Rondeletia includes perhaps 150 species of shrubs and trees that are characteristically found in seasonal vegetation. It is characterized by small to medium-sized leaves often with domatia; triangular, usually persistent stipules that are sometimes shortly united around the stem; inflorescences that are basically cymose and bracteate but vary in size and form whether they are terminal and/or axillary; small to medium-sized. 4--7-merous flowers; calyx llmbs with the lobes developed and often unequal in size; white to yellow, orange, or dark red corollas that are nearly always salverform with imbricate aestivation and rounded lobes; and rounded, rather small capsules that are loculicidal and contain numerous small flattened seeds. The leaves range from rather robust to quite small (ca. 2 x 2 mm) in various Antillean species (e.g., Rondeletia virgata). The flowers are homostylous and fragrant. The capsules frequently have a well developed disk portion that extends above the insertion of the calyx limb. The best-known species is probably Rondeletia odorata, which is widely cultivated as an ornamental. The most widespread and commonly collected species are Rondeletia inermis and perhaps Rondeletia hameliifolia.
Rondeletia is biogeographically a Caribbean genus, found on various islands and in the surrounding continental areas. The majority of the species are rather localized in range, and found on limestone. The species of Rondeletia vary markedly morphologically especially in amount and type of pubescence, size and shape of the leaves and calyx lobes, corolla size and color, flower merostiy, and capsule size. The circumscription of Rondeletia has been varied, problematic and controversial,in large part because of the morphological variation found among the species, especially in number of calyx and corolla lobes. Rondeletia is here circumscribed and morphologically characterized following Torres-Montúfar et al. (2020). This circumscription agrees with that of Steyermark (1967) and, in general, of Lorence et al. (2012) and Borhidi (2012, 2017). Rondeletia has not been studied as a whole, although Borhidi in several articles since 1980 has reviewed its species in several Spanish-speaking Antillean islands, Mexico, and Central America.
Rondeletia has a center of diversity in the Greater Antilles. Borhidi et al. (2017) recognized 67 species in Cuba, all endemic; Liogier (1995) recognized 43 species of Rondeletia in HIspaniola (9 as Stevensia, and an additional species later added by Borhidi and one removed by Torres-Montúfar et al., 2017), with almost all of them endemic there;. and Adams (1975) recognized 29 species in Jamaica, with all of them endemic there. Many of these Antillean species were incompletely known to these authors, and are distinguished in large part by leaf form and details of pubescence and several are quite similar to each other. Few Cuban and Hispaniolan specimens were available for this current review, and the taxonomy of these plants is catalogued but not evaluated here.
The name Rondeletia has been used since it was published for a morphologically varied, widely distributed group of Rubiaceae with generally interpetiolar stipules, cymose inflorescences, salverform to funnelform corollas with the lobes imbricated in bud, and capsular fruits with numerous small seeds. This group has been narrowed over time by the separation of various genera, starting with Wendlandia DC. for the Asian species. The neotropical species that have been included Rondeletia are morphologically quite varied, and have been included within a broadly circumscribed Rondeletia genus by some authors based on the lack of clear morphological separation of smaller groups (e.g., Lorence, 1999) and separated by other authors into a number of smaller genera based on particular details (e.g., Planchon, 1849; Steyermark, 1964; Borhidi, 1980, 1981. 1983, 2004, 2011, 2018, 2018). Molecular study of Rondeletia and the complex of its associated genera (the Rondeletia complex of Delprete, 1999) found this group to be notably complex, and to include lineages from two tribes, Rondeletieae and Guettardeae (Rova et al., 2002, 2009; Manns & Bremer, 2010; Torres-Montúfar et al., 2020). This molecular work clarified the identity of Guettardeae as well as limiting Rondeletieae to neotropical genera. The Rondeletia complex was narrowed most significantly by exclusion of Arachnothryx, with more species and a wider geographic distribution, and this genus is now included in Guettardeae. Some of the other genera that were separated from Rondeletia are also now included in Guettardeae: Rogiera, which is a well supported lineage, and Javorkaea and Renistipula if those are in fact distinct from Arachnothryx. The name Rondeletia was for some reason considered in 19th-century Asian taxonomic treatments to be possibly the same as Webera, a synonym of the Paleotropical genusTarenna, and that supoposed similarity has generated confusion among old names; Tarenna has convolute corolla lobes, fleshy baccate fruits with the calyx limb deciduous, and the seeds only a few and concave-discoid.
