Pteris cretica L. (pantrop.) – A very rare garden escape, first recorded on a basement wall in 2001 in Gent (soon destroyed subsequently). Discovered in 2006 on an old wall, near the greenhouses of the Antwerp Zoo and in 2007 on a basement wall in Deurne-Noord (Antwerpen). Also commonly seen as a greenhouse weed (indoors).
Nearly all Belgian records are referable to var. albolineata Hook. (syn.: Pteris nipponica W.C. Shieh), characterized by pinnae with a broad white, central stripe. Pteris nipponica and P. cretica var. albolineata are conspecific, as already shown by Shieh (1966). They are of hybrid origin, involving P. cretica var. cretica and an ancestral diploid of P. ryukyuensis Tagawa (Jaruwattanaphan & al. 2013).
Pteris cretica is increasingly found in urban areas in neighbouring countries as well, possibly as a result of climate change (Germany, the Netherlands, the British Isles).
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Literature:
Jaruwattanaphan T., Matsumoto S. & Watano Y. (2013) Reconstructing Hybrid Speciation Events in the Pteris cretica Group (Pteridaceae) in Japan and Adjacent Regions. Syst. Bot. 38(1): 15-27. [available online at: http://www.bioone.org/doi/pdf/10.1600/036364413X661980]
Shieh W.-C. (1966) A synopsis of the fern genus Pteris in Japan, Ryukyu, and Taiwan. Bot. Mag. 79: 283-292.