Chomelia includes about 55 species of Neotropical shrubs, trees, and lianas. Chomelia can be recognized in Guettardeae by a woody habit; interpetiolar, triangular, usually acute stipules; axillary inflorescences with one to several fragrant flowers each subtended by 2-3 floral bracts; 4-lobed, pale green to white, or sometimes pink or yellow corollas with a well developed, slender tube; corolla lobes that are valvate or induplicate-valvate in bud and often winged or appendaged; ellipsoid to fusiform, medium-sized, red to purple-black, drupaceous fruits; and usually 1 pyrene that is 2- or reportedly sometimes 3-locular. Chomelia also lacks of raphides in the tissues, and is frequently additionally characterized by several distinctive features that are not, however, found in all the species. Many though not all Chomelia species have dense strigose pubescence on outside surface of the stipules and corollas and frequently on the leaves, stems, and inflorescences; a number of species have stout short-shoots that bear the leaves and flowers; many species have short but strong axillary spines; and many species have acuminate stipules and corolla lobes. Chomelia is often recognized by a distinctive lineolate leaf venation, but this is not found in all species as discussed below. The stems are often rather densely lenticellate. The genus is characterized by most authors as distylous, but this has not been confirmed in for most species in this current study. Chomelia is widely described as sometimes having separate, 1-locular pyrenes or 3-locular ovaries, but whether these conditions are found in the species still included in Chomelia or correspond to species now excluded from it has not been confirmed in this review.
As detailed below, the name Chomelia has been used in various circumscriptions and sometimes has included Paleotropical plants. Chomelia is its modern circumscription is found only in the Neotropics, and the notes here apply only to Neotropical plants. Chomelia has centers of diversity in Mexico and Central America, and in northern to eastern South America; in spite of its diversity here, it has not been documented in the Greater Antilles. The most commonly collected species seem to be Chomelia spinosa, Chomelia protracta, Chomelia obtusa, and Chomelia ribesioides.
Little information seems to be available about Chomelia's floral biology, but perhaps at least some species are nocturnal. Whatever their biology, the mature, white corollas of several species turn yellow with age and fall quickly when collected, and corolla size also varies widely within some species. The anthers are positioned in the corolla throat in the specimens seen, and included or have only their tips protruding. The styles seen are of a length to position the stigmas as included and below the anthers or exserted and above them.Confirmation of distyly in most Chomelia species is limited by inadequate specimen documentation, but If some of these species are actually distylous then this arrangement is similar to the less-common form of distyly described from Guettarda (Richards & Koptur 1993).
A number of species of Chomelia have distinctive lineolate leaf venation, with the quaternary venation closely set and subparallel forming fusiform to elongate-oblong areoles, and this arrangement has been used to partially diagnose or at least characterize the genus (e.g., Taylor & Gereau, 2010). However, this arrangement is not present in all species, and it is present but not visible in some others with thick-textured leaves. Some other species have laxly areolate tertiary venation and the quaternary venation not visible (e.g., Chomelia barbata), or both of these laxly to closely areolate. The systematics of these leaf venation arrangements has not been investigated.
Corolla lobe characters of Chomelia have been variously described and interpreted. The corolla lobe aestivation has been widely characterized as variously valvate or imbricated (e.g., Steyermark, 1974), but this review and Pessoa (2016; pers. comm.) have confirmed that it is actually thinly valvate or valvate-induplicate throughout the genus (Taylor & Berger, 2021). Also, the corolla lobe margins vary from nearly straight to thinly winged, crisped, or appendaged with rounded petaloid protrusions. Anisomeris was separated based on its appendaged corolla lobes, vs. entire in Chomelia; however, more species have been discovered since Anisomeris was detailed by Standley, and several are intermediate in this feature and Anisomeris has since been synonymized (Bremekamp, 1934; Steyermark, 1967: 333-341).
