Dr Mary Morgan-Richards is on the verge of discovering the sex secrets of our well-travelled stick insects. Photo / Massey University
Dr Mary Morgan-Richards is on the verge of discovering the sex secrets of our well-travelled stick insects. Photo / Massey University
Scientist's challenge: work out if asexual returning expat stick insects still need male suitors.
It may be the strangest Kiwi OE ever - a gangly, hard-to-spot native bug hitches to Britain and evolves to reproduce without the need for the blokes back home.
Now, biologists at Massey University's Phoenix Lab have brought a few of the so-called smooth or teatree stick insects back to New Zealand to learn whether the naturalised females can still reproduce their old way - or are over men for good.
"There seems to have been a number of times where females have left males behind and have become asexual - and we are trying to understand whether they can return back to sexuality or not," said Associate Professor Mary Morgan-Richards, who is leading the work.
For scientists, solving the mystery of how the Clitarchus hookeri managed to become asexual is important because it could provide valuable insights into why reproduction, as we humans know it, is maintained in different multicellular organisms.
The insects at the centre of the study are found in the Isles of Scilly, a small archipelago off the southern coast of England, and are thought to have got there after hatching from soils shipped with New Zealand plant material more than half a century ago.
Soon after they arrived, they evolved to reproduce without the need for male sperm, effectively becoming just like the asexual New Zealand prickly stick insect, which reached the islands around the same time.
For the past 75 years, the tiny Kiwi expats have been enjoying the islands' temperate climate, much like that of home, and their famously diverse abundance of plants and flowers.
Recently, the Massey team brought back eggs and then watched as the returned insects eventually copulated with their long-lost male counterparts. Only after a new batch of nymphs hatch will they be able to tell whether the male sperm played a part.
"It may be that we find they're now an independent lineage that can no longer reproduce with the ones back here," Professor Morgan-Richards said. The study could potentially inform scientific debate on the advantages of sexual reproduction, and why it continued in many species, including our own.
"There's also a lot of interest in controlling pest insects, and whether we can use techniques that influence reproductive methods."
In a separate project, her team is investigating whether the Acanthoxyla stick insect genus, found in native forest and scrub throughout the North Island and large areas of the South Island, is the result of hybridisation, where two distinct species breed to create an entirely new lineage.
"We see it happen in plants a lot, but it's much more rare in animals for that to occur." New Zealand is home to more than 20 species of stick insect and, with two recently discovered in the North Cape area and the Poor Knights Islands, it is likely there are more, well-camouflaged amid our mountains and forests, still to be described.
"We've got a wonderful diversity of stick insects and, simply because they're right there in our rose plants, we can study them straight out of the garden window."
A bug's life
New Zealand's globe-trotting smooth stick insect:
• Possibly our most common stick insect, Clitarchus hookeri is green but sometimes also brown and red in colour, and typically measures about 90mm.
• More than half a century ago, the species arrived in Britain in the form of eggs buried in shipped New Zealand plant material.
• Turning up amid the colourful and diverse plant life of the Isles of Scilly, female Clitarchus hookeri managed to achieve parthenogenesis - asexual reproduction without the need for its male counterparts back home.
