Isoplexis

Additional recommended knowledge

Daily Visual Balance Check

Correct Test Weight Handling Guide: 12 Practical Tips

Weighing the right way

Isoplexis is a section of 4 species within the genus Digitalis. The species of section Isoplexis differ from other plants in the genus Digitalis in that their monosymmetric (sometimes called zygomorphic) flowers have a distinctive large upper lip rather than large lower lip and the species are endemic to the Canary Islands (the species D. canariensis, D. chalcantha, and D. isabelliana) and Madeira (D. sceptrum).

Two Isoplexis species were first described by Linnaeus in 1753 as part of the genus Digitalis, these were D. canariensis and D. sceptrum. Since then the section has undergone several changes, the addition of two more species and more importantly being moved to a separate genus, under the genus name of Isoplexis or sometimes Callianassa, back and forth many times (Lindley 1821, Loudon 1829, Bentham 1835, Webb 1845, Wetstein 1891, Himmelbaeur and Zwillinger 1927, Werner 1960-1966, Heywood 1972). The position of Isoplexis as a section within Digitalis was finally proven by Carvalho in 1999 using molecular data and published by Brauchler et al. in 2004. Isoplexis species grow in woody habitats: D.canariensis in humid woodland areas and rarely in dry woodland areas, D.isabelliana in Pinus canariensis woodland and open disturbed areas, D.sceptrum in the cloud zone community Clethro-Laurion (Sjogren 1972) near streams on steep slopes, and D.chalcantha in Canary Island laurel forest. The flowers of Isoplexis species are adapted for bird pollination. Bird pollinators may have become extinct from some of the Canary Islands and this may explain why Isoplexis species are rare and considered endangered species.

This text has been modified from Toomey, N (2004) Investigation of the phylogenetic utility of Cycloidea-like genes in various angiosperm lineages. PhD Thesis, The University of Reading, England.

References