Cristobal Villaseñor-Parada

Biological invasions are one of the major drivers of biodiversity decline and have been shown to have far‐reaching consequences for society and the economy. Preventing the introduction and spread of alien species represents the most effective solution to reducing their impacts on nature and human well‐being. However, implementing effective solutions requires a good understanding of where the species are established and how biological invasions develop over time. Knowledge of the status and trends of biological invasions is thus key for guiding research efforts, informing stakeholders and policymakers, for targeted management efforts, and preparing for the future. However, information about the status and trends of alien species is scattered, patchy, and highly incomplete, making it difficult to assess. Published reports for individual regions and taxonomic groups are available, but large‐scale overviews are scarce. A global assessment therefore requires a review of available knowledge with careful consideration of sampling and reporting biases. This paper provides a comprehensive global assessment of the status and trends of alien species for major taxonomic groups [Bacteria, Protozoa, Stramenopila, Alveolata, and Rhizaria (SAR), fungi, plants, and animals] for Intergovernmental Panel of Biodiversity and Ecosystem Services (IPBES) regions. The review provides irrefutable evidence that alien species have been introduced to all regions worldwide including Antarctica and have spread to even the most remote islands. The numbers of alien species are increasing within all taxa and across all regions, and are often even accelerating. Large knowledge gaps exist, particularly for taxonomic groups other than vascular plants and vertebrates, for regions in Africa and Central Asia, and for aquatic realms. In fact, for inconspicuous species, such as Bacteria, Protozoa, and to some degree SAR and fungi, we found records for very few species and regions. Observed status and trends are thus highly influenced by research effort. More generally, it is likely that all lists for alien species of any taxonomic group and region are incomplete. The reported species numbers therefore represent minima, and we can expect additions to all lists in the near future. We identified six key challenges which need to be addressed to reduce knowledge gaps and to improve our ability to assess trends and status of biological invasions.

Here we present a multi-taxa inventory of naturalized alien species recorded on continental Chile and adjacent marine habitats, including eight taxonomic groups. We identified 1,122 species. These comprise 790 vascular plants (terrestrial and aquatic); 31 nonvascular plants [Bryophyta (mosses), Marchantiophyta (liverworts) and Anthocerotophyta (hornworts)]; 18 marine and freshwater macro and micro algae; 71 fungi; 39 terrestrial vertebrates (amphibians, reptiles, mammals and birds); 108 insects; 37 marine and freshwater invertebrates and vertebrates (6 polychaetes, 3 mollusks and 28 Pisces); and 28 terrestrial gastropods. For all taxonomic groups, naturalized species were found to mainly be distributed in regions with Mediterranean and temperate climates, with few at either extreme of the country. The invasion curves show that naturalized species first underwent a positive increment, followed by an apparent plateau phase, mainly in vascular plants, insects and vertebrates. In fungi, marine and freshwater macro and microalgae, vertebrates and invertebrates, the cumulative number of naturalized species increased sharply starting in the early 20^th century; the lack of collections before 1900 is also evident. When considering naturalized species as a whole, this inventory highlights that the rate of new naturalizations consistently increased after 1950, especially for some taxonomic groups such as insects, fungi, and vascular plants. This multi-taxa inventory of naturalized species provides a platform for national reporting on biodiversity indicators and highlights areas where Chile must invest resources to manage biological invasions.

