Evolutionary theory aids species conservation
16 January 2006
Evolutionary theory aids
Two University of Canterbury biologists are part of a team whose evolutionary informed approach to conservation is aiding the recovery of New Zealand’s critically endangered parrot, the kakapo.
Dr Bruce Robertson and Associate Professor Neil Gemmell (Biological Sciences) are members of a research team that has just had a paper published in the Royal Society of London’s prestigious journal Biology Letters. The manuscript outlines how the team, led by Dr Robertson, used sex allocation theory to remedy a conservation dilemma. A key prediction of sex allocation theory is that females in good condition should produce more sons.
The kakapo, which today has a population of 86 located on a handful of small island sanctuaries, is the subject of much global conservation interest. They only breed every two to five years and about 58% of eggs do not hatch.
Providing breeding females with extra food over the past decade has improved breeding frequency and chick survival, but at a recently-recognised cost: females in better condition were producing more sons.
“Left unchecked, the recovery of this already male-biased species could be prolonged by more than 100 years, dramatically increasing the risk of losing this charismatic bird to extinction,” Dr Robertson said.
The team of researchers — which also includes Graeme Elliott and Daryl Eason of the Department of Conservation’s Kakapo Management Group and Mick Clout from the Centre of Biodiversity and Biosecurity at the University of Auckland — introduced a new feeding regime to the Comalco-sponsored Kakapo Recovery Programme.
Under previous feeding regimes kakapo were able to feed freely (ad libitum) from their food dispensers, but it had been noted by scientists that the supplementary fed females produced more sons.
Armed with a better understanding of how female condition affects the sex of their offspring the scientists initiated a new regime in winter 2001 on Codfish Island. Only females below a predicted December weight of 1.5 kg (breeding threshold) were given ad libitum food in the months before commencement of mating in mid-January to bring them up to the desired optimum weight. Females above the predicted December weight threshold were given restricted food provisions to avoid raising their body condition to that previously associated with male-bias sex allocation.
The new regime raised all female weights above the 1.5kg breeding threshold and molecular sexing of all the fertile eggs indicated that the deliberate manipulations removed the dilemma of the excess of sons by returning offspring sex ratios to parity.
Dr Robertson said it was rewarding to be a part of research that was helping a conservation icon take another step on the path to recovery.
“This is a world first, using evolutionary theory to inform conservation practises and the first time anyone has used sex allocation theory to manipulate sex ratios with a critically endangered species. Our work has not only remedied the immediate problem of an overproduction of sons, but also highlights the value of incorporating evolutionary theory into modern conservation practice."
Dr Robertson is involved in further research on kakapo including a molecular analysis of paternity and an investigation into the impact of genetic similarity of parents on the success of breeding attempts.