Orchid fruiting success is unrelated to surrounding floral resources in South Australian plant communities

To maintain recruitment in orchid populations in an ecosystem setting, we must understand how surrounding floral resources affect fruiting success. We studied fruiting success in two endemic Australian species, Diruis pardina and Glossodia major, in relation to surrounding floral resources. Diuris pardina has a visually deceptive pollination strategy via mimicry of pea flowers, attracting pollinators associated with co-flowering plants of Pultenaea. Glossodia major displays dummy anthers and has a more generalist pollination strategy. We expected fruit set of both species to positively correlate to conspecific and heterospecific floral density because orchid pollination should be enhanced by the attraction of higher densities of bees. We expected fruiting success of D. pardina to positively correlate with abundance of Pultenaea flowers. Surveying 18 plots in South Australia, we counted species, individuals and flowers of conspecifics and heterospecifics and returned to count flowers that set fruit. We conducted Pearson correlations between fruiting success and density of conspecific flowers, richness, abundance and Shannon index of surrounding floral resources and floral abundance of individual species. Fruiting success was correlated with conspecific floral density for Diuris pardina but not G. major. No relationship was found between fruiting success and heterospecific floral resources. Fruiting success of D. pardina was not correlated with abundance of Pultenaea; instead it was positively correlated with the invasive species Lavandula stoechas.

Toona ciliata (toon).

The family Meliaceace contains some of the world's finest grade cabinet timbers. These include the Honduran mahogany (Swietenia macrophylla), West Indian mahogany (S. mahogani), Ugandan mahogany (Entandrophragma sp.), Asian Chukrasia (Chukrasia tabularis) and the Australian red cedar or Indian Toon (T. ciliata). Timber of T. ciliata was exported from Australia to Calcutta, India, in 1795 just seven years after the first British settlement was established in Sydney, thus becoming Australia's first export. The harvesting of this species was very important to the economy of the early European settlement and the timber getters helped open up the coastal forests for later agricultural activities (Boland, 1997). The species was also arguably the first Australian plant species to have conservation measures placed upon it (Boland, 1997) when it was realised that the species was rapidly disappearing in areas near Sydney. In India, thirty years ago, timber of T. ciliata was said to be available in large quantities from Uttar Pradesh and in fair quantities from North Bengal and Assam (Anon, 1963). Timber is also available in small quantities from other areas; mainly from roadside trees and from trees on cultivated lands (Anon, 1963).

Diversity of CAM plant photosynthesis (crassulacean acid metabolism): a tribute to Barry Osmond

This special issue is a tribute to the Australian plant biologist Professor Charles Barry Osmond – Fellow of the Australian Academy of Sciences, the Royal Society of London, and Leopoldina, the German National Academy of Sciences – and his many contributions to our understanding of the biochemistry and physiological ecology of CAM (crassulacean acid metabolism) photosynthesis. This water-conserving photosynthetic pathway is characterised by nocturnal uptake of atmospheric CO2 and typically enables succulent plants to perform and survive in warm semiarid terrestrial and epiphytic habitats. The idea for this issue is to mark the occasion of Barry’s 80th birthday in 2019. The foreword highlights some of his outstanding contributions and introduces the research papers of the special issue.

Platysace (Apiaceae) of south-western Australia: silent story tellers of an ancient human landscape

High gene flow and a population structure corresponding to human rather than geographical drivers are likely to be genetic patterns of human-dispersed plant taxa. We examined variation in geographical structure and gene flow estimates based on three non-coding regions of plastid DNA in three south-west Australian members of the Platysace genus to identify whether a human influence on dispersion of utilized taxa was detectable. Edible tubers of Platysace deflexa and Platysace trachymenioides have been harvested historically by Noongar traditional owners, whereas Platysace effusa has no known cultural significance. We found differences between utilized and non-utilized taxa, particularly when considered against the generally complex phylogeographical patterning in south-west Australian plant taxa. Platysace effusa showed a pattern of high population divergence, low gene flow and multiple refugia, consistent with a long evolutionary history, past climatic oscillations and persistence in a highly fragmented landscape. In contrast, higher gene flow estimates, less divergence between populations and common haplotypes in P. deflexa and in P. trachymenioides over the south-eastern part of its range are consistent with anthropogenic influences. This study contributes to the understanding of human influences on south-west Australian plant taxa that have been present since the late Pleistocene, but to date have received little scientific attention.