The petaltail dragonflies (Odonata: Petaluridae): Mesozoic habitat specialists that survive to the modern day

Aim: To explore the phylogenetics and historical biogeography of the dragonfly family Petaluridae (known as 'petaltails'), a relict dragonfly group with unique habitat and life history attributes. Location: Australia, New Zealand, Japan, Chile and North America. Methods: Using five mitochondrial and three nuclear gene fragments we recovered garli-part maximum likelihood and Bayesian phylogenetic hypotheses for 10 of the 11 extant petaltail species. Biogeographical patterns were analysed using Lagrange and interpreted through beast relaxed clock dating analysis. Results: Petaluridae is monophyletic with an origin in the mid-Jurassic, c. 157 Ma. The family consists of two major clades: one with a Laurasian distribution containing the genera Tachopteryx and Tanypteryx, and another containing the genera Petalura, Phenes and Uropetala, distributed in Gondwanan remnants. Based on our beast molecular clock, these two clades separated c. 146 Ma. Species ages in Petaluridae range from c. 100 to c. 30 million years, with the majority of the species persisting for 70-75 million years. Analysis with Lagrange points to an origin for the family associated with New Zealand, with subsequent dispersal to other Gondwanan remnants (Australia and Chile) as well as Laurasia (eastern and western North America) and subsequent dispersal from western North America to Japan. Main conclusions: The extant species of Petaluridae are extremely old, with most species persisting as independent lineages since the Jurassic. Our results suggest that New Zealand was close to the origin point in the Jurassic; one possibility is that Antarctica was at the centre of the petalurid distribution, based on Permian fossil evidence. Such long persistence for species is surprising, especially considering the specialized habitat required by petalurid larvae; unlike the majority of modern dragonflies, which spend their larval stage in ponds or streams, petaltails live in fen habitats. Petaltails also take multiple years to develop from egg to adult, another trait uncommon in modern dragonflies. Specialization in a species is normally associated with higher extinction rates; the petaltails appear to be an exception to this rule.