A new species of Aloe (Asphodelaceae) is described from Somaliland. It differs from other species in forming large clumps and in having sap that is initially yellow but quickly turns bright red and then dark red or reddish-brown, paniculate red-flowered inflorescences and uniformly coloured leaves with red teeth. Its recognition raises the number of species known from the combined area of Somaliland and Somalia s.s. from 31 to 36. A map portraying species density of Aloe by country, as that genus is now interpreted, shows that Aloe has its highest density on islands in the Indian Ocean but that, within Africa, the greatest density is in countries along the eastern highlands. The data also reinforce the importance of field botanists in determining a country’s known plant diversity.

Asparagales , species density, Africa

The genus Aloe L. (Asphodelaceae) includes over 600 species, all native to Africa, islands in the western Indian Ocean or the Arabian Peninsula (Newton 2004; Carter et al. 2011; Klopper and Smith 2013). Its members are succulent plants with densely packed, spirally arranged leaves. They vary from stemless to having horizontal or vertical stems. The inflorescences vary from racemes to panicles with branches bearing spirally arranged pedicellate flowers that vary from being well-spaced to densely packed and distally concentrated. The flowers have a tubular perianth that is usually red to pink or scarlet but may be yellow, yellow-green or almost white. There are six stamens and a single gynoecium composed of three united carpels with many ovules. In most species, the fruits are capsules but a few form berries. Almost all species are considered to have medicinal and/or cosmetic value, but a few are poisonous. Only one, A. vera L., is widely cultivated. Because the species are often important to local people, there is considerable interest in the relationship among their use, distribution and phylogenetic relationships. This has resulted in publication of revisionary (Sebsebe and Nordal 2010; Klopper et al. 2012; Ruch et al. 2013; Klopper 2015; Cole and Forrest 2017) and phylogenetic (Grace et al. 2015) studies of the genus, plus development of an international database (Aloes of the World 2018) that enables easy visualisation of the distribution of the species richness by country.

Somaliland, which declared its independence from Somalia s.l. in 1991, lies along the south side of the Gulf of Aden. Its flora is treated in the "Flora of Somalia" (Thulin 1993, 1995, 1999, 2006) which was begun in 1988 (Thulin 1993, preface), before the breakdown of the central Somali government. In volume 4 of the "Flora of Somalia", Lavranos (1995) recognised 31 species of Aloe, all of them collected before 1990. In 1988, the unrest that eventually led to the breakdown of the central Somali government made botanical exploration challenging but, after its unilateral declaration of independence, Somaliland achieved a degree of peace and stability that, among other things, encouraged renewed exploration of its flora and fauna. This resulted in the addition of three previously undescribed species of Aloe to the country’s flora [A. orlandi Lavranos (Orlando 2003), A. rubrodonta T.A.McCoy & Lavranos and A. kahinii T.A.McCoy & Lavranos (McCoy and Lavranos 2007)] which were included in the appendices of the final two volumes of the flora to be published (Thulin 1999, 2006). A fourth species, A. nugalensis Thulin, was described later (Thulin 2012) based on plants grown from seeds collected in 1985. In this paper, we describe a fifth species, so far known only from Somaliland, locally known as “Dacar Cas” or “Red Aloe” but which we refer to, in English, as the Somali Red Aloe to distinguish it from the species currently associated with the English name “Red Aloe”, A. cameronii Hemsl. We also re-examined the distribution of Aloe, being interested in the extent to which recent discoveries have modified the information provided by Newton (2004).

In 2014, Awale noticed an Aloe growing alongside a road near Alala Adka (Alaala Cadka) [Names are shown in English, followed by the Somali name in parentheses], Marodi Jeh (Maroodi Jeex) Region, Somaliland, that was unlike other native species in the area in forming large, dense patches (Fig. 1). They also differed from other Aloe species in the region in having leaves with reddish teeth and, when cut, an exudate that rapidly turns from yellow to bright red. Local people had also noticed the plants, referring to them as “Da’ar As (Dacar Cas), or Red Aloe, to distinguish them from other Aloes in the region, such as Da’ar Buduk (Dacar Budhuq), the name used locally for A. retrospiciens Reynolds.

Figure 1. 

Aloe sanguinalis at Alala Adka showing the largest clump in October 2016.

In October 2016, Awale and Barkworth visited the Alala Adka site to take photographs and make measurements. The location is a treeless plain in the Oogo ecological zone (Ibrahim 2010), dominated by shrubs and showing signs of overgrazing (Fig. 1). Unfortunately, no flowers were present. Despite this, they attempted to determine the scientific name of the plants using "Flora of Somalia" (Lavranos 1995; Thulin 1999, 2006) but none of the descriptions fitted, nor did those of other publications consulted, such as Ruch et al. (2013). They sent images of the plants to Mats Thulin, the late John Lavranos and Tom McCoy, three individuals highly respected for their knowledge of the region’s flora, Lavranos and McCoy being the second and third most prolific describers of Aloe species (Klopper and Smith 2013). All stated that the images sent were not of a species with which they were familiar and advised returning when the plants were in flower, partly to enable preparation of a complete description, but also to investigate the possibility that the plants were hybrids.

