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C·I·B’S MOLECULAR ECOLOGY GROUP HEADS DOWN UNDER

Dr Jaco Le Roux and PhD student Miss Joice Ndlovu spent September 2009 in Australia on an extensive field collection trip. One of the current research foci at the C·I·B entails the molecular ecology of invasive wattles from Australia (Acacia species). For this research molecular genetic approaches are used to better understand invasion dynamics of wattles such as geographic source(s) and number(s) of species introductions, genetic inbreeding and landscape-scale spread and dispersal. The Australian continent spans more than 7.5 million km2 and many Australian species have equally impressive distribution ranges. Not surprisingly, Jaco and Joice had to cover vast distances to collect specimens of particular species throughout their natural distribution ranges. A typical day consisted of open road, more open road, and keeping a weary eye open for kangaroos crossing the road.

Joice Ndlovu in Heathcote National Park (New South Wales): One hour driving, R100.00; three hours hiking, R45.00; finally finding Acacia pycnantha, Priceless!

The first target species was Acacia pycnantha commonly known as the golden wattle and also Australia’s floral emblem. This species occurs throughout Southern and Eastern Australia (the states Victoria, South Australia and New South Wales). Armed with field equipment, lots of attitude and a Lonely Planet, Jaco and Joice set off on a 5000 km road trip from Victoria to Sydney (New South Wales) and back through South Australia to Adelaide. Along the way DNA samples of A. pycnantha were collected as well as specimens of its natural enemy, a wasp, Trichilogaster signiventris. This research will enable Joice to infer whether host-specific genetic lineages of the wasp are associated with geographic lineages of A. pycnantha throughout its natural distribution in Australia. Such research is paramount to current biological control programmes aimed at utilizing these host-specific associations to control invasive populations in South Africa. In addition, rhizobial symbiotic bacteria (root-nodule bacteria) associated with golden wattles were collected. These bacteria form a mutualistic association with plants by fixing, and thereby, making atmospheric nitrogen available to leguminous plants. This part of Joice’s PhD research will focus on the importance of this bacterial-plant association in facilitating invasions in nitrogen poor environments, such as the Cape Floristic Region.

Mount Compass, South Australia: Dave Richardson and Jaco Le Roux get down to business collecting root-nodule bacteria from Acacia pycnantha.

Joice and Jaco were joined by Prof Dave Richardson in Adelaide to attend a Weed Adaptation and Lag-phase Dynamics Mini Symposium. Here, Dave and Jaco gave presentations on their own research and Joice gave an overview of her PhD research. Dave also presented a seminar at the University of Adelaide’s Environment Institute entitled “Fifty years of invasion ecology: The legacy of Charles Elton?” that was well-received by numerous biologists from all over Australia. For the remainder of her stay Joice worked in a molecular laboratory at the University of Adelaide to isolate root-nodule bacteria, extract DNA from wasp samples and curate all the collected plant samples.

Jaco Le Roux sampling Acacia cyclops in Cape Arid National Park.

In the mean time Jaco set off for Perth (Western Australia) on an extensive collection trip that mainly focussed on Rooikrans (Acacia cyclops) throughout its distribution range from Perth to the border between Western and South Australia. This species has a coastal distribution and therefore took Jaco through the Nullarbor Plain. As the name indicates, this plain is characterized by shrubland vegetation with very few trees (Nullabor is derived from the Latin nullus, “no or zero”, and arbor, “tree”). Jaco had the opportunity to visit pristine outback vegetation in areas such as the Cape le Grand National Park and Cape Arid National Park. Five thousand kilometres and 200 kangaroos later, Jaco joined Joice in Adelaide. Jaco then spend his last week in Australia in Atherton (Queensland State) visiting a collaborator, Dr Denise Hardesty, at Australia’s Commonwealth Scientific and Research Organization (CSIRO). Their collaboration involves the investigation of molecular ecology of tropical tree invasions.

Overall the visit to Australia was an extremely productive and rewarding experience made even more interesting by beautiful and diverse landscapes, fauna and flora, and yes mate, culture!

View of Nullarbor Plain from the top of Medura Pass.

The road is long: The longest stretch of tarred road in Australia (approximately 147 km) while crossing the Nullarbor Plain.