Extending the Natural Distribution Range of Astroloba herrei Uitewaal (Asphodelaceae: Alooideae): Implications for Its Conservation Status

Abstract: Astroloba herrei Uitewaal (Asphodelaceae: Alooideae) is currently regarded as one of the rarest and most threatened species in the genus. The species is mostly recorded as having a small, restricted geographical distribution range, as well as a habitat that is vulnerable due, in part at least, to its proximity to human activity. Its distribution range is interpreted as disjunct, as the species is considered to be restricted to two widely separated areas: 1.) the immediate surrounds of Prince Albert in the Great Karoo, Western Cape Province, South Africa, and 2.) a contested spot north of Uniondale in the Little Karoo. We hypothesised that these two areas, separated by 100 km [60 miles], were contiguous, but not through the most frequented routes connecting these two spots. Map overlays for vegetation type, soil type, and geology were used to predict likely habitats in the more inaccessible region through which the areas could be connected, specifically along the northern (Great Karoo) slopes of the Swartberg. Based on the results, the most likely potential localities were identified and visited, and the species was found where predicted. Ground-truthing of the predicted range therefore confirmed that A. herrei is in fact far more widespread than previously believed. Its distribution stretches from west of Prince Albert, along the eastern Swartberg, and across the provincial border into the Eastern Cape Province, where it occurs along the R407 road that connects Prince Albert to Willowmore. At the eastern edge of its range it crosses the Swartberg to the south, and occurs north of Uniondale. Significantly, A. herrei has a natural range which in size by far outstrips that of a number of other Astroloba species. Based on the results of our work we propose that the conservation status of Astroloba herrei be changed from “Vulnerable D2” to “Least Concern”.