An island giant: describing a new species of rove beetle from the Chatham Islands

2010 REU Intern Mairead Baker


Sophomore Evolutionary and Developmental Biology major at Northwestern University

REU Mentor: Dr. Margaret Thayer (Curator, Zoology, Insects)

Symposium Presentation Title: An Island Giant: Describing a New Species of Rove Beetle from the Chatham Islands

Symposium Presentation Abstract: The Chatham Islands, located approximately 800 km from the New Zealand mainland, host a myriad of thriving habitats populated with a rich insect biodiversity and numerous giant plant species. Currently there are roughly 300 beetle species residing on the islands, 65 of which belong to the diverse family Staphylinidae – the rove beetles. One genus, Omaliomimus, inhabits this archipelago in a quite specialized habitat: the beach. Currently, three Omaliomimus species are found on the Chathams: O. robustus, O. actobius, and O. giganteus sp. nov. This new species, as its name suggests, is a physical giant. Consistent with the giant plant species endemic to the Chathams, this new organism appears to be a result of the biological phenomenon island gigantism. Our measurements support this hypothesis as O. giganteus appears to be roughly 15% larger than the next largest Chatham Island Omaliomimus species and 30% larger than the largest New Zealand mainland Omaliomimus. Additionally, our extensive examination, including numerous dissections and clearings, has shown that this giant is not by any means an inflated morph of the neighboring Omaliomimus species, but a new species altogether. Due to certain morphological constraints, the giant cannot afford a generalist approach to habitat selection like its relatives and neighbors, O. robustus and O. actobius. It seems to be restricted to substantially more stable environments, where it is protected by boulders and cliffs. The species-specific characters of Omaliomimus giganteus  include vestigial wings, and consequent lack of wing-associated structures such as the palisade fringe and abdominal wing folding patches. Among other characters, this flightlessness separates O. giganteus from the other Chathams Omaliomimus species. From the unusual size, unique habitat, and several distinctive characters, it is quite evident that this species is certainly new to science and evidence of island gigantism. Therefore, Omaliomimus giganteus will become the twelfth, and possibly the most remarkable, species of its genus.

Original Project Description: The rove beetle genusOmaliomimus is one of several in the large family Staphylinidae that live on ocean beaches - the edge of a habitat that is scarcely occupied by insects. The ten described Omaliomimus species are known from New Zealand proper, its subantarctic islands, and Australia's Macquarie Island (south of New Zealand and Australia), where they live in washed-up rotting seaweed or occasionally birds' nests or dead birds. The currently valid species were described between 1877 and 1911, but recent collecting in the Chatham Islands, east of New Zealand, has turned up a huge species not yet described and not known from anywhere else. At 6 mm long, the adults are much larger than any previously described Omaliomimus species and 50% longer than most. As is common in rove beetles, larvae of the new species were collected with the adults. As a contribution to ongoing broader studies of the fauna of the Chatham Islands by several researchers, we will prepare for publication a well-illustrated description of this new species, comparing both adults and larvae to those of already known Omaliomimus species. This will add significantly to the scanty published knowledge of Omaliomimus larvae. If time permits, we can also attempt to reconstruct a preliminary species level phylogeny to consider whether this might be a case of island gigantism.

Research methods and techniques: Research work will include training in beetle skeletal morphology; dissecting, microscopy, and imaging techniques (probably including SEM – scanning electron microscopy); databasing and georeferencing specimen collecting records; and using the georeferenced records to map the known distribution. Phylogenetic analysis would use software available for that purpose, such as TNT, to analyze a matrix of morphological character data. The intern will work with the sponsoring curator on writing, for publication, a modern description of the species with illustrations (drawings, digital macrophotos, SEM) and comparisons to other species of Omaliomimus. This project will also provide familiarity with scientific literature on the Chatham Islands fauna and on rove beetles.