Abstract
Agricultural land abandonment is recognized as one of the main environmental drivers in Southern Europe, affecting ecological communities. Lizards, as ectothermic species with low dispersal capacity, are particularly prone to the threats associated with land use changes. We investigated the effect of land abandonment on lizards in a remote mountainous area in Greece, using line transect sampling, in 20 randomly selected sites [1 km × 1 km], along a four grade abandonment gradient in terms of forest encroachment. We recorded four species: Algyroides nigropunctatus, Lacerta viridis/trilineata, Podarcis tauricus and Podarcis muralis, the latter being the most abundant. Our results did not provide evidence for a significant effect of forest encroachment or grazing on lizard diversity, given the dominance of P. muralis, the availability of all microhabitat types along the gradient and the low grazing intensity in the study area. Environmental parameters at the macrohabitat scale did not prove determinant for habitat variance, but microhabitat analysis showed a clear preference of P. muralis to bare ground. Despite the non-significant effects of land abandonment on lizard diversity, the dominance of P. muralis tends to indicate a lizard community shift towards species inhabiting forested habitats. The preservation of open microhabitats, such as bare land, is considered of great importance for promoting high levels of lizard diversity, as their loss would affect even species currently widespread in forested ecosystems. Low intensity grazing, as well as the enhancement of wild ungulate populations in abandoned areas, can contribute to halting forest encroachment and maintaining the required habitat heterogeneity.
Introduction
Agricultural land abandonment in remote and marginal areas of southern and south-eastern Europe, is a well-documented issue, directly affecting landscape heterogeneity (Farina, 1997), which is a key driver regulating species richness (Bohning-Gaese, 1997; Atauri and Lucio, 2001; Kati et al., 2010).
Mediterranean ecosystems have been shaped through thousands of years of human activities, such as wood-extraction, anthropogenic wildfires, grazing and low-intensity farming (Le Honerou, 1981). Agriculture, one of the main land uses all across Europe, encompassing nearly half of the European (EU-27) land area, has recently undergone profound changes (Blaxter and Robertson, 1995; Stoate et al., 2009). Farming practices in fertile and accessible land, usually located in lowlands, have become increasingly intensive in order to maximize production in a cost-effective way (Gardner, 1996; Robinson and Sutherland, 2002), while small and extensive farming systems, located in areas with low productivity, have always been vulnerable to marginalisation and abandonment (Baldock et al., 1996). Socio-economic circumstances have played a very important role in this process, as unfavourable living conditions and economically unviable management of agricultural land gradually lead to rural depopulation (Rey-Benayas et al., 2007). The later was the case in Greek mountains from the 1950s until the 1970s, when agricultural intensification and modernization led to agricultural income increase in the lowlands and, at the same time, agricultural income crisis in the hilly and mountainous agricultural communities (Petmezas, 2006; Papanastasis, 2007; Tzanopoulos, Mitchley and Pantis, 2007; Zomeni, Tzanopoulos and Pantis, 2008).
Land abandonment is nowadays recognized as adverse to vertebrate species that inhabit open landscapes (Farina, 1997; Moreira and Russo, 2007; Sirami et al., 2008; Nikolov, 2010), but favourable for forest-dwelling species (Regos et al., in press). For ectotherms, like invertebrates, its impact is well-known to be negative (Labaune and Magnin, 2002; Zografou et al., 2009; Plexida et al., 2012; Zakkak et al., 2014a). However, its effect on lizard communities has not been thoroughly studied so far. Current knowledge is predominated by studies in tropical regions, while reptiles and amphibians have received relatively little attention in comparison to birds, mammals and invertebrates (Bowen et al., 2007).
Lizards are one of the most prominent groups of vertebrates in Mediterranean ecosystems, playing a very important role in trophic chains (Edgar, Foster and Baker, 2010). Due to their ectothermic character, appropriate habitats should provide access to direct sunlight, as well as shelter from the wind, excessive heat and predators (Edgar, Foster and Baker, 2010). The low dispersal capacity of lizards and their restricted home ranges (Huey, 1982), make them sensitive to local habitat changes and habitat degradation, as well as good indicators of the impact of human activities, such as intensive grazing or forest cutting and burning (Castellano and Valone, 2006; Wilgers and Horne, 2006; Edgar, Foster and Baker, 2010). These characteristics also make lizards more prone to the threats associated with landscape changes than other vertebrate taxa (White et al., 1997).
