Cunninghamia : A Journal of Plant Ecology for Eastern Australia, Volume 20 (2020)
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Phenological studies are important to gain insights into the ecology of plant species, particularly those that are threatened and require specific management actions such as regular population monitoring. For many species of terrestrial orchids, limited fundamental knowledge on peak flowering, pollination and seed production restricts effective monitoring outcomes. In this single-season study, phenology data from one population of the vulnerable Diuris praecox were collected, with the aim of informing future management relating to monitoring surveys and to assist in conservation of this species. To this end, six sub-populations (three each in forest habitat and along maintained powerline easements) were visited weekly from the onset of flowering until seed release, with observations made on 134 tagged individuals within 10 x 10 m plots. During the 2019 flowering season, 37% of all plants developed capsules, and 35% released seed. However, success varied between locations, with greater floral displays along powerline easements resulting in stronger pollination rates, while sparse sub-populations in forested locations showed lower pollination. Significantly more flowers per inflorescence (range 1-7) were evident in forest than easement sites, but there was no significant difference in inflorescence height across these habitats. For most sub-populations at least one orchid set seed, even when occurring in low densities (<10 plants). Overall, substantial floral displays did not necessarily result in abundant fruiting, and impacts from desiccation, predation and grazing likely prevented more successful capsule production in any given sub-population. The synchronously flowering shrubs Daviesia ulicifolia and Pultenaea villosa co-occurred across all sub-populations, suggesting that the nectar-less Diuris praecox may mimic these species to attract pollinators. Peak flowering was determined to be approximately 20 days from the onset of flowering, with 83% of all plants in flower at that time. For ongoing monitoring, the timing of surveys to occur approximately three weeks after the first observed flowering, will likely maximize return-for-effort, particularly when survey resources are limited, although it is acknowledged that different seasons and populations may vary from this timeframe.
Sampling of day-active invertebrates visiting the flowers of Grey Mangrove Avicennia marina subsp. australasica (Walp.) J.Everett (family Acanthaceae) was undertaken at a study site on the Harrington estuary, northern New South Wales, Australia. The study extended over a 4 season period (from 2016 to 2020), with more than 170 anthophilous species being recorded. Nearly all were observed contacting flower stigmas and/or anthers during foraging episodes. At least 113 of the approximately 168 species examined for pollen loads, carried Avicennia pollen. None carried mixed pollen loads, indicating foraging constancy/fidelity. Although pollen carriage does not automatically assign the status of pollinator, nevertheless, the findings indicate Avicennia marina is pollinated by a taxonomically diverse suite of native invertebrates which sit within an assemblage of flower visitors that may include non-pollinating species. Although the invasive honeybee Apis mellifera was seasonally common during most days of observation, it was uncommon or absent on some days. The occurrence of native flower-visiting species was often found to be episodic, with many species being abundant during one day or season of observation, but then absent or rarely encountered at other times. Such behavioral events highlight the need for extended periods of field investigation to illuminate more fully the pollination ecology of individual plant species. Comparison with additional anthophilous insect records from a previous 1990 – 1994 study in an adjacent littoral rainforest community, indicated that this community may furnish a pool of native insects from which Avicennia marina can seasonally recruit a dynamic pollinator network.
Calochilus pulchellus (family Orchidaceae) (Pretty Beard Orchid) is a listed Endangered species with a highly restricted distribution in the Shoalhaven local government area. The species was only known from a small number of populations when described in 2006. Since then very few new populations of the species have been recorded and some previously known populations have not been observed for decades. This study summarised known information regarding the distribution and habitat preferences of Calochilus pulchellus, with the aim of identifying potential habitat where unknown populations of the species may be detected by targeted surveys. Areas of potential habitat for the species were identified based upon vegetation communities in which the species had previously been recorded. A subset of the initially large area of identified potential habitat was selected for targeted surveys based on the recorded occurrence of sympatric threatened orchid species. The targeted surveys resulted in an approximately three-fold increase in the previously known population size of Calochilus pulchellus, a small range extension for the species and a doubling of the extent of occurrence. Newly discovered individuals and populations of the species have increased the understanding of habitat for the species, with a greater proportion of the total known population of the species now known to occur within woodland and forest vegetation communities rather than heathlands. Despite the additional individuals of the species detected as part of this study, the species is still only known from a very low number of known individuals and a small number of populations and has a very high risk of extinction. Consequently, identifying and protecting additional populations of Calochilus pulchellus should remain a priority for the conservation of the species.
