A phylogenetic analysis of the genus Aloe (Asphodelaceae) in Madagascar and the Mascarene Islands

Abstract

Aloe (Asphodelaceae) is a typical element of the succulent flora of the eastern Indian Ocean islands of Madagascar, the Mascarene Islands of Mauritius, and Réunion and the Seychelles. In this region, there are 129 native Aloe spp., all of which are endemic. The most recent classification of Aloe in Madagascar, completed by Reynolds in the 1960s, defined nine morpho-groups. The present study is the first phylogenetic analysis of Aloe in Madagascar and the Mascarenes, encompassing approximately one-third of the regional species diversity. Bayesian inference and maximum likelihood analyses of ITS, matK and trnQ-rps16 DNA sequences suggest that numerous dispersal events occurred from the African continent to Madagascar. As a result, close evolutionary relationships exist among geographically distant aloes, such as A. suzannae, the nocturnal-flowered species and Kumara in southern Africa. Aloe section Lomatophyllum is the only morpho-group to correspond to a phylogenetic clustering. Our findings confirm that Aloe spp. native to the eastern Indian Ocean islands do not comprise a monophyletic unit and emphasize the need for a revised infrageneric classification of Aloe.