To our knowledge this is the first attempt to assess the effect of forest encroachment following agricultural land abandonment on lizard communities in Southern Europe. In this study, we investigate this effect, considering a remote Mediterranean mountainous area, Pindos Mountains – Greece, as a case study. We set the following objectives: (a) to investigate the effect of forest encroachment that follows agricultural land abandonment on lizard diversity and abundance, as well as on lizard microhabitat availability, (b) to reveal the relationships of environmental factors and grazing with lizard diversity and abundance in abandoned agricultural fields, (c) to explore the microhabitat preferences of Podarcis muralis, and (d) to interpret our findings under a conservation perspective.
Materials and methods
Site selection
Our study area was located in Pindos mountain range, including Epirus that has been recognised as the area with the greatest proportion of abandoned agricultural land in Greece (Tsoumas and Tasioulas, 1986). We focused on the “Pindos Mountains mixed forests” ecoregion (Olson et al., 2001), at an elevation range of 500 to 1000 m, covering 6900 km2 (1658 km2 within the elevation range of interest). The region has the highest precipitation rate in Greece, reaching more than 1500 mm of rain per year in the city of Ioannina (Pnevmatikos and Katsoulis, 2006). The abandoned sites were designated following Zakkak et al. (2014b) and were classified in four classes of forest encroachment (hereafter FE classes), after the cover of woody plants greater than 0.5 m height: (1: 0-25%, 2: 25-50%, 3: 50-75% and 4: 75-100%). These four classes, when grazing intensity is taken into consideration, well represent an abandonment gradient in terms of the abandonment period (Zakkak et al., 2014b). Five sampling sites per FE class were selected, using a random order algorithm, so as to conclude to a final set of 20 sites (fig. 1).
The study area and the 1 × 1 km randomly selected sites where line transects of 300 m total length were allocated for sampling lizards. Sites are placed within 500-1000 m altitude in the northern Pindos Mountain area in western Greece. Coordinates are given in Greek Grid (GGRS87) (Zakkak et al., 2014b).
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
The study area and the 1 × 1 km randomly selected sites where line transects of 300 m total length were allocated for sampling lizards. Sites are placed within 500-1000 m altitude in the northern Pindos Mountain area in western Greece. Coordinates are given in Greek Grid (GGRS87) (Zakkak et al., 2014b).
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
The study area and the 1 × 1 km randomly selected sites where line transects of 300 m total length were allocated for sampling lizards. Sites are placed within 500-1000 m altitude in the northern Pindos Mountain area in western Greece. Coordinates are given in Greek Grid (GGRS87) (Zakkak et al., 2014b).
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
Data collection
Within each site we sampled lizards along line transects of 300 m total length and 6 m width, that proportionally represented the woody vegetation cover of plants greater than 0.5 m height within that site. We replicated the sampling three times, in June 2011, July 2011 and May 2012, when the air temperature ranged between 15°C and 30°C. For each observation we recorded the species, number of individuals, perpendicular distance from the centre of the line, as well as the microhabitat, in terms of substrate type and vegetation, at the point where each lizard was first observed. We considered the two species of green lizard (Lacerta viridis and L. trilineata) as one taxonomic group, due to the difficulty of visually identifying adult specimens without capturing them (Frör, 1979). The substrate type was classified as “bare ground”, “dry leaves” and “grass”, while the vegetation was divided in two classes: <3 m tall, representing shrubs and small trees and >3 m tall, representing bigger trees.
We also sampled the microhabitat along each transect, in terms of substrate type and vegetation, using the same classification as during lizard sampling, in order to estimate microhabitat availability. For microhabitat sampling we used 1 × 1 m quadrats at 25 m intervals and estimated the proportional cover of each substrate and vegetation type. In addition, we estimated grazing intensity in livestock units (LSU), as defined by the European Commission (2013), by interviewing local authorities of the villages closest to each sampling site (Zakkak et al., 2014b) and calculated the topographic wetness index (TWI), reflecting the humidity gradient for each sampling site, following Zakkak et al. (2014a).
