Extreme convergence in stick insect evolution: phylogenetic placement of the Lord Howe Island tree lobster

Abstract

The 'tree lobsters' are an enigmatic group of robust, ground-dwelling stick insects (order Phasmatodea) from the subfamily Eurycanthinae, distributed in New Guinea, New Caledonia and associated islands. Its most famous member is the Lord Howe Island stick insect Dryococelus australis (Montrouzier), which was believed to have become extinct but was rediscovered in 2001 and is considered to be one of the rarest insects in the world. To resolve the evolutionary position of Dryococelus, we constructed a phylogeny from approximately 2.4 kb of mitochondrial and nuclear sequence data from representatives of all major phasmatodean lineages. Our data placed Dryococelus and the New Caledonian tree lobsters outside the New Guinean Eurycanthinae as members of an unrelated Australasian stick insect clade, the Lanceocercata. These results suggest a convergent origin of the 'tree lobster' body form. Our reanalysis of tree lobster characters provides additional support for our hypothesis of convergent evolution. We conclude that the phenotypic traits leading to the traditional classification are convergent adaptations to ground-living behaviour. Our molecular dating analyses indicate an ancient divergence (more than 22 Myr ago) between Dryococelus and its Australian relatives. Hence, Dryococelus represents a long-standing separate evolutionary lineage within the stick insects and must be regarded as a key taxon to protect with respect to phasmatodean diversity.

The spider family Micropholcommatidae (Arachnida: Araneae: Araneoidea): a relimitation and revision at the generic level

“…island 'stepping-stone') explanation is feasible (e.g. see Forster 1964;Buckley et al 2009). As for most animals and plants, dispersal can never be completely ruled out for the micropholcommatid taxa, but a further discussion on this hypothesis requires calibrated molecular data and a more rigorous understanding of micropholcommatid ecology.…”

“…One of the problems with dispersal biogeography is that such hypotheses are rarely falsifi able (Sanmartin and Ronquist 2004) -taxa could of course, potentially, have travelled anywhere at any time -although with the advent of DNA sequencing, the molecular dating of clades is one way of approaching the dispersal-vicariance debate (e.g. see Buckley et al 2009). For the Micropholcommatidae, no molecular dating data are currently available, and preliminary observations on live micropholcommatid specimens suggest that these spiders are ecologically restricted and highly prone to desiccation (see Natural History, below), rendering long-distance dispersal across the Pacifi c Ocean unlikely.…”

The phylogenetic system of Mantodea (Insecta: Dictyoptera)

“…It would be highly interesting to get a deeper insight into the potential combined effect of these two factors for these predators, and to compare them with other highly cryptic insects, for instance Orthoptera sensu stricto or Phasmatodea. It has recently been shown that several Phasmatodea lineages evolved convergently into the charismatic and robust Eurycanthinae ecomorph (Buckley et al 2009). …”

Comparative phylogeography of oceanic archipelagos: Hotspots for inferences of evolutionary process

“…progression rule | speciation | priority effect | community assembly | radiation zone E volutionists are drawn to the study of island biotas for their unique species (1)(2)(3)(4)(5), as refuges of extant, "relict" organisms (6,7), and most famously, for their displays of adaptive radiation (8,9). Likewise, ecologists have long recognized the value of islands as microcosms of the processes of community assembly (10,11).…”