Rediscovery of the Critically Endangered Primula esquirolii, a karst cave species with an extremely small population endemic to China

Abstract

The rare plant Primula esquirolii, a karst cave species in the family Primulaceae, endemic to Guizhou, China, and with a presumed extremely small population, had not previously been observed since 1910. It is categorized as Endangered on the China Species Red List. In surveys during 2018–2022, we were unable to locate the species in its type location in Pingba county, but we discovered a previously unrecorded population of 44 mature individuals, 37 of which were long homostylous and seven of which were heterostylous. These individuals were discovered in Xiuwen county in February 2022, in an area of c. 50 m2, c. 40 km from the type location. All seven heterostylous individuals showed the short-styled morph. The almost homostylous P. esquirolii potentially faces the same high genetic load as other homostylous plants, and this may have led to its small population size and potential sensitivity to habitat destruction. Field surveys and informal interviews with local people indicated that the main threats to this species are its small population size and the loss of suitable habitat as a result of human activities. The most urgent requirement for the conservation of this species is to protect the habitat of this single known extant population and to carry out ex situ conservation. Further field surveys and research are also required to improve our understanding of the status of this species.

Primula pingbaensis (Primulaceae), a new species from Guizhou, China

“…while P. esquirolii and P. pingbaensis occur in the karst areas of Guizhou (usually lower than 1500 m a.s.l.). Field surveys on P. esquirolii showed that it is a species with extremely small populations and was evaluated as‘Critically Endangered’ ( Wu et al 2022 ), like our new finding of P. pingbaensis .…”

“…Species with homostylous morphs are usually accompanied by a compatibility system that makes intramorph (and thus self-) crosses more successful ( Richards 2003 ). The selfing homostylous lineages often have a high genetic load, which makes them sensitive to environmental changes and renders population expansion over short periods difficult ( Wu et al 2022 ). Our observation on Primula species distribution indicated that homostylous species usually have fewer populations or smaller population sizes than closely related heterostylous species.…”

“…According to relevant literatures and Flora of China, there are more than a dozen species of Primula distributed in Guizhou, of which some species are endemic to Guizhou, such as P. esquirolii Petitm. ( Wu et al 2022 ), P. fangingensis Chen et C.M.Hu, P. kweichouensis W.W.Smith, P. lithophila F.H.Chen & C.M.Hu and P. levicalyx C.M.Hu et Z.R.Xu ( Smith et al 1977 ; Hu 1990 ). During the last decade, some newly published Primula species from the adjacent areas were also found within Guizhou, such as P. pelargoniifolia G.Hao, C.M.Hu & Z.Y.…”