Understanding the extent and impact of factors influencing the levels and structuring of genetic diversity within natural populations is a key objective of ecological genetics. For marine angiosperms, variation in abiotic environmental factors at the local scale can have a major influence on levels of clonality and spatial genetic structure, and thus influence mating systems, sexual reproduction, and recruitment. Identifying the key drivers of genetic structuring is critical for genetic management of ecological restoration success, especially in systems where the nature and extent of clonality is highly variable. Here, we quantify clonality and patterns of genetic structure in the temperate Australian seagrass Posidonia australis. We examine the location of meadows in relation to water movement and prevailing winds to assess their relative influence on local spatial genetic structuring. Measures of genetic diversity, assessed with 7 polymorphic microsatellite loci, were highly variable across 13 meadows sampled within and around a natural embayment on the west coast of Australia. The overall structure of P. australis meadows across this region is best explained as one of 'chaotic' genetic patchiness, with significant differentiation among most meadows (pairwise F ST values), high levels of genetic diversity in meadows that are in more open waters, and lower genetic diversity at inshore sites facing strong prevailing winds at the time of seed dispersal or that have little water movement. A strong isolation by distance relationship within the embayment is consistent with prevailing winds (which create surface currents) at the time of peak pollen and seed release, strongly influencing dispersal direction.

Aim To examine the population genetic structure in Posidonia australis meadows, a marine foundation species capable of long distance dispersal (LDD), and the role of historical versus contemporary processes in shaping post Last Glacial Maximum (LGM) re‐colonization. Location Southeastern Australia including the Bass Strait Islands. Methods We generated multilocus genotypes and assessed spatial patterns of genetic diversity. Relationships among meadows were assessed in terms of historical sea level changes, oceanic boundary currents and contemporary seed dispersal based on a hydrodynamic model. Results There was strong regional spatial genetic structuring among P. australis meadows in south‐eastern Australia, which was congruent with three recognized marine biogeographical provinces [Peronian (eastern), Flindersian (western and southern), and Maugean (south‐eastern)]. The genetic data suggest Maugean meadows persisted in isolation during the LGM, with evidence for admixture and contemporary gene flow. Simulated dispersal events identified high rates of local and regional demographic connectivity, with evidence for occasional LDD events. Main conclusions The strong regional differentiation is consistent with long‐term barriers to dispersal persisting in the marine environment through many sea level fluctuations. Bass Strait Island meadows all have strong signals of genetic admixture. A weak but significant isolation by distance relationship is consistent with a historical signal and contemporary seed dispersal mostly within the Bass Strait.

The first axenic synthesis of morphologically typical ericoid mycorrhizas of the Epacridaceae has been achieved in micropropagated Epacris impressa Labill. with eight fungi isolated from roots of two epacrid species, E. impressa and Astroloma pinifolium (R.Br.) Benth. Mycorrhizal synthesis has also been achieved between E. impressa and both Hymenoscyphus ericae (Read) Korf and Kernan and Oidiodendron griseum Robak, recognized endophytes of Ericaceae, suggesting that the endophytes of the Epacridaceae and Ericaceae are capable of cross-infection. Infection rate of epidermal cells on hair roots varied from 3-77 % infection and the density of hyphal coils varied widely. This synthesis makes possible studies of the roles of these endophytes in the Epacridaceae and comparison with their roles in the Ericaceae.

Survival at range edges often sees the development of novel responses in the struggle for survival and reproduction. This study documents a physiological response at the trailing edge, whereby reproductive strategy can adapt to fluctuating conditions and suggests that the lower-than-usual water temperature triggered unfertilized inflorescences to 'switch' to growing plantlets that were adventitious clones of their maternal parent. This may have important long-term implications as both genetic and ecological constraints may limit the ability to adapt or range-shift; this seagrass meadow in Shark Bay already has low genetic diversity, no sexual reproduction and no seedling recruitment.