Eriolaena rulkensii Dorr, sp. nov. is described and illustrated. This attractive shrub is endemic to coastal Mozambique. The new species has apically winged seeds, which place it in a group of Malvaceae (Dombeyoideae) that is found in Asia and Madagascar and which had not previously been found in continental Africa.

Dombeyoideae , Eriolaena , Malvaceae , Mozambique

When A.J.H. (Ton) Rulkens encountered a yellow-flowered shrub on the shore of Pemba Bay (Baia de Pemba) near the city of Pemba in north-eastern Mozambique, he could not identify it and sent photographs to John E. Burrows (BRNH) who also was unsure as to its identity. Burrows, in turn, shared photographs of the plant with several botanists including I. Darbyshire (K) who identified it as a species of Dombeyoideae (Malvaceae). Darbyshire noted that it did not match either Dombeya Cav. or Melhania Forssk., the two genera of Dombeyoideae known from the area (Wild and Gonçalves 1979; Cheek and Dorr 2007), and he observed that it closely resembled Helmiopsis H. Perrier, a genus of Dombeyoideae endemic to Madagascar. The lack of scales on the unidentified plant, however, led Darbyshire (personal communication) to doubt whether or not it belonged in that genus. Independently, photographs were sent to one of us (LJD) with a simple request for confirmation that the species belonged in the “Sterculiaceae” (i.e. Malvaceae sensu lato). An initial scepticism about this placement very quickly gave way to the realization that the photographs depicted a species that belonged to a genus of Malvaceae (Dombeyoideae) that had not yet been reported from continental Africa. More specifically, the new species appeared to belong to one of two endemic Malagasy genera, either Helmiopsis or Helmiopsiella Arènes.

One of us (LJD) identified the new species provisionally as a new species of Helmiopsiella, a genus of four species endemic to Madagascar (Barnett 1988a). This determination was based solely on photographs that bore a remarkable but, in retrospect, superficial resemblance to Helmiopsiella poissonii (Arènes) Capuron ex L.C. Barnett. Morphological characters that distinguish Helmiopsiella and Helmiopsis are weak (see also Skema 2012) and the attempt to place the new species from Mozambique underscored this problem. In any case, the provisional determination was adopted and it is used in Burrows et al. (2018; “Helmiopsiella sp. A”), on a Flickr website maintained by Rulkens (https://www.flickr.com/photos/47108884@N07/; “Helmiopsiella sp. Pemba”) and in an on-line version of the flora of Mozambique (Hyde et al. 2018; “Helmiopsiella sp. A”). However, once herbarium material was received and a molecular phylogenetic analysis was initiated (Dorr et al. in prep.), it became apparent that a better generic placement was with the Asian genus Eriolaena DC. The need to have a name for this endangered shrub, which can be used for checklists and conservation reports, leads us to validate E. rulkensii in anticipation of publishing a more comprehensive molecular phylogenetic study of the wing-seeded taxa of Dombeyoideae.

Within the Dombeyoideae, Barnett (1988b) recognized morphological and anatomical similarities that united the Asian Eriolaena and Malagasy Helmiopsis and Helmiopsiella as a group. All three genera have woody and ovoid- or obovoid-conical capsules as well as seeds with apical wings. Skema (2012) subsequently published molecular data that support the distinctive nature of this “winged-seed clade” and demonstrated that the clade was early diverging from Dombeya sensu stricto. Eriolaena rulkensii represents the first species of this “winged-seed clade” to be found in continental Africa.

Eriolaena rulkensii is not the only example of an Asian/Malagasy species that also occurs in Mozambique but is otherwise absent from continental Africa. Dianella ensifolia (L.) DC. (Asphodelaceae) is widespread around the Indian Ocean, but confined in continental Africa to the foothills of a few mountain ranges in Mozambique (Hyde et al. 2018). Additionally, there are numerous examples of genera, both plants and animals, found in Asia, Madagascar and continental Africa (Schatz 1996; Renner 2004; Warren et al. 2010).

We sincerely thank Ton Rulkens for bringing this new species to our attention and John Burrows (BNRH) for facilitating the gift of herbarium material. Alice R. Tangerini (US) prepared the illustration and Rose Gulledge (US) assembled the photographic plate. Martin Cheek (K), Iain Darbyshire (K) and Mersedeh Pejhanmehr (HAW) made helpful suggestions for improving an earlier version of this manuscript.