A survey for myxomycetes (plasmodial slime moulds or myxogastrids) was carried out on Norfolk Island in June 2019. The overall objective was to collect both specimens that had fruited in the field under natural conditions as well as specimens appearing in moist chamber cultures prepared with samples of dead plant material collected on the island. However, only three species were recorded as field collections over a period of almost two weeks, so the primary focus of the survey was redirected to collecting samples for moist chamber cultures. Approxmately 120 samples of dead plant material collected from 21 different sampling sites on the island and used to prepare 356 moist chamber cultures yielded a total of 497 specimens. These specimens included at least 48 species in 18 genera. This brings the total number of species and genera now known from Norfolk Island to 55 and 19, respectively.
The recruitment processes and resulting distribution pattern of bird-dispersed Canary Island Date Palm, Phoenix canariensis (family Arecaceae) in a riverine forest setting are described. All palms on a near-urban peninsula of the Murrumbidgee River near Hay, New South Wales were GPS mapped and classified into height-dependent age categories. The distribution of the plants was examined spatially in relation to possible source palms and in relation to elevation with regard to flooding levels. Successful recruitment is subject to a range of environmental parameters, primarily palatability to vectors and seedling mortality due to lack of moisture, frost or grazing by herbivores. If a seedling survives that critical period of the first 18 months, long-term success is (almost) guaranteed, unless catastrophic events (bushfires, prolonged flooding) intervene. Based on the findings, a conceptual model for the recruitment of Phoenix canariensis palms is provided. Even though the palms produce fruit for much of the year (March–December), the time window for successful recruitment is restricted to a period from August to mid-September with short shoulder periods on either side.
The present study took advantage of the availability of high resolution ADS40 digital imagery to 1) systematically resample the vegetation of the Lord Howe Island Group (LHIG, excluding Ball's Pyramid); 2) conduct a numerical analysis of the floristic data; 3) map vegetation extent and the distribution of vegetation communities and 4) compare the resultant classification and mapping with those of Pickard (1983). In July 2013, a total of 86 full floristic and 105 rapid floristic sites were sampled across the island, based on a stratified random sampling design. A hierarchical agglomerative clustering strategy (Flexible UPGMA) and Bray-Curtis dissimilarity coefficient with default beta, along with nearest neighbour analysis to identify anomalous site allocations, was used to analyze the floristic data. In total 33 vegetation communities were delineated and mapped: 19 mapping units from the full floristic analysis; 7 variants identified within five of the above 19 groups; 3 mapping units from analysis of canopyonly floristic data; and 4 mapping units recognised in previous studies that are mapped but were not sampled in this survey. The resultant list of vegetation communities and non-vegetation mapping units, along with their equivalence to Pickard (1983) and DECC (2007) units, is provided. 222 plant taxa were recorded in the survey, including 47 exotic taxa. Weeds are a common component of some communities, particularly coastal strandline communities, the shrublands of the southern mountains and regenerating vegetation on landslips. The threatened plants Xylosma parvifolia, Lepidorrhachis mooreana, and Geniostoma huttonii were recorded in floristic sites. Two communities, Gnarled Mossy Cloud Forest and Lagunaria Swamp Forest are listed as Critically Endangered Ecological Communities under the NSW Biodiversity Conservation Act 2016 (BC Act). Coastal Saltmarsh, an Endangered Ecological Community listed under the BC Act, also occurs on the main island. An assessment of the conservation status of the vegetation communities recognised in the present study is provided. A number of communities warrant further consideration for listing as threatened ecological communities. Significant improvement in vegetation community attribution and spatial resolution was possible with the highresolution digital imagery, however Pickard's 1983 classification and mapping was found to be a comprehensive and accurate description of the island’s vegetation considering the imagery available at the time. This project has resulted in greatly improved accuracy of vegetation mapping linework for the LHIG. The Pickard (1983) vegetation map comprised 321 individual polygons, whereas the new map includes 1 840 polygons of sufficient accuracy to support detailed environmental planning programs, particularly within the Settlement area where spatial accuracy in the delineation of native vegetation is critical. The new vegetation communities were applied to the updated linework to complete the project. Detailed profiles were compiled of each vegetation community for which enough information was available. These profiles should prove useful in field identification of vegetation types and the assessment of their conservation status.
