PlantLife Volume 57.3, July 2024. Marijordaania filiformis, the Red-flower Silky-bark

Gymnosporia, Maytenus and Marijordaania – name changes and a new monotypic genus to accommodate “Maytenus sp. A”

Text and images by Richard Boon except where stated otherwise

Nearly 100 years after it was first described, one of KwaZulu-Natal (KZN) and the Eastern Cape’s lesser known woody plants has recently been renamed Marijordaania filiformis. The name honours retired SANBI botanist Marie Jordaan. This shrub or small tree was known as Maytenus sp. A for 40 years, but it was originally described and named Gymonsporia filiformis by Davison in her 1927 taxonomic revision of the South African Celastraceae. Its common name is Red-flowered Silky-bark.

Photo 1.  The Red-flowered  Silky-bark has distinctive pink-red flowers with white margins that are held beneath the leaves on long, fine pedicels. (photograph by Sharon Louw)

While Davison took a broad view of Gymnosporia, Loesener felt that the spineless African species were distinct and he transferred them to Maytenus in his worldwide review of the Celastraceae published in 1942. Prior to that, Maytenus species were considered to be confined to the New World. While Loesener’s revision was otherwise thorough, he did not mention Gymnosporia filiformis and make the combination Maytenus filiformis.

Photo 2.  Gymnosporia polyacanthus Hedge Spikethorn with spines and clustered leaves on brachyblasts.

Sometime later, taxonomists decided to combine Maytenus and Gymnosporia again. Following that approach, the South African Gymnosporia species, including the spiny ones known as spikethorns, were included in a broad concept of Maytenus by Marais in 1960. Marais also included Maytenus cordata (Water Silky-bark) and Gymnosporia filiformis in a broadly defined Maytenus acuminata (Silky-bark).

Photo 3. Silky-bark Maytenus cordata at Harold Porter Botanic Garden. Note clusters of flowers held erect to spreading. Silky-bark flower are pink-tinged.

In the early 1980s Tony Abbott (1936–2013), who knew his trees of southern KZN and Pondoland well, started questioning how the four distinct Maytenus species he saw in local forests, could all be M. acuminata. His questions prompted Braam van Wyk to re-evaluate Marais’ broad concept of the species. Braam concluded that Tony was right and he described Maytenus abbottii (Pondo Silky-bark) in 1984.

Photo 4.  The Pondo Silky-bark is the only Maytenus species in southern Africa that has tetramerous lowers. The white flowers in this photograph have short stalks and four petals and stamens. The species was thought to be endemic to Pondoland, but there are at least two small outlying populations in the greater Durban area.

He also discovered that when first describing Gymonosporia filiformis, Davison cited four collections (syntypes), three matching Maytenus cordata and one matching her description of Gymnosporia filiformis. Davison’s error is unsurprising as pressed specimens of these two plants can be very similar, especially if they are sterile. Nowadays species’ descriptions must be based on a single type known as a holotype. Braam’s discovery meant that a new type needed to be designated (referred to as lectotypification), the description needed to be checked to ensure it matched just Gymnosporia filiiformis and the species had to be transferred to Maytenus because Gymnosporia was not recognized in South Africa at the time. Braam suggested that, until this work could be completed and the new name properly published, the plant should be known as Maytenus sp. A, which is how it was known for nearly 40 years.

In the meantime, Braam and Marie Jordaan, who was one of his Ph.D. students, reinstated the genus Gymnosporia in 1999 for African species that differ from Maytenus in several ways, including having spines, brachyblasts (short branchlets bearing leaves and flowers), leaves in fascicles (tightly clustered alternate arrangement) on older branches and unisexual flowers. When I started learning trees, there were no Gymnosporia species and many of the spiny Maytenus species were lumped in a diverse and confusing complex under catch-all names like Maytenus heterophylla. Marie went on to produce an excellent revision of the difficult genus Gymnosporia and described about ten new species.

While Marie and Braam were sorting out Gymnosporia, researchers based mainly in the USA and Brazil, but including Robert Archer from SANBI, used morphological and molecular techniques to conclude that Maytenus is indeed confined to the New World and Gymnosporia primarily to the Old World. They also determined that the species of Maytenus are not all closely related and African members of the genus need to be placed in new genera to better represent their evolutionary relationships.

