Phrymaceae accommodates 13 genera from warm-temperate and tropical regions (Mabberley 2008). Its boundaries were considerably re-defined as a result of molecular phylogenetic studies (Beardsley & Olmstead 2002) and this new circumscription is now widely accepted (APG III 2009). Some genera traditionally placed in Scrophulariaceae now belong here. In Belgium one non-native genus is involved, Erythranthe (formerly Mimulus section Erythranthe).
A related genus, Mazus Lour., was also transferred to Phrymaceae (Mabberley 2008) but more recent studies by Reveal (2011) tend to place it in a family of its own, Mazaceae. One species, Mazus pumilus (Burm.f.) Steenis, is a common weed and is sometimes seen as a bonsai-weed in Belgian plant nurseries. Future occurrences in the wild are not unlikely (see also Desfayes 1997).
APG III (2009) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. APG III. Bot. J. Linn. Soc. 161(2): 105-121.
Beardsley P.M. & Olmstead R.G. (2002) Redefining Phrymaceae: the placement of Mimulus, tribe Mimuleae, and Phryma. Am. J. Bot. 89(7): 1093-1102.
Desfayes M. (1997) Mazus pumilus (Scrophulariaceae), adventice nouvelle pour l’Italie, et Lemna minuta (Lemnaceae) espèce nouvelle pour la province de Pavie. Saussurea 28: 65-66.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Reveal J.L. (2011) Summary of recent systems of angiosperm classification. Kew Bull. 66: 5-48.