No abstract

Expansion of mining in the banded ironstone ranges of southern Western Australia has focussed attention on the genetic impacts of habitat loss on rare endemic taxa. One example is Tetratheca paynterae subsp. paynterae (Elaeocarpaceae), an insect-pollinated, perennial shrub confined to 4 ha of banded ironstone outcrops in the Windarling Range. Mining removed 1,900 of the 7,700 recorded plants in 2004. Further reductions could occur if it can be demonstrated that the viability of the remaining population is not threatened. To investigate the potential impact of reductions in population size due to mining we first used Bayesian clustering and principal coordinate analysis to define population boundaries based on differentiated gene pools. The level of genetic diversity and spatial genetic structuring was then compared among populations that ranged in size from 46 to 4400 individuals. Analysis with 11 microsatellite loci revealed lower genetic diversity in small populations (A R = 4.5-4.8) than a large population (A R = 6.3) together with significant pair-wise differences among populations separated by distances of 80 m or more. Spatial autocorrelation analysis showed the extent of spatial genetic structure differed among populations of different size, consistent with near-neighbour mating and limited dispersal. Fine scale spatial structure was consistent with historically low gene flow. Analysis of the impact of possible expansions in mining revealed small, isolated populations of T. paynterae subsp. paynterae were of high conservation value. While their removal would reduce plant numbers and genetic diversity by less than 5%, unique genotypes will be lost resulting in a 30% decline in genetic differentiation.

In an era characterized by recurrent large wildfires in many parts of the globe, there is a critical need to understand how animal species respond to fires, the rates at which populations can recover, and the functional changes fires may cause. Using quantified changes in habitat parameters over a~400-yr post-fire chronosequence in an obligate-seeding Australian eucalypt woodland, we build and test predictions of how birds, as individual species and aggregated into functional groups according to their use of specific habitat resources, respond to time since fire. Individual bird species exhibited four generalized response types to time since fire: incline, decline, delayed, and bell. All significant relationships between bird functional group richness or abundance and time since fire were consistent with predictions based on known time-since-fire-associated changes in habitat features putatively important for these bird groups. Consequently, we argue that the bird community is responding to post-fire successional changes in habitat as per the habitat accommodation model, rather than to time since fire per se, and that our functional framework will be of value in predicting bird responses to future disturbances in this and other obligate-seeder forest and woodland ecosystems. Most bird species and functional groups that were affected by time since fire were associated with long-unburned woodlands. In the context of recent large, stand-replacement wildfires that have affected a substantial proportion of obligate-seeder eucalypt woodlands, and the multi-century timescales over which post-fire succession occurs, it would appear preferable from a bird conservation perspective if fires initiating loss of currently long-unburned woodlands were minimized. Once long-unburned woodlands are transformed by fire into recently burned woodlands, there is limited scope for alternative management interventions to accelerate the rate of habitat development after fire, or supplement the resources formerly provided to birds by long-unburned woodlands, with the limited exception of augmenting hollow availability for key hollow-nesting species.

No abstract

We investigated the response of the Western Bristlebird Dasyornis longirostris to fire in the Fitzgerald River National Park (FRNP), Western Australia, over a 34-year period. This species is a threatened Western Australian endemic restricted to a highly fire-prone habitat. Commencing in 1985, we surveyed for occurrence of Western Bristlebirds within the FRNP. Monitoring that was specifically focused on fire impacts began at Fitzgerald Track in November 1994 following a fire the previous month. That site had been surveyed in June and August 1994 before the fire. Fires in other recently surveyed locations in 1997–1998, 2000, 2008 and 2019 allowed for comparisons to be made following further monitoring of these sites. Many Bristlebirds survived a fire then relocated along or near the fire edge, usually in clusters of home ranges where suitable habitat was available. Bristlebirds gradually re-occupied burnt areas when these became suitable, often to home ranges occupied before the fire. There was a tendency for a home range to be occupied for >1 year. A change independent of fire could occur. Areas of vegetation of different fire ages were used by Bristlebirds for differing time periods. Sites in the lower-rainfall areas required longer periods of time for habitat to be recolonised by Bristlebirds and the maximum age of vegetation occupied by Bristlebirds varied between sites. For these reasons, generalised prescriptions are not appropriate, but fire management of individual patches of Bristlebird habitat in the FRNP can be guided by these findings, ensuring that unburnt refuge areas are both protected and retained, with the timing of management actions informed by knowledge of population response and habitat condition.