One African baobab species or two? Synonymy of Adansonia kilima and A. digitata

Abstract

We assessed the validity of a recently described baobab species Adansonia kilima that was suggested to be a diploid occurring in both eastern and southern Africa at high elevations within the range of the well‐known tetraploid species A. digitata. We used a combination of phylogenetic analyses and statistical comparisons of various traits (e.g., flowers, stomata, pollen, chromosome counts) to test for the presence of two continental African baobab species. Ordination of the floral features of 133 herbarium specimens from across the natural range of A. digitata, including the putative type of A. kilima and other Tanzanian accessions as previously assigned A. kilima, revealed no distinct clusters of specimens. Likewise, stomatal size and density varied greatly across the specimens examined, with no clear bimodal pattern and no obvious association with altitude. The type specimen of A. kilima was found to have a chromosome number of 2n ≈ 166, showing it to be a tetraploid, like A. digitata. Phylogenetic analysis of the ITS region showed little resolution within the African baobab clade and a lack of distinction between the A. kilima type and A. digitata regional accessions. Among the 13 haplotypes detected, no distinct haplotype representing A. kilima was identified. Based on the data at hand we conclude that A. kilima is neither cytologically nor morphologically distinct and is here reduced to synonymy with A. digitata.

Leaf phenology of thirteen African origins of baobab (Adansonia digitata (L.)) as influenced by daylength and water availability

“…A possible interpretation is that the East African populations have a deeper dormancy and are less responsive to water once stress is relieved. The difference between groups is supported by earlier observations of differences in growth and stress response between western and eastern populations (De Smedt et al, 2012;Korbo et al, 2012) and also by studies of chloroplast and ITS (Internal Transcribed Spacers) haplotypes, showing a major division between western and eastern/southern populations (Cron et al, 2016;Pock Tsy et al, 2009 With its origin in a climate with less pronounced seasons, it could be a selective advantage to be more responsive to water availability. Similarly, Morogoro rural, the wettest origin in the East African group (Figure 1), had high levels of meristematic activity and number of leaves compared to other origins within the western group, confirming the opportunistic strategy of the species.…”

Fatty Acid Composition of Baobab Seed and Its Relationship with the Genus Adansonia Taxonomy

“…Baobabs ( Adansonia genus, Bombacaceae family, super family of Malvaceae) are woody plants characteristic of the dry tropical forest ecosystems of Sub‐Saharan Africa, the North‐West of Australia, the west coast of Madagascar as well as the coastal vegetation of the Comoro Islands. The genus is represented by eight species, divided into three sections established on botanical and molecular characteristics . The Brevitubae section includes two Malagasy endemic species: A .…”

“…kilima . But a recent study challenges this work and proposes a simple synonymy between A . digitata and A .…”

Radiocarbon investigation of a superlative grandidier baobab, the big reniala of Isosa

“…The Adansonia genus, which belongs to the Bombacoideae subfamily of Malvaceae, consists of eight or nine species. One or two species originate from the tropical (semi-)arid savanna of the African continent, six species are endemic to Madagascar and one species can be found only in Australia [1][2][3][4][5]. In 2005, we started an extensive research program to elucidate several controversial or poorly understood aspects of the architecture, development and age of the African baobab (Adansonia digitata L.).…”