This narrowed new circumscription of Rondeletia leaves the remaining plants of the Rondeletieae complex as a heterogeneous group of Rubiaceae found in Mesoamerica and the Greater Antilles, The further identification of lineages within this group has been difficult due to the close morphological similarity and also the wide morphological variation, sometimes within a species, in what are usually diagnostic features found within among these species. Torres-Montúfar et al. (2020) presented the most comprehensive and detailed analysis, with molecular, general morphological, and palynological characters. Their analysis found Rondeletia to be the largest gewnus in this tribe, and to be diagnosed morphologically by having a thickened glabrous ring in the corolla throat (i.e., a faucial ring), with this structure absent in other lineages in this group. Their analysis supported the separation from Rondeletia of Borhidi's segregate genera Rovaenathus, Donnellyanthus, Acunaeanthus, Suberanthus, Roigella, and Suberanthus, as well as an additional genus, Tainus. Morphologically, Torres-Montúfar et al. (2020) noted honestly that the characters distintinguishing lineages in this group are often subtle and small. Torres-Montúfar & Ochoterena (2019) separated several genera of the Rondeletia complex morphologicaly only by the combination of two or more flower characters that are each found in more than one genus, rather than a single unique feature. In particular, Torres-Montúfar & Ochoterena (2019: 122) considered two features of the corolla throat, pubescence and a fleshy thickening, to be "different and independent character states". In contrast to the separation of these various small genera, molecular studies found Stevensia to be included within Rondeletia. The separation of Rondeletia from some other genera, notably Arachnothryx, has been confused not only by the subtlety of the diagnostic characters, but also by some changing circumscriptions used by the same author with the same species classified differently at different times and inaccurate descriptions of the characters of these two genera.
Petesia was described in 1756 with three species from Jamaica, which were not named with binomials so only the genus name was validly published. Two of these were illustrated there in Browne's tabl. 2. Petesia was often treated subsequently quite broadly and with confusion over its actual identity (e.g., Candolle, 1830), and has included species of what are now various genera in both the Paleotropics and the Neotropics. The identity of Browne's Petesia species has also been confused, starting with Linnaeus's naming of them in which his morphological diagnosis did not agree with the figures he cited and continuing through the work of Moore (in Fawcett & Rendle, 1936), where Browne's species were each cited as equivalent to two or more different species of Rondeletia and Manettia. Rather early in our botanical history, however,Smith (1814) had noted that the name Petesia had been used for a morphologically varied group of species, and he excluded several of these from the circumscription of the genus and stated that Petesia stipularis is "the only authentic species" of Petesia. This species is now treated as Rondeletia stipularis, so Petesia is a syononym of Rondeletia; Smith's lectotypification has been widely overlooked but is effective. See the genus page for Petesia for more details about it.
Stevensia has been variously separated from and included within Rondeletia since its description. Stevensia was separated from Rondeletia for one species, Stevensia buxifolia, based on several unusual features: the flowers solitary or few and subtended by 4 bracts, a 2-lobed spathaceous calyx limb, and 6-7-lobed corollas. In addition, Stevensia was later included in Rondeletia by some authors (e.g., Grisebach, 1864), and separated again by others (e.g., Liogier, 1995). It was eventually expanded as a separate genus to include 11 species restricted to Hispaniola (Borhidi, 2001), but in contrast Grisebach (1864) had previously included it as a section of Rondeletia and included in it also four Jamaican species; Grisebach's treatment and its addtional species were not cited by Borhidi. The morphological features of Stevensia are distinctive, but found in various genera and often not diagnostic there of a separate Rubiaceae lineage or species group, Various molecular systematic studies, notably the detailed broadstudy using both molecular and morphological data of Torres-Montúfar et al. (2020), all found Stevensia nested in Rondeletia, and grouped there with Rondeletia species frum the Greater Antilles. Accordingly they synonymized Stevensia, as did Borhidi later (2010). In contrast to Borhidi's descriptions, Torres-Montúfar et al. (2020) noted that the species they saw of Stevensia do all possess the fleshy ring in the corolla throat and winged seeds that they used to diagnose Rondeletia; these morphological structures have also been confirmed in this study. Following them, Stevensia is synonymized here with Rondeletia; see its genus page for more detailed information.
Jamaicanthus was separated as a monotypic genus distinguished from Rondeletia (Borhidi, 2018: 285) by its funnelform, quite small corollas that are tomentellous, disk that is tomentellous, and details of pollen morphology, along with "subglobose" stigmas and corolla throat without a thickened ring. However, the first two characters are found in other Rondeletia species in Jamaica, the pollen of this group has not been fully surveyed, and the the stigmas are bilobed and the corolla does have a glabrous thickened ring in the throat on the materials seen (Proctor 37585, Adams 13091, MO). Torres-Montúfar et al. (2020) noted that they did not see material or include this species in their molecular analysis but it has all the characters of Rondeletia except possibly the thickened ring in the corolla throat. With this corolla throat ring confirmed as present, Rondeletia laurifolia is unusual in its small corollas but agrees with Rondeletia in taxonomy of Torres-Montúfar et al. For more details see the web page for that genus.
Tainus was separated from Rondeletia by Torres-Montúfar et al. (2017, 2020), with one species, Rondeletia pitreana from Hispaniola, base on molecular sequence data. As discussed above, they concluded that lineages in the Rondeletieae are characterized morphologically by details of the form and pubescence of the corolla, and separated Tainus by the densely papillate surface of the corolla lobes and interior of the corolla mouth, along with two trnL-F sequence repeats. See the web page for Tainus for more information.
Rondeletia has long been associated closely with Arachnothryx, which is often remarkably similar in general aspect even though it is now placed in a separate tribe. Arachnothryx generally has well developed pubescence, and differs from Rondeletia in its corollas that lack a thickened ring in the throat and also usually its habitat in wet vegetation. Several other genera have also been recently separated from Rondeletia, including Donnellyanthus, Rogiera, Rovaeanthus, and Suberanthus, see their web pages for more information.
Author: C.M. Taylor. The content of this web page was last revised on 5 November 2021.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml