Range extension of Leadbeater's possum (Gymnobelideus leadbeateri)

We report spotlight and camera-trap observations of Leadbeater’s possum (Gymnobelideus leadbeateri) at six locations up to 15km east of its described range. Half of our records occurred in fire-affected, mixed-species forest, with a tree species and seral stage composition that differs markedly from its predominant habitat: late-mature forests dominated by Eucalyptus regnans, E. delegatensis and E. nitens.

Life cycle expression of inbreeding depression in Eucalyptus regnans and inter-generational stability of its mixed mating system

Background and Aims Many plants exhibit a mixed mating system. Published models suggest that this might be an evolutionarily stable rather than a transitional state despite the presence of inbreeding depression, but there is little empirical evidence. Through field experimentation, we studied the role of inbreeding depression in eliminating inbred progeny from the reproductive cohort of the forest tree Eucalyptus regnans, and demonstrate a stable mixed primary mating system over two successive generations. Methods Two field experiments were conducted using seed from natural populations. We sowed open-pollinated seeds to simulate a natural regeneration event and determined isozyme genotypes of dominant and suppressed individuals over 10 years. We also planted a mixture of open-pollinated, outcross and selfed families with common maternal parentage; monitored survival of cross types over 29 years; and determined the percentage of outcrosses in open-pollinated seed from a sample of reproductively mature trees using microsatellite analysis. Key Results Both experiments demonstrated progressive competitive elimination of inbred plants. By 29 years, the reproductive cohort in the planted experiment consisted only of outcrosses which produced seed which averaged 66 % outcrosses, similar to the estimate for the parental natural population (74 %). Conclusions Selective elimination of inbred genotypes during the intense intra-specific competition characteristic of the pre-reproductive phase of the life cycle of E. regnans results in a fully outcrossed reproductive population, in which self-fertility is comparable with that of its parental generation. The mixed mating system may be viewed as an unavoidable consequence of the species’ reproductive ecology, which includes the demonstrated effects of inbreeding depression, rather than a strategy which is actively favoured by natural selection.

Inert Materials as Long-Term Carriers and Disseminators of Viable Leptosphaeria maculans Ascospores and Wider Implications for Ascomycete Pathogens

The viability of ascospores of the Phoma stem canker (blackleg) pathogen, Leptosphaeria maculans, was tested on a range of carrier materials, including metals, fabrics, woods, and plastics, and under different temperature conditions of 23 and 4, 36 and 14, and 45 and 15°C day and night, respectively. At 23 and 4°C (day and night, respectively), ascospores remained viable for up to 240 days on Tasmanian oak (Eucalyptus regnans) and pine wood (Pinus radiata). At 36 and 14°C (day and night, respectively), ascospores remained viable on pine wood for up to 180 days. At 45 and 15°C (day and night, respectively), ascospores remained viable up to 60 days on jute. There were also significant differences (P < 0.001) between carrier materials in their abilities to retain ascospores following washing. At least 30% of intact ascospores recovered from inert carrier materials were able to germinate on artificial growth media within 48 h of recovery and some ascospores were still viable after 240 days. These findings confirm that L. maculans ascospores remain viable for a much longer time in the absence of a host than previously considered. This demonstrates the importance of inert materials as long-term and long-distance carriers of viable L. maculans ascospores, and highlights their potential role for spread of L. maculans races to new regions and countries via farming equipment, clothing, and other associated materials. Local, national, and international biosecurity agencies need to be aware that the risks of spread of ascomycete plant, animal, and human pathogens via inert materials are significantly greater than currently assessed.

Plasticity and Stereotypy in Avian Foraging during Secondary Succession in Temperate Forests

Some bird species cannot persist during early secondary succession after natural or anthropogenic disturbance of Australian Mountain Ash ( Eucalyptus regnans) forest, whilst others remain abundant throughout regeneration. To conserve bird species diversity optimally in such forests, we need to know, inter alia, exactly why the latter species can persist after disturbance. Using a chronosequence approach, we documented four facets of foraging in a suite of these persistent species effectively covering 100 years of succession in E. regnans forest disturbed by wildfire or timber harvesting, namely the foraging strata, locations, substrates and behaviours used. Most species showed plasticity in their use of foraging strata and locations during succession, but four exhibited some limited stereotypy in these facets. In contrast, use of foraging substrates and behaviours was largely invariant within species during secondary succession. We suggest that switching foraging strata and locations was probably critical to persistence of most of these bird species during secondary succession, given the marked variation in structural and floristic variables that characterises this regeneration process. Some plasticity in foraging behaviour repertoire and substrate use was probably possible, but not beneficial. Although some resident bird species’ populations were severely reduced by disturbance in these forests, a substantial subset of species was sufficiently flexible in choosing foraging microhabitats to persist throughout secondary succession at pre-disturbance abundances.