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Dietary studies are essential to unravel the functioning of ecosystems and ultimately to understand biodiversity. This task, which at first may seem simple, becomes especially complex in those cases of omnivorous species with highly variable diets. In this regard, the emergence of next-generation DNA sequencing methodologies represents a powerful tool to address the problem. Here we implement a high-throughput metabarcoding strategy based on the analysis of four molecular markers aimed at sequencing both mitochondrial (animal prey) and chloroplast (diet plants) genome fragments from fecal samples of two lizard species endemic to the Balearic Archipelago (Podarcis lilfordi and P. pityusensis) obtained through non-invasive methods. The results allowed for the characterization of their diets with a high degree of taxonomic detail and have contributed a large number of new trophic records. The reported diets are based mainly on the consumption of arthropods, mollusks and plants from a diversity of taxonomic orders, as well as carrion and marine subsidies. Our analyses also reveal inter- and intra-specific differences both in terms of seasonality and geographical distribution of the sampled lizard populations. These molecular findings provide new insights into the trophic interactions of these threatened endemic lizards in their unique and isolated ecosystems.

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Gut microbial communities provide essential functions to their hosts and are known to influence both their ecology and evolution. However, our knowledge of these complex associations is still very limited in reptiles. Here we report the 16S rRNA gene faecal microbiota profiles of two lizard species endemic to the Balearic archipelago (Podarcis lilfordi and P. pityusensis), encompassing their allopatric range of distribution through a noninvasive sampling, as an alternative to previ- ous studies that implied killing specimens of these IUCN endangered and near-threatened species, respectively. Both lizard species showed a faecal microbiome composition consistent with their omnivorous trophic ecology, with a high representa- tion of cellulolytic bacteria taxa. We also identified species-specific core microbiota signatures and retrieved lizard species, islet ascription, and seasonality as the main factors in explaining bacterial community composition. The different Balearic Podarcis populations are characterised by harbouring a high proportion of unique bacterial taxa, thus reinforcing their view as unique and divergent evolutionary entities.

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Es wird über einen 1930 angesetzten Versuch berichtet, bei dem auf einem bis dahin eidechsenfreien Felseiland (Dado Grande bei Ibiza, Pityusen) Männchen einer melanistischen und Weibchen einer grünen Inselpopulation von Podarcis pityusensis ausgesetzt wurden. Die Untersuchung von sechs fünf Jahre später gefangenen Tieren ergibt, dass die Vermischung zu erhöhter Variabilität und gesteigertem Größenwuchs geführt hat. Eine erneute Kontrolle dieses noch vorläufigen Ergebnisses wird angeregt.

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Hemorrhois hippocrepis arrives at the beginning of the twenty-first century to the Pityusic Islands, like an invasive species and it has placed the endemic lizard Podarcis pityusensis at serious risk of extinction in the two major islands. It makes urgent to have an estimated population density of lizards in the various islets of the Pityusas. It has been used personal field notes with the indications that allow us to estimate the population density in the different visits realized to the islets from 1979 to 2024.

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In this study we compile data regarding lizard densities of the island populations of the Ibiza wall lizard, Podarcis pityusensis, which can serve as a baseline for future research and control of the invasive snakes, and in particular the horseshoe whip snake Hemorrhois hippocrepis, in the Pityusic Islands. Special attention has been given to the correct official spelling of 96 locations of which 89 are real rocks, islets and islands. For each island a short description, toponymy, faunal and floral aspects and some herpetological history is given, and a lizard density value was assigned. The results are very disturbing, with two confirmed- and three most likely extinct island populations of Podarcis pityusensis, and we call for coordinated action.

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The Ibiza wall lizard (Podarcis pityusensis), has a very limited distribution, being located only in the Pitiusas Islands of Balearic Islands, which are Ibiza and Formentera. In the Red List of Threatened Species of IUCN (International Union for the Conservation of Nature), this species went from being classified as `Near Threatened` (NT) and became `Endangered` (EN) on the 27th of June. This change in its category is due to a population decrease of more than 50% since 2010. The main reason for this population reduction is due to predation by invasive snake species, especially the horseshoe whip snake (Hemorrhois hippocrepis), which was accidentally introduced into the islands in 2003 and has since been a major threat to the lizard. Because its conservation status has recently been rectified, the recovery plan that it should have as being classified as an endangered species by IUCN has not yet been published. Thus, in this end-of-degree work it is intended to carry out this recovery plan for the Ibiza wall lizard (Podarcis pityusensis). This will include a review of the current status of the species (population status, critical areas, threats, etc.), definition of a set of objectives for the plan and identification of measures necessary to achieve the objectives, eliminate the threats facing the species, to restore their populations and ensure their long-term viability.

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The Ibizan wall lizard, Podarcis pityusensis, was the subject of several documented translocations by the German vertebrate zoologist Martin Eisentraut, in 1930. He aimed to initiate long-term experiments into the evolution of melanism and other morphological traits and accordingly he designed introductions into five islets that (he believed) contained no lizards. In this study, we analyzed the genetic and morphological characteristics of individuals we found there. We found no lizards on two of the islets, namely Escull de Tramuntana and Galera, but for the first time, detected a large population on a third islet, Es Vaixell. Eisentraut founded the Es Vaixell population with nonmelanistic Ibizan specimens, but the present day population of Es Vaixell was found to be fully melanistic. Genetic markers support a strong similarity between Es Vaixell and its neighbour islet, Na Gorra, and indicate that, in all likelihood, the individuals introduced by Eisentraut have left no descendants. It is likely that Es Vaixell already contained lizards prior to this introduction. Analyses of microsatellite DNA placed individuals from a fourth islet, Dau Gran, with those of one of its source islet, Escull Vermell. They are also morphologically close to individuals from Escull Vermell. This suggests that selection pressures could have favoured the Escull Vermell phenotype following introduction. For reasons we discuss, the translocations have revealed less than Eisentraut would have originally hoped for. Although evolutionary processes are normally time-consuming, these translocations do provide some potential insights into the rapid evolution of lizard morphology following colonization.

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In the spring of 193o, the German zoologist Martin Eisentraut performed some field experiments with the Ibiza wall lizard Podarcis pityusensis (Boscá, 1883). When he found out that the small rocky island of Illa Negra de Llevant, located at the entrance to the port of Ibiza Town and close to the coast, seemed to have no lizard population of its own, he released a total of 5o specimens of the melanistic subspecies Podarcis pityusensis maluquerorum from the island of Bleda Plana. Although, these translocation experiments were published by Eisentraut (193o, 1949), they were obviously not known to all subsequent authors, and so the lizards encountered on the Illa Negra de Llevant in the period from 1979 onwards were always assigned to the nominate form Podarcis pityusensis pityusensis due to their similarity to the lizards of Ibiza. Previous investigations could not clarify whether the lizards of the Illa Negra de Llevant are descendants of the animals released by Eisentraut or whether they are specimens of a new introduction. With the results of our own investigations, we would like to contribute to solve the mystery of the lizards of the Illa Negra de Llevant.