Acacia meiantha Tindale & Herscovitch, (Fabaceae) a low to medium shrub with root suckering, is only known to occur at three locations, Clarence, Carcalgong and Mullion Creek in Central West New South Wales. These disjunct populations each separated by >60 km, are considered as isolated subpopulations. A compilation of recent field surveys shows that of the 42,000 stem clusters/aggregates of Acacia meiantha estimated across the three geographic locations, the majority, 39,900 (96%) occur in the Mullions Range State Forest subpopulation, where 61% of clusters occur in the remnant native forest areas and 39% in the plantation forestry compartments. At Carcalgong 1,566 stem clusters were recorded along narrow roadside reserves. The Clarence subpopulation consists of < 400 stem clusters precariously situated among a confluence of road, railway and electricity power-line easements. Ecological observations of habitat are presented; information relating to genetic diversity, seed biology, reproductive biology and response to fire is found to be Data Deficient. The threatened species listing as Endangered under both State and Commonwealth legislation is warranted; the species does not occur on any conservation lands, has restricted distribution and abundance, and is vulnerable to ongoing threats. The area (AOO) and extent of occupancy (EOO) are calculated. It occurs at three locations (< 5), has an estimated EOO of 2,900 km2 (< 5,000 km2) and an AOO of 80 km2 (< 500 km2) (IUCN (2019) thresholds in brackets); there are significant threats to the extent and quality of habitats. Additional opportunities for improving the conservation of the species, particularly in the Mullions Range State Forest, over and above those outlined in the site-managed initiatives of the current Saving our Species program, are presented.
Phytophthora cinnamomi is an oomycete (water mould) with a large host range. It infects plants through their roots and in some cases will kill them. The pathogen is readily dispersed in soil and water, over short distances by its swimming spores and over large distances by humans. While Phytophthora cinnamomi has been well-studied in other parts of Australia, its distribution and impact are poorly known in New South Wales (NSW). In the current study we compiled existing data on Phytophthora cinnamomi occurrence and filled spatial gaps in sampling. We found about 1000 records of Phytophthora cinnamomi presence in over 5000 tests of soil and root material, and collected a further 457 samples from areas where no sampling had previously been done. The resulting data set enabled modelling of Phytophthora cinnamomi habitat suitability using the software program MaxEnt with climate and soil spatial layers. We found that coastal areas and adjacent tablelands were most suitable for the pathogen, although some areas within that may be unsuitable because of soil properties. We then modelled assets (threatened species) potentially affected by Phytophthora cinnamomi to produce a layer of risk. Using projected climate layers, we found that habitat suitability and risk will decline in parts of northern NSW by 2070 but be amplified in the south. New susceptible species in places such as the Australian Alps are likely to be exposed to the pathogen in the future. We offer advice for managing Phytophthora cinnamomi in NSW. Management is difficult where the effects of this pathogen are often inconspicuous and its distribution is widespread. However, basic hygiene to limit spread to susceptible assets will have great benefit regardless.
For more than 100 years, behavioural biologists have extensively studied satin bowerbirds (Ptilonorhynchus violaceus) to understand the complexities of bower construction and courtship, but this research has not accounted for the ecologically important role the species plays as a seed disperser in eastern Australia. In this study, we have used a simple method involving pans of water and mirrors to collect scats from male satin bowerbirds on the Dorrigo Plateau of northeastern New South Wales. Based on seeds identified from scats collected using this method, we identify the fruits of 37 plant species in 22 families that are eaten by satin bowerbirds and show that 35 of these species germinated after passage through the digestive system of bowerbirds. This method was developed for bush regenerators to collect rainforest tree seeds that are otherwise inaccessible and/or difficult to germinate; it is applicable throughout the range of satin bowerbirds. We hope the method will be adopted by bush regenerators for harvesting seeds otherwise difficult to source, and by ornithologists studying the diets and seed dispersal of these ecologically significant birds.
Genoplesium baueri R.Br. (family Orchidaceae), an endangered terrestrial orchid species endemic to the Sydney Basin, New South Wales, Australia, is known from 13 populations but little is known about its population demographics. To assess the emergent population size, plant size and reproductive output of two key northern Sydney populations, at Ku-ring-gai Chase National Park (KCNP) and Ku-ring-gai Wildflower Garden (KWG), and how these fluctuate through time, intensive field surveys of these populations were carried out over a ten-year period (2009-18). Plants emerged at both sites in every year with a total of 1,249 plant counts made over the 10-year period. From this, we estimate that a total of approximately 500 perennial individuals may exist across both populations, more than previously thought. Although emergent population size did not differ between populations, we found significant differences between the populations in the other measures. The KWG population had taller plants that produced more flowers per plant than the KCNP population, while the plants in the KCNP population had more pollinated flowers and fruit per plant. All of these measures significantly fluctuated through time. This 10-year study has shown that the resilience of key Genoplesium baueri populations is greater than previously thought. However, it has also shown the boom-and-bust nature of emergence, flowering and fruit set in this species, which has highlighted the need for multiyear intensive studies when assessing likely persistence of endangered terrestrial orchid species.