Lukea gen. nov. (Monodoreae-Annonaceae) with two new threatened species of shrub from the forests of the Udzungwas, Tanzania and Kaya Ribe, Kenya

Summary A new genus, Lukea Cheek & Gosline (Annonaceae) , is erected for two species to science, quentinii from Kaya Ribe, SE Kenya, and triciae the Udzungwa Mts, Tanzania. characterised by a flattened circular bowl-shaped receptacle-calyx with corolla of three free petals that give buds flowers unique appearance in African Annonaceae. Both are extremely rare shrubs small surviving areas lowland evergreen forest under threat habitat degradation destruction provisionally assessed as Critically Endangered respectively using IUCN 2012 standard. illustrated mapped. Material had formerly been considered be possibly Uvariopsis Engl. Diels, genus placed clade Monodoreae (consisting genera Uvariodendron (Engl. Diels) R.E.Fries, Uvariopsis, Mischogyne Exell, Dennettia Baker f., Monocyclanthus Keay). The often conspicuous, finely reticulate quaternary nervation, incomplete or absent connective shields (in Annonaceae shield usually complete) (except some ). Morphologically distinct its broad, turbinate, fleshy pedicel, potential synapomorphy within Monodoreae. It appears closest morphologically West monotypic since it shares trait unusual Annonaceae: calyx both forms shallow bowl (calyx lobes vestigial), barely enclosing base at anthesis, which persists, living green, mature fruit. However, on recent molecular phylogenetic evidence, sister split c. 20 million years BP while Dennettia. placement discussed.