A tree of leaves: Phylogeny and historical biogeography of the leaf insects (Phasmatodea: Phylliidae)

The insect order Phasmatodea is known for large slender insects masquerading as twigs or bark. In contrast to these so-called stick insects, the subordinated clade of leaf insects (Phylliidae) are dorso-ventrally flattened and therefore resemble leaves in a unique way. Here we show that the origin of extant leaf insects lies in the Australasian/Pacific region with subsequent dispersal westwards to mainland Asia and colonisation of most Southeast Asian landmasses. We further hypothesise that the clade originated in the Early Eocene after the emergence of angiosperm-dominated rainforests. The genus Phyllium to which most of the similar to 100 described species pertain is recovered as paraphyletic and its three non-nominate subgenera are recovered as distinct, monophyletic groups and are consequently elevated to genus rank. This first phylogeny covering all major phylliid groups provides the basis for future studies on their taxonomy and a framework to unveil more of their cryptic and underestimated diversity.Bank et al. investigate the phylogenetic relationships of all major lineages of leaf insects, identify 15 to 20 putatively new species, and show these insects likely originated in the Australasian/Pacific region with dispersal to the mainland. This phylogenetic work is the first to include all major groups of leaf insects and highlights cryptic diversity.

Automated summary

The study reveals the origin of leaf insects in the Australasian/Pacific region, with subsequent dispersal to Asia mainland, and provides insight into their underestimated diversity through phylogenetic analysis.