pp; Ad 72,33%	Lt; Em; Ak 70,59%	Em; Ak; Lt; Sm 75,4%	Lt; Ak; Pp 75,21%
Ánimas Mountain	R= 0,006 p= 0,338		Ak; Pp; Em; Ad; To 74,46%	Ak; Em; Pr; To; Ad 72%	Lt; Em; Ak 70,78%	Em; Ak; To; Sm 77,71%	Lt; Ak; To 75,45%
Ranch Las Mercedes I	R= 0,195 p< 0,05	R= 0,198 p< 0,05		Ak; Em; Ad; Pp 71,72%	Lt; Em; Ak; Pp; Sm 75,62%	Em; Ad; Pp; Ak 72,83%	Lt; Ak; Em; Pp; Ad 78,82%
Ranch Las Mercedes II	R= 0,009 p= 0,368	R= 0,038 p= 0,237	R= 0,049 p= 0,252		Lt; Em; Ak; Sm 73,75%	Em; Ak; Ad; Pr 75,49%	Lt; Ak; Em 70,4%
Boca de la Sierra	R= 0,094 p= 0,064	R= 0,378 p< 0,05	R= 0,407 p< 0,05	R= 0,525 p< 0,05		Lt; Em 72,77%	Lt; Em; Ak 71,64%
Trébol de 4 Hojas	R= 0,123 p< 0,05	R= 0,308 p< 0,05	R= 0,194 p< 0,05	R= 0,202 p< 0,05	R= 0,252 p< 0,05		Lt; Em; Ak 78,99%
Paititi	R= 0,078 p= 0,071	R= 0,280 p< 0,05	R= 0,463 p< 0,05	R= 0,432 p< 0,05	R= 0,099 p= 0,053	R= 0,479 p< 0,05

• Above the diagonal the species that contributes to the dissimilitude between pairs of sites with accumulated value >70% are indicated; below the diagonal the R statistic and p values are indicated. See the species references in Table II.

The rank-abundance curves highlighted differences in reptile assemblage structures among the studied sites (Fig. 3). Amphisbaena kingii was dominant in three sites (Sierra del Tigre, Ánimas Mountain, and Ranch Las Mercedes I), while Liolaemus tandiliensis was the most abundant species in Boca de la Sierra and Paititi remnants. Epictia munoai prevailed in Ranch Las Mercedes II and Trébol de 4 Hojas. Among snakes, Philodryas patagoniensis was particularly dominant in Ánimas Mountain and Sierra del Tigre. In contrast, amphisbaenians were among the least abundant reptile groups in Boca de la Sierra. Amphisbaena darwinii was restricted to three remnants: Ranch Las Mercedes (I and II) and Trébol de 4 Hojas, and surpassed Amphisbaena kingii in abundance in the latter. Ophiodes vertebralis was the only small-sized lizard observed in Ranch Las Mercedes I and II, albeit with very low abundance. Similarly, the small snake Tachymenis ocellata appeared exclusively in these two patches and was rarely detected. Regarding lizard dominance, Liolaemus tandiliensis led in Boca de la Sierra, Paititi, and Sierra del Tigre. However, Teius oculatus was notably more abundant in Ánimas Mountain. Salvator merianae stood out as one of the most abundant reptiles in the Trébol de 4 Hojas.

Figure 3
Rank–abundance curves for reptile assemblages in the Tandilia Mountains. Each panel represents a grassland patch, with abundances shown on a log10 scale (ni = individuals of species i; N = total individuals).

Remnant characteristics and reptile diversity

The highest levels of reptile diversity were associated with remnants exhibiting high habitat connectivity, low shape index and a greater portion of native habitat, as observed in Ranch Las Mercedes I and II (Fig. 4). In contrast, patches such as Boca de la Sierra and Paititi, characterized by elevated shape index values, increased exotic vegetation cover, and relatively high agricultural land use, presented lower reptile diversity and uniformity, likely due to their reduced habitat integrity and connectivity. The Trébol de 4 Hojas remnant presented an intermediate scenario: although it possessed relatively good habitat, its small size, moderated shape index and low connectivity likely restrained species richness and assemblage evenness.