Data analysis
For the analysis we used all the data from the line transects. Records were checked for double counts during the three replicates, taking into consideration the exact location where each individual was found, given the territorial character of lizards. All data collected within each sampling site were merged and we estimated total species richness and number of individuals.
In order to estimate the contribution of each of nine variables (FE class, grazing intensity, elevation, topographical wetness index, the proportion of dry leaves, bare ground and grass substrate, and the woody vegetation cover of more than 3 m and less than 3 m at a microhabitat scale) to habitat variation we implemented Principal Component Analysis (PCA), rotated as varimax normalized way. To do so, we first standardized the variables (mean = 0, standard deviation = 1), to ensure that the values of the regression coefficients are proportional to the contributions made by the respective explanatory variables. We then classified the sampling sites into four new groups as determined by the first two components. In addition, we classified the scores of the first three PCA axes into four distinct groups each, using equal intervals. Finally, we investigated whether lizard diversity, in terms of abundance and species richness, differed among these classes of the combination first two components, as well as each of the first three components separately, by conducting Kruskal-Wallis Analysis of Variance.
We used Spearman correlation to see how microhabitat availability changes along the abandonment gradient. We then tested the assumption that macro-habitat differences among the FE classes are reflected on microhabitat availability with Permutational Multivariate Analysis of Variance Using Distance Matrices (ADONIS) (‘adonis’ function in R-package ‘vegan’ (Oksanen et al., 2012)), with the “Bray-Curtis” dissimilarity index, using a site-microhabitat matrix and FE class, the period of abandonment and grazing as factors. We then fitted Generalized Linear Models for Multivariate Abundance Data (MAD-GLMs) (package ‘mvabund’; Wang et al., 2013) to pinpoint the microhabitat components that contribute most to the dissimilarities. Finally, we estimated micro-habitat diversity for each site, using the Simpson diversity index and performed ANOVA to see if it varies among the FE classes.
In order to see whether lizard community composition is affected by any of the factors taken into consideration, as expressed by the three first PCA axes, we performed ADONIS, using the “Bray-Curtis” dissimilarity index.
Contribution of the first three Principal Components (PC) to habitat variance and range of PCA scores assigned to each of four sampling site groups. PCA scores per site are presented in online supplementary table S4.
The effect of microhabitat composition was tested only for Podarcis muralis, for which sufficient data were available, with the implementation of univariate GLMs, using the proportional cover of each substrate type and each vegetation class as predictors and P. muralis abundance as response. We also tested the deviation of micro-habitat use from random with compositional analysis, comparing substrate availability with the observed substrate use, in order to find out which substrate types are preferred. Following Aebischer et al. (1993), we ranked habitat types in order of use, based on comparisons of the pairwise differences between matching log-ratios of the available and utilised habitat compositions and , where x is the species’ use of each habitat type in proportions and a is the proportional availability of each habitat. i and j are habitat types, where . If , habitat i is used more than expected, relative to j and vice versa. Compositional analysis was performed for P. muralis within each FE class separately, as well as for the whole study area, so as to investigate if substrate type preference of the species differs among the different FE classes. Habitat types were ranked by calculating a matrix with all the pairwise d values for each substrate combination. The rows of the matrix were indexed by the habitat type used as numerator in the log-ratio, and the columns by the denominator. We then counted the number of positive elements in each row which was a value between 0 and 2 (total number of substrate types considered minus 1) that ranked the habitats in order of increasing relative use, where 0 is “worst” and 2 is “best”. For non-utilized but available habitat types was replaced by 0.01, an order of magnitude less than the smallest recorded non-zero percentage (0.03). The statistical significance of the deviation of habitat use from random was estimated pairwise using the Monte-Carlo method with 999 permutations.
Results
Lizard community and microhabitat availability vs land abandonment
During sampling we totally recorded 157 individuals of four species: Algyroides nigropunctatus (3 individuals), Lacerta viridis/trilineata (8 individuals), Podarcis muralis (124 individuals) and Podarcis tauricus (2 individuals), as well as 20 unidentified individuals. The largest proportion (80%) of the individuals recorded belonged to a single species, P. muralis (online supplementary tables S1 and S2).
