The Wollemi pine, Wollemia nobilis (Araucariaceae), was discovered in 1994 as the only extant member of the genus, previously known only from the fossil record. With fewer than 100 trees known from an inaccessible canyon in southeastern Australia, it is one of the most endangered tree species in the world. We conducted a comparative population genetic survey at allozyme, amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) loci in W. nobilis, Araucaria cunninghamii and Agathis robusta - representatives of the two sister genera. No polymorphism was detected at 13 allozyme loci, more than 800 AFLP loci or the 20 SSR loci screened in W. nobilis. In Ag. robusta only one of 12 allozyme loci, five of 800 AFLP loci and none of the 15 SSR loci were variable. For A. cunninghamii, 10 of > 800 AFLP loci and five of 20 SSR loci were variable. Thus low genetic diversity characterizes all three species. While not ruling out the existence of genetic variation, we conclude that genetic diversity is exceptionally low in the Wollemi pine. To our knowledge this is the most extreme case known in plants. We conclude that the combination of small population effects, clonality and below-average genetic variation in the family are probable contributing factors to the low diversity. The exceptionally low genetic diversity of the Wollemi pine, combined with its known susceptibility to exotic fungal pathogens, reinforces current management policies of strict control of access to the pines and secrecy of the pine locations.

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Our aim was to uncover the drivers of seedling growth in a rare rainforest conifer. Wollemia nobilis is limited to canyons, characterized by deeply shaded understories and acid soils. In a glasshouse experiment, we grew seedlings at a range of pH and light levels. Growth increased with increasing light, and was higher at low pH, regardless of light. Number of stems, however, was greatest in lower light. Wollemia nobilis seedlings may vary their architecture - growing up when light is high, and growing out when light is lower. Nevertheless, low light is likely the key limitation of W. nobilis growth in the wild.

The branch-base xylem constriction would appear to facilitate branch abscission, while the associated Huber values show that W. nobilis supplies a relatively large leaf area through a relatively small diameter 'pipe'. It is tempting to suggest that the pronounced decline of W. nobilis in the Tertiary is related to its unusual branch-base structure but physiological studies of whole plant conductance are still needed.

Wollemia nobilis W.G.Jones, K.D.Hill D J.M.Allen isrepresented in the wild by about 40 adult trees; therefore, understanding therequirements for seed germination is important for the conservation of thismonotypic Australian conifer. Constant-temperature experiments found that seedgermination proceeded most rapidly at temperatures between 24 and 30˚C.Few seeds germinated when incubated for 112 days at 10 and 16˚C but latergerminated when transferred to 24˚C, whereas seeds initially incubated at35˚C were killed. Unstratified seeds showed a pattern of prolongedgermination taking 130 days to achieve 40% germination at 24˚C and40 days at 27˚C. Seeds stratified at 6˚C for 14 days and incubatedat 27˚C in the light achieved 40% germination within 20 days whilethose incubated at 10 and 16˚C for 112 days and transferred to 24˚Cachieved 40% germination by 15 and 24 days, respectively. Initialgermination of unstratified seeds was fastest when incubated at 30˚C inthe light, averaging 23 days. Exposure to 12-h diurnal periods of 10–15mol m–2 s–1 lightsignificantly increased 28-dayincubation germination percentages, but for onlythose incubated at 30˚C. Additions of gibberellic acid(GA3) at 1 mM had no effect on seed germination ofW. nobilis. The field observations and laboratoryexperiments indicate that following seed shed in summer and early autumn whentemperatures are high, W. nobilis seeds germinate,especially if exposed to light. The seeds that remain ungerminated or that areshed late in the season survive over winter, but germinate rapidly oncetemperatures rise in the next spring.