In Search of the ‘Other 95%’ - Werrikimbe

For decades Dan Bickel, Research Fellow at the Australian Museum, and I have ventured to the subtropical rainforests of eastern Australian seeking out the wealth of invertebrate biodiversity that resides there.

Colloquially termed the 'Other 95%' invertebrates, those diverse organisms without backbones, literally make up the vast wealth of the Earth's terrestrial biodiversity. Our subtropical rainforests are an invertebrate treasure trove, and despite past surveys, we still know little about them. The life history of most, and how they interact with other plants and animals, remains much a mystery.

And so in January, with museum post-doc researcher Keith Bayless, and family and friends in company, we journeyed to the high mountain forests of Werrikimbe National Park on the New South Wales north coast. Included within the Gondwana Rainforests World Heritage Area, Werrikimbe is a realm of cool and warm temperate rainforests placed in a vegetation matrix of eucalypt-dominated forests. A particular research focus was on Diptera (flies), but I particularly wanted to obtain photographs of animals for my subtropical invertebrate book project. Having a 'wish list' is always an exercise in chance as seasonal occurrences can't always be predicted, and organisms, even when known to inhabit a particular forest site don't always show on cue. 'Uncertainty' rules. And this proved to be the case. Species hopefully to be encountered, such as Australia's largest land snail Hedleyella falconeri, was found only in the form of occasional dead and broken shells, Dan's target fly group Hilara was rarely in evidence, and thanks to unusually cool weather at night insect sampling using a mercury vapour light was poor to say the least.

But the field trip was far from a disappointment. I located the aberrant buprestid beetle Castiarina variegata, a species once placed in a genus, Hypostigmodera, all by itself owing to males possessing highly biserrate antennae (serrated on both sides); occurring in two sexually distinct forms otherwise unknown among this iconic Australian group. Spot-lighting at night in the cool temperate rainforests near Plateau Beech exposed two species of the spider family Gradungulidae; Progradungula carraiensis and a Tarlina species of uncertain determination. Gradungulidae, or 'Long-clawed spiders', occur only in Australia and New Zealand and are of ancient arachnid lineage. The 'Carrai Cave spider'; Progradungula carraiensis is one of only two species in the genus, and is unusual in that individuals build ladder-like web snares into which they cast their prey. Of additional interest was finding more individuals of Australia's largest native dung beetle, Aulacopris maximus, 'perching' on tree trunks.

I had first discovered this unexpected habit several decades ago in the nearby Banda Banda Beech Reserve, now incorporated into the national park. So it was encouraging to reaffirm this behaviour. 'Perching' is an otherwise rarely reported behaviour among dung beetles (Scarabaeinae) and the reason as to why they do it remains uncertain. Other entomologists have suggested it may be a strategy that optimizes the beetle's ability to locate food resources.

These are just a few personal highlights. Dan and Keith had theirs. Collectively such records, built over countless hours by numerous field workers, allow us to construct a better understanding of our diverse and highly endemic fauna - one that is central to the function and well-being of the rainforest ecosystems with which we are still so richly endowed. For invertebrates, regardless of the ecosystems they inhabit, are responsible for pollination, the recycling of nutrients, and sit as the basis for broader food chains within the Australian landscape.

Geoff Williams OAM, PhD (UNSW), Research Associate.