The family Lauraceae are a prominent component of broad-leaved evergreen forests in the tropics and subtropics. However, the biogeographical history of the family is poorly understood, because of the difficulty of assigning macrofossils to living genera, poor pollen preservation, and the absence of sufficiently resolved or well-supported phylogenies.
In a study published in Taxon, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Guangxi Normal University utilized plastid genome sequencing to reinvestigate the phylogenetic and biogeographic history of trees in the tribe Cryptocaryeae,with around 800 species that rely on vertebrate frugivores to disperse their seeds.
The researchers compiled a dataset composed of 45 newly generated plastomes, 34 published plastomes, and 97 trnK and related barcode sequences to represent 176 species spanning all clades identified in the Cryptocaryeae.
Their topology provided strong support for sisterhood between the Beilschmiedia clade and Cryptocarya clade, with Aspidostemon and Dahlgrenodendron being the next sister group, followed by Eusideroxylon. Both the Beilschmiedia and Cryptocarya clades are 100% supported monophyletic in the analysis.
According to their molecular clock approaches and biogeographical inferences, the timing of divergence of crown lineages within the Cryptocaryeae was estimated around 102？Ma (124–79？Ma) in the Cretaceous, and Asia or Africa might be the ancestral area for the Cryptocaryeae. After that, accelerations in both lineage accumulation and colonization within the Cryptocaryeae were estimated at around 73？Ma (107–59？Ma) in Africa or South America.
Their phylogeny suggested that the Cryptocaryeae originated in and diversified with the first angiosperm-dominated broad-leaved evergreen forests, from the Cretaceous in Africa or Asia to their maximum global extent in the Paleogene.
Moreover, long-distance seed dispersal, probably by birds, although possibly also by flotation, has allowed the tribe to track these forests in space and time, despite a failure to adapt to cold, dry, or highly seasonal environments.
YAO Xin Ph.D
Center for Integrative Conservation, Xishuangbanna Tropical Botanical China
First published: 23 November, 2023