La costa chilena presenta menos reportes de especies introducidas respecto a otras costas a nivel mundial, lo que podría corresponder a un fenómeno natural generado por condiciones oceanográficas, o bien a un artefacto producido por falta de información disponible. Mediante el análisis de 71 trabajos indexados en Web of Science, relacionados con ecología de invasiones marinas en la costa chilena, publicados entre 1998-2014, determinamos el estado actual de esta disciplina en Chile, e identificamos las tendencias de las investigaciones realizadas. La mayoría de las publicaciones se relacionan con especies en etapa de naturalización, y pocas con especies invasoras. El número de publicaciones por año incrementa linealmente, sugiriendo un creciente interés de la comunidad científica respecto al tema. La cantidad de información disponible (i.e., número de publicaciones) no es homogénea entre las regiones administrativas, y la mayoría de los trabajos son realizados sectores puntuales dentro de cada región (usualmente cercanos a la capital regional). Regiones con alto tráfico marítimo (e.g., Valparaíso, Magallanes) han sido muy poco estudiadas. A excepción de la región de Coquimbo y Los Lagos, los trabajos por región apuntan a unos pocos taxa. Muy pocos trabajos abarcan grandes escalas espaciales, aunque varios de ellos realizan experimentos a escalas de tiempo mayores (e.g., mensual, anual). Nuestros resultados permiten sugerir que el número de especies reportadas como introducidas en Chile podría estar subestimado. Observaciones en terreno, actualización periódica de catastros y utilización de herramientas moleculares, son propuestos como medidas para una mayor comprensión del tema a nivel nacional.

Plant species that growth close to or under the canopy of Acacia dealbata Link (Fabaceae, subfamily: Mimosoideae) within its non-native range, survive with difficulty or not at all, especially if they are native. This phenomenon has been attributed to allelopathy; one of the strategies used by A. dealbata to trigger an invasion process. Native species Quillaja saponaria Molina (tree) and Helenium aromaticum (Hook.) H.L. Bailey (herb), share A. dealbata’s range in South-central Chile. This study was performed on the Mediterranean Biobío Region of Chile. We evaluated the effect of leaves, flowers, pods and seeds of A. dealbata on the germination and early growth of these native species. Biological assays were carried out under laboratory conditions, based on aqueous extracts and the direct effect of plant material. Leaf litter prevented the germination of both species and seeds of the invasive species impeded the germination of Q. saponaria. Other plant parts from A. dealbata also induced reductions of hypocotyl and radicle lengths in the native species, reaching over 50 % in some treatment values. All plant parts caused radicle necrosis, preventing the formation of root hairs and, consequently, jeopardizing the survival possibility of the recipient species. The results show that A. dealbata can interfere with the establishment of pioneer herbaceous species in ecological succession and can also affect trees if they are reached by the invasion front.

The invasion process of Acacia dealbata is partially mediated by releasing allelochemicals that affect native plants and soil microbes. However, non-volatile chemical compounds responsible for the allelopathic effect remain unknown, even though the allelopathic potential of this species has been studied under Europe conditions. We examined the allelopathic potential of aqueous extracts obtained from different plant materials of A. dealbata: litter from leaf, flowers, pods and seeds and fresh leaves and also litter extract's phytotoxicity evolution on germination and early seedling growth of Lactuca sativa L. Bioassays based on aqueous extracts and direct effect of plant materials showed that radicle length (RL), degree of root necrosis and germination percentage were the variables that gave the best prediction for assessing the inhibitory allelopathic effect. Chemical compounds present in all types of litter significantly reduced the hypocotyl and RL of L. sativa. GC–MS analysis reveals the presence predominantly of resorcinol, maculosin and moretenone in leaves; stigmasterol, d-alpha-tocopherol quinone, and lupanin in pods; and methyl p-anisate, p-anisyl alcohol, stigmasterol and anisal were identified in flowers. The inhibitory effect induced on L. sativa by the different plant parts supports the hypothesis that A. dealbata exerts its allelopathic potential throughout its phenological cycle.

The macroalga Codium fragile ssp. tomentosoides is characterized by exclusive asexual reproduction through parthenogenesis. We describe the spatial (within thallus) and temporal (seasonal) variability in the abundance of reproductive structures (gametangia) in specimens of C. fragile collected from the subtidal zone of Caldera, Chile. Gametangia are more frequent on newer sections of the thallus (apical and middle), increasing during austral spring-summer, and with thallus size (i.e., length and number of dichotomies). Given that apical fragments are highly buoyant and thallus fragmentation increases during the summer, drifting fragments may be important dispersal vectors contributing to the spread of this species to new sites.