The three first components of the PCA explained 72.4% of the total habitat variance (table 1). PC1 was positively strongly correlated to “Woody vegetation cover” (PCA loadings: ), to “Dry leaves” () and to vegetation cover “More than 3 m tall” (), PC2 was positively correlated to “Grazing Intensity” () and “Bare ground” () and negatively to “Grass” () and PC3 was positively correlated to vegetation cover “Less than 3 m tall” () (fig. 2).
PCA diagram, taking into consideration the woody vegetation cover, grazing intensity, elevation, topographical wetness index, the proportion of dry leaves, bare ground and grass substrate, and the woody vegetation cover of more than 3 m and less than 3 m at a microhabitat scale, and the four respective sampling site clusters as determined by the first two components.
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
PCA diagram, taking into consideration the woody vegetation cover, grazing intensity, elevation, topographical wetness index, the proportion of dry leaves, bare ground and grass substrate, and the woody vegetation cover of more than 3 m and less than 3 m at a microhabitat scale, and the four respective sampling site clusters as determined by the first two components.
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
PCA diagram, taking into consideration the woody vegetation cover, grazing intensity, elevation, topographical wetness index, the proportion of dry leaves, bare ground and grass substrate, and the woody vegetation cover of more than 3 m and less than 3 m at a microhabitat scale, and the four respective sampling site clusters as determined by the first two components.
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
Lizard diversity in both terms of abundance and species richness did not differ significantly across any of the individual principal components (Kruskal-Wallis PC1: , and , ; PC2: , and , ; PC3: , and , , respectively), or the combination of the first two (Kruskal-Wallis: , and , ).
The proportion of woody vegetation cover at the microhabitat scale changed along the abandonment gradient, with vegetation more than 3 m tall increasing (Spearman , ) (fig. 3a). Regarding the main substrate types, “dry leaves” increased with forest encroachment (, ), while “bare ground” decreased, though not significantly so (, ) (fig. 3b). At the same time, lizards were observed at spots associated with all types of substrates, at different proportions, depending on the species (fig. 3c, d).
(a) Average woody vegetation cover, (b) main substrate type and (c) proportional use of substrate types by Podarcis muralis at the microhabitat scale (1 km2 plots sampled in Pindos Mountains in 2011-2012) along the land abandonment gradient, in terms of forest encroachment, and (d) overall substrate use of lizards per species observed during sampling in Pindos Mountains in 2011-2012 (FE class 1: 0-25% WVC, FE class 2: 25-50% WVC, FE class 3: 50-75% WVC, FE class 4: 75-100% WVC, WVC: woody vegetation cover).
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
(a) Average woody vegetation cover, (b) main substrate type and (c) proportional use of substrate types by Podarcis muralis at the microhabitat scale (1 km2 plots sampled in Pindos Mountains in 2011-2012) along the land abandonment gradient, in terms of forest encroachment, and (d) overall substrate use of lizards per species observed during sampling in Pindos Mountains in 2011-2012 (FE class 1: 0-25% WVC, FE class 2: 25-50% WVC, FE class 3: 50-75% WVC, FE class 4: 75-100% WVC, WVC: woody vegetation cover).
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
(a) Average woody vegetation cover, (b) main substrate type and (c) proportional use of substrate types by Podarcis muralis at the microhabitat scale (1 km2 plots sampled in Pindos Mountains in 2011-2012) along the land abandonment gradient, in terms of forest encroachment, and (d) overall substrate use of lizards per species observed during sampling in Pindos Mountains in 2011-2012 (FE class 1: 0-25% WVC, FE class 2: 25-50% WVC, FE class 3: 50-75% WVC, FE class 4: 75-100% WVC, WVC: woody vegetation cover).
Citation: Amphibia-Reptilia 36, 3 (2015) ; 10.1163/15685381-00003002
We found that forest encroachment following land abandonment did not affect microhabitat diversity in terms of Simpson diversity index (ANOVA: , ), but significantly affected microhabitat availability (Permutational Multivariate Analysis of Variance Using Distance Matrices , ). The vegetation higher than 3 m was important for differences in habitat availability between the first two FE classes and the fourth (GLMs for Multivariate Abundance Data: , and , , respectively) (online supplementary table S3).
Environmental parameters effect on lizard community
Lizard community composition was not significantly affected by any of the three principal components (ADONIS , ; , and , , respectively).
