Spot the Difference

One of the challenges of identifying species in the fynbos is that sometimes very different looking plants are classified under the same species. This is not surprising when species have a wide distribution range, but is more challenging when they grow in close proximity. This variation may be just due to growing conditions, e.g. luxuriant shade forms versus compact ones growing in full sun, but if the distinction is correlated with other factors then further investigation is required. One such species is the winter-flowering Gladiolus maculatus. Here at Phillipskop we get two distinct forms, which grow in their own unique habitats, and yet are classified under the same species.

Typical Gladiolus maculatus is widespread in the southern Cape as far east as Grahamstown. This has a base yellow to cream colour, which is heavily spotted, the spots often merging, with brownish orange to deep purple throughout, especially along the upper halves of the petals. This distinctive mottled coloration gives the plant its scientific name: “maculatus” means spotted in Latin. The unusual brownish colour is responsible for the common name Brown Afrikaner (Afrikaner being a common name used for a number of species of Gladiolus). The dull coloration makes it difficult to spot but the flowers usually have a sweet scent, which attracts its pollinators.

However, there is another form of Gladiolus maculatus that grows here and is quite distinct in its coloration, with a white to cream base to the flower and lilac to mauve spotting. The flowers are also slightly smaller but otherwise, in leaf and stem characters, the two forms barely differ, even flowering at the same time of the year. Leaf characters are very important for Gladiolus identification and in Gladiolus maculatus, both forms, there are 3 or 4 leaves, the lower two at the base and the others with short blades inserted up the flowering stem. The blades of the leaves are flat without either prominent midrib or margins (characters present in other similar looking species such as Gladiolus liliaceus).  As these characters are the same, as also are the more difficult to spot corm characters, the two forms are regarding as conspecific.

In some ways, that should be the end of it but the two forms, although growing within half a kilometre of each other, are found in quite distinct habitats and there are no intermediate plants between the two. This suggests that there are barriers to interbreeding, a character that leads to speciation. The lilac form is found on steep slopes, often shady in winter, usually on the edge of streams. More importantly, it is found exclusively in areas where the sandstone outcrops, even growing out of cracks in the rock. The brown form is more variable in its habitat but usually found in fynbos on shale bands or clayish soils, even in renosterveld. The difference in habitat therefore suggests that more is going on than just natural colour variation.

In the 1940s revision by Gwendoline Lewis of Gladiolus, Gladiolus maculatus was described as having four subspecies due to its variation. When the genus was revised by Goldblatt and Manning in 1998 they regarded that two of those subspecies should be recognised as distinct species (Gladiolus albens and Gladiolus meridionalis). The fourth subspecies (subsp. hibernus) though they considered just a variation of the widespread and variable Gladiolus maculatus. Subspecies hibernus was based on plants from the Overberg and had been described by collectors as “pale mauve, grey mauve or creamy white, densely speckled with purplish or maroon dots”. It also had long narrowed petal tips, a feature that is evident in our lilac form. It therefore appears likely that our form was first described as Gladiolus hibernus before it was adopted as a subspecies of Gladiolus maculatus by Lewis and then subsumed completely by Goldblatt and Manning.