Figure 4
Remnant characteristics and reptile diversity. Arrows: environmental covariates; AGRI: agriculture cover; AREA: patch area; CI: connectivity index; EXO: exotic vegetation; HAB: habitat cover; SI: shape index; blue dots: grassland remnants (see the references in Fig. 1). See the species references in Table II.

DISCUSSION

This is the first study addressing a complete analysis of reptile diversity in the Tandilia Mountains. Moreover, we assessed the influence of habitat fragmentation on reptile diversity by analyzing edge effect, area, connectivity, and land use of each grassland remnant. As a result of our fieldwork, we found 20 species across seven grassland remnants.

The reptile assemblage showed a clear dominance of a few highly abundant species over several rare ones, in line with the ecological theory of the logarithmic series (Fisher et al. 1943, Krebs 1989). This pattern is also consistent with other snake study in a similar mountain range (i.e., Ventania Mountains) where only five out of 15 species were found to be very abundant (Bothrops alternatus, Epictia australis, Erythrolamprus poecilogyrus, Lygophis elegantissimus, and Philodryas patagoniensis) (Di Pietro et al. 2018). Our results contrast with those from Ventania mountain range, where Epictia australis was one of the most abundant snakes and Epictia munoai was found at low frequencies (Di Pietro et al. 2018). Another difference with Di Pietro et al. (2018), is that Bothrops alternatus and Erythrolamprus poecilogyrus, which were highly abundant in Ventania, are not dominant in our study area. Liolaemus tandiliensis was the most abundant species among lizards, and Liolaemus absconditus was found only occasionally, agreeing with the findings of Vega & Bellagamba (1990). Unlike what was Vega & Bellagamba (1990) reported, Philodryas patagoniensis is very frequent in the area. The absence of small- sized lizards in Ranch Las Mercedes I and II, and their presence in the other patches, is notable and should be addressed in future research by exploring other factors, such as habitat type.

According to the theory of island biogeography (MacArthur & Wilson 1967), larger areas tend to support more species. However, when comparing grassland remnants in the Tandilia Mountains, Ranch Las Mercedes I and II exhibit higher reptile diversity, whereas Ánimas Mountain, Boca de la Sierra, Paititi, and Sierra del Tigre encompass larger areas but show lower diversity. Ranch Las Mercedes I and II exhibit a higher connectivity, greater habitat cover, and lower edge effects, supporting greater reptile diversity. Therefore, the reptile diversity in Tandilia Mountains is influenced not only by remnant area, but also by connectivity, edge effect and land use. Other taxonomic groups are likely to respond similarly to habitat fragmentation in this region. These findings also have important implications for land-use planning in the Tandilia Mountains. Maintaining habitat corridors and minimizing land conversion near high-value remnants, such as Ranch Las Mercedes I, could help preserve connectivity and mitigate biodiversity loss. Integrating biodiversity metrics into local development strategies may enhance the long-term conservation of native grassland ecosystems. To confirm this hypothesis, future studies should examine biodiversity patterns across the entire mountain system.

While our study emphasizes the role of landscape-level variables such as area, connectivity, and land use in shaping reptile diversity, future research should also consider other ecological and historical factors that may influence species assemblages. Microhabitat structure, vegetation complexity, availability of refuges (e.g., rocks, logs), and soil characteristics can strongly affect reptile presence and abundance. In addition, incorporating the land-use history of each remnant—such as past grazing intensity, afforestation, or burning—could help explain current diversity patterns, particularly in patches with similar structural attributes but contrasting reptile communities. These factors may act synergistically with fragmentation to filter species in different ways. Moreover, climate change may exacerbate the effects of fragmentation by altering thermal niches and reducing habitat suitability for thermoregulating species, especially in highly fragmented landscapes. Accounting for these finer-scale and long-term drivers will be essential for refining our understanding of how reptile assemblages respond to habitat loss and for improving conservation strategies in the Tandilia Mountains.

