{{Italic title ''Isoplexis'' is a

section Section, Sectioning or Sectioned may refer to: Arts, entertainment and media * Section (music), a complete, but not independent, musical idea * Section (typography), a subdivision, especially of a chapter, in books and documents ** Section sign ...

of four

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s within the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Digitalis ''Digitalis'' ( or ) is a genus of about 20 species of herbaceous perennial plants, shrubs, and biennials, commonly called foxgloves. ''Digitalis'' is native to Europe, western Asia, and northwestern Africa. The flowers are tubular in sha ...

'' in the

plantain Plantain may refer to: Plants and fruits * Cooking banana, banana cultivars in the genus ''Musa'' whose fruits are generally used in cooking ** True plantains, a group of cultivars of the genus ''Musa'' * ''Plantaginaceae'', a family of flowerin ...

family

Plantaginaceae Plantaginaceae, the plantain family, is a large, diverse family of flowering plants in the order Lamiales that includes common flowers such as snapdragon and foxglove. It is unrelated to the banana-like fruit also called "plantain." In older cl ...

. The species of section ''Isoplexis'' differ from other plants in the genus ''

'' in that their monosymmetric (sometimes called

zygomorphic Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirall ...

) flowers have a distinctive large upper lip rather than large lower lip and the species are endemic to the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

(the species ''D. canariensis'', ''D. chalcantha'', and ''D. isabelliana'') and

Madeira ) , anthem = ( en, "Anthem of the Autonomous Region of Madeira") , song_type = Regional anthem , image_map=EU-Portugal_with_Madeira_circled.svg , map_alt=Location of Madeira , map_caption=Location of Madeira , subdivision_type=Sovereign st ...

(''D. sceptrum''). Two ''Isoplexis'' species, ''D. canariensis'' and ''D. sceptrum'', were first described by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

in 1753 as part of the genus ''Digitalis''. 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 ''Pinus canariensis'', the Canary Island pine, is a species of gymnosperm in the conifer family Pinaceae. It is a large, evergreen tree, native and endemic to the outer Canary Islands of the Atlantic Ocean. Description ''Pinus canariensis'' is a ...

'' 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 Laurel forest, also called laurisilva or laurissilva, is a type of subtropical forest found in areas with high humidity and relatively stable, mild temperatures. The forest is characterized by broadleaf tree species with evergreen, glossy and elo ...

. The flowers of ''Isoplexis'' species appear to be adapted for

bird pollination Ornithophily or bird pollination is the pollination of flowering plants by birds. This sometimes (but not always) coevolutionary association is derived from insect pollination (entomophily) and is particularly well developed in some parts of the w ...

. It was once thought that the original pollinators of ''Isoplexis'' and the other Canarian bird pollinated plants (such as members of the genera ''

Canarina ''Canarina'' is a genus of flowering plants within the family Campanulaceae. They are herbaceous perennial vines with bell-shaped flowers. The best known species is ''Canarina canariensis'' from the laurel forests of the Canary Islands which is ...

'' and '' Lotus'') were

sunbird Sunbirds and spiderhunters make up the family Nectariniidae of passerine birds. They are small, slender passerines from the Old World, usually with downward-curved bills. Many are brightly coloured, often with iridescent feathers, particularly i ...

s which had become extinct on the Canary Islands; this might explain why ''Isoplexis'' species are rare and considered

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

(Vogel 1954; Vogel et al. 1984; Valido et al. 2004). However more recent work has shown that these plants are adequately pollinated by non-specialist flower visiting birds, particularly the

Canary Islands chiffchaff The Canary Islands chiffchaff (''Phylloscopus canariensis'') is a species of leaf warbler endemic to the Canary Islands, Spain. Sometimes the English name is spelled Canary Island chiffchaff. Taxonomy Previously the Canary Island chiffchaff was ...

(''Phylloscopus canariensis''), and the Canary Sardinian warbler (''

Sylvia melanocephala The Sardinian warbler (''Curruca melanocephala'') is a common and widespread typical warbler from the Mediterranean region. Like most ''Curruca'' species, it has distinct male and female plumages. The adult male has a grey back, whitish underpart ...

leucogastre'') (Olesen 1985, Ollerton et al. 2008), and in fact show some specific adaptations to infrequent pollination by these birds, such as extended flower lifespans (Ollerton et al. 2008), and a

hexose In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. The chemical formula for all hexoses is C6H12O6, and their molecular weight is 180.156 g/mol. Hexoses exist in two forms, open-chain or cyclic, that easily convert ...

