Two genera of Urodela—Salamandraand Ommatotriton—are found in Israel. They are distributed together in some areas, and scattered separately in others, making them difficult to segregate [1][2]. Salamander species are prevalent throughout Europe, extending from North Africa, where Salamandraalgira thrives, to the Near East, with Salamandrainfraimmaculata [1]-[3]. Studies have extensively documented the characteristics and behaviors of this latter yellow-spotted black Salamandra species, found in Europe and Israel [4]. Degani et al. [4] delved into the diverse color-pattern manifestations of the yellow markings on the dorsal surface of S. infraimmaculata across different habitats along the southern edge of its distribution in Israel. At Tel Dan, 454 salamanders were documented thriving in moist environments with perennial water flow, and their images were captured. From this group, 100 individuals were sampled to assess the proportion of yellow and black pigmentation on their backs, as well as the number of spots on their heads. Similarly, at Kibbutz Sasa, 201 salamanders were photographed, and measurements were conducted on 62 of them. In Kibbutz Yehiam, another 200 salamanders were documented, and measurements were conducted on 60 of them [4]. Skin mucus metabolites in S. infraimmaculata and S. salamandra from Europe and Israel have been described in several studies [5][6].

The banded newt, scientifically known as Ommatotritonvittatus (formerly Triturus vittatus), is among the trio of Ommatotriton species, which also includes O. nesterovi and O. ophryticus [7], that inhabit regions spanning Türkiye, Syria and Israel, showcasing their remarkable adaptability to highly unpredictable environmental conditions [8]. Notably, O. ophryticus and O.vittatus display distinct traits, such as in the number of vertebrae in their trunk, genome size and allozyme composition [9]. Furthermore, O. ophryticus, the northernmost species, exhibits a geographical division into two segments: the “western group” residing in western Anatolia Türkiye, and the “eastern group” scattered across the remainder of Türkiye and Western Caucasus. O.vittatus, which inhabits Israel [2], marks the southernmost extent of the genus’ distribution. Israel’s environment exhibits notable seasonal fluctuations and extreme changes. For instance, one study site forO.vittatus, Nahalit pool in the upper Galilee [10]-[12], is aquatic for only about a month annually. This pattern is typical of newt habitats in Israel, whereas northern habitats tend to remain partially aquatic for most of the year. This environmental context underscores newt species’ remarkable adaptability, which is crucial to their survival, particularly in coping with such drastic changes. This adaptability likely faces stronger selective pressures in arid climates such as in Israel compared to regions farther north with milder climates [2]. The present study compares biological, ecological, and genetic variables between two species—S. infraimmaculata and O.vittatus—to understand the characteristics enabling the broader distribution of O.vittatus in semi-arid regions in central and southern Israel as compared to the more limited distribution ofS. infraimmaculata in the Mediterranean coastal area of northern Israel (Figure 1).

Significant distinctions were observed in the distribution patterns of the two urodeles,O.vittatusand S. infraimmaculata, within Israel. While both species were present in the northern regions characterized by a Mediterranean climate, O.vittatus was also found in the central parts of the country and in the southern areas, limited to the border with arid regions extending into the desert (Figure 1).

Water bodies could be categorized into three types based on the presence of breeding tadpoles of the two distinct species. The first type was characterized by the exclusive breeding of salamanders, while in the other type, only newts were bred. Nevertheless, there were bodies of water where both salamanders and newts coexisted and bred (Figure 2 and Figure 3).

Salamander tadpoles inhabit streams, freshwater springs, and pits in caves without newt tadpoles. Only newt tadpoles were found in winter pools and ponds, not salamander tadpoles. Both species of tadpole were found together in relatively large ponds where the water is stagnant from winter to summer (Figure 2 and Figure 3). In northern Israel, only the larvae of newts were discovered in the small and fluctuating aquatic habitats (Figure 3).

Testing the water quality in habitats where both species have adapted, it was discovered that newt tadpoles thrive in warmer temperatures, reaching up to 30˚C., whereas salamander tadpoles prefer cooler waters, typically below 22˚C. No differences in other water-quality parameters were detected among the breeding sites (Figure 4).

(a) (b)

Figure2. (a) Map of various regions in Israel colonized by Salamandrainfraimmaculata. (b) In the northern region of Israel, salamander tadpoles were discovered inhabiting various aquatic environments, including swiftly flowing streams, natural springs, seasonal water sources and man-made wells.

Figure3. (a) Illustration depicting the assorted territories across Israel inhabited by O.vittatus. (b) Bodies of water making up breeding sites for O.vittatus.