Microhabitat preferences for Podarcis muralis
Podarcis muralis did not use microhabitats at random, showing a preference for bare ground against dry leaves, particularly in semi-open landscapes of FE class 2 (Monte-Carlo ; table 2). However, no significant correlation between microhabitat composition and the species’ abundance occurred (GLMs, ).
Discussion
Forest encroachment impact on lizard community
Abandoned agricultural fields that are under a dynamic vegetation succession process towards the expansion of thermophilous oakwoods, held small populations of species that are typically encountered in open agricultural landscapes, such as L. viridis/trilineata, or prefer open grassy habitats, field edges and meadows, such as P. tauricus (Böhme et al., 2009a). They similarly held small numbers of A. nigropunctatus, a species mostly found at sub-Mediterranean thermophilous vegetation with well-developed shrub understorey, such as the one found in abandoned agricultural land, but depending mainly on rocky substrate availability at the microhabitat level (Bressi, 2004). On the other hand, they held comparatively large populations of P. muralis, a widespread and adaptable species that is encountered in a wide range of habitats and prefers thermophilous forested and bushy areas (Guillaume, 1997; Burton and Burton, 2002; Arnold, 2003; Kati et al., 2007; Böhme et al., 2009b).
Scores of each substrate type for Podarcis muralis within each FE class, estimated with compositional analysis. Habitats with the highest score indicate preference while those marked with an asterisk (∗) are significantly preferred against the substrate in the parenthesis.
Our results showed that forest encroachment, as defined a priori in our study, is largely reflected by PC1, significantly contributing to habitat variance, along with the dry leaves substrate, and the vegetation cover of plants more than 3 m tall, at the microhabitat scale, which are directly linked to forested areas. Although our study showed that lizard diversity and community structure was not significantly altered across the four site groups defined according to PC1, the dominant population of P. muralis provides evidence for a gradual lizard community shift, favouring species that inhabit forested habitats and particularly thermophilous oak forests. Our results regarding the preference of P. muralis for thermophilous oak woods are in agreement with previous findings in Italy, where high densities of the species have been recorded in sites largely covered by Quercus species (Maura et al., 2011). At the same time a clear preference for pine plantations and locations with lower tree canopy cover has been observed in Spain (Amo, Lopez and Martín, 2007). However, as vegetation succession in the study area is still an on-going process, its effects on lizards may not yet be fully revealed and further studies, considering longer periods since land abandonment, as well as temporal community and demographic changes, might be required to draw safe conclusions.
It is recognised that forest encroachment can be a threat for reptile populations (Ballinger and Watts, 1995; Jaggi and Baur, 1999), in particular for species that are positively related to landscape heterogeneity (Martin and Lopez, 2002; Russo, 2006). Nevertheless, the effects of land abandonment on reptile species richness remain understudied. The negative effect of land abandonment is known for passerine birds and ground spiders for the study area (Zakkak et al., 2014a, b), although it is argued that in some cases these effects might as well be positive, supporting closed shrubland and forest species of conservation concern in areas where open-habitat species are preserved in cultivated land within the wider region (Regos et al., in press). Previous studies have also reported that vegetation succession can have a significant impact upon habitat availability for ecthotherms, by changing habitat’s thermal characteristics and hence reducing prey abundance and availability of basking sites (Meik et al., 2002; Webb, Shine and Pringle, 2005). In our case, microhabitat composition significantly differed in terms of vegetation more than 3 m tall, which was more abundant in FE class 4, supporting this statement. However, vegetation succession up to a certain threshold can favour many species, as long as habitat heterogeneity is preserved (Glor et al., 2001; Kati et al., 2007; Ribeiro et al., 2009). Shrub presence can enhance reptile abundance by providing shelter, and by allowing the selection of different microclimatic conditions and degrees of exposure to sun (Martin and Lopez, 2002; Meik et al., 2002; Shine, 2005). In conclusion, land abandonment was not found to affect lizard communities in our study area, though some evidence is provided for community composition change towards species favoured by forested habitats. However, low statistical power due to small sample size might be the reason for this lack of effect. It might also be the case that the effects of land abandonment may need a longer period to be reflected on lizard communities, given their longer life span and lower dispersal abilities, in comparison to other groups with either shorter life span such as invertebrates, or higher dispersal abilities, such as birds and large mammals.