-dominated sugar ratio in the composition of the nectar (Dupont et al. 2004). File:Isoplexis canariensis - Berlin Botanical Garden - IMG 8784.JPG, ''Digitalis'' (''Isoplexis'') ''canariensis'' File:Isoplexis isabelliana - Berlin Botanical Garden - IMG 8781.JPG, ''Digitalis'' (''Isoplexis'') ''isabelliana''

References

*Some of this text has been modified from Toomey, N. (2004). "Investigation of the phylogenetic utility of Cycloidea-like genes in various angiosperm lineages". PhD thesis. University of Reading, England. *Brauchler, C.; Meimberg, H. & Heubl, G. (2004). "Molecular Phylogeny of the genera ''Digitalis''. L and ''Isoplexis'' (Lindley) Loudon (Veronicaceae) based on ITS- and trnL-F sequences". ''Plant Systematics and Evolution''. 248 (1-4) 111-128. *Bentham, G. (1835). In: ''Edwards's Botanical Register''. (Lindley, J.). Vol. 21 pp. , ind.ad 1770 1 June 1835, London *Carvalho, J. A. S. S. (1999). "Systematic studies of the genera ''Digitalis'' L. and ''Isoplexis'' (Lindl.) Loud. (Scrophulariaceae: Digitaleae) and conservation of ''Isoplexis'' species". PhD thesis, University of Reading, England *Dupont, Y. L.; Hansen, D. M.; Rasmussen, J. T. & Olesen, J. M. (2004). "Evolutionary changes in nectar sugar composition associated with switches between bird and insect pollination: the Canarian bird-flower element revisited". ''Functional Ecology''. 18 670-676. *Heywood, V. H. (1972). "Flora Europaea: notulae systematicae ad floram Europaeam spectantes no. 13. Scrophulariaceae: ''Digitalis'' L. Sect. Macranthae Heywood, sect nov." ''Botanical Journal of the Linnean Society''. 65 (4): 357. *Himmelbaeur, W. & Zwillinger, E. (1927). "Biologische-chemische Formenkreise in der Gattung ''Digitalis'' L." ''Biologia Generalis''. 3 595-684. *Lindley, J. (1821). ''Digitalium Monographia''. H. H. Bohte, Londini, pg 27. *Linnaeus, C. (1753). ''Species Plantarum''. Vol II 561–1200. Impensis Laurentii Salvii, Holmaniae. *Loudon, J. C. (1829). ''Encyclopaedia of Plants''. 528 528-529. *Olesen, J. M. (1985). "The Macaronesian bird-flower element and its relation to bird and bee opportunists". ''The Botanical Journal of the Linnean Society''. 91: 395-414. *Ollerton, J.; Cranmer, L.; Stelzer, R.; Sullivan, S. & Chittka, L. (2008)
"Bird pollination of Canary Island endemic plants"
''Nature Precedings''. *Sjögren, E. (1972). "Local climatic conditions and zonation of vegetation on Madeira". ''Agrronomia Lusitana''. 36 (2) 95-139. *Valido, A.; Dupont, Y. L. & Olesen, J. M. (2004). "Bird-flower interactions in the Macaronesian islands". ''Journal of Biogeography'' 31: 1945-1953. *Vogel, S. (1954). "Blütenbiologische Typen als Elemente der Sippengliederung". ''Botanische Studien (Jena)''. 1: 1-338. *Vogel, S.; Westerkamp, C.; Thiel, B. & Gessner, K. (1984). "Ornithophilie auf den Canarischen Inseln". ''Plant Systematics and Evolution'' 146: 225-248. *Webb, P. B. (1845). ''Histoire Naturelle des Isles Canaries'' 3 (2-3): 144. *Werner, K. (1960). "Zur nomenklatur und taxonomie von ''Digitalis'' L." ''Botanische Jahrbucher fur Systematic, Pflanzengeschichte und Pflanzengeographie''. 79 (2): 218-254. *Werner, K. (1962). "Die kultivieten ''Digitalis''" Arten. Feddes Repertorium. 70: 167-182. *Werner, K. (1964). "Die verbreitung der ''Digitalis''. Arten. Wiss. Z. Marin-Luther Univ. Halle-Wittenberg, Math. Naturwiss. Reihe 13: 453-486. *Werner, K. (1965). "Taxonomie und phylogenie der gattungen ''Isoplexis'' (Lindl.) Benth und ''Digitalis'' L. ''Feddes Repertorium'' 70: 109-135. *Werner, K. (1966). "Die wuschformen der gattungen ''Isoplexis'' (Lindl.) Benth. und ''Digitalis'' L." ''Botanische Jahrbucher fur Systematic, Pflanzengeschichte und Pflanzengeographie''. 85 (1): 88-149. *Wettstein, V. (1891). "Scrophulariaceae. Rhinantoideae-Digitaleae". In: ''Die Naturlichen Pflanzenfamilien'' IV 3b (Engler, A. & Prantl, K. Eds.) pp. 83–90. Wilhelm Engelmann, Leipzig. Plantaginaceae Endemic flora of Macaronesia