A new species of Standleya (Rubiaceae, Coussareeae) with a new record for Bahia, Brazil

Abstract

Standleya glomerulata, a new species and a first record for the semiarid region of Bahia, Brazil, is described and illustrated. It differs from all other known species of the genus by its prostrate decumbent and reptant habit, glomerulate sessile inflorescences, and a calyx with two unequal lobes. S. prostrata has a similar habit, but can be distinguished by the pedunculate inflorescences and a calyx with four equal lobes. The new species is known from only a few localities in two protected areas and must therefore be considered threatened.

Phylogeny of Coussareeae (Rubioideae, Rubiaceae)

“…Piesschaert et al (2000) proposed "stipules bearing a central colleter-tipped awn extending to the next stipule in a distinct ridge" (paraphrased) to be a potential synapomorphy for Coccocypselum, Declieuxia, and Hindsia, previously described by Kirkbride (1976) for Declieuxia. This type of stipule has also been described for Standleya glomerulata by Jardim and Costa (2015), but they do not mention or show a stem ridge. Contrastingly, a stem ridge can be seen in the images of Oliveira and Sobrado's (2016) description of Bradea borrerioides, but they do not mention or show stipules with a central colleter-tipped awn.…”

“…1) is supported by some potentially synapomorphic morphological and palynological features (Tables 1, 2). All genera in the clade except Coccocypselum are characterized by septicidal fruit dehiscence, even the baccate schizocarps of Declieuxia (Müller Argoviensis 1881; Schumann 1891; Jardim and Costa (2015). Septicidal dehiscence is similarly uncommon in Rubioideae (e.g., Schumann 1891), and the indehiscent fruits of Coccocypselum could be the cause of an independent reversal.…”

“…Cruckshanksia and Oreopolus are native to the "arid diagonal" (predominately cool and arid climate) with Cruckshanksia found from central Chile to northwestern Argentina and Oreopolus from central to southern Argentina (Taylor 1996;Tropicos 2018). The Coccocypselum clade on the other hand has a clear center of diversity in southeastern Brazil; Bradea, Hindsia, and Standleya are all endemic to the region, with Hindsia growing primarily in montane, sandy Cerrado (Steyermark 1978;Di Maio 1996), whereas Bradea and Standleya grow in partial to full sun on well-drained, rocky outcrops in the Atlantic Rainforest (Jardim and Costa 2015;Oliveira and Sobrado 2016). Coccocypselum and Declieuxia are more widely distributed (southeastern South America to southern Mexico; Tropicos 2018), but most species in both genera are endemic to southeastern Brazil; both genera grow in partial to full sun, with the former widespread in the Atlantic Rainforest biomes and the latter primarily on savannas (Kirkbride 1976;Robbrecht 1993;Costa and Mamede 2002;Costa 2007).…”

“…Flowers are hermaphroditic or rarely dioecious (Bawa and Beach 1983;Taylor et al 2004;Maruyama et al 2010) and mostly heterostylous, with white, blue, or yellow corollas (Schumann 1891;Taylor et al 2004); some species additionally have showy calycophylls (Cruckshanksia, Taylor 1996) or petaloid calyx lobes (Faramea, Taylor et al 2004). There is also a wide range of fruit types represented in the tribe (Hooker 1873;Schumann 1891;Taylor 1996;Jardim and Costa 2015;Oliveira and Sobrado 2016): blue, baccate schizocarps with few-seeded, hollow mericarps (Declieuxia); blue, hollow, multi-seeded baccate indehiscent fruits (Coccocypselum); green-white-yellow (Coussarea) or dark blue-purple-black (Faramea) 1(-2)-seeded drupes; lignified, septicidal capsules (Bradea, Hindsia, Standleya); and chartaceous, loculicidal capsules (Cruckshanksia, Heterophyllaea, Oreopolus). With the tribe's members displaying such high level of morphological diversity, it is hardly surprising that the eight genera were formally assigned to several distantly related tribes in pre-molecular classifications of Rubiaceae (e.g., Hooker 1873;Verdcourt 1958;Bremekamp 1966).…”