Gonzalagunia Ruiz & Pav. includes ca. 34 species of tropical shrubs and small trees found in moist to wet vegetation, rather widely in the Neotropics. These species are characterized by generally opposite leaves; triangular interpetiolar stipules; racemiform or spiciform, slender, terminal (or rarely axillary) inflorescences and with bracts usually rather small; 4-merous flowers; salverform, generally white to pink corollas with the lobes imbricate or valvate in bud; 2- or 4-locular ovaries and stigmas of corresponding number; and unusual drupaceous fruits with 2 or 4 pyrenes containing numerous seeds. The pyrenes are tough-walled, and the fruits are generally fleshy with a white or blue, thin to spongy outer wall. The numerous ovules are numberous in each locule, and the pyrenes contain these as numerous dry, angled seeds. The flowers are usually distylous, with the anthers held within the corolla in both floral forms but the stigmas sometimes exserted, but these appear to be homostylous in some species (Andersson & Stahl, 1999). The lateral branches are generally flexuous with a distichous leaf arrangement TThe plants sometimes have distincttve dense, lanose-floccose pubescence that seems to be consistently developed within a species. The center of species diversity for Gonzalagunia is in southern Central America and northwestern South America. Gonzalagunia panamensis, Gonzalagunia dicocca, and Gonzalagunia cornifolia are the most commonly collected species.
The information here applies to the "traditional" recent circumscription of Gonzalagunia; as noted below, these species are closely related to Arachnothryx (Torres-Montúfar et al., 2020), and the circumscription of these genera may change in the future. Gonzalagunia has not been comprehensively reviewed, but it has been studied in several floras where it is well represented. The synopsis here is intended to present the floristic information as a basis for further study. Modern morphological genus descriptions of Gonzalagunia were presented by Ståhl (in Andersson & Ståhl, 1999), Steyermark (1974), and Taylor (in Taylor et al., 2004, and in Lorence et al., 2012). No infrageneric classification has been recognized by any recent authors.
Gonzalagunia has several unusual features within the Rubiaceae. In particular the fruits are often dimorphic, within a species and sometimes on the same plant. Ståhl (in Andersson & Ståhl, 1999) noted that in Ecuadorian species the same infructescence produces both fruits with thin outer walls and fruits with spongy thickened outer walls, and regarded some of these fruits as dry and schizocarpous at maturity. Also, plants of Gonzalagunia spicata in the Antilles produce fruits with consistently spongy walls but that are variously white on some infructescences and blue on others, with plants consistent or sometimes variable on the same plant (C.M. Taylor, pers. obs.). Also the inflorescence bracts subtending the flower groups vary from reduced to linear and well developed, to 15 mm long. This range of bract form is found within most species of Gonzalagunia. The genus Gonzalagunia was described until recently as sometimes having numerous well developed inflorescence bracts, but the single Gonzalagunia species that had that characteristic is no longer included in this genus, it is now classified as Bertiera bracteosa. Not previously noted is the occasional occurrence of axillary inflorescences, in Gonzalagunia congesta. The stipules are bilobed on the type specimen of Gonzalagunia bifida, however they are triangular in some others specimens of that species.
The number of ovary locules, 2 or 4, appears to be consistent within a species; most species have 4 locules. These ovary locules usually separate as individual pyrenes in fruit but appear to possibly remain fused in some cases. The inflorescences are thyrisform in arrangement, but the primary axis is well developed often prolonged and flexuous while the secondary axes are characteristically reduced to a sessile short cyme of flowers. This arrangement give the inflorescences a distinctive appearance: generally there are flowers maturing and opeining along the length of the primary axis, as the individual cymes with different numbers of species develop, rather than the flowers in one zone of the inflorescence all being at the same stage as in most racemose inflorescences. The corollas of Gonzalagunia vary in size rather notably, with those of most of the species of average size for Neotropical Rubiaceae (corollas ca. 10-15 mm long) but the corollas of a few species quite small (to as small as 3-4 mm long in Gonzalagunia brachyantha, Gonzalagunia ovatifolia, and Gonzalagunia rudis). Some species of of this genus have dense white floccose or lanose pubescence on the undersides of the leaves, and this seems to be characteristic of particular species (Gonzalagunia chiapasensis, Gonzalagunia killipii, Gonzalagunia dependens).
Gonzalagunia is also similar to Bertiera, which has inflorescences with developed secondary axes, homostylous flowers, the corolla lobes convolute in bud, and baccate fruits. Several species long treated in or confused with Gonzalagunia are now included in Bertiera, notably Bertiera bracteosa and Bertiera viburnoides.
Gonzalagunia is also similar to some species of Arachnothryx with narrow elongated inflorescences and 4-merous flowers, and sometimes also lanose pubescence. Arachnothryx has been separated in large part by its dehiscent capsular fruits, and sometimes classified in a separate tribe. However, Manns & Bremer (2010) and Torres-Montúfar et al. (2020) found that Gonzalagunia is actually nested within Arachnothryx. The variation in fruit form noted by Andersson & Stahl (1999), with some species occasionally producing dry, schizocarpous or perhaps subcapsular fruits, had already blurred the morphological lines between these genera. Torres-Montúfar et al. presented the new systematic view of these genera as a cladogram; we look forward to seeing this new evolutionary view incorporated into an updated classification.
The name Duggena Vahl in H. West has sometimes been used for these plants, and first appeared in print in 1793 before the name Gonzalagunia was published in 1794. However the citation there of Duggena Vahl did not meet the current criteria for valid publication of plant names, so Gonzalagunia is the oldest validly published name for this genus. In 1916 Standley found and used the name Duggena, but its valid publication only dates from his works, long after the publication of Gonzalagunia.
Author: C.M. Taylor.
The content of this web page was last revised on 24 June 2021.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml