Two new threatened Inversodicraea (Podostemaceae) species from waterfalls in Sierra Leone: I. joulei and I. lebbiei

Summary Two threatened new species of Podostemaceae belonging to the genus Inversodicraea , I. joulei and I. lebbiei , both from the Republic of Sierra Leone, are described and illustrated. A first record in Sierra Leone of the genus Lestestuella is also reported. Inversodicraea is the most species-rich genus of Podostemaceae in Africa and now comprises 38 species. Inversodicraea joulei is recognised because it has a persistent spine distally on the median rib of each fruit valve, and scattered, membranous scale-leaves with broadly rounded apices, while I. lebbiei is distinct in having narrowly triangular robust scale-leaves which are inrolled, spreading distally, and completely covering the stem, arranged in five ranks. Inversodicraea joulei is known from a single location with three sites, while I. lebbiei is known from two locations each with one site. Using the latest IUCN Red List guidance, I. joulei is assessed as Critically Endangered and I. lebbiei is assessed as Endangered, due to threats from dam construction projects, agricultural practices and mining activities, resulting in high levels of siltation on rocks in the fast-flowing rivers where these species grow.