Stick and leaf insects are a diverse and strikingly bizarre group of insects with a world-wide distribution, which are more common in tropical and subtropical areas. They are famous for their impressively large body size, compared to other insects, and their remarkable ability to camouflage themselves as twigs, leaves or bark in order to hide from potential predators. A team of international researchers led by the University of Gottingen has now generated the first phylogenomic tree of these insects.
The most surprising finding is that the relationships between the early emerging groups of stick and leaf insects largely disprove the earlier assumptions. In fact, the genealogy reflects more the geographic distribution than the anatomical similarity of the animals. The authors revealed a New World lineage of purely North and South American species and a group of Old World origin that comprises species from Africa to New Zealand.
The biogeographic history was reconstructed by Sarah Bank, PhD student at the University of Gottingen and coauthor of the study, which resulted in further unexpected results: "The flamboyant stick insects of Madagascar, for instance, descended from a single ancestral species who colonised the island approximately 45 million years ago."
The age estimation of the phylogenetic tree suggests that most of the old lineages emerged after the dinosaurs became extinct 66 million years ago. Thus, the remarkable camouflage of stick and leaf insects most probably evolved afterwards as adaptation against predatory mammals and birds.
"Stick insects become more and more important as model organisms for evolutionary research. The new comprehensive molecular dataset won't be exhaustively analysed for quite some time and will provide exciting insights into the function of the numerous detected genes," explains Bradler with regard to future studies.
The study has been published in the journal Frontiers in Ecology and Evolution.
Source: University of Gottingen [October 07, 2019]
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