Papers by Patricia F Meagher
AoB PLANTS, 2014
Seedling growth rates can have important long-term effects on forest dynamics. Environmental vari... more Seedling growth rates can have important long-term effects on forest dynamics. Environmental variables such as light availability and edaphic factors can exert a strong influence on seedling growth. In the wild, seedlings of Wollemi pine (Wollemia nobilis) grow on very acid soils (pH ∼4.3) in deeply shaded sites (∼3 % full sunlight). To examine the relative influences of these two factors on the growth of young W. nobilis seedlings, we conducted a glasshouse experiment growing seedlings at two soil pH levels (4.5 and 6.5) under three light levels: low (5 % full sun), medium (15 %) and high (50 %). Stem length and stem diameter were measured, stem number and branch number were counted, and chlorophyll and carotenoid content were analysed. In general, increased plant growth was associated with increased light, and with low pH irrespective of light treatment, and pigment content was higher at low pH. Maximum stem growth occurred in plants grown in the low pH/high light treatment combin...
AoB PLANTS, 2014
Seedling growth rates can have important long-term effects on forest dynamics. Environmental vari... more Seedling growth rates can have important long-term effects on forest dynamics. Environmental variables such as light availability and edaphic factors can exert a strong influence on seedling growth. In the wild, seedlings of Wollemi pine (Wollemia nobilis) grow on very acid soils (pH ∼4.3) in deeply shaded sites (∼3 % full sunlight). To examine the relative influences of these two factors on the growth of young W. nobilis seedlings, we conducted a glasshouse experiment growing seedlings at two soil pH levels (4.5 and 6.5) under three light levels: low (5 % full sun), medium (15 %) and high (50 %). Stem length and stem diameter were measured, stem number and branch number were counted, and chlorophyll and carotenoid content were analysed. In general, increased plant growth was associated with increased light, and with low pH irrespective of light treatment, and pigment content was higher at low pH. Maximum stem growth occurred in plants grown in the low pH/high light treatment combin...
The Wollemi pine, Wollemia nobilis (Araucariaceae), was discovered in 1994 as the only extant mem... more 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.
The Wollemi pine, Wollemia nobilis (Araucariaceae), was discovered in 1994 as the only extant mem... more 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.
Annals of Botany - ANN BOT, 1999
The two known populations of the recently discovered rare and threatened Wollemi Pine (Wollemia n... more The two known populations of the recently discovered rare and threatened Wollemi Pine (Wollemia nobilis Jones, Hill and Allen) consist of a small number of large multi-stemmed adult trees and small seedlings. Female and male cones are produced on adult trees with pollen release occurring in spring (October–November). Seed cones mature 16–19 months later in late summer and autumn and appear to be produced annually. Approximately 10% of seed produced in two consecutive years was viable, 25% of which was damaged by animals. Glasshouse studies showed that seed germination at 25 °C (day)/16 °C (night) proceeded slowly but steadily at approx. 4% per week until, after 6 months, 88% of apparently viable seed had germinated with the remainder of the seed rotting. Growth of potted seedlings in this temperature regime was continuous (after a lag period of 4–6 months) with the monopodial axis growing 0.05–0.25 m in the first year, 0.5–0.6 m in the second year and 0.25–0.35 m in the third year, ...
Molecular Ecology, 2003
The Wollemi pine, Wollemia nobilis (Araucariaceae), was discovered in 1994 as the only extant mem... more 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.
Seed production varies from year-to-year in most species. Factors influencing this variation can ... more Seed production varies from year-to-year in most species. Factors influencing this variation can include pollination and dispersal mechanisms, seed predation and resource availability. Here we examine a long-term (12– year) photographic record of seed cone production for the Australian endemic conifer Wollemia nobilis (Araucariaceae). Coefficient of variation (a commonly used measure of variation in seed production) was low for the two trees analysed, compared with published values for other polycarpic plants. Nevertheless, cone production decreased with increasing spring minimum temperatures (during pollination) and increased with summer total rainfall (during cone initiation). Hence, Wollemia nobilis cone production was correlated with weather, in line with the resource-matching hypothesis. Impacts of variation in cone production on the Wollemia nobilis population are likely to be buffered by the shade-tolerant, slow-growing juvenile life stage of Wollemia nobilis.
Uploads
Papers by Patricia F Meagher