While others will handle splitting African Maytenus into segregate genera, Braam and I decided to tackle Maytenus sp. A. We felt that we knew the species well and had access to information and photographs to support a comprehensive revised description of the taxon. Although molecular studies mentioned above suggest that Maytenus sp. A is closely related to M. abbottii, in our view they are sufficiently distinct to be placed in separate genera. Some of these differences are M. abbotti has four petals vs five, short vs long pedicels, no disc vs disc present, latex present (see below) vs no latex and the arils and stamens and their attachment differ. We decided to name the new genus Marijordaania and Maytenus sp. A becomes Marijordaania filiformis. Incidentally, when Marie’s name is Latinised the e is dropped. We could not use Jordaania because the rules of botanical nomenclature suggest that is not allowed to prevent confusion with the existing genus Jordania.

Photo 5.  The white aril almost covers the seed in a freshly opened Marijordaania filiformis fruit capsule. The seed is dark brown.

Photo 6.  In the Pondo Silk-bark only the base of the seed is covered by the white aril and the arils have long, finger-like extensions. The aril also differs from its closest apparent relatives in being minutely hairy. I think the difference in the seed colour may also be significant, but that needs further observation.

The Red-flowered Silky-bark is easy to separate from similar species in the field. Several South African members of the Celastraceae, including some members of Maytenus, have elastic threads in their leaves. These are visible when a leaf is broken in half and gently separated. The Red-flower Silky-bark lacks threads, but they are found in the other silky-barks, namely Maytenus abbottii, M. acuminata and M. cordata. Identifying sterile pressed specimens is difficult because the threads are hard to detect. Red-flowered Silky-bark plants flower and fruit infrequently, but the remarkably long, fine pendent flower and fruit stalks are very distinctive, hence filiformis or threadlike. The pink-red flowers with white margins are unlike the white or pink-tinged flowers in the other species and the attachment of the stamens is different. Maytenus and Gymnosporia have arils and the colour and extent to which these fleshy structures envelope the seed are important characters for separating species. In Marijordaania filiformis the aril is white and when fresh it covers nearly the whole seed. In Maytenus abbottii it is also white, but only the lower part of the seed is covered. In the other two species it is orange.

Photo 7.  Maytenus cordata (shown here) and M. acuminata have orange arils that cover the seed. The leaf in the middle on the right has been broken to show the elastic threads. These are absent in Marijordaania filiformis.

We used IUCN methods to do a preliminary conservation assessment for the Red-flowered Silky-bark. Our results suggest that the species is probably Endangered because there are only about 15 sub-populations between Dwesa-Cwebe Nature Reserve in the Eastern Cape and Ongoye Forest in KZN and the overall population is probably <1500 plants. It also occurs at two localities in Eswatini. These occurrences were excluded from our analysis because there are no voucher specimens and if included the result would not change. The known sub-populations are effectively isolated because plants are restricted to disjunct, old forest patches where they are normally associated with rocks and rivers where there is no threat from fire. Most reproduction appears to be from root suckers. Fortunately, several populations occur in formal conservation areas.

As mentioned in the introductory paragraph, this is a poorly known species and I encourage anybody who sees it to post observations on iNaturalist. Even better, if you have a permit, make a collection with detailed notes and lodge the specimen at one of SANBI’s herbaria or at the Bews Herbarium at UKZN.

The article with all references is available free from https://doi.org/10.5091/plecevo.116544

About the author. Richard lives and in Melbourne, Australia and works as an ecologist for the Victorian government. He formerly worked for EThekwini Musicality as a manager in the Environmental Planning and Climate Protection Department. Richard is the author of Pooley’s Trees of Eastern South Africa, A complete Guide (2010) published by the Flora and Fauna Publications Trust, Durban. Since the field guide was published, he has worked mainly with Prof. Braam van Wyk to formally describe several of the region’s woody plants, which were as yet un-named when the field guide was published. Richard has assisted Graham and Kate Grieve edit Plantlife articles since the journal went online several years ago.