Invasive alien species (IAS) are one of the major drivers of change that can negatively affect biodiversity, ecosystem functions and services and human health; islands are particularly vulnerable to biological invasions. Horizon scanning can lead to Electronic supplementary material The online version of this article (

Accurate measures of species abundance are essential to identify conservation strategies. N-mixture models are increasingly used to estimate abundance on the basis of species counts. In this study we tested whether abundance estimates obtained using N-mixture models provide consistent results with more traditional approaches requiring capture (capture-mark recapture and removal sampling). We focused on endemic, threatened species of amphibians and reptiles in Italy, for which accurate abundance data are needed for conservation assessments: the Lanza’s Alpine salamander Salamandra lanzai, the Ambrosi’s cave salamander Hydromantes ambrosii and the Aeolian wall lizard Podarcis raffonei. In visual counts, detection probability was variable among species, ranging between 0.14 (Alpine salamanders) and 0.60 (cave salamanders). For all the species, abundance estimates obtained using N-mixture models showed limited differences with the ones obtained through capture-mark-recapture or removal sampling. The match was particularly accurate for cave salamanders in sites with limited abundance and for lizards, nevertheless non-incorporating heterogeneity of detection probability increased bias. N-mixture models provide reliable abundance estimates that are comparable with the ones of more traditional approaches, and offer additional advantages such as a smaller sampling effort and no need of manipulating individuals, which in turn reduces the risk of harming animals and spreading diseases.

Biological invasions have become a major cause of biodiversity loss. Tracing the origin of the populations of alien species is essential to infer the dispersal pathway and finally to set conservation policies aimed at preventing new introductions. The Italian wall lizard, Podarcis sicula, is one of the reptile species most widely introduced, with allochthonous populations occurring from the United States to Turkey. For some of them, instances of geographic expansion and competition/hybridization with autochthonous Podarcis sp. have been indicated. In the Iberian Peninsula, five introduced populations are known: Lisbon (W Portugal), Noja, Cantabria (N Spain), La Rioja (N Spain) and Almería (S Spain) and Sant Celoni, Barcelona (NE Spain) while the species now widely ranges Menorca Island in the Balearics. Here we assess the origin of four populations (Barcelona population will not be included) by comparing in a phylogenetic framework the cytochrome b gene sequences of specimens from the introduced and native populations. The results from this study provide evidence for distinct sources, pathways, and timing of introduction in Iberian Peninsula and Balearics by P. sicula from Tuscany, Calabria, Sicily, and Sardinia. This finding underpins the fact that P. sicula holds considerable potential invasiveness and advises for conservation strategies based on a global and preventive plan for avoiding new introductions as well as on eradication and control measures when prevention fails.

Aim:The Mediterranean basin has a long history of interactions between humans and biota, with multiple ancient and recent introductions of alien species. Such a multitude of introductions makes it difficult to distinguish between alien and native species but provides an excellent opportunity to investigate factors related to introductions and long-term persistence of alien species. In this study, we combined genetic and distribution data to identify the factors promoting the presence of alien reptiles on islands, considering human-related, geographic and species features.Furthermore, we assessed whether the use of genetic evidence to identify alien species improves inference of the factors determining their distribution.Location: Mediterranean islands. Methods:We combined genetic data and distribution databases to obtain information on biological traits and on the native/alien status of reptiles on >900Mediterranean islands, and we gathered data on geographic and human features of islands. We then used spatially explicit generalized additive mixed models to identify the factors associated with the establishment of alien reptiles. Results:Alien reptile populations are more frequent on islands far from the native range and with large human population. Alien populations of reptiles that are able to feed on plants are particularly frequent. Traditional data sources underestimate the frequency of alien reptiles on Mediterranean islands, and using genetic evidence to assess the status of populations provided a more complete picture of the factors associated with the presence of alien populations. Main conclusions:Humans are key drivers of the distribution of alien reptiles on Mediterranean islands, but the distributions are determined by a complex interplay between human activities, geographic factors and species features. Genetic data are essential for obtaining reliable biogeographic assessments of invasive species, particularly in systems with a long history of human influence.

Biological invasions are a major conservation threat for biodiversity worldwide. Islands are particularly vulnerable to invasive species, especially Mediterranean islands which have suffered human pressure since ancient times. In the Balearic archipelago, reptiles represent an outstanding case with more alien than native species. Moreover, in the last decade a new wave of alien snakes landed in the main islands of the archipelago, some of which were originally snake-free. The identification of the origin and colonization pathways of alien species, as well as the prediction of their expansion, is crucial to develop effective conservation strategies. In this study, we used molecular markers to assess the allochthonous status and the putative origin of the four introduced snake species (Hemorrhois hippocrepis, Malpolon monspessulanus, Macroprotodon mauritanicus and Rhinechis scalaris) as well as ecological niche models to infer their patterns of invasion and expansion based on current and future habitat suitability. For most species, DNA sequence data suggested the Iberian Peninsula as the potential origin of the allochthonous populations, although the shallow phylogeographic structure of these species prevented the identification of a restricted source-area. For all of them, the ecological niche models showed a current low habitat suitability in the Balearic, which is however predicted to increase significantly in the next few decades under climate change scenarios. Evidence from direct observations and spatial distribution of the first-occurrence records of alien snakes (but also lizards and worm lizards) suggest the nursery trade, and in particular olive tree importation from Iberian Peninsula, as the main pathway of introduction of alien reptiles in the Balearic islands. This trend has been reported also for recent invasions in NE Spain, thus showing that olive trees transplantation may be an effective vector for bioinvasion across the Mediterranean. The combination of molecular and ecological tools used in this study reveals a promising approach for the understanding of the complex invasion process, hence guiding conservation management actions.

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The phylogenetic relationships and possible origin of a putative non-native population of Podarcis muralis in Ukraine were assessed based on sequences of the mitochondrial gene cytochrome b. Phylogenetic analysis showed that the Ukrainian lizards belong to two distinct mitochondrial lineages (haplogroups), both occurring within the Central Balkan clade, which includes most of central and south-eastern European populations. From overall three detected Ukrainian haplotypes, one haplotype share same genetic signal with the hyplotype from the locality Bjala (Bulgaria), the other two are unique for Ukrainian population. Two of haplotypes correspond with haplogroup covering large geographic region of Bulgaria, Serbia, and Romania. These results reinforce previous findings that the species has the ability to establish new populations out of its native range. While most introductions to Germany and Britain have been deliberate, it appears likely that human transport of goods via the Danube river of goods is responsible for the range expansion into Ukraine.

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