Aim We examine the regional dominance of California as a beachhead for marine biological invasions in western North America and assess the relative contribution of different transfer mechanisms to invasions over time.
Location Western North America (California to Alaska, excluding Mexico).
Methods We undertook extensive analysis of literature and collections records to characterize the invasion history of non‐native species (invertebrates, microalgae and microorganisms) with established populations in coastal marine (tidal) waters of western North America through 2006. Using these data, we estimated (1) the proportion of first regional records of non‐native species that occurred in California and (2) the relative contribution of transfer mechanisms to California invasions (or vector strength) over time.
Results Excluding vascular plants and vertebrates, we identified 290 non‐native marine species with established populations in western North America, and 79% had first regional records from California. Many (40–64%) of the non‐native species in adjacent states and provinces were first reported in California, suggesting northward spread. California also drives the increasing regional rate of detected invasions. Of 257 non‐native species established in California, 59% had first regional records in San Francisco Bay; 57% are known from multiple estuaries, suggesting secondary spread; and a majority were attributed to vessels (ballast water or hull fouling) or oysters, in some combination, but their relative contributions are not clear. For California, more than one vector was possible for 56% of species, and the potential contribution of ballast water, hull fouling and live trade increased over time, unlike other vectors.
Main conclusions California, especially San Francisco Bay, plays a pivotal role for marine invasion dynamics for western North America, providing an entry point from which many species spread. This pattern is associated historically with high propagule supply and salinity. Any effective strategies to minimize new invasions throughout this region must (1) focus attention on California and (2) address current uncertainty and future shifts in vector strength.
Species in the cycad genus Encephalartos are listed in CITES Appendix I and as Threatened or Protected Species in terms of South Africa's National Environmental Management: Biodiversity Act (NEM:BA) of 2004. Despite regulations, illegal plant harvesting for medicinal trade has continued in South Africa and resulted in declines in cycad populations and even complete loss of sub-populations. Encephalartos is traded at traditional medicine markets in South Africa in the form of bark strips and stem sections; thus, determining the species traded presents a major challenge due to a lack of characteristic plant parts. Here, a case study is presented on the use of DNA barcoding to identify cycads sold at the Faraday and Warwick traditional medicine markets in Johannesburg and Durban, respectively. Market samples were sequenced for the core DNA barcodes (rbcLa and matK) as well as two additional regions: nrITS and trnH-psbA. The barcoding database for cycads at the University of Johannesburg was utilized to assign query samples to known species. Three approaches were followed: tree-based, similarity-based, and character-based (BRONX) methods. Market samples identified were Encephalartos ferox (Near Threatened), Encephalartos lebomboensis (Endangered), Encephalartos natalensis (Near Threatened), Encephalartos senticosus (Vulnerable), and Encephalartos villosus (Least Concern). Results from this study are crucial for making appropriate assessments and decisions on how to manage these markets.Key words: cycads, core barcoding regions, muthi, nrITS, trnH-psbA.
Résumé
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