A revision of Xylopia L. (Annonaceae): the species of Tropical Africa

Abstract

A revision of the 45 species of the pantropical genusXylopiain Tropical Africa includes descriptions of six new species and a new section of the genus. The fruits and seeds ofXylopiashow specializations that promote vertebrate dispersal, primarily by hornbills and monkeys. Over half of the African species have an Area of Occupancy (AOO) less than 80 km2, suggesting that they are in need of protection. African species are classified into five sections. Section Neoxylopia , with four species, is centered in the Guineo-Congolian Region and includesX.globosasp. nov.Section Ancistropetala, with three species, occurs in the same region. Both of these sections are endemic to Africa. Section Xylopia, which extends to Madagascar and the American tropics, has only a single species in Africa,X.aethiopica. The three species of section Verdcourtiasect. nov.are restricted to the East African coast and Madagascar. The largest number of African species, (34) belong to section Stenoxylopia, in which the seeds lack the arils found in the other sections and instead have a fleshy sarcotesta. Section Stenoxylopia is divided into two informal groups, one centered in eastern and southern Africa (X.odoratissimagroup) and the other centered in the wetter forests of western and central Africa (X.acutifloragroup). Five new species are described in section Stenoxylopia:Xylopianiloticasp. nov.from Sudan, South Sudan, and Uganda,Xylopiacalvasp. nov.from Nigeria and Cameroon, which is allied toX.phloiodora, andXylopiamonticolasp. nov.from Nigeria and Cameroon,X.pirataesp. nov.from Ivory Coast and Ghana, andX.unguiculatasp. nov.from Gabon. The latter three species are segregates of the formerXylopiaacutifloras. l. One new combination is made at the species level,X.shirensiscomb. nov.Keys, descriptions, illustrations, distribution maps, and an index to numbered collections document diversity and assist with species identification. The nameUnonaoliverianaBaill. was found to pre-date the nameUnonalepidotaOliv., requiring the combinationMeiocarpidiumoliverianumcomb. nov.

Biogeography and ecology in a pantropical family, the Meliaceae

“…Many other rain forest groups, such as Xylopia (Annonaceae), also show maximum levels of diversity along this Atlantic belt ( Fig. 35; data from Johnson & Murray, 2018). Xylopia has 45 species in tropical Africa, and maximum species diversity occurs in a zone extending from SW Cameroon to SW Republic of Congo (10-11 species per degree square).…”

“…(Annonaceae) is endemic to the area (Fig. 10), and is unusual in African Xylopia species, as it inhabits mossy, montane forest; most species are in the lowlands (Johnson & Murray, 2018).…”

Which frugivory‐related traits facilitated historical long‐distance dispersal in the custard apple family (Annonaceae)?

“…We also find strong support that moniliform fruits (long strings of bead‐like fruitlets, found in e.g., extant Dasymaschalon , Desmos and Monanthotaxis , Guo, Hoekstra, et al., ; Wang et al., , Figures a and j), dehiscent fruits (e.g., found in extant Xylopia and Cymbopetalum , Figures j and i), and (relatively) small seeds (Figure c) are traits associated with long‐distance dispersal. Both moniliform and dehiscent fruits have been shown to be particularly attractive to birds (Gautier‐Hion et al., ; Guo, Hoekstra, et al., ; Lomáscolo & Schaefer, ), although Xylopia has been observed to be fed on by both birds and primates (Johnson & Murray, ). These vertebrate dispersers facilitate germination in these species by removing the aril, the sarcotesta, or both (i.e., structures that inhibit germination) (Stull et al., ).…”

Accelerated diversification correlated with functional traits shapes extant diversity of the early divergent angiosperm family Annonaceae

“…Several genera have shifted the dispersal unit from fruits to individual seeds (Supplementary Fig. S4F): Cardiopetalum , Cymbopetalum , Trigynaea [64], and Xylopia [65], for example, possess dehiscent monocarps that split along a dorsal suture to expose bird-dispersed seeds with a brightly colored aril or sarcotesta (Fig. 6F).…”