In May 2017, Awale and Barkworth revisited the site and found flowers. They prepared specimens, recorded measurements and took photographs both in the field and in the herbarium (Fig. 2). Awale also collected cuttings to grow and observe in Hargeisa. The flowers were protandrous, forming plump, well-filled anthers that matured before the styles had fully elongated. Both the anthers and the styles appeared fully functional. These observations made it unlikely that the plants were hybrids.

Figure 2. 

Aloe sanguinalis from Alala Adka, June 2017. A Whole inflorescence, including peduncle B Sap, showing color after 10–15 minutes C Leaves freshly cut near their base showing color of sap when fresh D Decumbent offset, showing roots from some nodes E Inflorescence branch and flowers from another branch, arranged from top to bottom of the branch F Flower after maturation of style.

In January 2018, Awale discovered another population growing near Lafarug (Lafaruug), in Sahil (Saaxil) Region, alongside the road to Hiin-Weyne village. Later that month, Barkworth and Awale revisited the location to learn more about the plants there and to make measurements. Lafarug is in the subcoastal area below the Golis escarpment and has sandy soil with semi-desert vegetation that includes Vachellia tortilis (Forssk.) Galasso & Banfi, Dobera glabra (Forssk.) Poir., Salvadora persica L., Indigofera sparteola Chiov. and Commiphora Jacq. (Fig. 3A). There were no flowering inflorescences in January but some old ones were collected and examined for seeds. Awale revisited the site in June 2018, at which time the plants were in flower (Fig. 3B), and again in August 2018. During the August trip, he collected seeds.

Figure 3. 

Aloe sanguinalis at Lafarug. A One of the larger clumps, with Awale, in January 2018 B Inflorescence of Aloe sanguinalis at Lafarug, June 2018.

Most capsules collected in January at Alala Adka had no seeds; none had more than 3. Capsules collected from the Lafarug population in August 2018 had several seeds. A total of about 50 seeds from the Lafarug area were planted in a pot and kept moist. By November 2018, 12 had germinated and one had developed three leaves (Fig. 4).

Figure 4. 

Seedling of Aloe sanguinalis, grown from seeds collected at Lafarug in August 2018.

Based on the comments by Thulin, Lavranos and McCoy and the apparent functionality of the anthers and styles, we proposed recognising the Somali Red Aloe as a new species in July but, at the urging of the reviewers, Barkworth reviewed all the Aloe images made available by the Royal Botanical Gardens, Kew (Kew 2018), specimens in the herbarium of the Missouri Botanical Garden and, together with Gelle, those in the East African Herbarium of National Museums, Kenya. Because many of the distinguishing features of Aloes are poorly preserved in herbarium specimens, we also reviewed the species descriptions for specimens that could not, based on the herbarium specimens seen, readily be distinguished from the Somali Red Aloe. These studies supported our earlier conclusion that the Somali Red Aloe should be described as a new species. In preparing the description, we have used terminology that is consistent with Klopper et al. (2013) but avoided use of the term “raceme” because of inconsistencies in how it is used [compare, for example, Klopper et al. 2013 with Harris and Harris (2001) and Beentje (2016)].

To examine current knowledge about the distribution of species richness in Aloe, we updated Newton’s table with data from multiple sources [(Reynolds 1954; Klopper et al. 2012; Ruch et al. 2013; Rakotoarisoa et al. 2014; Klopper 2015; Rakotoarisoa and Grace 2017; Cole and Forrest 2017; Aloes of the World (2018)] and calculated the number of species per km². In doing so, we used the current interpretation of Aloe which excludes Aloidendron (A. Berger) Klopper & Gideon F. Sm., Aloiampelos Klopper & Gideon F. Sm. and other small genera previously included in it.

We are grateful to the University of Hargeisa for encouraging and providing space and infrastructure support for the Biodiversity Museum. We also thank Tom McCoy, Mats Thulin and the late John Lavranos for responding to our early enquiries about the Somali Red Aloe, Helen Pickering for sharing information concerning Sudan and South Sudan, Garrett Billings for preparing the map and the library of Utah State University for having purchased Aloes: the definitive guide. In addition, we thank the herbaria and staff of the Missouri Botanical Garden and National Museums Kenya for enabling us to examine the wide range of Aloe species in their collections and the Royal Botanic Gardens Kew for making so many images available online. We are also greatly appreciative of Ronell Klopper’s willingness to share her knowledge of the genus and data from the Aloe database with us. Her assistance enabled us to add more countries to Table 1 and be more consistent in the interpretation of Aloe adopted. The manuscript has also benefited significantly from the comments of the two reviewers assigned to the paper. We thank them for their efforts. Reviewing herbarium specimens was both time consuming and expensive because it required travel to distant herbaria, but it improved our understanding of the genus.