HELLAS-ALIENS. The invasive alien species of Greece: time trends, origin and pathways

The current paper presents the first effort to organize a comprehensive review of the Invasive Alien Species (IAS) of Greece. For this purpose, a database was developed with fields of information on the taxonomy, origin, ecology and pathways of introduction of terrestrial, freshwater and marine species. Our database includes a) taxa in the Union’s list that are present in Greece, b) taxa already present in Greece and considered to be invasive, and c) taxa highly likely to enter Greece in the next 10 years and become invasive. The Database served as the starting point for the compilation of the National List of Alien Invasive Species (HELLAS-ALIENS) in compliance with the EU Regulation 1143/2014. Overall, the HELLAS-ALIENS comprises 126 species, i.e. 32 terrestrial and freshwater plant species, 14 terrestrial invertebrates, 28 terrestrial vertebrates, 30 freshwater fishes and invertebrates and 22 marine species. Terrestrial invertebrates, birds and mammals are mainly of Asiatic origin. Most of the terrestrial plants have their native geographical distribution in the Americas (North and South). Most of the freshwater invertebrates and fishes are of North American origin, while the majority of the marine species are of Indo-Pacific origin. The first records of IAS concern terrestrial plant species, and date back to the 19th century, while those in freshwater and marine ecosystems seem to have been systematically recorded some decades later. Regarding the pathways of introduction, most of the taxa arrived in Greece or are expected to arrive through escape from confinement and unaided. The majority of the terrestrial, freshwater and marine species have been evaluated as of High-risk for the indigenous biodiversity and only 3% of the species listed have been evaluated of Low-risk. Our results provide an important baseline for management and action plans, as required by the priorities set by the European Union through the Biodiversity Strategy for 2030

ARES(2014)2425342 - 22/07/2014. Organisation and running of a scientific workshop to complete selected invasive alien species (IAS) risk assessments

The introduction and spread of invasive alien species (IAS) constitutes one of the most important drivers of global change in biodiversity and ecosystem services. Robust risk assessment methods are required for IAS to provide the foundation upon which to prioritise appropriate action. In a previous study (Roy, Schonrogge et al. 2014) minimum standards were developed to provide an assessment framework for risk assessments and ultimately for underpinning the development of a proposed list of “IAS of EU concern”, in accordance to the provisions of the Regulation (EU) No 1143/2014 of the European Parliament and of the Council of 22 October 2014 on the prevention and management of the introduction and spread of invasive alien species. In practice, of the protocols assessed in detail, only four (GB NNRA, EPPO DSS, Harmonia+ and ENSARS) were sufficiently compliant with the minimum standards to be considered and of these only the GB NNRA and EPPO DSS have published IAS risk assessments. As a result, using the information from such “substantially compliant” protocols, a draft list of approximately 50 species was compiled. It is important to note that this list of species is based on availability of robust risk assessments already completed through methods which are almost compliant with the minimum standards, and it does not constitute the list of “IAS of EU concern”. In view of the application of the forthcoming EU Regulation on IAS (and building-on ENV.B.2/ETU/2013/0026) the Commission hosted a 2-day scientific workshop to examine the selected risk assessments and pool the existing knowledge existing in the EU to complete the missing information, on the basis of robust scientific evidence, in order to make them fully compliant with the minimum standards, wherever possible. The workshop was led by Helen Roy (CEH) and Riccardo Scalera (ISSG). An additional 16 experts from fifteen member states were selected based on their expertise in invasion biology and represented a breadth of expertise from a variety of perspectives including taxonomic (all taxa), environmental (freshwater, marine and terrestrial), impacts (environmental, socio-economic and health) and disciplines (ecologists, conservation practitioners, scientists, policy-makers, risk assessors). In view of the gaps across risk assessments for ecosystem services and climate change two experts were invited to guide the development of approaches for these specific themes. In total the risk assessments for 56 species were considered. The GB NNRA and EPPO DSS have published IAS risk assessments which, when considering species that score medium to high impact, together cover 51 species (noting that Fallopia japonica and F. sachalinensis are separate species). Two further risk assessments were suggested for consideration by the GB Non-Native Species Secretariat which follow the GB NNRA protocol: coati (Nasua nasua) and skunk (Mephitis mephitis), although scored as low impact. Finally an additional three species have been considered through new European–wide risk assessments, with the reported outcome of high impact, for this project which again follow the GB NNRA protocol: Pallas squirrel (Callosciurus erythraeus), grey squirrel (Sciurus carolinensis) and coypu (Myocastor coypus). The main gaps across all risk assessments were in relation to climate change and ecosystem services but additional information was also required on benefits as mentioned with minimum standard “Description (Taxonomy, invasion history, distribution range (native and introduced), geographic scope, socio-economic benefits)” and in some cases information to support the minimum standard “Includes status (threatened or protected) of species or habitat under threat“ was missing. It was agreed that systematic consideration of a list of questions in relation to the minimum standards on ecosystem services and climate change would be useful guidance for experts. An outline of the approaches agreed through the workshop for the minimum standards “Includes possible effects of climate change in the foreseeable future“ and “Can broadly assess environmental impact with respect to ecosystem services” were developed as guidance for documenting information in relation to climate change and ecosystem services. Each species was considered separately with the experts providing an overview of the information available for addressing the identified gaps. After all species had been considered the workshop participants (excluding the EC, Helen Roy and Riccardo Scalera) adopted a consensus approach to confirm whether or not the risk assessment was compliant with the minimum standards and whether the overall score of the risk assessment remained applicable. No changes were made to the scores but any recommendations were noted. There were very few recommendations for change. The outcome for each risk assessment was agreed and summarised as “compliant” or “not compliant” with the minimum standards. Of the risk assessments for the 56 species considered through this project, 53 were agreed to be fully compliant with the minimum standards. However, Pacific oyster, Crassostrea gigas, although compliant with the minimum standards should be excluded as it is not within the scope of the regulation (see art 2.e) because it is listed in annex IV of Council Regulation (EC) No 708/2007 of 11 June 2007 concerning use of alien and locally absent species in aquaculture. Four of the risk assessments were not considered to be compliant because of major information gaps: Elodea canadensis (Canadian pondweed), Heracleum mantegazzianum (giant hogweed), M. mephitis (skunk), N. nasua (coati)

