Population structure of an arborescent aloe (Aloe marlothii) in Botswana

Abstract

Aloe marlothii A. Berger (Asphodelaceae) (ALMA), an arborescent CAM succulent, were measured in two populations of historical significance near Molepolole, Botswana with the objective of determining size class distribution and therefore assess future population viability. It was found that plant height and a variety of other plant attributes were strongly correlated, including being reproductive and number of capsules. The most common size class was seedlings for one population, and 11 to 50 cm size class for the other population. There were more individuals in the 101 to 200 cm size class than in some of the small size classes indicating a potential population decline. Seedlings were very patchy in distribution and the majority of ALMA, both seedlings and smaller mature individuals, were found under nurse plants. Seed production was high and seed viability averaged 62%. In a third population in the Mokolodi Nature Preserve, individuals were all >4.5 m in height and were sparsely distributed. It was concluded that the Molepolole populations appear to be stable but that steps should be taken to establish long-term monitoring and protect the Molepolole populations. The Mokolodi population appears to be at risk.