In 1887, Australian Museum scientists undertook a pioneering expedition to Lord Howe Island, a tiny patch of land off the east coast of Australia. Among their many discoveries they recorded “a big Swamp“ – a kind of cockroach – under a decaying log.
This was later described as Panesthesia lataLord Howe’s wood-feeding cockroach. P. lata It was noted to be very abundant, playing a key role in nutrient recycling and possibly a food source for the many birds on the island.
Alas, in 1918 the rats arrived on the island from a shipwreck. At the end of the 20th century, P. lata it could not be found despite extensive searches over many decades and was presumed extinct due to predation by rats.
But could it have survived in some unexplored pocket of the island?
Putting the cockroach back where it belongs
In 2019, the NSW Department of Planning and Environment (NSW DPE) implemented the final stage of its highly successful (if at times controversial) rat eradication program on the island.
After this, myself and my colleagues from NSW DPE, Lord Howe Island Museum, Chau Chak Wing Museum, Australia’s National Insect Collection CSIRO and the University of Melbourne became interested in the biology of P. lata and the possibility of recolonizing the island with this insect.
This was on paper because, in 2001, P. lata it had been discovered on Blackburn and Roach Islands, two small islands near Lord Howe Island.
But wait a minute: Why would we want to reintroduce cockroaches, one of the most offensive creatures on Earth, to a beautiful island after their seemingly random extermination?
Good, P. lata it is, believe it or not, quite cute and cuddly and has no interest in entering people’s homes. It is wingless, about 4 cm (1.6 in) long, and remains hidden in the forest, where it eats the soil and feeds on leaf litter and rotting wood at night.
In July we received funding from the Australian Pacific Science Foundation to investigate genetics and ecology P. lata from Blackburn and Roach islands. So Maxim Adams, an honors student in our lab at the University of Sydney, and Nicholas Carlile from the NSW DPE headed to Lord Howe Island to begin the study.
Bad weather prevented them from going to Blackburn Island, so they decided to look at possible sites on Lord Howe Island that may once have been full of P. lata before the rats arrived.
They walked to a secluded area in the north of the island and decided to overturn some rocks. Literally the first rock they checked revealed a small cluster of cockroaches! I was supposed to meet them three days later, but they called me that afternoon very excited to break the news.
They found a few more a few meters away under the same fig tree, but extensive searching over the next few days turned up none in other nearby areas or on other parts of the island.
Not the same as their neighbors
We did some preliminary DNA testing on our return to Sydney, finding that the rediscovered Lord Howe Island roach population was different from those found on Blackburn and Roach Islands.
It is possible that the population was suspended as a result of rodent baiting in the area. Baiting has been done in recent decades to aid the survival of various other endangered species.
We are now carrying out more extensive DNA studies, including historical museum samples collected from the late 19th and early 20th centuries, and samples from Ball’s pyramid, about 20 kilometers (12 miles) southeast of Lord Howe Island, collected by Dick Smith in the 1960s.
Through these studies, we hope to determine the relationship of the rediscovered population to those originally collected on the island a century or more ago and those on the outer islands. We also hope to uncover its origins and evolutionary history P. lata.
The Lord Howe Island Group is a UNESCO World Heritage Site of Global Natural Significance and is home to more than 100 plant species found nowhere else on Earth, as well as many more endemic animal species. The biology of many of these species, especially the island’s invertebrates, remains mysterious.
We hope that the use of DNA techniques will help establish us P. lata as a model for understanding millions of years of evolution in Lord Howe’s archipelago and to help re-establish this shy but charismatic creature in its homeland.
Nathan Lo, Associate Professor, Faculty of Biological Sciences, University of Sydney
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