Carphalea today includes three species in Madagascar of shrubs and small trees that are found in sclerophyllous, dry, and xeric vegetation, not a common habitat among Rubiaceae even in Madagascar. These plants are also notable for their enlarged calyx limbs. Carphalea is characterized by its persistent stipules with 1 to several linear lobes or setae with glandular tips, its slender tubular-funnelform corollas, and its dry indehiscent fruits with several seeds. The flowers are distylous. Some of the species are apparently deciduous, at least at times. The calyx limb is green to brightly whitened and enlarges after anthesis, as the fruits develop. Two of the species have symmetrically lobed calyx limbs, but Carphalea linearifolia differs in having three small calyx lobes and one that is enlarged and petaloid, simlarly to species of Paracarphalea (discussed below). The tribal classification of this genus has varied, and it was placed by several authors in the Albertieae.

Carphalea has previously been circumscribed more broadly, to include nearly a dozen species from southeastern Africa, Socotra, and Madagascar (Puff 1988). It has subsequently been divided twice, with the species Puff studied now included in three genera. In the first molecular systematic study of this group, Kårehed & Bremer (2007) found the African plants were not closely related to the plants of Madagascar and separated the African plants in Dirichletia (including Placopoda). Kårehed & Bremer also classified Carphalea in the tribe Knoxieae, rather than Hedyotideae as some previous authors suggested. The six species from Madagascar that remained in Carphalea in their analysis all have calyx limbs that enlarge variously before or after anthesis, are 4- or 5-lobed, range from symmetrical to markedly asymmetric, and vary from green to white, orange, or red. Kårehed & Bremer also found the Carphalea species from Madagascar that they studied were paraphyletic and grouped on two separate clades, and they suggested these clades might comprise two distinct genera. One of their clades comprised species with green calyx to white limbs that enlarging after anthesis, including Carphalea madagascariensis, the type of the genus. Their other clade had species with the calyx usually strongly asymmetrically lobed, bright red to orange or sometimes dully colored, and enlarged before anthesis; these calyx limbs presumably function to attract pollinators. . Their analysis was not strongly resolved and did not include Carphalea linearifolia, and Kårehed & Bremer did not taxonomically separate these groups

Ferm et al. (2016) studied Carphalea as Kårehed & Bremer circumscribed it in more detail and included Carphalea linearifolia in their analysis. They found a well supported clade of three species that included the type of Carphalea, and that the remaining species were grouped together with moderate to good support. They also found these remaining species were not included in any sister clades, and they separated these three species in the newly described genus Paracarphalea. Carphalea linearifolia was placed within Carphalea s. str. by their analysis. These two genera differ as outlined in the key below.

Carphalea is similar to several other genera in addition to Paracarphalea in its enlarged calyx lobes and slender corollas, in particular to Razafimandimbisonia and Nematostylis. A key to separating all of these is below. Carphalea pubescens has sometimes been reported from Madagascar, but that a species of Africa now treated as Dirichletia pubescens. Dirichletia has the calyx limbs much larger than in Carphalea, not or hardly lobed, and very strongly ovate in outline.

Author: C.M. Taylor.
The content of this web page was last revised on 9 March 2017.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

• Puff, C. 1988. Observations on Carphalea Juss. (Rubiaceae, Hedyotideae), with particular reference to the Madagascar taxa and its taxonomic position. Bull. Jard. Bot. Natl. Belg. 58: 271–323.
• Kårehed, J. & B. Bremer. 2007. The systematics of Knoxieae (Rubiaceae)-molecular data and their taxonomic consequences. Taxon 56(4): 1051-1076.
• Ferm, J., J. Kårehed, B. Bremer & S. G. Razafimandimbison. 2016. Paracarphalea, a new genus of the coffee family segregated from the Malagasy endemic genus Carphalea (Rubiaceae, Rubioideae, Knoxieae). Phytotaxa 263(2): 98–112.