First report of the invasive oriental bittersweet ( Celastrus orbiculatus Thunb.) naturalised on the island of ireland: An investigation into the identity, history and habitat affinities of this neophyte

abstract: A newly discovered naturalised specimen of Celastrus orbiculatus in Newry, Northern Ireland, was identified using DNA barcoding of nuclear ribosomal ITS and plastid trn L–F region sequences, phylogenetic tree reconstruction of closely related species and morphological trait comparisons. It represents the first report of this potentially invasive alien species on the island of Ireland. Historical archival records and dendrochronological examination were utilised to estimate when and how this exotic liana was introduced and to determine the age of the current specimens. The oldest aboveground living stem was estimated to be 24 years old from ring counts and it is likely that the specimen is a nursery escape given its proximity to the abandoned Daisy Hill Nursery. We provide initial evidence on habitat interactions of the Newry C. orbiculatus specimens and found that it exerts dominance over the community during the reproductive period from May to November (total coverage = 50–60%). Our findings suggest that the climate in Ireland and Northern Ireland (Köppen's Cfb zone) is favourable for the growth and reproduction of C. orbiculatus . In addition, the edaphic conditions in Daisy Hill Wood (pH = 5.6 ± 0.1; average soil organic matter = 14.3 %) matched the preferences of this introduced neophyte. We therefore anticipate that, without human control, the Newry C. orbiculatus specimens will persist and potentially expand in distribution.