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

Cheek, Martin; Luke, W. R. Quentin; Gosline, George

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

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Cheek, Martin

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Luke, W. R. Quentin

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Gosline, George

Date published

August 19, 2022

Abstract

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