This study highlights the need to prevent further fragmentation of the remaining grasslands to conserve reptile diversity. Special attention should be given to remnants harboring endemic and threatened species (such as Ranch Las Mercedes and Paititi) when planning conservation strategies for Tandilia’s reptile fauna. Certain species identified in this study, such as Liolaemus tandiliensis and Tachymenis ocellata, due to their restricted distributions and ecological requirements, may serve as focal species for conservation. Protecting them and their habitats could provide umbrella protection to other less-documented or cryptic taxa within the same ecosystems. However, it is important to consider that the different grassland patches will require distinct conservation strategies, according to their spatial characteristics, reptile diversity, and the presence of species of particular interest. For example, in patches dominated by exotic vegetation (e.g., Paititi), controlling invasive plant species becomes a management priority. In other hand, for highly connected patches with high quality habitat (e.g., Ranch Las Mercedes I and II), priority should be given to maintaining habitat corridors and preventing further land conversion. Some proposed actions from previous studies include expanding protected areas, developing sustainable grazing programs and restoring native habitats by removing exotic vegetation (Di Pietro et al. 2025, Vera et al. 2025). Finally, this study is a first step in understanding reptile diversity in Tandilia. To gain a more comprehensive picture, is essential to analyze a greater number of grassland patches and how their reptile assemblages respond to human-driven environmental changes. Beyond species richness, it is also important to consider the ecological roles that reptiles play as predators, prey, and contributors to nutrient cycles. Their decline could disrupt ecological interactions and reduce the functional integrity of native grasslands. In addition, long-term monitoring is essential to detect temporal shifts in species composition and abundance in response to ongoing land-use changes and climate variability. Such efforts will be crucial for anticipating conservation challenges and designing adaptive management strategies.

Acknowledgements

We would like to thank field assistants and collaborators (Agustina Cortelezzi, Borja Baguette-Pereiro, Estrella Montalibet, Florencia Aranguren, Florencia Bazán, Florencia Dosil Hiriart, Gimena Pizzarello Milanese, Gonzalo Reuter, Habib Delfino Ahumada, Irene Negri, Marcos Cogno, Mauro Rozas, Micaela Mardones, Natalia Moro, Pilar Plantamura, Scarlett Mendez Herrera, Sofía Vivani and Tomás Martínez-Aguirre) for their kind assistance and support during the fieldwork activities. We are also grateful to Federico Juana (Ranch Las Mercedes), Roberto Berkunsky (Trébol de 4 Hojas) for granting us access to their properties. We thank Claudio Barletta (Sierra del Tigre Natural Reserve), Emilio Fernandez (Granja Los Pibes), Esteban Zugasti (Paititi Private Natural Reserve), Gustavo Ridao (Boca de la Sierra Refugee) and Oscar Espinosa (Azul Military Facilities) for their attention and collaboration. David Gustavo Vera, Melisa Celia Jazmín Rolón, Rodrigo Calvo and SJ were supported by fellowships from Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET). Germán Tettamanti was supported by fellowships from Universidad Nacional de La Plata (UNLP). Diego Omar Di Pietro, Federico Pablo Kacoliris and Igor Berkunsky are Research Fellows of CONICET. We also thank Dirección de Flora y Fauna of Buenos Aires province, for providing the necessary permits to carry on this research. We thank the anonymous reviewers for their constructive comments, which greatly improved the manuscript, and we also extend our appreciation to the journal’s editors for their support throughout the review process.

• Data availability
  Data will be made available on request.

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Edited by

• Handling editor
  Marcia Couri

Data availability

Data will be made available on request.

Publication Dates

• Publication in this collection
  20 July 2026
• Date of issue
  2026

History

• Received
  11 May 2025
• Accepted
  23 Dec 2025