Abstract:

Aims Climate change has significantly influenced the evolutionary history of various biological groups. Among these, succulents represent special plant groups adapted to arid conditions. Didiereaceae, a small family within Caryophyllales, consist of about 20 species representing 6 genera and 3 subfamilies. Members of this family are succulent plants found in the arid regions across southern to eastern African as well as Madagascar. However, the link between the family’s evolution and the establishment of arid climates in its habitats remains unclear.

Methods In this study, we reconstructed the phylogenetic relationships among Didiereaceae species based on analyses of six plastid DNA markers (rps16, rpl16, trnL-F, trnT-trnL, trnG-S, trnQ-rps16). Additionally, molecular dating and diversification analyses of the family were also conducted.

Important findings The monophyly of Didiereaceae was strongly supported, and a robust phylogenetic framework for the family was established. The crown age of the family was estimated at about 62.3 million years ago (Ma) in the middle Paleocene. However, the two subfamilies (Didiereoideae and Portulacarioideae) with multiple species began to diverge about 11.1 Ma and 14.9 Ma, respectively, during the mid-late Miocene. Results from diversification analysis further revealed an increased diversification rate shift about 11 Ma. These findings align closely with the timing of the establishment of arid climates (15-10 Ma) in the family’s distribution range. Thus, we suggest that the onset of aridity in southern and eastern Africa and Madagascar during the mid-late Miocene likely played a key role in driving species diversification within Didiereaceae. This study enhances our understanding of the evolutionary history of Didiereaceae and contributes to broader knowledge of species diversification patterns in succulent plants.

Key words: succulents, Didiereaceae, divergence time, phylogeny, species diversification