Polhillia ignota Boatwr.
Status and Criteria
Critically Endangered B1ab(iii)+2ab(iii); C2a(i,ii); D
|I. Ebrahim, N.A. Helme, D. Raimondo & D. van der Colff|
|A single, small subpopulation of 13 plants remain in a renosterveld fragment near Eendekuil (EOO 4 km², AOO <4 km²). The population is expected to continue to decline due to ongoing threats of habitat degradation and competition from alien invasive plants.|
|South African endemic|
|Northern Swartland between Vredenburg, Eendekuil and Porterville.|
Habitat and Ecology
|Swartland Shale Renosterveld|
|Polhillia ignota occurs in Critically Endangered Swartland Shale Renosterveld, of which <10% remains, after extensive loss to agricultural expansion. The only known subpopulation occurs in a small fragment of renosterveld among crop fields. It is potentially threatened by habitat degradation due to overgrazing - small remnants of renosterveld are often overstocked with livestock, but grazing pressure on the site is currently low. This fragment is unlikely to be lost to crop cultivation, as it is too steep and rocky to plough. Alien invasive plants are present in the habitat, and may become a threat to the population in future if it is not cleared.|
Polhillia ignota was described in 2010 based on two herbarium collections dating from 1904 and 1928 (Boatwright 2010). Both did not have precise locality details, but came from an area that has been extensively modified for crop cultivation, and the species was presumed extinct, as searches in the general area between 2005 and 2014 failed to locate any surviving populations. In 2016, volunteers of the Custodians of Rare and Endangered Wildflowers (CREW) Programme came across a small subpopulation much further north from the area it was previously recorded, suggesting that it may have had a much wider distribution in the past. It is a large, conspicuous shrub, and therefore unlikely to be overlooked. With less than 10% of its habitat remaining intact, it is very unlikely that many other subpopulations still exist, and the subpopulation discovered in 2016 is quite possibly the last remaining. It consists of 13 mature individuals. The population trend is not known, but it is expected to continue to decline due to the ongoing threat of habitat loss and degradation.
|Ebrahim, I., Helme, N.A., Raimondo, D. & van der Colff, D. 2016. Polhillia ignota Boatwr. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2020/04/06|