Chomelia has not been reviewed as a whole, nor studied systematically. Manns & Bremer (2010) included two species of Chomelia in their molecular analyses of Guettardeae, and found them to be sisters and placed on a poorly resolved clade with the other Guettardeae genera with drupaceous fruits. Torres-Montúfar et al. (2020) included two different Chomelia species in their analysis, and found similar results. Pessoa (2016) in her dissertation presented a molecular analysis of the genus and its relationship, with a focus on the Brazilian species, and treated it as a single genus but this analysis has not yet been formally published. The analysis by Chavez et al. (2021) included three Chomelia species as outgroups that were found placed on two separated clades; this genus includes two apparently distinct morphological groups, with acuminate vs. rounded corolla lobes, and further study may find that more than one lineage is currently included here. As noted by Chavez et al., in general generic cirumscriptions have been controversial and are not fully resolved in Guettardeae. The two apparently separate lineages found by Chavez et al. do not correspond to Chomelia vs. Anisomeris.
No infrageneric classification is in use for Chomelia. Mueller (1881) recognized three sections of Chomelia in his treatment of the Brazilian species, one of them with only two species and another with only one species. He distinguished these by the shape of the corolla tube (cylindrical vs. "obovoid"), the relatively length of the corolla tube to the lobes and to the stamens). However, the Brazilian species comprise a rather small minority of the entire genus and its morphological variation, and the characters he used to separate his sections do not clearly distinguish any broader infrageneric groups across the entire genus. Mueller's sections were not recognized by Steyermark (1967) and are not recognized here pending comprehensive systematic analysis of this genus. The taxonomy here is based on published floras, Steyermark's review of the genus (1967), and Pessoa (2016 and in the Brazil Catalogue).
The identity and circumscription of Chomelia were confused for some time, due to Limmaeus and Jacquin both publishing it nearly simultaneously for differnt Rubiaceae genera. Linnaeus's Chomelia iwas published in 1758 and included one species from Asia, and corresponded to the pre-1753 use of this same name by Linnaeus in his Genera Plantarum of 1737, and Hortus Malabaricus 1: tab. 23, 1703. Jacquin's Chomelia was published in i1760 and ncluded one species from the Caribbean coast region of northern South America. These two names were considered the same for some time, and the two genera were conflated taxonomically. These genera are distinct morphologically and biogeographically, however: Linnaeus's Chomelia corresonds to Paleotropical plants with baccate fruit today treated as Tarenna, and Jacquin's Chomelia is now the accepted use ofr this genus name and correspond to Neotropical plants with drupaceous fruits with a single pyrene. Jacquin's slightly later name was therefore an illegitimate later homonym when published, because Linnaeus has previously published this same name. This situation was clarified by Kuntze (1891: 278), who accepted Linnaeus's genus Chomelia and provided the replacement name Caruelina for Jacquin's Chomelia, and subsequently Schumann (1891) synonymized Anisomeris C. Presl (1833) with Chomelia Jacq. and used that as the name for this group. Later, Jacquin's Chomelia was formally conserved against Linnaeus's Chomelia, reversing this usage. Before this nomenclatural conservation clarified the [new] situation, Linnaeus's name Chomelia had been confused with Jacquin's Chomelia, and Linnaeus's name was later given the replacement name Webera, and Jacquin's name has sometimes also been considered a synonym of Webera, which is now a synonym of Tarenna. This has led to Jacquin's name being synonymized with Tarenna, sometimes under its superfluous replacement name Webera, and this confusion is still found in some floras (e.g., Burger & Taylor 1993).
Chomelia is simillar to several other Neotropical Guettardeae genera that have been problematic as to their separation (Delprete & Achille, 2010; Taylor & Gereau, 2010: 353, a key to similar genera), and some of these differ in corolla aestivation and can otherwise be difficult to separate. In particular, several Chomelia species are similar to Stenostomum acreanum. Chomelia is also similar to Tournefortiopsis, which can be separated by its pyrenes with apical horns. Chomelia is also similar to Pittonitis, with 5-merous flowers.
Author: C.M. Taylor The content of this web page was last revised on 28 January 2022.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml