Study of seed dispersal by Emu (Dromaius novaehollandiae) in the Jarrah (Eucalyptus marginata) forests of south-western Australia through satellite telemetry

Global positioning system (GPS) technology for tracking wildlife continues to evolve at a remarkable pace. As animal movement is increasingly recognised as being critical for several ecological processes, advanced telemetry technology permits collection of a high volume of data across short time intervals that was previously unobtainable. Here we describe the use of GPS telemetry to track the movements of five tagged Emus (Dromaius novaehollandiae Latham) released within the Jarrah (Eucalyptus marginata Sm.) forests of south-western Australia. The Emu plays a significant role as a seed disperser for many species. Describing the movement patterns of this species is a key requirement in refining the extent and significance of its contribution to seed dispersal, both locally and over long distances. We found that Emus followed a typical correlated random walk pattern and that each bird demonstrated a variable response to the landscape in terms of behaviour, extent of movement and habitat selection. From a methodological perspective, 50% of our devices detached before 30 days of GPS locations could be collected, reflecting a need for device refinement for future studies on large ratites. Nevertheless, our preliminary data provide useful insights into the movements of the Emu and potential impacts on seed dispersal within the Jarrah forests

Fire-stimulated reproduction in the resprouting, non-serotinous conifer Podocarpus drouynianus (Podocarpaceae): the impact of a changing fire regime

Species with fire stimulated reproduction (fsr) are common in Mediterranean climate ecosystems. We investigated how season of, and time since, fire affects seed production in Podocarpus drouynianus F. Muell., a dioecious resprouting coniferous shrub endemic to the jarrah (Eucalyptus marginata Sm.) forests of southwestern Australia, and if the now largely managed fire regime in these forests poses a risk to its persistence. We hypothesised that, like other species showing fsr, seed production in P. drouynianus would be limited to the first few years following fire and seed set would be lower after spring burns. Mature plants regenerated rapidly from buried stem tissue (lignotuber) after fire, producing abundant sporophylls in autumn 12–18 months later. Stands burnt in autumn showed peak seed production 1 year later, while for those burned in spring, peak seed production was delayed until the second autumn after fire. Limited seed production occurred for up to 3 years following fire, but no seed production was observed in longer unburnt (>10 years since fire) stands. While we did not observe a significant impact of fire season on seed production, seed weight and viability were lower for spring-burnt plants. Population-level effects associated with plant density may also have negative impacts on P. drouynianus demography, with females within a small population burnt in autumn producing very few seeds 12 months following fire. Interactions between climate change, fire regimes and fire management practices need to be considered in order to best safeguard the long-term persistence of this conifer species

Serotiny in southern hemisphere conifers

Serotiny is a widespread trait in angiosperms in the southern hemisphere; however, it is less common in conifers and has been little examined in the only two genera of southern conifers (Callitris and Widdringtonia) that have serotinous cones. There is variation across the family in the size of cones, the amount of seed contained and the time over which the cones stay closed on the plant. Cones from most of the species were collected in the field and various morphometric measurements made including cone wet and dry weight, the number of seeds contained and their likely viability. Cones from a selection of species with different cone sizes were heated to increasing temperatures, to investigate the ability of cones to protect the contained seeds from heat. In comparison to the flowering plants, serotiny has developed comparatively recently in southern conifers (in the last 10-20 million years). In Widdringtonia, serotiny is relatively weak, whereas in Callitris, it varies from strong to non-existent. Cone size and fertile-seed production across the two genera varies and the number of fertile seeds produced is positively related to the size of the cone. In some species, there are sterile seed-like bodies. These may have developed to confuse seed predators, so fertile seeds have a better chance of survival. Larger (heavier) cones are more effective in protecting the contained seeds from the heat of fires than are smaller ones. There is no simple relationship between the cone size and type of environment occupied by the species. In regions where fire is unlikely, predictable but mild or completely unpredictable, the species tend to be non-serotinous. In temperate regions where hot fires are likely to have been a selective agent, the species tend to be more strongly serotinous, although fire is not essential to open the cones. The community and environment in which a species has evolved is likely to have influenced the development of the degree of serotiny for each species and this may still be a variable property among populations of some species, depending on the fire regime of the area in which they grow

Regeneration failure threatens persistence of Persoonia elliptica (Proteaceae) in Western Australian jarrah forests

The severe disruption of herbivore relationships can result in catastrophic, demographic consequences for plant populations. We investigated the potential roles of herbivory, fire and their interaction, in the observed long-term regeneration failure of Persoonia elliptica R.Br. (Proteaceae), an understory tree species of fire-prone jarrah (Eucalyptus marginata Sm.) forests in southwestern Australia. Seed production, storage and viability were assessed, as was seedling recruitment in both the presence and absence of fire (a potential germination cue), using experimental herbivore exclosure plots. We also sought to determine the ‘herbivory zone’ (height) within which P. elliptica was susceptible to browsing. Herbivores, primarily the western grey kangaroo, preferentially consumed leaves of P. elliptica up to a browsing height of 1.5 m. Viability of fresh seeds was low at ca. 39 % and rapid viability loss was observed in the soil seed bank, with only ca. 5 % of seeds remaining viable for >1 year. Germination was restricted almost solely to burned areas and survival of recruits to the confines of herbivore exclosures. We suggest that an increase in the primary herbivore, combined with low viable seed supply, is the likely cause of continuing regeneration failure in this species. The slow growth of the species suggests that without intervention, seedlings and juvenile plants will be unable to escape the herbivory zone. Management actions to facilitate recruitment might best focus on the combination of managed fires to break seed dormancy, followed by fencing to protect seedlings from large herbivores

Reproductive biology, post-fire succession dynamics and population viability analysis of the critically endangered Western Australian shrub Calytrix breviseta subsp. breviseta (Myrtaceae)

Calytrix breviseta Lindl. subsp. breviseta is a critically endangered, obligate-seeder shrub within fire-prone kwongan of south-west Western Australia. Little is known about the species' reproductive biology and how threatening processes, particularly altered fire regimes and exotic species invasion, will impact the long-term viability of the species. This study aims to elucidate the species' reproductive biology and patterns of seedling recruitment during succession after fire. The effects of changes to the fire return interval and exotic species invasion on the long-term viability of the species is also described. The species exhibits abundant recruitment following fire and the application of a smoke treatment significantly improves germination, similar to many other Western Australian shrubs. However, significant inter-fire recruitment was observed up to 10 years following fire, leading to the presence of multi-aged subpopulations, although seedling recruitment was negligible >20 years after fire. The juvenile period is short at 34 years to first flowering. Population viability analysis (PVA) predicted that the optimal fire return interval to maintain C. breviseta subsp. breviseta was dependent on the carrying capacity (K) of the community and the number of individuals present. Carrying capacity will be related to site quality and competition from invasive species. PVA showed that if K remains high, then the optimal fire return interval is ∼1520 years, but under lower carrying capacity, (i.e. weed competition) fires decrease the likelihood of population survival

Detecting plant spatial pattern change after disperser loss: A simulation and a case study

Disruption of seed dispersal processes may affect plant population spatial structure. We used a spatial simulation model and an empirical case study to assess the conditions under which the loss of seed dispersers has a detectable effect on a species' spatial pattern. Our simulation experiments suggested that detecting spatial change following disperser loss will be difficult, except when rates of fruit removal are initially high and then completely disappear. To contextualize the simulation modeling, we used spatial point pattern analyses to characterize the spatial pattern of two large‐seeded species (Leucopogon nutans, a fire‐killed seeder shrub and Macrozamia riedlei, a long‐lived, resprouting cycad) in the jarrah (Eucalyptus marginata) forests of southwestern Australia. The plant species' primary disperser, the emu (Dromaius novaehollandiae), was absent from one of the sites we considered, but present at the other two. There was no detectable difference for either plant species in the strength of aggregation between sites with and without emu. However, even if disperser loss may not greatly affect local spatial structure for most plant species, it is likely to be important for long distance dispersal and genetic structuring of populations, so accurate characterization of the dispersal kernel is critical, especially in terms of plant emigration

The spatial complexity of seed movement: Animal‐generated seed dispersal patterns in fragmented landscapes revealed by animal movement models

1. Large animals provide crucial seed dispersal services, yet face continued threats and are susceptible to changes in landscape composition and configuration. Thus, there is a growing imperative to improve understanding of animal‐generated seed dispersal using models that incorporate spatial complexity in a realistic, yet tractable, way. 2. We developed a spatially explicit agent‐based seed dispersal model, with disperser movements informed by biotelemetry data, to evaluate how landscape composition and configuration affect seed dispersal patterns. We illustrated this approach for the world's second largest ratite, the emu (Dromaius novaehollandiae), a highly mobile generalist frugivore considered an important long‐distance disperser for many plant species across Australia. 3. When animal movement is unrestricted, model parameters related to seed gut passage largely determine seed dispersal kernels. However, as habitat loss and fragmentation increase, the extent of long‐distance dispersal events is reduced and seed shadows became progressively more aggregated. This effect is due to the emu not being able to move between disconnected parts of the landscape, with small changes in habitat structure causing decreased long‐distance dispersal. 4. We simulated seed dispersal patterns generated by three commonly used generic models of animal movement – unbiased and biased correlated random walks and Lévy walks – to evaluate how different representations of movement affect estimations of animal movements and emergent seed dispersal patterns. Simulated movements informed by the emu biotelemetry data resulted in longer median seed dispersal distances than do the three generic models. 5. Synthesis. Changes in landscape composition and configuration can dramatically alter patterns of zoochorous seed dispersal as they influence animal movement. However, when models are used to simulate the patterns of seed dispersal, decisions about how animal movement is represented also affect estimates of seed dispersal

Maltreatment of Strongyloides Infection: Case Series and Worldwide Physicians-in-Training Survey

10.1016/j.amjmed.2006.05.072American Journal of Medicine1206545.e1-545.e8AJME