Hidden in plain view: First UAE record of the wadi grass Saccharum kajkaiense and notes on its distribution in the UAE and neighbouring Oman

The genus Saccharum (SAK-er-um) consists of some 200 species, subspecies, varieties and/or cultivars including the cultivated sugar cane, S. officinarum (eFloras 2009; ZipcodeZoo.com 2009). In the UAE and northern Oman the genus is represented principally by the conspicuous S. ravennae, which grows in large clumps in and alongside gravel wadi beds. The clumps can be more than 2 metres tall, with the plumed inflorescence on spikes up to another metre taller. S. ravennae has an Old World temperate and tropical distribution ranging from the circum-Mediterranean region through the Caucasus and Arabia to Central Asia, China, India and Indo-China (Clayton et al. 2006 onwards). It has also been introduced as an ornamental in the United States, where, under names such as "Ravenna Grass", "Hardy Pampas Grass" and "Plume Grass", it is advertised for its large size, distinctive appearance and large plumose inflorescence as one of the most attractive decorative grasses, although it is considered moderately invasive. Two other sugar cane congeners have been mentioned in earlier literature for the UAE and northern Oman. S. griffithii, which has a primarily South Asian distribution (Clayton et al. 2006 onwards), has been recorded in the UAE from anthropogenic sites in Abu Dhabi and at Al-Wigan, in the south-eastern desert (Jongbloed 2003). S. spontaneum, sometimes called "Kans Grass" or "Wild Sugar Cane", is an invasive species which is considered to have a South Asian origin but is now widely distributed in the Old World (Clayton et al. 2006 onwards). It was recorded from northern Oman (Ghazanfar 1992) and from an unspecified wadi site in the UAE or neighbouring Oman (Jongbloed 2003). Both S. griffithii and S. spontaneum are, like S. ravennae, potentially very large plants, and both are typically associated with relatively damp conditions, whether natural or irrigated. S. spontaneum, for example, forms thick stands on alluvial plains along South Asian rivers which flood seasonally (Wikipedia 2009). It also grows, spontaneously, in damp fields and is considered excellent fodder for most South Asian livestock. The UAE and northern Oman records of S. spontaneum have subsequently been revised, as discussed below, but in any case the prior records other than S. ravennae were generally treated as exceptional and there is no evidence that the significant presence of any other Saccharum species in Hajar Mountain wadis was recognised or suspected by most of the many field investigators in the UAE and northernmost Oman (see, e.g., Western 1989, Boer & Chaudhary 1999, Curtis 1999, Karim 2002, Jongbloed 2003, and Karim & Fawzi 2007). Nevertheless, another regional congener, Saccharum kajkaiense (Meld.) Meld., had in fact been recorded by the mid-1990s, when lepidopterist Matthew Cock obtained an identification from Thomas Cope at the Royal Botanical Gardens, Kew, for the grass species on which Cock had collected larvae of the Millet Skipper butterfly Pelopidas thrax (Cock 2008/2009, in this volume) at several locations in Wadi Qahfi (the locally popular "Hatta Pools" wadi), situated in the middle of the Hajar Mountains in northernmost Oman. Cope was able to comment at that time that S. kajkaiense was found in Iran and Afghanistan and had a localised distribution in northern Oman (the type specimen is from Iran and the species is also found in the North West Frontier Provinces of Pakistan (eFloras 2009)). Cock himself had not distinguished between S. ravennae and S. kajkaiense, considering that only a single species was present (which he understood to be S. kajkaiense), but he did observe that P. thrax larvae were more common on smaller plants near the wadi walls. It appears that the occurrence of S. kajkaiense in northern Oman was not actually published until the appearance of Flora of the Arabian Peninsula and Socotra, Vol. 5, Part 1 (Cope 2007). In that volume, Cope rejects the earlier determinations of S. spontaneum from Oman and considers them to be in part S. griffithii and in part S. kajkaiense. Cope plotted the Arabian distribution of S. kajkaiense on the basis of professionally determined specimens, which are limited to two sites in the Western Hajar Mountains of northern Oman and several along the coast of the Eastern Hajar, including the Sur area (Cope 2007, Map 421). Its habitat is described as "Wadis; 50-650m" and its known range outside Arabia is given as Iran, Afghanistan and Pakistan. However, this information remains to be widely disseminated locally and S. kajkaiense first came to the authors' attention in late 2008 through a communication from Cock, who wrote to request a review of the local geographical nomenclature used in a draft of Cock (2008/2009).