We studied how leaf litter, water and fungal pathogens affect the establishment, survivorship, and growth of Eucalyptus obliqua using glasshouse and field experiments. In a glasshouse experiment, the presence of leaf litter of E. obliqua increased the establishment of seedlings when the seeds were placed beneath the litter, but dense litter layers reduced seedling emergence when seeds were placed on top. Results from a complementary experiment suggest that the effect of litter may be mediated by the high humidity microenvironment it creates, which may enhance imbibition of unburied seeds. In another glasshouse experiment, litter in combination with excessive water applications reduced seedling emergence and increased seedling mortality, but the addition of fungicide reverted these effects. Litter with lower water application or fungicide added increased seedling emergence. In all cases higher biomass in seedlings growing in litter treatments was associated with earlier emergence. In two recently burnt sites, the density of seedlings of E. obliqua was positively correlated to the presence of litter. Experimental addition of litter in the field reduced soil temperature during the summer, and together with watering, increased soil water content, and the water potential of established seedlings. However, neither treatment had any positive effect on their growth or survivorship. On the contrary, litter addition reduced the height and number of leaves, probably as a result of increased herbivory. We conclude that in Mediterranean-type systems litter may produce various effects on seedling establishment depending on their developmental stage, and the season.

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Ross River virus (RRV) is responsible for the most notifications of human arboviral infection in Australia. Seroprevalence and experimental infection studies have implicated macropods (e.g., kangaroos) as the major reservoir hosts. However, transmission ecology varies spatially, and infections in urban areas have prompted the question of what animals serve as reservoirs in regions where macropods are scarce. In South Australia (SA), human infection rates for RRV vary greatly by region as do vector and reservoir abundance. We hypothesized that mosquito abundance and feeding patterns would vary among ecoregions of SA and could help explain divergent human case rates. To test our hypothesis, we amplified and sequenced a 457 base pair region of the cytochrome B segment of mitochondrial DNA from blood fed mosquitoes collected in three main ecoregions of SA and identified sequences using a BLAST search in NCBI. Domestic livestock made up the vast majority of bloodmeals from the region with the highest human infection rate. Livestock are generally not considered to be important reservoir hosts for RRV, but our results suggest they may have a role in transmission ecology in some places. Surprisingly, none of the 199 bloodmeal samples were identified as macropod in origin. In the context of these findings, we consider the possible RRV vectors and reservoir hosts in these regions and propose that diverse spatial and temporal transmission ecologies occur in SA, depending on vector and reservoir availability.

Understanding the factors influencing mosquito distribution is important for effective surveillance and control of nuisance and disease vector mosquitoes. The goal of this study was to determine how trap height and distance to the city center influenced the abundance and species of mosquitoes collected in Adelaide, South Australia. Mosquito communities were sampled at two heights (<2m and ~10m) along an urban-rural gradient. A total of 5,133 mosquitoes was identified over 176 trap nights. Aedes notoscriptus, Ae. vigilax, and Culex molestus were all more abundant in lower traps while Cx. quinquefasciatus (an ornithophilic species) was found to be more abundant in high traps. Distance to city center correlated strongly with the abundance of Ae. vigilax, Ae. camptorhynchus, Cx. globocoxitus, and Cx. molestus, all of which were most common at the sites farthest from the city and closest to the saltmarsh. Overall, the important disease vectors in South Australia (Ae. vigilax, Ae. camptorhynchus, Ae. notoscriptus, and Cx. annulirostris) were more abundant in low traps farthest from the city and closest to the saltmarsh. The current mosquito surveillance practice of setting traps within two meters of the ground is effective for sampling populations of the important disease vector species in South Australia. Journal of Vector Ecology 39 (1): 48-55. 2014.