A review of chromosome cytology in Hyacinthaceae subfamilies Urgineoideae and Hyacinthoideae (tribes Hyacintheae, Massonieae, Pseudoprospereae) in sub-Saharan Africa

The chromosome cytology of subfamilies Hyacinthoideae and Urgineoideae of the monocot family Hyacinthaceae are reviewed for their centres of diversity in sub-Saharan Africa within the framework of a recent molecular-based classification. We also provide some new chromosome counts for genera or species that are unknown or poorly known cytologically. We conclude that the ancestral basic chromosome number for Hyacinthoideae is x = 10 but tribe Pseudoprospereae evidently has x = 9, the most likely base in Hyacintheae. Tribe Massonieae has five of the nine (out of 10) genera counted apparently ancestrally tetrapaloid with 2n = 40 and we infer a basic chromosome number for the tribe of x = 10 based on patterns within the tribe and by outgroup comparison. An extensive descending dysploid series is present in Lachenalia, ranging from a possible ancestral base of x = 10 to n = 5, and several species are polyploid or have diploid and polyploid populations. Basic number in Urgineoideae is also x = 10 and the subfamily exhibits little divergence from that base among sub-Saharan species. Polyploidy at species rank is relatively rare among the sub-Saharan members of both subfamilies. Based on available data just 7% of species of Urgineoideae and 15% of sub-Saharan Hyacinthoideae are species level polyploids but several more have diploid and polyploid populations. This conforms to the pattern of low level of polyploidy in subfamily Ornithogaloideae of Hyacinthaceae and other sub-Saharan families of geophytic plants.

► An ancestral chromosome number of x = 10 is inferred for Urgineoideae and Hyacinthoideae.
► Pseudoprospereae evidently has x = 9.
► Neopolyploidy is uncommon among sub-Saharan Hyacinthoideae: 20 species out of 101 species counted are exclusively polyploid; 16 species have diploid and polyploid populations.
► Modest neopolyploidy in sub-Saharan Hyacinthoideae is consistent with levels in Ornithogaloideae and other geophytic families well represented there.
► Five of nine genera of Massonieae counted are palaeopolyploid (Merwilla, Schizocarphus and Veltheimia (x = 40), Eucomis (x = 15) and Daubenya (hypotetraploid).