Predicting species dominance shifts across elevation gradients in mountain forests in Greece under a warmer and drier climate

The Mediterranean Basin is expected to face warmer and drier conditions in the future, following projected increases in temperature and declines in precipitation. The aim of this study is to explore how forests dominated by Abies borisii-regis, Abies cephalonica, Fagus sylvatica, Pinus nigra and Quercus frainetto will respond under such conditions. We combined an individual-based model (GREFOS), with a novel tree ring data set in order to constrain tree diameter growth and to account for inter- and intraspecific growth variability. We used wood density data to infer tree longevity, taking into account inter- and intraspecific variability. The model was applied at three 500-m-wide elevation gradients at Taygetos in Peloponnese, at Agrafa on Southern Pindos and at Valia Kalda on Northern Pindos in Greece. Simulations adequately represented species distribution and abundance across the elevation gradients under current climate. We subsequently used the model to estimate species and functional trait shifts under warmer and drier future conditions based on the IPCC A1B scenario. In all three sites, a retreat of less drought-tolerant species and an upward shift of more drought-tolerant species were simulated. These shifts were also associated with changes in two key functional traits, in particular maximum radial growth rate and wood density. Drought-tolerant species presented an increase in their average maximal growth and decrease in their average wood density, in contrast to less drought-tolerant species

Biological invasions and biodiversity: experimental investigation of the impact of plant invaders on mediterranean grasslands of varying initial diversities and compositions