In comparing the water quality in the water bodies where salamander and newt tadpoles grew, one clear difference was found. The growth curves of newt (Figure 5(a)) and salamander (Figure 5(b)) tadpoles in different bodies of water from the time of hatching to the completion of metamorphosis are shown in Figure 5. The growth period of newt tadpoles was significantly shorter (Figure 5(a)), by 100 days, compared to salamander tadpoles, the latter taking 250 days and sometimes more (Figure 5(b)). In all stages of growth until the completion of metamorphosis, the newt tadpoles (Figure 5(a)) were significantly smaller than the salamander tadpoles (Figure 5(b)).

The phylogenetic tree of O.vittatus and S. infraimmaculata from various breeding places in Israel based on the Cyt b sequence is presented in Figure 6. The differences between different populations in Israel were greater between newt populations than between salamander populations.

We examined the ecological, biological and genetic differences between two urodele species. S. infraimmaculata is found in the Mediterranean region of northern Israel, whereas O.vittatus inhabits dry, semi-desert areas in central and southern Israel [1][2]. By comparing these two amphibian species, the study aimed to shed light on how they adapt to dry environmental conditions.

The ability of amphibians to adapt to the various water environments in which they breed is crucial for their survival during droughts. We found that O.vittatus survives in temporary water bodies, such as temporary ponds and pools,

Figure4. (a) Ecological conditions of O.vittatus larval habitats in northern Israel: oxygen levels (measured in mg/L), ammonium concentration (measured in mg/L), temperature (measured in ˚C), conductivity (measured in µS/cm), and pH. Each axis on the graph represents one of the ecological variables. (b) S. infraimmaculata larval habitats in northern Israel.

(a) (b)

Figure 5. Graphs depicting the development of larvae ofO.vittatus (a) and S. infraimmaculata (b). These curves represent the Von Bertalanffy growth model. On the vertical axis, larval size is measured in centimeters, while the horizontal axis represents the duration, in days, of larval habitation of the aquatic environment until metamorphosis.

Figure 6. Evolutionary relationships among O.vittatus and S. infraimmaculata in Israel by comparisons of genetic sequences, specifically focusing on the nucleotide sequences of the Cyt b gene obtained from specimens collected at various locations in Israel.

which are more commonly found in semi-continental regions, compared to S. infraimmaculata that breed in permanent bodies of water with relatively low temperatures.

Newts are well-suited to temporary water bodies such as ponds, where water is present for shorter durations, typically 1 to 3 months [1][2][10][13][20]. Conversely, salamanders require more permanent water sources. These findings align with earlier research and can be attributed to the rapid growth and efficient molting process observed in newt tadpoles [21]-[23].

The results of this study suggest that O.vittatus, adapted to semi-arid habitats with dry climates, exhibits greater genetic diversity compared to S. infraimmaculata, which resides in environments that are less arid.

The genetic profiles of aquatic larvae, male and female terrestrial adults, and male and female aquatic adults have been examined [8], with a focus on life in water versus on land during adulthood, and the distinct genetic expressions associated with different adult phenotypes. In addition, we investigated how shifts in gene expression during the metamorphosis from larvae to adults contribute to these adaptations.

Understanding the functions of these pathways and specific genes is crucial for investigations into habitat transitions, particularly those impacted by climate fluctuations. Moreover, the adaptability of the newt’s physical traits and the mechanisms governing gene expression provide valuable insights into the evolutionary processes of land-dwelling vertebrates [8].

Previous studies have detailed the life cycle, behavior, and genetic diversity within O.vittatuspopulations across various habitats in northern Israel, extending to the central coastal plains and near desert regions (see Degani [11] for review). Recent studies have identified transcriptomic distinctions not only between aquatic larvae and adult newts, but also between the terrestrial and aquatic adult stages characteristic of the Ommatotriton genus [7]. Historically, most “omics” investigations of Ommatotriton species have concentrated on population variance and phylogenetic aspects. Our study presents the first examination of changes in developmental gene expression within an Ommatotriton species.

There have been many studies on S. infraimmaculata genetic variation among larvae at various breeding sites compared to O.vittatus, but they are difficult to compare because they used various methods, e.g., amplified fragment length polymorphism [24], microsatellite loci and the mitochondrial D-loop [25], to analyze the gene expression [26].

Findings similar to ours have been observed not only in Urodela but also in Anura. For instance, the green toad, which displays high adaptation to arid conditions among anuran species in Israel, exhibits more genetic variation than other species in the region [1][27].

In conclusion, this study sheds light on the adaptations of O.vittatus to semi-arid and nearly desert environments. These adaptations include their ability to survive in fluctuating and unpredictable ponds, i.e., water sources that are transient and short-lived, a short tadpole phase, and rapid completion of metamorphosis. In addition, there is notable genetic diversity among O.vittatus populations compared to S. infraimmaculata, further contributing to their resilience and adaptability in these challenging habitats.