Environmental parameters
Humidity and elevation were not strongly linked to any of the three principal components explaining habitat variance. The homogeneity of our study area in terms of microclimatic conditions and restricted elevation range might be part of the explanation. The diversity of the reptile communities is furthermore known to be mainly determined by the presence of appropriate microhabitats on a fine scale, rather than by attributes at the landscape level (Atauri and Lucio, 2001; Jellinek et al., 2004). Microhabitat heterogeneity is a determining factor in groups with a lesser capacity for dispersion, such as amphibians and reptiles (Mazerolle and Villard, 1999; Martin and Lopez, 2002). For instance, the degree of humidity at microhabitat scale, as well as the elevation when areas of wider altitudinal range are some of the factors that have been previously reported to determine important reptile habitats in Mediterranean areas (Ioannidis and Bousbouras, 1997; Kati et al., 2007; Soares and Brito, 2007; Michaelides and Kati, 2009).
The effect of grazing
In our study area grazing activity was of very low intensity (5 LSU/km2 on average), falling far below the average livestock density in Greece (170 LSU/km2) or Europe (100 LSU/km2) (Eurostat, 2013). Overgrazing can lead to low structural complexity, which is reported to have a strong negative impact on lizard diversity, as it directly affects predation risk, food abundance and alters the thermoregulatory environment (Glor et al., 2001; Martin and Lopez, 2002). This was not the case in our study area, where low grazing intensity, as reflected by PC2, did not significantly affect lizard communities. Contrariwise, it might as well be the main reason for maintaining vegetation succession below a certain threshold and thus preserving habitat heterogeneity (Lumley and Miller, 2009; Zakkak et al., 2014b), so that both open microhabitats for thermoregulation and shrubs for cover against predators are available (Martin and Lopez, 2002; Woinarski and Ash, 2002).
Podarcis muralis microhabitat in abandoned fields
Podarcis muralis was the dominant species in our study area, encountered in all stages of forest encroachment, but showing a preference towards bare ground substrates. The species has been previously reported in high abundances on rocky substrates, as well as at low distances from shelters (Amo, Lopez and Martín, 2007), a tendency we also observed during sampling. Microhabitat selection in lizards lies in the optimization of their thermoregulatory, antipredator and foraging requirements (Martin and Lopez, 2002; Amo, Lopez and Martín, 2007; Michaelides and Kati, 2009). Open habitat availability at a fine scale along vegetation succession is therefore needed even for more forest-dwelling species, such as P. muralis.
Conservation implications
Although in many regions, forest conservation policies are mainly addressed to prevent deforestation, there is an increasing awareness that an excess of forest cover above a certain threshold may be also problematic for some taxa, especially in human altered landscapes in temperate regions (Greenberg, Neary and Harris, 1994). In our study area, the vegetation succession that follows land abandonment seems not to negatively affect lizard community as expected, due to their ectothermic character, but rather to favour species that also inhabit forested habitats. Forest encroachment is hence not negative for lizard communities, as long as microhabitat availability is maintained. We argue that low intensity grazing can serve as an intermediate disturbance factor, halting forest encroachment and maintaining the required habitat heterogeneity that guarantees high levels of lizard diversity (Smart, Whiting and Twine, 2005). Open habitat maintenance could as well be promoted through rewilding, enhancing the populations of wild ungulates in abandoned areas (Navarro and Pereira, 2012). Open microhabitat loss, such as bare land would be negative even for species currently widespread in such ecosystems, like P. muralis.
Acknowledgements
The present research was undertaken in the frame of “Impact of AGRicultural Abandonment on Landscape structure” (AGRALE) project, funded under South East European Era-Net PLUS (SEE-ERA.NET PLUS) scheme (Greek Ministry of Development and the 7th Framework Programme for Research and Technological Development). We would like to thank Lefteris Kakalis, Stefan Schindler, Andreja Radovic, Stoyan Nikolov, Kiril Vasilev and Hristo Pedashenko, for the fruitful discussions on site selection. We would also like to thank the Natural History Museum of Crete and specially Petros Lyberakis for his advice. Finally, we would like to thank KTIMATOLOGIO S.A. for providing us with aerial imagery of the study area.
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Footnotes
Associate Editor: Miguel Carretero.