Η παρούσα διατριβή διαπραγματεύεται τη σημασία της ποικιλότητας στη διαμόρφωση της δεκτικότητας χορτολιβαδικών κοινοτήτων σε εισβολές νέων ειδών. Αντλεί τη θεωρητική της βάση από τη σχετική διεθνή επιστημονική βιβλιογραφία και τα ευρήματά της από πολλαπλή πειραματική μελέτη σε Μεσογειακά συνθετικά ποολίβαδα διαφορετικής αρχικής ποικιλότητας και σύνθεσης ειδών που διεξήχθη μεταξύ των ετών 1998-2003 στη Λέσβο. Σκοπός της διατριβής είναι να μελετήσει διαφορετικά συστατικά στοιχεία της απόδοσης των εισβολέων σε συνάρτηση αφενός µε την ποικιλότητα των κοινοτήτων υποδοχής και αφετέρου µε την επίδραση της διαταραχής της φωτιάς, αλλά και να εξετάσει τη χρονική μεταβολή της σχέσης ποικιλότητας και δεκτικότητας στην εισβολή. Τα ερωτήματα στα οποία αποπειράται να απαντήσει είναι τα εξής: 1. ποια η συσχέτιση μεταξύ της ποικιλότητας των κοινοτήτων υποδοχής και του αριθμού ειδών των εισβολέων; 2. πώς επηρεάζουν τα βιοτικά και αβιοτικά χαρακτηριστικά των κοινοτήτων υποδοχής την αφθονία των εισβολέων; 3. ποια είναι τα μορφώματα εμφάνισης των εισβολέων σε σχέση µε την ποικιλότητα και ταξινομική σύνθεση των κοινοτήτων υποδοχής; 4. πώς επιδρά η φωτιά στη δεκτικότητα των κοινοτήτων στην εισβολή; 5. ποια η απόκριση της ανθεκτικότητας στην εισβολή στην αλληλεπίδραση ποικιλότητας και φωτιάς; 6. πώς διαμορφώνεται μακροχρόνια η συσχέτιση της αρχικής ποικιλότητας των κοινοτήτων υποδοχής και της δεκτικότητάς τους στις εισβολές; 7. ποια κοινοτικά χαρακτηριστικά καθορίζουν, μακροχρόνια, την ανθεκτικότητα των κοινοτήτων στην εισβολή; Η πορεία που θα ακολουθηθεί είναι η εξής: Στο Κεφάλαιο 1 γίνεται αναφορά στη φύση του φαινομένου των εισβολών και στις επιπτώσεις του σε οικοσυστηµικό, διαχειριστικό και οικονομικό επίπεδο. Κατατίθονται, επίσης, κάποιοι προβληματισμοί σχετικά µε τις κοινωνικές διαστάσεις του ζητήματος και την εμπλοκή της επιστημονικής αντίληψής του στη διαμόρφωση των διαστάσεων αυτών. Στο Κεφάλαιο 2 διατυπώνονται βασικοί ορισμοί γύρω από τις εισβολές και γίνεται αναφορά στη σημασία των εισβολών και στα ερωτήματα που εγείρουν στο θεωρητικό πλαίσιο της Οικολογίας. Το κύριο μέρος αυτού του κεφαλαίου αφορά στην επισκόπηση παλαιότερης και πρόσφατης βιβλιογραφίας για τη σχέση ποικιλότητας-εισβολών και στις βασικές υποθέσεις ερμηνείας που έχουν προταθεί γι’ αυτή τη σχέση. Στο Κεφάλαιο 3 περιγράφεται ο πειραματικός σταθμός και η διαδικασία που ακολουθήθηκε για τη μορφοποίησή του, για τη δημιουργία των πειραματικών κοινοτήτων και για την επιλογή των φυτικών ειδών των κοινοτήτων υποδοχής. Το Κεφάλαιο 4 µας εισάγει στο κυρίως πείραμα που πραγματοποιήθηκε στο πλαίσιο της παρούσας διατριβής. Κατά την αρχική φάση της διαδικασίας της φυσικής εισβολής, εξετάζεται η επίδραση της ποικιλότητας των κοινοτήτων υποδοχής στη δεκτικότητά τους στις εισβολές. Στο Κεφάλαιο 5 περιγράφονται τα αποτελέσματα του δεύτερου πειράματος που, και πάλι κατά το αρχικό στάδιο της διαδικασίας, εξετάζει την επίδραση της φωτιάς, της ποικιλότητας και την αλληλεπίδρασή τους στην ανθεκτικότητα των κοινοτήτων υποδοχής στην εισβολή. Στο Κεφάλαιο 6 παρουσιάζονται τα αποτελέσματα της µμακροχρόνιας μελέτης της εισβολής. Πέντε χρόνια μετά την έναρξη της φυσικής εισβολής διερευνάται η συσχέτιση της αρχικής ποικιλότητας και των συστατικών στοιχείων της εισβολής, καθώς και η μεταβολή της στο χρόνο. Γίνεται, επίσης, απόπειρα ερμηνείας των παρατηρούμενων µμορφωμάτων της δεκτικότητας στην εισβολή, µε βάση κάποια χαρακτηριστικά της δομής των κοινοτήτων υποδοχής. Η διατριβή ολοκληρώνεται στο κεφάλαιο 7 µε µια γενική συζήτηση για τα ευρήματα, τα συμπεράσματα και τα νέα ερωτήματα που προέκυψαν από τα παραπάνω πειράματα. Ακολουθούν δύο παραρτήματα µε τα δημοσιευμένα άρθρα των μελετών που περιγράφονται στα Κεφάλαια 4 και 5, στην αγγλική. Συγκεκριμένα, τα Παραρτήματα I και II αφορούν σε δημοσιεύσεις στα διεθνή επιστημονικά περιοδικά Oikos 98: 239-250 (2002) και Oecologia 143: 428-437 (2005), αντιστοίχως. Τέλος, το Παράρτημα ΙΙΙ περιλαμβάνει κατάλογο των συμμετοχών σε συνέδρια και των δημοσιεύσεων σε περιοδικά µε κριτές, µε θέματα σχετικά του αντικειμένου της διατριβής αλλά και ευρύτερου επιστηµονικού-οικολογικού ενδιαφέροντος

