New taxa of Barleria sect. Prionitis (Acanthaceae) from the Horn of Africa biodiversity hotspot in Somalia
From Firenze University Press Journal: Journal of Plant Taxonomy and Geography (Webbia)
Ellie Defty, Royal Botanic Gardens, Kew and University of Leeds
Iain Darbyshire, Royal Botanic Gardens, Kew, Richmond
The Horn of Africa biodiversity hotspot-one of only two entirely arid bio-diversity hotspots globally-ranges across the drylands of northeast continental Africa, the southern Arabian Peninsula and the Socotra archipelago. It cov-ers most of Somalia, Djibouti, parts of Ethiopia, Eritrea, Kenya, Yemen and Oman, and a small portion of northeastern Sudan (CEPF 2024). This hotspot is particularly important for its rich endemic flora, with many plant species having highly restricted ranges (Thulin2004; Friis et al. 2005; Marshall et al.2016; CEPF 2024). For example, in Somalia, Thulin(2006a) reports a total flora of 3,165 species, of which approximately 800 (25%) are endemic.Northeast Africa in general, and in particular the Horn of Africa hotspot, is amongst the most diverse areas globally for the Acanthaceae family (Manzitto-Tripp et al.2022). For example, in the species-rich genus Barleria L. (Acanthaceae: Acanthoideae: Barlerieae; Manzitto-Tripp et al.2022), 32 species are known from Somalia alone, 12 (37.5%) of which are endemic (numbers modified from POWO 2024), this representing over 10% of the total species richness in Barleria. Several of the endemic species from this region have been described relatively recently, including B. albomarginata Hedrén, B. compacta Malombe & I.Darbysh., B. den-tata Hedrén, B. ensermui I.Darbysh., B. ilicifolia Hedrénand B. shebelleensis Ensermu & I.Darbysh.from Somalia, and B. gidoleensis Ensermu & I.Darbysh., B. ferox Ensermu & I.Darbysh.and B. negeleensis Ensermu & I.Darbysh. from Ethiopia (Hedrén 2006a; Malombe and Darbyshire 2010; Ensermu and Darbyshire 2018). Many are known from few botanical collections, and B. enser-mui and B. ilicifolia are both known only from the type collections, despite being showy, large-flowered species. Hence, the likelihood of further new discoveries in Bar-leria within this region is high, particularly as large areas remain under-explored botanically. However, the Horn of Africa is one of the most degraded biodiversity hotspots in the world due to over-grazing, charcoal production, political instability and infrastructure development (Thulin2004; CEPF 2024). Therefore, it is important that the endemic species of the region are identified and described in light of the high levels of threat faced in this region and the urgent need for effectively targeted conservation efforts.As part of a planned monograph of Barleria, two interesting taxa within sect. Prionitis Nees that have come to light amongst herbarium specimens from Somalia are here investigated morphologically for their taxonomic status. The first is a taxon from central Somalia that has been previously included within Barleria punctata Milne-Redh. by Hedrén (2006b) in the Flora of Somalia treatment of Barleria. That species is otherwise known only from northern Somalia and north-east Ethiopia, and is disjunct from the central Soma-lian populations both geographically and ecologically. The second taxon is from arid coastal northeast Somalia and is closely allied to Barleria compacta Malombe & I.Darbysh., described in 2010 from the same region, although with most collections from further inland (Malombe and Darbyshire 2010).
DOI: https://doi.org/10.36253/jopt-15729
Read Full Text: https://oaj.fupress.net/index.php/webbia/article/view/15729
