
Until now, the majority of the walking leaves were grouped under the name Phyllium. However, numerous species were united here that are not at all closely related to each other. The scientists now introduced some new genera in order to be able to describe the natural relationship. "Many of the species studied have not even been described scientifically," explains Sarah Bank, first author of the study and a doctoral candidate in the Biodiversity and Ecology program at the University of Göttingen. "We also identified many cryptic species - those that are not outwardly distinct but genetically very different."
Göttingen evolutionary biologist Dr Sven Bradler adds, "A few years ago, just 50 species had been described. Through our studies and especially through the collaboration with the New York expert on walking leaves, Royce Cumming, this number has now doubled. This shows that our knowledge of biodiversity is often heavily dependent on the expertise of individuals. For many groups of organisms, such knowledge is simply lacking."
The team also reconstructed the phylogenetic distribution of the insects. According to the study, the origin of the walking leaves is in the Southern Pacific, from where they spread throughout tropical Asia over the past 50 million years - as far east as Fiji and as far west as the Seychelles. "The age of the walking leaves is a scientifically controversial topic," Bank says. "Other studies had placed their temporal origin in the Cretaceous or even Jurassic, 100 to 150 million years ago. At that time, however, the angiospermous flowering plants whose leaves so perfectly mimic insects were not even common. Consequently, the results of our work seem more plausible to us, favoring a more recent origin."
Original publication: Sarah Bank et al. A tree of leaves: Phylogeny and historical biogeography of the leaf insects (Phasmatodea:Phylliidae). Communications Biology (2021). https://doi.org/10.1038/s42003-021-02436-z