Reproductive biology of the rare and endangered Banksia brownii Baxter ex R. Br. (Proteaceae)

Abstract Banksia brownii is an endangered species, now limited to ～ 15 disjunct populations in southwestern Western Australia. Data on flowering phenology, plant size, fruit set, pollination and the mating system were gathered for two of these populations between March and October 1993. Flowering for both populations followed a similar pattern, with open flowers first evident in April, and the number of inflorescences with open flowers peaking in June. At both locations, trees differed considerably with respect to their size, the total number of inflorescences produced and the length of their flowering season. Fruiting success was typically low, with approximately half of all inflorescences failing to develop into infructescences. Only 1. 8% of the flowers originally present on inflorescences developed into follicles. The distribution of follicles along each infructescence was non-random, with most forming in the middle third of the infructescence for reasons relating to nutrient supply and pollinator behaviour. More flowers opened during the day than at night, although pollen was lost from individual flowers during both periods. Honeyeaters such as Phylidonyris novaehollandiae were common at the two study sites, and often carried large loads of B. brownii pollen. Though less frequently caught, the nocturnal mammals Rattus fuscipes and Tarsipes rostratus also bore substantial amounts of pollen. Most inflorescences from which these mammals and birds were excluded remained barren. Fruiting success was further reduced when invertebrates such as Apis mellifera were also prevented from visiting inflorescences. The ability of B. brownii to set at least some fruit in the absence of biotic poli-nators indicates that the species is partially self-compatible. Honeyeaters foraged preferentially at inflorescences with one to two thirds of their flowers open, probing mainly along the ‘advancing front’ of open flowers. These animals moved more frequently between inflorescences on the same plant than between those on different plants, and were often recaptured in the same locations. Mammals also appeared to be sedentary. Both B. brownii populations had mixed mating systems, with genetically determined outcrossing rates of ～0.7. The unusually high level of selfing in each population is presumably a reflection of the species’ self-compatibility and the foraging behaviour of its pollinators.     

First synthesis of ericoid mycorrhizas in the Epacridaceae under axenic conditions

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.     

Growth rate and substrate-related mortality of a benthic brachiopod population

Collins, M. 1991 01 15: Growth rate and substrate-related mortality of a benthic brachiopod population. Lethaia , Vol. 24, pp. 1–11. Oslo. ISSN 0024–1164.
Vital staining and careful examination of potential substrates enabled an accurate census of Terebratulina retusa to be made and prompted a study of their population dynamics. Seasonal samples of T. retusa from a deep water Modiolus -brachiopod assemblage were always dominated by small (>1 mm) individuals as growth rate of the post-larvae, estimated from changes in mean cohort length. was unexpectedly slow. Six months after settlement the animals had barely doubled in length, a rate of increase consistent with laboratory studies, but an order of magnitude less than conventional estimates. As the attainment of a size refuge is the only documented strategy by which articulate brachiopods counter overgrowth or disturbance this observation has profound implications for survival. Mortality of T. retusa in the Firth of Lorn, from different substrates, followed an unexpected pattern. Virtually the only substrate on which adult T. rehusa were recorded was the surface of M. modiolus shells, although juvenile T. retusa attached to this substrate suffered enhanced levels of mortality. Grazing pressures and spatial competition, believed to be reduced on complex surfaces, may account for the elevated mortality levels of M. modiolus-attached post-larvae prior to the apparent size refuge at a length of 2 mm. * Brachiopoda, Terebratulina, growth rate, disturbance, ecology, population structure .     

The Effects of Temperature on Leaf Growth in Cyperus longus, a Temperate C4 Species

Plants of the C₄ sedge Cyperus longus L. were grown at 10, 20and 30 °C. An asymptotic growth curve, the Richards function,was fitted to growth data for successive leaves. The mean rateof leaf appearance was a linear function of temperature with0.014 leaves appearing per day for every 1 °C increase intemperature. The instantaneous relative rate of leaf extensionshowed a marked ontogenetic drift which was most rapid at 30°C and slowest at 10 °C. The mean absolute extensionrate for foliage had a temperature coefficient of 0.16 cm d^–1° C^–1 in the range from 10 to 30 °C. The durationof leaf growth was independent of leaf number at 10 and 20 °Cbut increased linearly with leaf number at 30 °C. The smalldifferences in relative growth rate at the three temperaturesresulted in large differences in foliage area produced at theend of a 30 d growth period. The final foliage areas at 20 and10 °C were 51 and 9% respectively of that at 30 °C. Cyperus longus, temperature, leaf growth, Richards function, growth analysis     

A comparative study of epiphytic algal communities on two common genera of sea-grasses in eastern Australia

Fifty-seven epiphytic species were found to occur on the two sea-grass hosts Zostera and Posidonia in Botany Bay and Jervis Bay, N.S.W. Among the algal epiphytes on Posidonia australis several indicator species were identified and it was found that their relative frequency of occurrence can be used to differentiate sites within the two bays. These indicator species can be used also to classify a collection from an unknown site within the region, and their relative occurrences may provide a useful index for early detection of changes in the bay environments.