Population structure, habitat profile and regeneration of Haworthia koelmaniorum, a vulnerable dwarf succulent, endemic to Mpumalanga, South Africa

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Population size and structure, flowering and foliar damage were quantified for the seven known populations of the vulnerable Mpumalanga endemic Haworthia koelmaniorum Oberm. & Hardy (Asphodelaceae). Differences in sites where H. koelmaniorum was found compared with similar sites where it did not occur were assessed by the quantification of biotic and abiotic variables at the plant and community scales. Population size varied from 25 to 588, with 1591 plants in total. Size structures (leaf number per plant or rosette diameter) did not vary between populations, but no seedlings were found. Overall, 67% of plants were damaged by fire and herbivory, but all appeared to survive fire. The percentage of plants flowering per population varied from 24–76%, Percentage germination was high (78–88%), but seeds apparently have short-term (5–7 month) persistence and thus no seed bank is formed Plants grow preferentially on northern aspects above the mid-slope position of quartzite ridges and within rock fissures. These were characterized by a high cover of fixed and exposed rock, high overstorey shade, low understorey shade and live vegetation cover. Reduced competition from herbaceous plants and reduced probability of fire damage are distinctive features of these sites. Population dynamics may be characterized by adult persistence as seedling establishment is most likely episodic, linked to high rainfall periods, and coinciding with dispersal of seeds produced in the same year to the few suitable rock fissures (safe sites) available. Present threats, small population sizes, low rates of seedling establishment and a very restricted distribution, dictate that H. koelmaniorum remains in the Vulnerable IUCN category.