Evaluating Hypotheses of Plant Species Invasions on Mediterranean Islands: Inverse Patterns between Alien and Endemic Species

Invasive alien species cause major changes to ecosystem functioning and patterns of biodiversity, and the main factors involved in invasion success remain contested. Using the Mediterranean island of Crete, Greece as a case study, we suggest a framework for analyzing spatial data of alien species distributions, based on environmental predictors, aiming to gain an understanding of their spatial patterns and spread. Mediterranean islands are under strong ecological pressure from invading species due to their restricted size and increased human impact. Four hypotheses of invasibility, the “propagule pressure hypothesis” (H1), “biotic resistance hypothesis vs. acceptance hypothesis” (H2), “disturbance-mediated hypothesis” (H3), and “environmental heterogeneity hypothesis” (H4) were tested. Using data from alien, native, and endemic vascular plant species, the propagule pressure, biotic resistance vs. acceptance, disturbance-mediated, and environmental heterogeneity hypotheses were tested with Generalized Additive Modeling (GAM) of 39 models. Based on model selection, the optimal model includes the positive covariates of native species richness, the negative covariates of endemic species richness, and land area. Variance partitioning between the four hypotheses indicated that the biotic resistance vs. acceptance hypothesis explained the vast majority of the total variance. These results show that areas of high species richness have greater invasibility and support the acceptance hypothesis and “rich-get-richer” distribution of alien species. The negative correlation between alien and endemic species appears to be predominantly driven by altitude, with fewer alien and more endemic species at greater altitudes, and habitat richness. The negative relationship between alien and endemic species richness provides potential for understanding patterns of endemic and alien species on islands, contributing to more effective conservation strategies

Monitoring rapid evolution of plant populations at scale with pool-sequencing

The change in allele frequencies within a population over time represents a fundamental process of evolution. By monitoring allele frequencies, we can analyze the effects of natural selection and genetic drift on populations. To efficiently track time-resolved genetic change, large experimental or wild populations can be sequenced as pools of individuals sampled over time using high-throughput genome sequencing (called the Evolve & Resequence approach, E&R). Here, we present a set of experiments using hundreds of natural genotypes of the model plant Arabidopsis thaliana to showcase the power of this approach to study rapid evolution at large scale. First, we validate that sequencing DNA directly extracted from pools of flowers from multiple plants -- organs that are relatively consistent in size and easy to sample -- produces comparable results to other, more expensive state-of-the-art approaches such as sampling and sequencing of individual leaves. Sequencing pools of flowers from 25-50 individuals at ∼40X coverage recovers genome-wide frequencies in diverse populations with accuracy r > 0.95. Secondly, to enable analyses of evolutionary adaptation using E&R approaches of plants in highly replicated environments, we provide open source tools that streamline sequencing data curation and calculate various population genetic statistics two orders of magnitude faster than current software. To directly demonstrate the usefulness of our method, we conducted a two-year outdoor evolution experiment with A. thaliana to show signals of rapid evolution in multiple genomic regions. We demonstrate how these laboratory and computational Pool-seq-based methods can be scaled to study hundreds of populations across many climates